CN106965421B

CN106965421B - Three-dimensional printing method

Info

Publication number: CN106965421B
Application number: CN201710297915.7A
Authority: CN
Inventors: 梁福鹏
Original assignee: Nanjing Taitao Intelligent System Co ltd
Current assignee: Nanjing titanium ceramic Intelligent System Co., Ltd.
Priority date: 2017-04-29
Filing date: 2017-04-29
Publication date: 2020-10-20
Anticipated expiration: 2037-04-29
Also published as: CN106965421A; WO2018196868A1

Abstract

The invention discloses a three-dimensional printing method, which mainly comprises the following steps: placing the molten raw materials into a forming area used by the three-dimensional printing equipment, accumulating the molten raw materials in the forming area and converting the molten raw materials into a printing body, and accumulating the molten raw materials on the basis of the printing body until an object to be printed is formed; the method is characterized in that: in the process of accumulating the molten raw materials, the position of the printing body, at which the molten raw materials are to be accumulated, is melted or softened by means of electromagnetic induction heating, and/or the position of the printing body, at which the molten raw materials are being accumulated, is melted or softened. The invention has the beneficial effects that: the interlayer bonding force of the printing body is high, and the structural strength of the printing body is high; the detachable auxiliary supporting body can be synchronously generated to realize the printing of a complex structure; the equipment structure is simple; large components can be printed; the three-dimensional printing of conductive materials such as metal, metal ceramic, plastic mixed with metal powder and the like can be realized by using various types of applicable materials; the cost is low. The invention has substantial progress.

Description

Three-dimensional printing method

Technical Field

The invention relates to a three-dimensional printing technology, in particular to a three-dimensional printing method based on electromagnetic induction heating, and belongs to the technical field of additive manufacturing.

Background

Three-dimensional printing technology was originally originated in the united states at the end of the 19 th century until the seventies and eighties of the 20 th century, where it was perfected and commercialized in japan and the united states. Mainstream Three-dimensional printing technologies such as StereoLithography (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), Three-dimensional powder bonding (Three dimensional printing and glucing, 3DP) are now commonly commercialized in the united states in the eighties and ninety years of the 20 th century. Technologies for three-dimensional printing of metallic materials that have been commercialized at present mainly include Selective Laser Melting (SLM), Electron Beam Melting (EBM), and Laser near net Shaping (LENS), but the SLM, EBM, and LENS technologies also have many disadvantages, such as: the manufacturing cost is high, the maintenance cost is high, the mechanical strength of printed parts is not high (enhancement processing is required after printing, especially SLS/SLM technology), the printing breadth of SLM and EBM technology is small, and LENS technology cannot print complex structures and has low printing precision although the printing breadth is large. In order to improve the mechanical properties of metal parts printed by the above-mentioned techniques, a number of techniques have also appeared, for example, chinese patent application No. 201410289871.X entitled "a processing method for improving the properties of 3D printed metal parts". In view of the above disadvantages of SLM, EBM, and LENS technologies, low-cost metal three-dimensional printing technologies using other forming methods have also appeared, such as chinese patent application No. 201510789205.7 entitled "method and apparatus for direct 3D printing and manufacturing using liquid metal", chinese patent application No. 201510679764.2 entitled "a metal 3D printing rapid prototyping apparatus", and chinese patent application No. 201410206527.X entitled "extrusion metal flow 3D printer", but these technologies have problems of low forming accuracy or low interlayer bonding force of printed and formed metal parts. There are also three-dimensional metal printing methods based on the principle of arc heating, such as chinese patent application No. 201410617953.2 entitled "metal member electrofusion forming method", which, although low in cost, have a number of disadvantages, such as: the forming precision is extremely low, the electric arc can damage the previously formed structure, the controllability of the electric arc is poor, the electric arc is difficult to focus and miniaturize, and the complicated and fine structure cannot be manufactured.

Disclosure of Invention

The invention aims to provide a three-dimensional printing method based on an electromagnetic induction heating principle, