WO2021073107A1

WO2021073107A1 - Three-dimensional printing method and three-dimensional printing device

Info

Publication number: WO2021073107A1
Application number: PCT/CN2020/092877
Authority: WO
Inventors: 梁福鹏
Original assignee: 南京钛陶智能系统有限责任公司
Priority date: 2019-10-18
Filing date: 2020-05-28
Publication date: 2021-04-22
Also published as: CN112024885A; CN112024885B; CN110918996A; CN110918996B; CN110523990A

Abstract

A three-dimensional printing method, using an arc or plasma directly heat the surrounding of a region, where molten raw materials are accumulated, of a printed body (8, 36, 46). The heat energy generated by the arc or plasma directly heating the surrounding of the region where the molten raw materials are accumulated enables a molten pool is formed on the printed body. The energy that creates the molten pool can create, without penetrating printed raw materials, a controllable small area molten pool below the accumulated molten raw materials. And a three-dimensional printing device. The printing method and the printing device can form a transitional temperature field between the region where the molten raw materials are accumulated and other non-molten regions of a printed body, and the residual stress is small. No damage is caused to a previously generated structure of the printed body. The forming precision is high, equipment costs, material costs and maintenance costs are low, and large components can be printed.

Description

Three-dimensional printing method and three-dimensional printing equipment

Technical field

The present invention relates to three-dimensional printing technology, in particular to a low-cost three-dimensional molding method and three-dimensional printing equipment that utilizes arc or plasma heating to generate a thin-layer molten pool to achieve high strength and high controllability, and belongs to the technical field of additive manufacturing.

Background technique

Three-dimensional printing technology originated in the United States at the end of the 19th century, and was gradually commercialized in the United States, Europe and other countries after the 1980s. Common mainstream 3D printing technologies, such as Stereo Lithography Apparatus (SLA), Fused Deposition Modeling (FDM), Selecting Laser Sintering (SLS), and 3D powder bonding ( ThreeDimensional Printing and Gluing, 3DP), was commercialized in the United States in the 1980s and 1990s. In the metal three-dimensional printing technology that uses metal as the printing material, the common ones are Selective Laser Melting (SLM), Laser Engineered Net Shaping (LENS), Electron Beam Melting (EBM), Wire and Arc Additive Manufacture (WAAM) all need to melt solid metal raw materials, and at the same time, it is necessary to melt the area of the printed body where the molten metal raw materials are accumulating, so that the printed body and the melted raw materials can pass between The way of melting is combined together. The use of laser or electron beam as the technology of melting energy requires high equipment manufacturing costs and high technical barriers. SLM, LENS, and EBM technologies use powder as a raw material, such as metal powder. The cost of metal powder for 3D printing is usually much higher than that of metal wire. SLM technology is currently the most mainstream metal three-dimensional forming technology. In addition to the aforementioned problems, there are many other problems. For example, due to the small laser spot, the extremely small molten pool, and the extreme temperature difference between the molten pool and other solidification zones, large residual stresses are generated. Crack, in order to solve this problem, there are many related technical researches, such as the research paper "Reducing residual stress by selective large-area diode surface heating during laser powder bed fusion additive manufacturing" (author John D.Roehling, etc. Journal Additive Manufacturing (2019). DOI: 10.1016/j.addma.2019.05.009) Use a high-power secondary laser to project to a larger area to post-heat the surface of the area heated by the main laser spot in the SLM technology to reduce the temperature gradient and decrease in the molding area The cooling rate was found to reduce the residual stress. WAAM technology uses electric arc as melting energy and metal wire as raw material. It is an important development direction of low-cost metal 3D printing technology. However, the existing technology in this direction has problems such as low controllability and low molding accuracy, which seriously restricts WAAM technology. Development and application. Existing WAAM technology, such as the Chinese patent application with the application number 201610908203.X, titled "A method for arc 3D printing spatial mesh structure", WAAM technology is low in cost, but because the energy range of the arc is low in controllability , The arc is unstable, and the liquid metal formed after the wire is melted by the arc mainly relies on its own gravity to drip onto the molten pool of the printed body. The drop process of the liquid metal is low in controllability, and the shape of the liquid metal is poor in controllability As a result, the accuracy of WAAM three-dimensional molding is extremely low, and complex monitoring systems are required (such as simultaneous monitoring of the liquid metal raw materials and the state of the molten pool through multiple methods such as cameras and spectroscopy equipment). The popularity of WAAM technology is far less than that of SLM technology. Using the compressed arc sprayed by the plasma torch as the melting energy technology, although the cost is also low, it also has the problem of low molding accuracy, and the plasma compression arc will blow off the melted area when the air flow rate is high, causing damage to the printed body ; The energy density of the plasma compression arc is extremely high (the center temperature can reach 20,000 degrees Celsius). The electrodes and nozzles of the plasma torch are consumable parts. The life of the electrodes and nozzles is short, and it is difficult to apply to the long-term three-dimensional printing process; The three-dimensional printing technology using plasma compression arc as a heating source rarely has commercial applications.

Summary of the invention

The purpose of the present invention is to provide a low-cost three-dimensional printing method and a three-dimensional printing device, especially a low-cost metal three-dimensional printing method and a metal three-dimensional printing device.

Another object of the present invention is to provide a three-dimensional printing method that uses arc or plasma as the preheating energy of the printed body and uses resistance heating to generate molten material on the printed body in real time, which will generate the molten material and the heating energy of the molten pool. Separation, to realize the melting connection between the newly accumulated molten raw material and the previously molded printed body, which has remarkable characteristics such as high molding strength, high controllability, and high molding accuracy.

In order to achieve the above-mentioned purpose of the invention, according to one aspect of the present invention, the technical solution adopted by the present invention is: a three-dimensional printing method, the main process of which is: melting solid raw materials to obtain molten raw materials, and the molten raw materials are placed in the three-dimensional printing equipment. In the forming zone used, the molten raw materials are accumulated in the forming zone and transformed into a printed body. The newly generated molten raw materials are accumulated on the basis of the printed body until the object to be printed is formed; among them: in the process of accumulating the molten raw materials, the molten raw materials are The position to be placed is determined by the shape and structure of the object to be printed; the forming area used by the 3D printing device refers to the space used by the 3D printing device when printing the object;

Its characteristics are:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating; the area of the printing body surrounded by the arc or plasma direct heating area is the current accumulation zone, and the arc or plasma affects the printing body The heat of direct heating around the area where the molten raw material is accumulating causes a molten pool to be formed on the printed body, the current accumulation zone is located in the molten pool, and the molten raw material accumulates on the current accumulation zone. This heating method can heat and melt the area of the printing body where the molten material is accumulating by thermal conduction, that is, it does not directly heat the area of the printing body where the molten material is accumulating. It can realize that the heating energy is Heating the accumulation zone below the raw material without penetrating the raw material can obtain many beneficial effects, which are described in the specific embodiments. There are many ways to generate molten raw materials. For example, after the solid raw materials are in contact with the current accumulation zone, the heat of the current accumulation zone is transferred to the solid raw materials and the solid raw materials are melted; or the solid raw materials are first melted and then transferred. To the current accumulation zone; it can also be that after the solid raw material contacts the current accumulation zone, the heat in the current accumulation zone is transferred to the solid raw material. At the same time, the plasma surrounding the current accumulation zone is in partial contact with the solid raw material. Part of the energy heats the part of the solid raw material close to the current accumulation zone. The heat transmitted by these two ways heats the solid raw material together, thereby melting the solid raw material; the plasma surrounding the current accumulation zone has a local contact with the solid raw material. The adjustment can be adjusted according to the empirical value obtained after multiple actual measurements; the plasma surrounding the current accumulation zone is in partial contact with the solid raw material, and the proportion of the contact amount to the overall energy of the plasma can be adjusted, which can be adjusted according to the multiple actual measurements. The experience value obtained is adjusted.

Optionally:

During the three-dimensional printing process, the solid raw material moves to the current accumulation area of the printed body, and the solid raw material is not heated and melted by the arc or plasma; during the three-dimensional printing process, the solid An electrical connection is provided between the raw material and the printing body, a current is applied between the solid raw material and the current accumulation area of the printing body, and the part of the solid raw material that is in contact with the current accumulation area of the printing body or the current accumulation area of the printing body is heated by resistance. The connected parts are heated and melted (that is, the part of the solid material that is heated and melted by the resistance during the three-dimensional printing process is the newly generated molten material); the solid material is a conductive material;

The said contact means that the solid raw material is directly in contact with the current accumulation area of the printing body before being melted (there are many situations where the contact occurs, for example: when printing is just started, the time when the molten raw material is ready to be generated; and For example, take the XYZ three-axis motion platform used by the 3D printing equipment as an example. The XY axis controls the horizontal movement and the Z axis controls the vertical movement. During the 3D printing process, when the conveying rate of the solid material is greater than that of the solid material on the current printing layer When the speed of horizontal movement, or when the current intensity applied between the solid material and the current accumulation area of the printing body cannot meet the requirement of fully melting the solid material to move toward the printing body, the aforementioned contact may occur. Case);

The connection means that the solid raw material does not directly contact the current accumulation area of the printing body before melting, and the solid raw material is in contact with the current accumulation area of the printing body through the previously produced molten material before melting, that is, in There is a previously generated molten material between the solid raw material and the current accumulation area of the printing body (that is, the solid raw material is in indirect contact with the current accumulation area of the printing body). (There are many situations where the connection occurs. For example: Take the XYZ three-axis motion platform of the 3D printing device as an example. The XY two-axis controls the horizontal movement, and the Z-axis controls the vertical movement. During the 3D printing process, when the conveying rate of the solid material is When it is less than the horizontal movement rate of the solid material on the current printing layer, or when the current intensity applied between the solid material and the current accumulation area of the printing body exceeds the demand for the advancement of the fully melted solid material in the direction of the printing body, both The mentioned connection may happen.)

Explanation: There are two ways to generate plasma: balanced discharge (high temperature plasma), non-balanced discharge (low temperature plasma), arc discharge belongs to the first type; arc is a self-sustaining gas conduction, that is, the electricity in ionized gas Conduction, the carriers are electrons and ions, and the arc is a way to generate plasma; the plasma arc or plasma arc is a compressed arc, which is compressed when the arc passes through the nozzle of the plasma torch to form a plasma arc.

Optionally:

The printed body includes a target object to be printed (target object) and auxiliary structures (such as supports) required by the molding process.

Optionally:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating. The direct heating means that the arc column area or the arc root of the arc or plasma arc directly acts on or directly contacts Around the area of the printing body where the molten material is accumulating; or,

The direct heating also means that the arc or plasma does not directly heat the area of the printing body where the molten material is accumulating (the "arc or plasma" here refers to the current arc or plasma when the molten material is accumulating, and It does not refer to the previous arc or plasma), that is, the main part of the arc or plasma does not reach the area of the printed body where the molten material is accumulating.

Optionally:

The use of plasma to directly heat the surrounding area of the printing body where the molten material is accumulating, and the direct heating means that the main part of the plasma directly contacts the area of the printing body where the molten material is accumulating Surrounding (the main part of the plasma: take the plasma beam as an example: the part of the plasma beam close to the center of the plasma beam that contains 60% to 99% of the energy of the plasma beam).

Optionally:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating means that the arc or plasma does not directly heat the area of the printing body where the molten material is accumulating, that is, the arc or plasma The main body part does not reach the region of the printed body where the molten material is accumulating (the main part of the arc or plasma: the part containing 60% to 99% of its total energy).

Optionally:

The area of the printing body surrounded by the area directly heated by the arc or plasma is the current accumulation area, wherein the enclosure refers to a complete enclosure or a partial enclosure.

Optionally:

The area of the printed body directly heated by the arc or plasma is continuous or discontinuous.

Optionally:

The area of the printing body surrounded by the area directly heated by the arc or plasma is the current accumulation area, and the current accumulation area is heated by the heat conducted by the area directly heated by the arc or plasma (the current accumulation area is heated and melted) Or soften).

Optionally:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and a direct heating zone is generated around the area where the molten material is accumulating; in the three-dimensional printing process, the printing body is accumulated layer by layer. , The part of the direct heating zone that is in the front of the accumulation direction of the current forming layer's molten material is converted into the future accumulation zone of the molten material. The part of the direct heating zone that is in the front of the accumulation direction of the current forming layer's molten material is defined as the upcoming accumulation zone; set the upcoming accumulation The distance between the zone and the current accumulation zone in the current forming layer plane is L, the movement speed of the current accumulation zone in the current forming layer plane is V, the ratio of L to V is t, that is, L/V=t, the current accumulation The time T required for the zone to transform from a molten state to a non-melted state; when t<T, when the accumulation zone is about to transform into the current accumulation zone, it can rely on the heat it previously carried to maintain the molten state. The heat conducted from the heating zone to the current accumulation zone is superimposed on the current accumulation zone that is already in a molten state; by adjusting the movement rate V of the current accumulation zone in the current forming layer plane and adjusting the heating power of the arc or plasma to the printed body Adjust the temperature or melting state of the current accumulation zone.

Optionally:

The electrical connection between the solid raw material and the printing body means that the solid raw material and the printing body are connected to the same circuit, and the solid raw material and the printing body are connected in series in the circuit, and the current accumulation zone is in contact with the solid raw material Or the connected part is heated by the current resistance in the circuit, and a high resistance zone is formed between the solid raw material and the area of the printed body where the molten raw material is accumulating.

Optionally:

The current is applied between the solid raw material and the current accumulation area of the printing body, and the part of the current accumulation area that is in contact with or connected to the solid raw material is heated by the current resistance (the current accumulation area is further heated).

Optionally:

The shape of the area directly heated by the arc or plasma of the printing body is a ring. There are many types of rings, such as common circular ring, square ring, triangular ring, polygonal ring, and irregular ring; the solid raw material is a linear solid raw material capable of conducting electricity.

Optionally:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and the arc or plasma is controlled by the air flow to directly heat the surrounding area of the printing body where the molten material is accumulating. Direct heating is performed on the area of the printed body where the molten material is accumulating.

Optionally:

When the solid raw material passes through the circular arc or circular plasma beam, it comes into contact with the arc or plasma part and is heated and melted by the arc or plasma.

Optionally:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to form a circular arc or a circular plasma beam by controlling the arc or plasma by airflow, so as to realize the accumulation of the molten material on the printing body. Direct heating is performed around the area to form an annular direct heating zone, and the solid raw material is not heated and melted by the arc or plasma when passing through the annular arc or the annular plasma beam.

Optionally:

Said arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating. The arc or plasma is controlled by a rotating air current or a non-rotating air current to form a circular arc or a circular plasma beam to realize the printing The body is directly heated around the area where the molten raw material is accumulating. Vortex airflow is a type of swirling airflow.

Optionally:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and the arc or plasma is controlled by a magnetic field or electric field to directly heat the surrounding area of the printing body where the molten material is accumulating. Avoid direct heating of the area of the printed body where the molten material is accumulating.

Optionally:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to generate a rotating arc or a rotating plasma arc through a magnetic field control (driving) the arc or plasma arc to realize the printing Direct heating is performed around the area of the body where the molten material is accumulating, avoiding direct heating of the area of the printing body where the molten material is accumulating; the magnetic field is a static magnetic field, a rotating magnetic field, an alternating magnetic field, or an oscillating magnetic field. (If the magnetic field lines of the magnetic field reach the molten pool on the printed body, while the magnetic field drives the arc or plasma arc to rotate, when printing alloy materials, it can also be achieved using Abe force to magnetically stir the molten pool to obtain fine crystal grains, The equiaxed grains and the low melting point second phase are finely dispersed, inhibit segregation, reduce the brittle temperature range, inhibit thermal cracks, eliminate bubbles, reduce residual stress, and obtain excellent material mechanical properties beyond traditional forging technology.)

Optionally:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to generate a rotating arc or a rotating plasma arc through a magnetic field control (driving) the arc or plasma arc to realize the printing Direct heating is performed around the area of the body where the molten material is accumulating, avoiding direct heating of the area of the printing body where the molten material is accumulating; the magnetic field is a static magnetic field, a rotating magnetic field, an alternating magnetic field, or an oscillating magnetic field.

Optionally:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to generate a rotating arc or a rotating plasma arc through a magnetic field control (driving) the arc or plasma arc to realize the printing Direct heating is performed around the area where the molten material is accumulating on the body to avoid direct heating of the area where the molten material is accumulating on the printed body; the arc or plasma arc passes through the annular discharge electrode or the hollow discharge electrode and the printed body Inter-discharge formation; the solid material moves through the annular discharge electrode or the space (channel) in the hollow discharge electrode to the printing body, and the solid material is not affected by the arc or plasma during the process of moving to the current accumulation area of the printing body. Heat to melt. (In the process of moving the solid material to the printing body, the rotating arc or rotating plasma arc uses the solid material as the axis of rotation. For example, when the solid material is made of metal wire, it is between the annular or hollow discharge electrode and the printing body. The metal wire is the axis of rotation of the rotating arc or the rotating plasma arc. At this time, the metal wire is preferably insulated from the annular or hollow discharge electrode.)

Optionally:

The current is applied between the solid raw material and the current accumulation zone of the printing body, and the current further heats the current accumulation zone of the printing body, so that the temperature of the current accumulation zone and the molten material contact surface on the side of the printing body is further increased. Raise to ensure that the side of the printing body that is in contact with the molten material in the current accumulation zone is fully melted.

Optionally:

The area of the printing body surrounded by the area directly heated by the arc or plasma is the current accumulation area, and the current accumulation area is heated by the heat conducted by the area directly heated by the arc or plasma on the printing body.

Optionally:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and the heat obtained by the direct heating of the surrounding area is partially transferred to the area of the printing body where the molten material is accumulating by conduction.

Optionally:

By using arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating, the heat obtained by the direct heating of the surrounding area is partially transferred to the area of the printing body where the molten material is accumulating by conduction. A high-resistance zone is formed between the printed body and the area where the molten raw material is accumulating (the resistivity of materials such as metal increases with increasing temperature). (The maximum voltage partial pressure is obtained in the high resistance area, and the resistance heating energy is concentrated in the high resistance area, which improves the energy utilization rate of resistance heating and obtains a small molten material, which is beneficial to improve the molding accuracy.)

Optionally:

A circular airflow is sprayed on the periphery of the area directly heated by the arc or plasma of the printing body, and the circular airflow is used to impinge on the softening area around the directly heated area. The forging effect can be obtained. In the plasticity stage before the material is cooled and solidified, the impact of external force can change the internal microstructure characteristics of the material, such as the grain size and compactness of the alloy material.

Optionally:

The printing body is heated as a whole to increase the basic temperature of the printing body.

According to another aspect of the present invention, the technical solution adopted by the present invention is: a three-dimensional printing device for realizing the above-mentioned three-dimensional printing method, including a molding zone for placing molten raw materials, where the molten raw materials are accumulated and combined Converted into a printing body, the newly generated molten material is accumulated on the basis of the printing body, until the object to be printed is formed; among them: in the process of accumulating the molten material, the position where the molten material is placed is determined by the shape of the object to be printed and the shape of the object to be printed. Structural decision; the forming area used by the three-dimensional printing device refers to the space used by the three-dimensional printing device when printing objects;

It also includes an arc generator or a plasma generator. The arc or plasma of the arc generator or the plasma generator directly heats the surrounding area of the printing body where the molten material is accumulating, and the printing body is directly heated by the arc or plasma. The area surrounded by the area is the current accumulation area. The arc or plasma directly heats the surrounding area of the printing body where the molten material is accumulating, so that a molten pool is formed on the printing body, and the current accumulation area is located in the printing body. In the molten pool, the molten raw material is accumulated on the current accumulation zone.

Optionally:

The solid raw material is not heated and melted by the arc or plasma during the process of moving to the current accumulation zone of the printing body; an electrical connection is provided between the solid raw material and the printing body, and the solid raw material is connected to the printing body. A current is applied between the current accumulation zone of the body, and the part of the solid material that is in contact with or connected to the current accumulation zone of the printing body is heated and melted by means of resistance heating; the solid material is a conductive material; The “contact” means that the solid raw material directly contacts the current accumulation zone of the printing body before melting; the “connection” means that the solid raw material does not directly contact the current accumulation zone of the printing body before melting, and the solid material does not directly contact the current accumulation zone of the printing body before melting. Before melting, the raw material comes into contact with the current accumulation area of the printing body through the previously produced molten raw material, that is, there is the previously produced molten raw material between the solid raw material and the current accumulation area of the printing body.

Optionally:

The plasma generator includes a plasma torch with an annular hollow structure and an annular gas passage, an annular electrode, and a vortex ring arranged inside the plasma torch. The plasma torch is provided with an airflow inlet and an annular nozzle. The space in the annular nozzle is annular, that is, the air flow jetted from the annular nozzle is an annular air flow; the working gas enters the plasma torch from the air flow inlet, flows through the vortex ring, and then enters the plasma torch. The annular gas passage forms a rotating airflow, and the rotating airflow drives the plasma arc to rotate, and the rotating plasma arc is ejected through the annular nozzle to form an annular plasma beam, thereby generating the annular direct heating zone on the surface of the printing body;

The solid raw material is a linear solid raw material capable of conducting electricity, and further includes a solid raw material guiding device for guiding the movement of the linear solid raw material, and the linear solid raw material is guided by the solid raw material guiding device When reaching the surface of the printing body, the space surrounded by the circular plasma beam serves as a passage for the linear solid material to leave the solid material guiding device;

The linear solid raw material is not heated and melted by the circular plasma beam during the passage through the passage, and remains solid; an electrical connection is provided between the solid raw material and the printing body, between the solid raw material and the current accumulation zone of the printing body Electric current is applied to heat and melt the part of the solid raw material that is in contact with the current accumulation area of the printing body or the connected part by means of resistance heating; the contact means that the solid raw material is directly in contact with the printing body before being melted. The current accumulation zone is in contact with the current accumulation zone; the connection means that the solid raw material does not directly contact the current accumulation zone of the printing body before melting, and the solid raw material passes the current accumulation zone of the printing body through the previously produced molten raw material before melting. The accumulation zone is in contact, that is, between the solid raw material and the current accumulation zone of the printing body, there is a previously generated molten raw material, or,

The linear solid raw material is heated and melted by the circular plasma beam as it passes through the passage. The circular plasma beam makes a small amount of contact with the linear solid raw material. The contact area between the circular plasma beam and the linear solid raw material is located at the lower edge of the linear solid raw material. In the area adjacent to the printing body, the linear solid raw material obtains heat from the circular plasma beam through the contact area and is melted to form a molten raw material; the heat transferred from the molten pool on the surface of the printing body to the linear solid raw material also participates in the melting of the raw material The resistance heating circuit applies an instantaneous strong current when there is no need to produce molten raw materials to instantly fuse the linear solid raw material and the molten raw material to separate the two; the resistance heating circuit also monitors the linear solid The contact state between the raw material and the printed body is determined by whether there is an electrical connection between the linear solid raw material and the printed body.

Optionally:

The solid raw material is a conductive linear solid raw material, the arc generator is provided with a number of electrode arrays arranged at intervals along the circumferential direction, and further includes an airflow control seat and a movement for the linear solid raw material. Guided solid material guide device, the linear solid material is guided by the solid material guide device to reach the surface of the printing body;

The airflow regulating seat is arranged at the lower end of the arc generator, and the working airflow sprayed by the arc generator forms an annular airflow after being regulated by the airflow regulating seat;

The annular airflow covers the electrode array of the arc generator, the molten pool on the surface of the printed body, the molten material, and the unsolidified part; the annular airflow distributes the arc array generated by the electrode array of the arc generator around the molten material , The arc array does not touch the molten material;

An electrical connection is provided between the solid raw material and the printing body, a current is applied between the solid raw material and the current accumulation area of the printing body, and the solid raw material is compared with the current accumulation area of the printing body by means of resistance heating. The contact part or the connected part is heated and melted; the term “phase contact” means that the solid raw material directly contacts the current accumulation zone of the printing body before melting; the term “connection” means that the solid raw material does not contact the current accumulation area of the printing body before melting. The current accumulation area of the printing body is in direct contact, and the solid raw material is in contact with the current accumulation area of the printing body through the previously produced molten raw material before being melted, that is, between the solid raw material and the current accumulation area of the printing body There is previously produced molten raw material.

The beneficial effects of the present invention are as follows:

(1) The heat obtained by the direct heating of the direct heating zone is partially transferred to the current accumulation zone by conduction, so that the current accumulation zone is heated and melted, that is, the current accumulation zone of the printed body is not directly heated, which can be realized in If there are raw materials above the current accumulation zone, the heating energy will heat the accumulation zone below the raw materials without passing through the raw materials. The benefits of this heating method are at least the following four points:

a: The volume of the raw material is small. If the raw material is solid, the energy intensity required to melt the solid raw material is much lower than the energy required to melt the current accumulation zone (the current accumulation zone is integrated with other areas of the printing body, if the printing body is hot Good conductor, such as metal, the printing body will quickly conduct heat away from the current accumulation zone), if the same beam energy (such as plasma beam, or laser beam, or electron beam) is used to pass through the raw material directly from above the raw material and reach the bottom of the raw material In the current accumulation zone, it often leads to excess energy for heating the raw materials, which partially evaporates the raw materials, and the partial evaporation of the raw materials will also cause bubbles/honeycomb defects to the accumulated raw materials; if the raw materials are melted, if the same beam energy is used directly Passing the raw material from above the raw material and reaching the current accumulation zone below the raw material, the raw material itself is already in a molten state, which will cause more serious evaporation of the raw material.

b: The use of "arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating" leads to the superimposition of heat in the area of the printing body where the molten material is accumulating, which reduces the overall heating power density of the arc or plasma. Under the premise of, a thin molten pool is formed in the area of the printing body where the molten material is accumulating, which can effectively protect the thin-walled structure or fine structure of the previously formed printing body. The opposite of the present invention is: the existing arc-based The three-dimensional metal forming technology of heating or plasma beam heating has caused great damage to the thin-walled structure or fine structure of the previously formed printed body, and the consequence is that the objects printed and formed in the prior art that people have seen are very rough. In addition, the thin molten pool (small penetration depth) can suppress the deep penetration pool of the prior art (for example, the molten pool generated by the prior art WAAM, such as the molten pool generated by fusion electrode welding, argon arc welding, and plasma welding). Defects (for example: thick crystal branches, uncontrollable molten pool morphology).

c: Achieve a larger heating zone and a smaller temperature gradient, which can effectively reduce stress and reduce cracks inside the material, and can achieve higher temperatures with low heating power density. The opposite of the present invention is : Existing metal three-dimensional forming technology, such as SLM (Selective Laser Melting) due to the small laser spot and extremely high power density, resulting in a large temperature difference between the molten pool and the surrounding printing material, resulting in large internal stress and many cracks in the material. It is necessary to eliminate these defects through later heat treatment (such as hot isostatic pressing).

d: Heating and accumulating energy in the area of the molten raw material does not interfere with the generation process of the molten raw material, and the coupling between the generation of the molten pool and the generation of the molten raw material is low, so that the molding process of the three-dimensional printing technology of the present invention is highly controllable, More reliable and robust.

(2) The present invention obtains higher controllability by separating the melting energy required to generate the molten raw material from the heating energy required to melt the region of the printed body where the molten raw material is accumulating; while the existing linear solid Three-dimensional printing technology of raw materials (such as metal wire), such as wire arc melting molding (WAAM): Relying on metal wire as a self-worn electrode to discharge the printed body, generating a molten pool on the surface of the printed body where the molten raw material is accumulating , The molten metal wire produces the molten raw material and produces the molten pool to share the same heating energy (arc). When the wire diameter of the metal wire used is small (for example, the stainless steel wire with a wire diameter of 0.6mm), the electric power that the metal wire can carry is not effective. To melt the surface of a larger volume of printed body (workpiece), the energy required to melt the metal wire to produce molten material is much lower than the energy required to produce the molten pool. The energy of the molten metal wire to produce molten raw material and the energy to produce the molten pool cannot be separated Independent control makes the WAAM technology unable to use small wire diameter metal wire, especially when printing high melting point materials, this problem is more prominent, for example, when printing pure titanium material, use 0.6mm wire diameter titanium Silk, when the current is sufficient to melt the titanium printing body to produce a molten pool, the melting zone of the titanium wire will produce severe spattering/spatter (the internal vaporization/evaporation of the melting end is intense), making the process of 3D printing uncontrollable; However, because the present invention separates the energy of the molten raw material and the energy of the molten pool, and independently controls them, there is no such problem, and a wire with a smaller wire diameter can be used, thereby improving the molding accuracy and having extremely high flexibility. , It is easier to realize complex and flexible 3D printing and forming process control.

(3) The present invention generates a small amount of molten raw material in the contact area between the solid raw material and the printing body by applying an electric current between the solid raw material and the printing body to generate a resistance heating effect. Adhere to the unmelted solid raw material, the position of the molten raw material can be controlled by controlling the position of the solid raw material, making the position and shape controllability of the molten raw material extremely controllable; in contrast, the existing wire arc The molten metal raw material of the melt molding (WAAM) technology falls onto the printing body molten pool by its own dripping method, the controllability of the molten raw material is low, and the molten raw material merges with the molten pool to form a free melt (the shape becomes coarse and uncontrollable) , The printing accuracy is extremely poor, and a complex monitoring system is required to adjust the dripping process of the molten material in real time (for example: real-time high-speed collection of images of metal droplets and molten pools, analysis of the images, and dynamic adjustment of the droplets of metal droplets based on the analysis results Drop position and fill up the defect position caused by incorrect accumulation of metal droplets before, and inhibit the sputtering of droplets at the end of the wire); therefore, the present invention can achieve higher molding accuracy and higher controllability of the molding process, so The required control system is simpler.

(4) In the present invention, a high-resistance zone is formed between the solid raw material and the melted layer on the printed body (the resistivity of metal and other materials increases with increasing temperature). In the series circuit formed by the solid raw material and the printed body, The maximum voltage partial pressure is obtained in the high-resistance area, and the resistance heating energy is mainly concentrated in the part between the solid raw material and the printed body. The molten raw material formed in real time during the three-dimensional printing process is limited to the high-resistance area, and a small volume of melting can be obtained. Zone (melted raw material), the volume of the molten raw material produced is small and limited; the heat generated by the molten raw material in the present invention is generated from the inside of the material itself. When the contact between the solid raw material or the molten raw material and the printed body is interrupted, the heating energy is instantaneously automatic Disappear (for example, when using a resistance heating voltage lower than 12V, an arc cannot be formed between the free end of the solid material and the printed body), the molten material carried by the free end of the formed solid material is limited and cannot be continuously heated. The free end of the raw material cannot form a liquid raw material ball; in contrast, the prior art uses laser beams, electron beams, plasma beams, electric arcs (discharges between special electrodes and the printing body to produce electric arcs) and other heat sources to print and print on the metal wire. The body is heated at the contact parts and adjacent areas at the same time. While the metal wire is melted to obtain the molten material, a molten pool is simultaneously generated on the surface of the printed body. This heating method determines that the melting method of the metal wire is from the outside to the inside (heating Energy penetrates the wire from the outside of the wire), the molten raw material merges with the molten pool to form a free melt (the shape becomes coarse and uncontrollable), and when the contact between the solid raw material or the molten raw material and the printed body is interrupted, If the heating energy is not cut off in time, it will result in the formation of a large liquid metal ball on the free end of the wire (liquid metal has a large viscosity, high surface tension, and has a tendency to self-aggregate), causing the liquid raw material to be uncontrollable or even Cause the failure of 3D printing, so a complex monitoring system is required for real-time monitoring (for example: real-time high-speed collection of images of metal droplets and molten pools, analysis of images) and dynamic adjustment (for example: according to the results of monitoring data analysis to ensure the molten material at the end of the wire) And the molten pool is always in a connected state, dynamically adjusts the accumulation position of metal droplets, and fills up the defect positions that have not been correctly accumulated before the metal droplets); compared with the existing three-dimensional printing technology using metal wire raw materials, the liquid state of the present invention If the raw material is generated in real time, if the contact between the raw material and the printed body is interrupted, it is self-limiting, which makes the control system required for the three-dimensional molding process of the present invention far less complex than the prior art, higher reliability, and occurrence of molten raw material The location is limited to the high resistance zone, the volume of the molten raw material is small, and the molding accuracy is higher.

(5) In the present invention, a high resistance zone is formed between the solid raw material and the melted layer on the printed body (the resistivity of metal and other materials increases with increasing temperature). In the series circuit formed by the solid raw material and the printed body, The maximum voltage partial pressure is obtained in the high-resistance area, and the resistance heating energy is mainly concentrated in the part between the solid raw material and the printed body. The molten raw material formed in real time during the three-dimensional printing process is limited to the high-resistance area, and a small volume of melting can be obtained. Zone (melted raw material), the volume of the molten raw material produced is small and limited. The mechanical force generated when the solid raw material is conveyed acts on the raw material accumulation area of the molten raw material and the printing body, and the solid raw material accumulates the accumulated molten raw material and the raw material of the printing body. The zone produces smoothing and squeezing effects, which can obtain a better surface morphology than the existing 3D printing technology based on plasma beam and arc heating source, eliminate gaps and pores inside the material, and obtain a forging-like effect.

(6) The present invention generates a small amount of molten raw material in the contact area between the solid raw material and the printed body by applying an electric current between the solid raw material and the printing body to generate a resistance heating effect, and the molten raw material is in contact with the melting zone on the surface of the printing body at the same time. Adhere to the unmelted solid material, the position of the molten material can be controlled by controlling the position of the solid material. When printing the cantilever structure (the newly generated molten material is in partial contact with the printing body in the horizontal direction), a small amount of the molten material is It adheres to the end of the solid raw material without dripping due to gravity. Therefore, the present invention can realize unsupported printing cantilever structure, or reduce the dependence on support, making the process of printing complex three-dimensional structures simpler.

(7) Compared with the prior art such as selective laser melting (SLM) and electron beam melting (EBM), the present invention uses linear solid raw materials such as metal wires, and the material cost is low; there is no problem of materials reflecting laser energy, and no Choose materials, common conductive solid inorganic materials (especially metals) can be used as printing materials; heating source uses plasma or arc, the cost of heating source equipment is much lower than laser and vacuum electron beam system, and arc or plasma heating And the molding efficiency is higher than that of laser and electron beam.

(8) The present invention generates a small amount of molten raw material between the solid raw material and the printed body by applying an electric current between the solid raw material and the printed body to generate a resistance heating effect. The small amount of molten raw material is rapidly accumulated on the printed body and then begins to cool, and There is no need to heat a container (such as a micro melting furnace) to melt more solid raw materials and then spray them onto the surface of the printed body, and only need to produce a thin melting layer (thin molten pool) on the surface of the printed body to meet the needs of three-dimensional molding, melting the raw materials (especially Alloy materials, such as titanium alloys, nickel-based superalloys, etc., have no chance of segregation, and the material composition of the printed body is uniform; while the existing three-dimensional printing technology that uses a heating vessel (such as a miniature furnace) to melt solid raw materials, because the solid raw materials It takes time to melt. In order to ensure the stable output of molten materials and to meet the demand for printing speed, the higher the printing speed, the more molten materials are needed per unit time, and more solid materials need to be melted in advance. It is an alloy. The different components of the molten alloy have a chance to diffuse unevenly in the micro-furnace, resulting in the chemical composition of the alloy droplets sprayed successively, resulting in a decrease in the material performance of the printed body; wire arc melting forming (WAAM ) Technology does not use a heating vessel (such as a micro melting furnace) to melt more solid raw materials first, but WAAM technology produces a larger molten pool on the printed body, which will cause the internal crystal branches of the material to be coarse, and produce a larger amount of the previously generated printed body The present invention does not have the above-mentioned problems: there is no segregation in the printed body, the chemical composition of the material is uniformly distributed, the internal crystal branches of the material are not coarse, and the required surface of the printed body is thin and does not damage the printed body. Structure, can achieve fine structure printing.

(9) The present invention generates a small amount of molten raw material in real time between the solid raw material and the printed body by applying an electric current between the solid raw material and the printed body, and generates a small amount of molten raw material on the printed body through arc or plasma. The surrounding area is heated in an annular shape to generate a molten pool, which separates the melting energy required to generate molten material from the heating energy required to melt the area of the printing body where the molten material is accumulating, and only a thin micron thickness is generated on the surface of the printing body. Layer (thin molten pool) can meet the needs of three-dimensional molding, thin molten pool (small penetration depth) can inhibit the existing deep penetration pool (such as the existing technology WAAM pool generated, such as fusion electrode welding, argon arc welding, plasma Defects caused by the molten pool generated by body welding (for example: coarse crystal branches, uncontrollable molten pool shape).

(10) The present invention performs annular heating on the peripheral area of the accumulated molten material area on the printed body. Compared with the existing metal three-dimensional printing technology that uses metal powder or metal wire as solid raw material, the present invention can realize the accumulation position of molten material. The 360° heating at the center can obtain a more uniform and stable heating effect in the area where the molten material is accumulated on the printed body, and form a transition with a smaller temperature gradient between the area where the molten raw material is accumulated and other non-melted areas of the printed body The temperature field is beneficial to reduce the internal stress of the material after the three-dimensional molding and reduce the thermal cracks, and finally obtain higher material properties.

(11) The present invention can realize 360° annular heating centered on the accumulation position of the molten material on the printing body, so that the area where the molten material is accumulated is always located in the center of the thermal field, and the heat of the annular heating zone is conducted and concentrated to the center, and the center of the thermal field The melting state is more stable and reliable; no matter the solid raw material moves in any direction in the plane of the current forming layer of the three-dimensional printing, the generated molten raw material always accumulates in the center of the thermal field, ensuring the fusion between the molten raw material and the printed body High reliability, so that the molding process using the three-dimensional printing technology of the present invention is stable and reliable.

(12) The present invention can realize 360° annular heating centered on the accumulation position of the molten material on the printing body, the heat of the annular heating zone is conducted and concentrated to the center, and the heat of the annular heating zone is superimposed in the center of the thermal field, thereby achieving the The low heating power density realizes higher temperature, so that the heating device (such as the annular plasma nozzle or the annular arc discharge electrode) of the present invention that generates the annular heating zone needs to bear a small heating power density, and the present invention produces the annular heating zone. The heating equipment has a long life, and the existing plasma torch nozzles and electrodes required for jetting plasma beams, as well as the electrodes that generate arcs (such as tungsten electrodes used in argon arc welding), are extremely easy to withstand high power density. Damaged and difficult to apply in the long-term 3D printing process.

(13) The present invention can realize 360° annular heating centered on the accumulation position of the molten material on the printing body, the heat of the annular heating zone is conducted and concentrated to the center, and the heat of the annular heating zone is superimposed in the center of the thermal field, so that it can be realized in The accumulation position of the molten material on the printed body forms a controllable small-area molten pool (that is, a small-area molten pool is formed under the molten material), which does little damage to the previously generated structure on the printed body; while the existing use The three-dimensional printing technology with metal wire as the raw material, plasma beam as the heating source, or arc as the heating source cannot form a controllable small-area molten pool under the molten raw material, which will damage the previously generated structure on the printed body. .

(14) The present invention can realize 360° circular heating centered on the accumulation position of the molten material on the printed body. The heat accumulates in the area where the molten material is accumulated. The energy for heating the area of the accumulated molten material does not need to pass through the raw material. A melting zone (melt pool) is formed on the surface of the printed body directly below the raw material. Heating and accumulating the energy of the molten raw material area does not interfere with the production process of the molten raw material. The generation of the molten pool and the production of the molten raw material have a low coupling, thus making The molding process using the three-dimensional printing technology of the present invention has high controllability, more reliability and high robustness.

(15) The present invention can realize 360° annular heating centered on the accumulation position of the molten raw material on the printing body, the heat of the annular heating zone is conducted and concentrated to the center, and the heat of the annular heating zone is superimposed in the center of the thermal field, so that it can be realized in The accumulation position of the molten material on the printed body forms a controllable small-area molten pool (that is, a small-area molten pool is formed below the molten material), so that the heating device of the present invention that generates an annular heating zone (such as an annular plasma nozzle or The heating power density required by the annular arc discharge electrode is small, the required airflow velocity is low, and the low velocity airflow will not cause damage to the molten pool on the surface of the printing body and the newly accumulated molten raw materials.

(16) The present invention can realize 360° annular heating centered on the accumulation position of the molten material on the printing body. The heat of the annular heating zone is conducted and concentrated to the center, and the heat of the annular heating zone is superimposed at the center of the thermal field, resulting in the formation of the molten material. The energy is separated from the energy that generates the molten pool on the printed body (independent of each other), only a thin layer of molten pool is generated on the printed body, the power density required for heating the printed body is low, and the material in the molten pool on the printed body can be suppressed Compared with the existing metal three-dimensional printing technology (for example, the metal three-dimensional printing technology that uses arc or plasma or electron beam as heating energy), the present invention There is less material gasification/evaporation, and there are fewer pores inside the material due to gasification.

(17) In the present invention, if the print head and the printing platform are directly exposed to the atmosphere, the outside atmosphere (oxygen, nitrogen, etc.) is resisted by the annular air flow (especially resisted by the rotating annular air flow), and at least the molten material located in the center of the annular air flow is formed And the current accumulation zone on the printing body, the tight inert atmosphere protection zone of the arc or plasma direct heating zone, the tight inert atmosphere protection zone generated on the printing body forms a protective gas film with a diameter larger than the plasma heating zone, which can obtain excellent The molding quality (low oxygen content), so that large metal parts can be printed on a large open platform, which is of great significance to aerospace and military industries.

(18) In the present invention, if the arc or plasma arc is controlled (driven) by a magnetic field to generate a rotating arc or a rotating plasma arc, it is possible to directly heat the surrounding area of the printing body where the molten material is accumulating, avoiding the printing The area of the body where the molten material is accumulating is directly heated, and the magnetic field lines of the magnetic field that drives the arc or plasma arc to generate a rotating motion reach the area on the printing body where the molten material is accumulating. When the printing material and the printing body are conductive materials, the magnetic field Generate magnetic stirring effect on the molten pool in the area where the molten material is accumulating on the printed body (principle: there is current flowing in the molten pool, the current is arc current, or the current is composed of arc current and resistance heating current that produces molten material, The direction of the current is not parallel to the lines of magnetic force, and the magnetic field produces Abe force on the material in the molten pool); under the action of Abe force, the molten alloy material moves inside to regulate the growth mode (mode) of the grains in the material, and produce fine grains, etc. Axial grains and low-melting second phase are finely dispersed, inhibit segregation, reduce brittle temperature range, inhibit thermal cracking, reduce residual stress, and the stirring effect also inhibits the generation of bubbles and drives out bubbles that have been generated to obtain excellent materials The mechanical properties can surpass traditional forging; the magnetic field that generates the rotating arc or the rotating plasma arc and the magnetic field that generates the magnetic stirring effect on the molten pool of the present invention are the same magnetic field, and the structure is simple. While direct heating is performed around the area, it also obtains a magnetic stirring effect on the molten pool, which achieves two goals.

(19) The present invention generates molten raw material in real time during the three-dimensional printing process through resistance heating generated by applying a current between the solid raw material and the printed body. The current that generates the molten raw material is formed around the current (or solid raw material) as the center And the circular magnetic field perpendicular to the center, the circular magnetic field lines produce Lorentz force on the moving charged particles that are not parallel to the magnetic field lines, and the circular magnetic field lines affect the trajectory of the charged particles, which can produce focusing or defocusing effects, for example: When the positive electrode of the arc or plasma control circuit is connected to the printed body, and the positive electrode of the control circuit for generating molten material is connected to the printed body, the control circuit for generating arc or plasma and the control circuit for generating molten material are common anode with the printed body as the intermediary. , The circular arc or circular plasma between the print head and the printing body is affected by the circular magnetic field lines generated by the current flowing in the solid raw material passing through the center of the circular arc or circular plasma, the electrons and anions in the arc or plasma The combined force generated by the driving force of the airflow and the Lorentz force focuses on the current accumulation area on the printed body, that is, surrounds and gathers around the instantaneously generated molten material, so that the heating range of the arc or plasma on the printed body is reduced. It has little damage to the existing structure (such as thin-walled structure) on the printed body, and has great benefits for printing fine structures. It can obtain laser-like (high-cost) under the premise of using low-cost heat sources such as arc or plasma Focusing effect: Compared with the existing wire arc melting molding (WAAM) technology or the three-dimensional printing technology based on a plasma heat source, the present invention can achieve higher molding accuracy.

In summary, the beneficial effects of the present invention: the process control of the three-dimensional molding has extremely high flexibility and reliability; the monitoring system of the three-dimensional printing equipment is simple and low in cost; it adopts a 360° annular heating method, and the heat is in the center of the annular heating zone. Superimposed to form a stable high temperature zone, which can form a controllable small area of molten pool under the accumulated molten material; form a transitional temperature with a smaller temperature gradient between the area where the molten material is accumulated and other non-melted areas of the printed body Residual stress is small; the heating source of the 3D printing equipment has a long life; the material of the printed body produced is uniform, no segregation, and the internal crystal branches of the alloy material are not coarse; the material gasification can be suppressed, and the internal pores of the material are less; The material properties of traditional forging technology; the molten raw material produced is small in size, controllable in shape, and positionable; it does not damage the previously generated structure on the printed body; high molding accuracy; the connection between the molten raw material and the molten pool on the printed body After the interruption, the formation of molten raw materials and the form of residual molten raw materials adhering to the solid raw materials are self-limiting; the linear solid raw materials with small and large diameters can be used, and the solid raw materials with small diameters can be used to obtain higher Forming accuracy; can realize printing of complex structures while reducing the use of support; low equipment cost and consumable cost, low maintenance cost; can be directly printed in the atmosphere to form large metal parts with low oxygen content, which is useful for aerospace and military industries This field is of great significance; the molding process using the three-dimensional printing technology of the present invention has high controllability, high reliability, and high robustness.

Description of the drawings

Figure 1 is a three-dimensional schematic diagram for explaining the print head involved in the first specific embodiment of the present invention;

Figures 2 to 6 are two-dimensional schematic diagrams for explaining the principle of the first specific embodiment of the present invention. Arrows D1 and D2 indicate the direction of movement, and arrow F1 indicates the direction of airflow; among them, Figure 3 is AA in Figure 2 Cross-sectional view of the direction;

7 to 8 are three-dimensional schematic diagrams for explaining the print head involved in the second specific embodiment of the present invention;

Figures 9 to 11 are two-dimensional schematic diagrams for explaining the principle of the second specific embodiment of the present invention. Figure 10 is an enlarged view of the part indicated by the dashed frame CC in Figure 9, where the arrows D3 and D4 indicate the direction of movement. , The arrow F2 indicates the direction of air flow;

Figures 12 to 13 are two-dimensional schematic diagrams for explaining the principle of the third embodiment of the present invention. Figure 13 is an enlarged view of the part indicated by the dashed frame BB in Figure 12, where the arrow D5 represents the direction of movement, and the arrow F3 represents the direction of air flow;

The label:

1-Plasma generator, 2-ring electrode, 3-air inlet, 4-ring nozzle, 5-working gas, 6-solid material guide device, 7-linear solid material, 8-printed body, 9- Plasma generator control circuit, 10-resistance heating circuit one, 11-melt pool one on the surface of the printed body, 12-circular plasma beam one, 13-melting raw material one, 14-uncured part one, 15-accumulating layer The cured part one, 16-vortex ring, 17-current accumulation area on the printed body, 18-the area directly heated by plasma (direct heating area), 19-the heated area of plasma, 21-on the printed body Current accumulation area two, 22-area directly heated by arc, 23-heated area of arc, 26-arc generator array, 27-gas interface of arc generator array, 28-electrode of arc generator array, 29-linear Solid raw material two, 30-solid raw material guiding device two, 31-resistance heating circuit two, 32-melting raw material two, 33-unsolidified part two, 34-cured part two of the accumulating layer, 35-printed body Surface molten pool two, 36-printing body two, 37-arc array, 38-working gas two, 39-arc generator array control circuit, 40-air flow control seat, 41-linear solid material three, 42-circular plasma Body beam three, 43-melting raw material three, 44- molten pool three on the surface of the printed body, 45- resistance heating circuit three, 46-printed body three, 47- non-ionized working gas, 48- toroidal plasma beam and wire The contact area of the solid raw material.

Detailed ways

Hereinafter, the preferred specific embodiments of the present invention will be listed and the present invention will be described in detail with reference to the accompanying drawings.

The first specific embodiment of a three-dimensional printing method of the present invention as shown in FIGS. 1 to 6, the main process is: melting solid raw materials (ie linear solid raw materials 7) to obtain molten raw materials (ie molten raw materials 7). 13). The molten raw material is placed in the forming area used by the three-dimensional printing device. The molten raw material is accumulated in the forming area and transformed into a printed body (printed body 8). The newly generated molten raw material is accumulated on the basis of the printed body until The object to be printed is formed; among them: in the process of accumulating the molten raw material, the position where the molten raw material is placed is determined by the shape and structure of the object to be printed; the forming area used by the three-dimensional printing device refers to three-dimensional printing The space used by the device when printing objects; the technical key of the first specific embodiment of the present invention lies in:

Plasma (i.e. circular plasma beam-12) is used to directly heat the surrounding area (peripheral area) of the printing body where the molten material is accumulating, thereby generating a direct heating zone 18 (as shown in the figure) around the area where the molten material is accumulating The area 18 directly heated by the plasma shown in 4) (This heating method can heat and melt the area of the printing body where the molten material is accumulating by thermal conduction, that is, it does not directly heat the area of the printing body where the molten material is accumulating, which can be realized In the case of raw materials on the area, heating the accumulation area below the raw materials without the heating energy passing through the raw materials can obtain many beneficial effects, which will be explained in the following content); the printed body is directly heated by the plasma The area surrounded by the zone is the current accumulation zone (as shown in FIG. 4 on the current accumulation zone 17 on the printed body, the heat obtained by the direct heating zone 18 is directly transferred to the current accumulation zone 17 by conduction) So that a molten pool is formed on the current accumulation zone 17 and the molten material is accumulated on the current accumulation zone 17);

In the process of three-dimensional printing, the solid raw material (ie, linear solid raw material-7) moves to the current accumulation zone (ie, current accumulation zone-17 on the printed body) of the printed body (ie, printed body-8), and the solid The raw material is not heated and melted by the plasma (that is, the toroidal plasma beam-12) (During this process, the solid raw material is heated by the plasma, for example, heated by the energy of the plasma radiation, and is heated between the solid raw material and the plasma beam. The heat carried by the non-ionized gas is heated, but the energy is not enough to heat and melt the solid raw material);

In the process of three-dimensional printing, as shown in Fig. 2, Fig. 5 and Fig. 6, an electrical connection is provided between the solid raw material (i.e. linear solid raw material 7) and the printing body (i.e. printing body 8). The raw material and the printed body are connected to the same circuit, and the solid raw material and the printed body are connected in series in the circuit, that is, the linear solid raw material 7 is connected with the resistance heating circuit 10 through the solid raw material guide device 6, and the printed body One 8 is connected to the resistance heating circuit 10 through a conductive printing platform (not shown in the figure), the linear solid raw material 7 is in contact with or connected to the printing body 8; the linear solid raw material 7 is connected to the printing body A current is applied between the current accumulation zone 17 on the upper surface, and the part of the linear solid raw material 7 that is in contact with the current accumulation zone 17 on the printing body or the connected part is heated and melted by means of resistance heating (that is, in the During the three-dimensional printing process, the part of the solid raw material that is melted by resistance heating is the newly generated molten raw material). A current is applied between the solid raw material and the current accumulation area of the printing body (the current accumulation area 17 on the printing body as shown in FIG. 4), and the parts of the current accumulation area that are in contact with or connected to the solid raw material will also be described Current resistance heating can further increase the temperature of the current accumulation zone. Figure 4 illustrates: on the surface of the printing body, the positional relationship between the area directly heated by the plasma and the current accumulation area of the printing body; the heating range of the surface of the printing body by the plasma includes the heating area 19 of the plasma and the area surrounded by it That is: the area surrounded by the plasma heating area 19 includes the area 18 directly heated by the plasma and the current accumulation area 17 on the printed body; except for the area 18 directly heated by the plasma, the other areas are heated by heat conduction, that is Indirect heating. Since the area 18 directly heated by the plasma is annular, the heat obtained by the annular heating area is conducted and diffused to the central area, so that the current accumulation area 17 on the printing body is also heated, and reliable heating can be obtained (as long as the plasma heating If it continues to exist, the heat will continue to be conducted to the current accumulation area 17 on the printed body). The heat of the annular plasma beam 12 in the annular direct heating zone on the surface of the printing body 8 (that is, the region 18 directly heated by the plasma) is conducted and diffused to the periphery and the surrounding area, forming a molten pool 11 on the surface of the printing body. (That is, the thin melting layer on the surface of the printed body).

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and a direct heating area (for example: the area 18 directly heated by the plasma) is generated around the area where the molten material is accumulating; During the three-dimensional printing process, the printed body is accumulated layer by layer, and the part of the direct heating zone that is located in front of the accumulation direction of the current forming layer's molten material is converted into the future accumulation zone of molten material, and the direct heating zone is located in front of the accumulation direction of the current forming layer's molten material. The position is defined as the upcoming accumulation zone; set the distance between the upcoming accumulation zone and the current accumulation zone in the current forming layer plane as L, the movement speed of the current accumulation zone in the current forming layer plane as V, and the ratio of L to V as t, that is, L/V=t, the time T required for the current accumulation zone to transform from the molten state to the non-melted state; when t<T, the accumulation zone is about to be transformed into the current accumulation zone and maintained by the heat it previously carried Melting state, the heat conducted from the direct heating zone around the current accumulation zone to the current accumulation zone is superimposed on the current accumulation zone that is already in a molten state; by adjusting the current accumulation zone's moving speed V in the current forming layer plane and adjusting the arc Or the heating power of the plasma to the printed body to adjust the temperature or melting state of the current accumulation zone. For example: in Figure 6, if the printing head and the linear solid material 7 are moving in the direction indicated by arrow D2 fast enough, they are located in the direction indicated by arrow D2 (arrow D2 indicates the front of the moving direction of the current accumulation zone ) Is directly heated by the circular plasma beam 12 (that is, the accumulation zone) when it becomes the current accumulation zone, it only relies on the previously carried heat to maintain a molten state, that is: the area directly heated by the circular plasma beam 12 The distance L between the part (that is, the accumulation area) and the current accumulation area on the printing body in the direction indicated by arrow D2 (that is, the advancing direction of the print head) and the print head movement speed V, L/V=t , The time T required for the current accumulation zone 17 on the printed body to change from the molten state to the non-melted state, when t<T, the accumulation zone will become the current accumulation zone (that is, the current accumulation zone 17 on the printed body) It only relies on the heat it previously carried to maintain the molten state. The area 18 directly heated by the annular plasma transfers the heat to the current accumulation zone 17 on the printed body superimposed on the current accumulation zone one on the printed body that is already in the molten state. 17 to further ensure that the current accumulation zone 17 on the printed body is in a reliable melting state. That is, the distance L between the accumulation zone and the current accumulation zone-17 on the printed body is at least equal to the inner radius of the zone 18 directly heated by the annular plasma.

The solid raw material (ie, linear solid raw material-7) is a conductive material, and a metal wire (for example, a 316 stainless steel wire with a wire diameter of 1 mm) is used.

The said contact means that the solid raw material (ie, the linear solid raw material-7) is in physical contact with the current accumulation area of the printing body (ie the current accumulation area-17 on the printing body) before being melted. There are many situations in which contact occurs, such as: when printing is just started, when the molten material is ready to be generated; another example: taking the XYZ three-axis motion platform of the three-dimensional printing device as an example, the XY two-axis control horizontal plane movement, and the Z-axis control Moving in the vertical direction. During the three-dimensional printing process, when the conveying rate of the solid material (in the direction shown by the arrow D1 in Figure 6) is greater than the horizontal moving rate of the solid material on the current printing layer (as indicated by the arrow D2 in Figure 6) Shown in the direction), or the current intensity applied between the solid material and the current accumulation area of the printing body cannot meet the requirement to fully melt the solid material to move toward the printing body (as shown by the arrow D1 in Fig. 2, Fig. 5, and Fig. 6) When the demand for the progressive amount of the direction), the aforementioned contact situation may occur.

The connection means that the solid raw material does not directly contact the current accumulation area of the printing body before melting, and the solid raw material passes the current accumulation area of the printing body through the previously (last moment) molten raw material before melting. Contact occurs, that is, between the solid raw material and the current accumulation area of the printing body, there is a previously (last moment) molten raw material (that is, the solid raw material is in indirect contact with the current accumulation area of the printing body) (There are many situations where the connection occurs. For example: Take the XYZ three-axis motion platform of the 3D printing device as an example. The XY two-axis controls the horizontal movement, and the Z-axis controls the vertical movement. During the 3D printing process, when the conveying rate of the solid material is When it is less than the horizontal movement rate of the solid material on the current printing layer, or when the current intensity applied between the solid material and the current accumulation area of the printing body exceeds the demand for the advancement of the fully melted solid material in the direction of the printing body, both The aforementioned connection may occur).

In this first specific embodiment, the core part of the print head used is shown in Figure 1: It is mainly composed of a plasma generator 1 and a solid material guiding device 6, and the plasma torch (ie, the plasma generator 1) adopts a ring shape With a hollow structure, the solid material guiding device 6 is arranged in the space surrounded by the plasma generator 1. The plasma generator 1 has an annular structure as a whole, and an annular gas passage, a ring electrode 2 and a vortex ring 16 are arranged inside the plasma generator 1. The plasma generator works in the "transfer arc" mode: the ring electrode 2 is used as a cathode and connected to the negative electrode of the power supply (plasma generator control circuit 9), and the printed body 8 is used as an anode and connected to the power supply (that is, the plasma generator control circuit 9) The positive electrode of the printing body 8 is equivalent to the "workpiece" in the welding process of the welding industry. The arc roots on both sides of the plasma arc are located on the surface of the ring electrode 2 and the printing body 8 respectively; the arc column area of the plasma arc passes through the ring nozzle 4 When it is compressed, the cross-sectional area becomes smaller and the energy density becomes larger. The space in the annular nozzle 4 is circular, that is, the air flow sprayed from the annular nozzle 4 is an annular air flow. The working gas 5 uses argon (inert gas), which enters the plasma generator 1 from the gas inlet 3, flows through the vortex ring 16 and then forms a rotating (vortex) gas flow in the annular gas passage inside the plasma generator 1 (as shown in Figure 3). (Shown), the rotating airflow drives the plasma arc to rotate, and it also rotates during the process of passing through the annular nozzle 4. The annular plasma beam 12 is ejected through the annular nozzle 4, and a circular ring shape is produced on the surface of the printing body 8. Area 18 directly heated by the plasma. The region 18 directly heated by the plasma has a continuous circular ring shape. Before the circular plasma beam 12 reaches the surface of the printing body 8, the cylindrical (or inverted cone) space surrounded by the circular plasma beam 12 serves as a path after the linear solid material 7 leaves the solid material guiding device 6 , The linear solid raw material 7 is not heated and melted by the circular plasma beam 12 while passing through the passage, and remains solid. If the linear solid material 7 is heated and melted by the plasma during the process of passing through the passage, it will cause the linear solid material 7 to be melted by the plasma during the process of applying a large current to the resistance heating circuit 10 to perform resistance heating. Fuse. One of the important purposes of manufacturing the circular plasma beam 12 is to prevent the linear solid raw material 7 from being directly heated and melted by the plasma. As shown in Figure 2, Figure 5 and Figure 6, before the circular plasma beam 12 reaches the surface of the printing body 8, due to the inertia of the air flow and the space enclosed by the circular nozzle 4, the solid material guide device 6 and linear The solid raw material 7 is occupied. The cylindrical space surrounded by the circular plasma beam 12 is a relatively closed space. After the circular plasma beam 12 reaches the printing body 8, it can only be discharged to the outside against the surface of the printing body 8. Can not flow to the inside, forming a ring-shaped direct heating zone, which is essentially through the air flow (including fluid inertia, pressure gradient and other factors) to control the plasma arc heating area on the printed body; such benefits can be obtained: If the print head and The printing platform is directly exposed to the atmosphere, and the outside atmosphere (oxygen, nitrogen, etc.) is resisted by the annular airflow (rotating annular airflow), and at least forms the current accumulation zone 17 on the printing body and the molten raw material 13 located in the center of the annular airflow. Plasma The tight inert atmosphere protection zone of the area 18 where the body is directly heated. The tight inert atmosphere protection zone generated on the surface of the printing body 8 forms a protective gas film with a diameter larger than that of the plasma heating zone 19, and excellent molding quality can be obtained. Printing large metal parts on a large open platform is of great significance to aerospace and military industries.

In the first specific embodiment of the present invention, the above-mentioned printed body includes the purpose (target) object to be printed and auxiliary structures (such as supports) required by the molding process.

In the first specific embodiment of the present invention, plasma (transfer arc) is used to directly heat the surrounding area of the printing body where the molten material is accumulating, and the direct heating refers to: one side of the circular plasma beam 12 The arc root acts directly on the periphery of the printed body where the molten material is accumulating (the area 18 directly heated by the plasma as shown in FIG. 4) (the arc root on the other side is located on the surface of the ring electrode 2).

In Figure 2, the heat of the circular plasma beam 12 in the circular direct heating zone on the surface of the printing body 8 is conducted and diffused to the periphery and the area surrounded by it, forming a molten pool 11 on the surface of the printing body (that is, the printing body surface The thin melting layer); the linear solid raw material 7 starts to move to the printing body 8 (that is, the direction shown by the arrow D1), but has not yet contacted the molten pool 11 on the surface of the printing body, and the resistance heating circuit 10 has not Started, no molten material was produced.

In Figure 5, the linear solid raw material 7 is in contact with the molten pool 11 on the surface of the printed body, that is to say, the linear solid raw material 7 is in contact with the current accumulation zone 17 on the printed body, and the resistance heating circuit 10 is activated. The contact surface between the linear solid material one 7 and the current accumulation zone 17 on the printed body forms a high resistance zone, and the area of the linear solid material one 7 that is in contact with the current accumulation zone 17 on the printed body melts and melts. The formation of molten raw material-13.

In Fig. 6, the linear solid raw material 7 passes through the solid raw material guide device 6, and moves to the molten pool 11 on the surface of the printed body in the direction indicated by the arrow D1. At the same time, the print head and the linear solid raw material 7 are integrated. Moving in the direction shown by arrow D2, the circular plasma beam 12 moves along with the print head (causing the molten pool 11 on the surface of the printing body to also move), and the resistance heating circuit 10 is in working condition, continuously producing molten raw material 1. 13 and continue to accumulate on the molten pool 11 on the surface of the printing body; the linear solid raw material 7 and the current accumulation area 17 on the printing body are connected by the molten raw material 13 (indirect connection, not direct contact) ; The previously accumulated molten material on the printed body forms the solidified part 15 of the layer being accumulated after the temperature is lowered; there is an unsolidified part between the molten material 13 and the solidified part 15 of the accumulated layer 14. This is a transition zone. There is a softening zone in the transition zone. Rolling, hammering, impacting, or vibrating the softening zone can affect the physical properties of the softening zone after it is completely solidified (for example, (Grain/dendritic characteristics within the material). Since the circular plasma beam 12 is circular, after the molten material is accumulated on the printing body, it will be directly heated by the circular plasma beam 12, and the surface morphology will become smoother. For this first specific embodiment, the molten raw material is generated in real time on the upper surface of the current accumulation zone 17 (part of the molten pool) on the printed body by resistance heating, and there is no need for a deep molten pool, which has a thickness of micrometers. The melting layer/melt pool can meet the demand, which can effectively protect the thin-walled structure or fine structure of the previously formed printed body; heating the printed body 8 to generate the molten pool 11 on the surface of the printed body does not require penetration lines Like solid raw material 7 or molten raw material 13, the power density required for heating energy is low, and it is also beneficial to protect the thin-walled structure or fine structure of the previously formed printed body.

In the first specific embodiment, plasma is used to directly heat the surrounding area (periphery) of the printing body where the molten material is accumulating, and the heat obtained by the direct heating of the surrounding area is partially transferred to the printing body by conduction. The area where the molten material is accumulating forms a high resistance area between the solid material and the area of the printing body where the molten material is accumulating. In the series circuit, the maximum voltage partial pressure is obtained in the high-resistance area, and the resistance heating energy is concentrated in the high-resistance area, which improves the energy utilization rate of the resistance heating and obtains a small molten material, which is beneficial to improve the molding accuracy. This method of obtaining a small volume of molten raw material on the contact surface is different from directing linear solid raw materials through laser, electron beam, plasma beam or independent arc (discharge between special discharge electrode and printed body to form an arc) (E.g. metal wire) and the surrounding printing body are melted together in the existing three-dimensional printing technology; the heating energy of the prior art needs to penetrate the linear solid raw material and reach the printing body below it, and the heating energy required is high. The large volume of the molten material and the large molten pool on the printed body result in lower molding accuracy; in the prior art, when the contact between the solid raw material or the molten material and the printed body is interrupted, if the heating energy is not timely Cutting off will result in the formation of large liquid metal balls on the free end of the wire (liquid metal has a high viscosity, high surface tension, and a tendency to self-aggregate), resulting in uncontrollable liquid raw materials and even failure of 3D printing. These existing technologies require image monitoring of the current forming area and real-time adjustment of the position of the linear solid raw material, the feed amount of the linear solid raw material, the position of the molten raw material, the shape of the molten pool on the printed body, and the real-time adjustment of the position of the linear solid raw material according to the image data. The size and heating position of heating energy can timely repair the defect accumulation area or the formed area. The control technology required by the prior art is very complicated and the technical threshold is high. The technical scheme of the present invention can ensure the correct positional relationship between the molten raw material and the thin melting layer (thin layer molten pool) on the surface of the printed body in the current molding area, the shape of the molten raw material is controllable, the molding accuracy is higher, and the printing accuracy is higher. The damage of the body is smaller (only a thin layer of melting is formed in the current accumulation area of the printing body, a larger and deeper molten pool is not required, and the power density of the plasma beam is lower); the liquid state of the present invention If the raw material is generated in real time, if the contact between the raw material and the printed body is interrupted, the resistance heating current will be naturally interrupted (when the resistance heating voltage is lower than 12V, there will be no arc between the formed raw material end face and the printed body). The limitation is that the molten raw material remaining at the end of the solid raw material loses the opportunity to agglomerate; the control system required by the three-dimensional printing device corresponding to the present invention is simple and the cost is lower.

In this first specific embodiment, a circular impinging gas flow (not shown in the figure) is nested on the outer circumference of the circular plasma beam-12, and the circular impinging gas flow is coaxial with the circular plasma beam-12, using the circular impinging gas flow. The softening area of the heating zone 19 of the plasma on the surface of the printed body is impacted to obtain a further forging effect and improve the material properties of the printed body after being formed. The heating zone 19 of the plasma on the surface of the printed body includes two parts: the first part. After the plasma beam heats the printed body, the heating zone will form a temperature gradient. The zone that is not melted but has plasticity and is not completely melted belongs to the softened zone. ; The second part, during the three-dimensional printing process, the print head or printed body needs to move to continuously change the current accumulation area. The area previously heated and melted by the plasma beam and the accumulated molten material will experience a softening state after the temperature decreases.

As shown in FIG. 7 to FIG. 11, the second specific embodiment of a three-dimensional printing method of the present invention uses 4 independent arcs to heat around the current accumulation area on the surface of the printed body. The heat of each area directly heated by the arc is conducted and diffused to the periphery, forming a molten pool with an area larger than the area directly heated by the arc (ie, the second 35 of the molten pool on the surface of the printed body), especially in the four arc directly heated areas. The area (that is, the current accumulation area) generates heat stacking, causing the area to melt (form a molten pool). The four areas directly heated by the arc are not directly connected to each other, that is, the areas directly heated by the arc are not coherent.

The main part of the print head shown in Figures 7 and 8 is mainly composed of an arc generator array 26, an air flow regulating seat 40 and a solid material guiding device 30, in which an air flow regulating seat 40 is provided at the lower end of the arc generator array 26, The working airflow ejected by the arc generator array 26 is regulated by the airflow adjusting seat 40 to form a circular airflow; the arc generator array 26 is composed of 4 arc generators, and each arc generator is provided with a gas interface and a discharge electrode. The four gas ports constitute the gas ports 27 of the arc generator array, and the four discharge electrodes constitute the electrodes 28 of the arc generator array. The second linear solid material 29 is guided by the solid material guiding device 30 to reach the surface of the second printing body 36.

9 and 10 (FIG. 10 is an enlarged view of the area shown by the dashed box CC in FIG. 9) as shown in the working principle of the second specific embodiment: the working gas 38 uses argon (inert gas), Enter the arc generator array 26 from the gas interface 27 of the arc generator array (as shown by the arrow F2), and then spray out through the air flow regulating seat 40 and form a circular air flow. The circular air flow connects the electrodes 28 of the arc generator array and the surface of the printing body. The second molten pool 35, the second molten material 32, and the unsolidified part 33 are covered; the electrode 28 of the arc generator array is connected to the negative electrode of the arc generator array control circuit 39, and the printing body 2 36 is controlled by the arc generator array The positive connection of the circuit 39 (printed body two 36 is equivalent to the "workpiece" in argon arc welding in the ordinary welding field); the circular air flow distributes the arc array 37 generated by the electrode 28 of the arc generator array around the molten material two 32, and the arc The array 37 does not touch the second molten material 32; the linear solid material two 29 passes through the solid material guide device two 30, and moves to the molten pool two 35 on the surface of the printed body along the direction indicated by the arrow D3. At the same time, the print head and the linear The two solid materials 29 move together in the direction shown by the arrow D4, the arc array 37 moves with the print head (causing the molten pool two 35 on the surface of the print body to also move), and the resistance heating circuit two 31 is in working condition and continues to generate The molten material 2 32 continues to accumulate on the molten pool 2 35 on the surface of the printing body; the molten material previously accumulated on the printing body forms a solidified part 2 34 of the layer that is accumulating after the temperature is lowered; in the middle of the molten material 2 There is an uncured part two 33 between 32 and the cured part two 34 of the layer being accumulated, which is a transition zone in which there is a softening zone.

As shown in FIG. 11, the current accumulation area 21, the area directly heated by the arc 22, and the heating area 23 of the arc on the surface of the printed object are shown in the second embodiment of the printed object. The positional relationship of the arc on the surface of the printed object The heating area includes the heating area 23 of the arc and the area surrounded by it, that is: the area surrounded by the heating area 23 of the arc includes the current accumulation area 21 on the printed body and the area 22 directly heated by the arc; except for the area directly heated by the arc 22. Other areas are heated by heat conduction, that is, indirect heating. The area 22 directly heated by the arc is composed of 4 smaller and close to each other arc direct heating areas. The heat of each small arc direct heating area will be conducted and diffused to the surroundings, forming a molten pool two 35 on the surface of the printing body, especially It is the current accumulation zone two 21 on the printed body surrounded by the area 22 directly heated by the arc. It is the superimposed area of heat conducted by 4 small arc direct heating zones. The current accumulation zone two 21 on the printed body forms a reliable melting zone. . By adjusting the overall power of the arc generator array 26, a thin melting layer can be formed on the surface of the printed body. For the second specific implementation, the molten raw material is generated in real time on the upper surface of the current accumulation zone 21 (part of the molten pool) on the printed body by resistance heating, and a deep molten pool is not required, and the melting of micron thickness is not required. The layer/melt pool can meet the demand, which can effectively protect the thin-walled structure or fine structure of the previously formed printed body.

The third specific embodiment of the three-dimensional printing method of the present invention shown in FIGS. 12 to 13 is only slightly different from the first specific embodiment of the three-dimensional printing method of the present invention: the molten raw material three 43 does not pass through Generated by resistance heating, the circular plasma beam three 42 and the linear solid raw material three 41 have a small amount of contact, and the contact area (the contact area 48 between the circular plasma beam and the linear solid raw material shown in FIG. 13) is located in the linear solid raw material three. The area adjacent to the bottom edge of 41 and the printing body three 46 (melt pool three 44 on the surface of the printing body), the linear solid raw material three 41 obtains heat from the circular plasma beam three 42 through this contact area and is melted to form a molten raw material three 43; The heat transferred from the molten pool three 44 on the surface of the printing body to the linear solid raw material three 41 also participates in the generation of the molten raw material three 43; the resistance heating circuit three 45 applies an instantaneous strong current when the molten raw material does not need to be generated, and the linear solid The raw material three 41 and the molten raw material three 43 fuse instantaneously to separate the two; the resistance heating circuit three 45 also monitors the contact state between the linear solid raw material three 41 and the printed body three 46, through whether there is any between the two Electrical connection to judge. The circular plasma beam three 42 has a small amount of contact with the linear solid material three 41. The ratio of the contact area to the circular plasma beam three 42 print body three 46 needs to be obtained through multiple actual measurements, or the circular plasma beam three 42 is used to directly heat the linear solid raw material three 41 to generate the energy of the molten raw material three 43 and the energy ratio of the toroidal plasma beam three 42 to directly heat the printed body three 46 to generate the molten pool three 44 on the surface of the printed body is required Obtained after actual testing. The non-ionized working gas 47 forms a protective atmosphere. The source of the non-ionized working gas 47 is a neutral working gas formed after the non-ionized working gas and the anions and cations of the annular plasma beam 42 are combined. In the third specific embodiment, when the parameters are: the diameter of the linear solid material three 41 is 1 mm, the progressive amount of the linear solid material three 41 is 50 mm/s, and the movement speed of the print head is 50 mm/s, The material is 316 stainless steel, the outer diameter of the direct heating zone (ring) of the toroidal plasma beam three 42 on the printing body three 46 is 5mm, and the printing body three 46 is a square with length 100mm*width 100mm*height 50mm, the current printing body The accumulation zone is located at the center of the upper surface of the printing body 3 46, the overall base temperature of the printing body 3 46 is an average of 300 ℃, the circular plasma beam 3 42 arc voltage is 80V, the current is 80A, then: the circular plasma beam 3 42 is used for direct heating The ratio of the energy of the hot linear solid raw material three 41 to generate the molten raw material three 43 and the energy of the circular plasma beam three 42 for directly heating the printing body three 46 to generate the molten pool three 44 on the surface of the printing body is approximately 1:6.

The arrow D6 in FIG. 12 indicates that the linear solid raw material three 41 is advancing to the printed body three 46, and the arrow F3 indicates the flow direction of the working gas.

In the third specific embodiment, the formation of the molten pool three 44 on the surface of the printing body does not rely on the energy of the circular plasma beam three 42 penetrating the linear solid raw material three 41 to conduct downwards, and the circular plasma beam three 42 The direct heating of the printing body three 46 is circular heating to ensure that the generated molten material three 43 is always located in the inner central area of the circular direct heating zone. Therefore, it can be ensured that the print head moves in any direction on the surface of the printing body three 46. When the molten material is accumulated, the molten material three 43 always accumulates on the molten pool three 44 on the surface of the printing body. This does not require a complicated control system, and the reliability is extremely high.

The heating method of the present invention "using arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating" is not directly heating the area of the printing body where the molten material is accumulating, and can be realized on the area In the presence of raw materials, heating the accumulation zone below the raw materials without the heating energy passing through the raw materials can achieve many beneficial effects. Here are some examples:

Example 1: The volume of the raw material is small. If the raw material is solid, the energy intensity required to melt the solid raw material is much lower than the energy required to melt the current accumulation zone (the current accumulation zone is integrated with other areas of the printing body, if the printing body is hot Good conductor, such as metal, the printed body will quickly conduct away the heat in the current accumulation area), if the same beam energy (such as plasma beam, or laser beam, or electron beam) is used to directly pass through the raw material and reach the raw material The current accumulation zone below often leads to excess energy for heating the raw materials, which partially evaporates the raw materials, and the partial evaporation of the raw materials will also cause bubbles/honeycomb defects to the accumulated raw materials; if the raw materials are molten, if the same beam energy is used Passing directly from the top of the raw material and reaching the current accumulation zone below the raw material, the raw material itself is already in a molten state, which will cause more serious evaporation of the raw material.

Example 2: Using "arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating" results in the superimposition of heat in the area of the printing body where the molten material is accumulating, which reduces the overall heating power of the arc or plasma. Under the premise of density, a thin molten pool is formed in the area of the printed body where the molten material is accumulating, which can effectively protect the thin-walled structure or fine structure of the previously formed printed body. The opposite of the present invention is: the existing based on The metal three-dimensional forming technology of arc heating or plasma beam heating has caused great damage to the thin-walled structure or fine structure of the previously formed printed body. The consequence is that the printed and formed objects that people have seen in the prior art are very rough.

Example 3: Realizing a larger area of heating zone and a smaller temperature gradient can effectively reduce stress and reduce cracks in the material. The opposite of the present invention is: the existing metal three-dimensional forming technology, such as SLM (selective Laser melting) Due to the small laser spot and extremely high power density, the temperature difference between the molten pool and the surrounding printing material is extremely large, resulting in extremely large internal stress and many cracks in the material, which need to be eliminated by later heat treatment (such as hot isostatic pressing) These flaws.

Example 4: Adopting 360° annular heating method, no matter the print head moves in any direction in the current forming layer plane, it can ensure that the current accumulation area on the printed body is surrounded by the annular heating area and is effectively heated, and the movement control of the print head is flexible , The control system matched with the print head is simple.

Example 5: Adopting a 360° annular heating method, heating again after accumulating molten materials to melt the surface of uneven (such as burrs) areas again to obtain a smoother surface. The lines may not be completely fused during the process of accumulating molten materials. , Melting again is conducive to the fusion between the lines.

Example 6: Compatible with powdered solid raw materials, when the channel in the middle of the guiding device is replaced with a nozzle, the powder raw material is carried by the airflow, and the powder raw material is sprayed on the current accumulation area, and the powder raw material adheres to the current accumulation area in the molten state, and then It is heated again by the circular plasma beam or circular arc to ensure that the powder material and the printed body are completely fused.

Example 7: The heating energy for producing the molten material and the heating energy for the molten pool producing the surface of the printed body are independent of each other, which can realize a flexible molding process and easily realize the printing of materials with high melting point and high thermal conductivity.

The above are only preferred specific embodiments of the present invention, and cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the claims of the present invention and the contents of the description still belong to the scope of the present invention. Range.

Claims

A three-dimensional printing method, the main process of which is: melting solid raw materials to obtain molten raw materials. The molten raw materials are placed in the forming area used by the three-dimensional printing equipment. The molten raw materials are accumulated in the forming area and transformed into printed bodies, and the newly generated molten raw materials Accumulate on the basis of the printed body until the object to be printed is formed; wherein: in the process of accumulating the molten material, the position where the molten material is placed is determined by the shape and structure of the object to be printed; the three-dimensional printing device described The used forming area refers to the space used by the 3D printing equipment when printing objects;

Its characteristics are:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating; the area of the printing body surrounded by the arc or plasma direct heating area is the current accumulation zone, and the arc or plasma affects the printing body The heat of direct heating around the area where the molten raw material is accumulating causes a molten pool to be formed on the printed body, the current accumulation zone is located in the molten pool, and the molten raw material accumulates on the current accumulation zone.
The three-dimensional printing method according to claim 1, wherein:

During the three-dimensional printing process, the solid raw material moves to the current accumulation area of the printed body, and the solid raw material is not heated and melted by the arc or plasma; during the three-dimensional printing process, An electrical connection is provided between the solid raw material and the printing body, a current is applied between the solid raw material and the current accumulation area of the printing body, and the solid raw material is in contact with the current accumulation area of the printing body by means of resistance heating. The part or the connected part is heated and melted; the solid raw material is a conductive material; the contact refers to that the solid raw material directly contacts the current accumulation area of the printing body before melting; the connected refers to the solid The raw material does not directly contact the current accumulation zone of the printing body before melting, and the solid raw material contacts the current accumulation zone of the printing body through the previously produced molten raw material before melting, that is, when the solid raw material is in contact with the current accumulation zone of the printing body. The previously produced molten material exists between the current accumulation zones of the printed body.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

The arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating. The direct heating means that the arc column area or the arc root of the arc or plasma arc directly acts on or directly contacts Around the area of the printing body where the molten material is accumulating; or,

The direct heating also means that the arc or plasma does not directly heat the area of the printing body where the molten material is accumulating, that is, the main part of the arc or plasma does not reach the area of the printing body where the molten material is accumulating.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

The area of the printed body directly heated by the arc or plasma is coherent or discontinuous;

The area of the printing body surrounded by the arc or plasma directly heated area is the current accumulation area, wherein the enclosure refers to a complete enclosure or a partial enclosure;

The printed body includes the target object to be printed and auxiliary structures required by the molding process.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

The shape of the area directly heated by the arc or plasma of the printing body is a ring;

The solid raw material is a linear solid raw material capable of conducting electricity.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

Said arc or plasma is used to directly heat the surrounding area of the printing body where the molten material is accumulating. The arc or plasma is controlled by a rotating air current or a non-rotating air current to form a circular arc or a circular plasma beam to realize the printing Direct heating around the area where the molten material is accumulating in the body;

When the solid raw material passes through the circular arc or circular plasma beam, it is not heated and melted by the arc or plasma; or,

When the solid raw material passes through the circular arc or the circular plasma beam, it partially contacts the arc or plasma and is heated and melted by the arc or plasma.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

In the three-dimensional printing process, the printed body is accumulated layer by layer, the part of the direct heating zone located in front of the accumulation direction of the current forming layer melted material is converted into the future melted material accumulation zone, and the direct heating zone is located at the current forming layer melted material The position in front of the accumulation direction is defined as the upcoming accumulation zone; set the distance between the upcoming accumulation zone and the current accumulation zone in the current forming layer plane as L, and the movement speed of the current accumulation zone in the current forming layer plane as V, L and The ratio of V is t, that is, L/V=t, the time T required for the current accumulation zone to change from the molten state to the non-melting state; when t<T, the previous accumulation zone can be relied on when it is about to transform into the current accumulation zone. The carried heat remains molten, and the heat transferred from the direct heating zone around the current accumulation zone to the current accumulation zone is superimposed on the current accumulation zone that is already in a molten state; by adjusting the movement of the current accumulation zone in the current forming layer plane Speed V and adjust the heating power of the arc or plasma to the printed body to adjust the temperature or melting state of the current accumulation zone.
The three-dimensional printing method according to claim 2, wherein:

The electrical connection between the solid raw material and the printing body means that the solid raw material and the printing body are connected to the same circuit, and the solid raw material and the printing body are connected in series in the circuit.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to generate a rotating arc or a rotating plasma arc by controlling the arc or plasma arc by a magnetic field, so as to realize the operation of the printing body. Direct heating is performed around the area where the molten material is accumulated, avoiding direct heating of the area of the printed body where the molten material is accumulated.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

The use of arc or plasma to directly heat the surrounding area of the printing body where the molten material is accumulating is to generate a rotating arc or a rotating plasma arc by controlling the arc or plasma arc by a magnetic field, so as to realize the operation of the printing body. Direct heating is performed around the area where the molten material is accumulated, avoiding direct heating of the area where the molten material is accumulating on the printed body; the arc or plasma arc is through the discharge between the annular discharge electrode or the hollow discharge electrode and the printed body Formation; the solid material moves to the printing body through the space in the annular discharge electrode or the hollow discharge electrode, and the solid material is not heated and melted by the arc or plasma during the process of moving to the current accumulation area of the printing body.
The three-dimensional printing method according to claim 1 or 2, characterized in that:

A circular airflow is sprayed on the periphery of the area directly heated by the arc or plasma of the printing body, and the circular airflow is used to impinge on the softening area around the directly heated area.
A three-dimensional printing device for realizing the three-dimensional printing method of claim 1, comprising a molding zone for placing molten raw materials, the molten raw materials are accumulated in the molding zone and transformed into a printed body, and the newly generated molten raw materials are printed The object to be printed is accumulated on the basis of the volume until the object to be printed is formed; where: in the process of accumulating the molten material, the position where the molten material is placed is determined by the shape and structure of the object to be printed; the three-dimensional printing equipment used The forming area refers to the space used by the 3D printing equipment when printing objects;

Its characteristics are:

It also includes an arc generator or a plasma generator. The arc or plasma of the arc generator or the plasma generator directly heats the surrounding area of the printing body where the molten material is accumulating, and the printing body is directly heated by the arc or plasma. The area surrounded by the area is the current accumulation area. The arc or plasma directly heats the surrounding area of the printing body where the molten material is accumulating, so that a molten pool is formed on the printing body, and the current accumulation area is located in the printing body. In the molten pool, the molten raw material is accumulated on the current accumulation zone.
The three-dimensional printing device according to claim 12, wherein:

The solid raw material is not heated and melted by the arc or plasma during the process of moving to the current accumulation zone of the printing body; an electrical connection is provided between the solid raw material and the printing body, and the solid raw material is connected to the printing body. A current is applied between the current accumulation zone of the body, and the part of the solid material that is in contact with or connected to the current accumulation zone of the printing body is heated and melted by means of resistance heating; the solid material is a conductive material; The “contact” means that the solid raw material directly contacts the current accumulation zone of the printing body before melting; the “connection” means that the solid raw material does not directly contact the current accumulation zone of the printing body before melting, and the solid material does not directly contact the current accumulation zone of the printing body before melting. Before melting, the raw material comes into contact with the current accumulation area of the printing body through the previously produced molten raw material, that is, there is the previously produced molten raw material between the solid raw material and the current accumulation area of the printing body.
The three-dimensional printing device according to claim 12 or 13, characterized in that:

The plasma generator includes a plasma torch with an annular hollow structure and an annular gas passage, an annular electrode, and a vortex ring arranged inside the plasma torch. The plasma torch is provided with an airflow inlet and an annular nozzle. The space in the annular nozzle is annular, that is, the air flow jetted from the annular nozzle is an annular air flow; the working gas enters the plasma torch from the air flow inlet, flows through the vortex ring, and then enters the plasma torch. The annular gas passage forms a rotating airflow, and the rotating airflow drives the plasma arc to rotate, and the rotating plasma arc is ejected through the annular nozzle to form an annular plasma beam, thereby generating the annular direct heating zone on the surface of the printing body;

The solid raw material is a linear solid raw material capable of conducting electricity, and further includes a solid raw material guiding device for guiding the movement of the linear solid raw material, and the linear solid raw material is guided by the solid raw material guiding device When reaching the surface of the printing body, the space surrounded by the circular plasma beam serves as a passage for the linear solid material to leave the solid material guiding device;

The linear solid raw material is not heated and melted by the circular plasma beam during the passage through the passage, and remains solid; an electrical connection is provided between the solid raw material and the printing body, between the solid raw material and the current accumulation zone of the printing body Electric current is applied to heat and melt the part of the solid raw material that is in contact with the current accumulation area of the printing body or the connected part by means of resistance heating; the contact means that the solid raw material is directly in contact with the printing body before being melted. The current accumulation zone is in contact with the current accumulation zone; the connection means that the solid raw material does not directly contact the current accumulation zone of the printing body before melting, and the solid raw material passes the current accumulation zone of the printing body through the previously produced molten raw material before melting. The accumulation zone is in contact, that is, between the solid raw material and the current accumulation zone of the printing body, there is a previously generated molten raw material, or,

The linear solid raw material is heated and melted by the circular plasma beam during the process of passing through the passage. The circular plasma beam contacts the linear solid raw material in a small amount, and the contact area between the circular plasma beam and the linear solid raw material is located at the lower edge of the linear solid raw material. In the area adjacent to the printing body, the linear solid raw material obtains heat from the circular plasma beam through the contact area and is melted to form a molten raw material; the heat conducted by the molten pool on the surface of the printing body to the linear solid raw material also participates The generation of molten raw material; the resistance heating circuit applies an instantaneous strong current when the molten raw material does not need to be generated to instantly fuse the linear solid raw material and the molten raw material to separate the two; the resistance heating circuit also monitors the wire The contact state between the linear solid material and the printed body is determined by whether there is an electrical connection between the linear solid material and the printed body.
The three-dimensional printing device according to claim 12 or 13, characterized in that:

The solid raw material is a conductive linear solid raw material, the arc generator is provided with a number of electrode arrays arranged at intervals along the circumferential direction, and further includes an airflow control seat and a movement for the linear solid raw material. Guided solid material guide device, the linear solid material is guided by the solid material guide device to reach the surface of the printing body;

The airflow regulating seat is arranged at the lower end of the arc generator, and the working airflow sprayed by the arc generator forms an annular airflow after being regulated by the airflow regulating seat;

The annular airflow covers the electrode array of the arc generator, the molten pool on the surface of the printed body, the molten material, and the unsolidified part; the annular airflow distributes the arc array generated by the electrode array of the arc generator around the molten material , The arc array does not touch the molten material;

An electrical connection is provided between the solid raw material and the printing body, a current is applied between the solid raw material and the current accumulation area of the printing body, and the solid raw material is compared with the current accumulation area of the printing body by means of resistance heating. The contact part or the connected part is heated and melted; the term “phase contact” means that the solid raw material directly contacts the current accumulation zone of the printing body before melting; the term “connection” means that the solid raw material does not contact the current accumulation area of the printing body before melting. The current accumulation area of the printing body is in direct contact, and the solid raw material is in contact with the current accumulation area of the printing body through the previously produced molten raw material before being melted, that is, between the solid raw material and the current accumulation area of the printing body There is previously produced molten raw material.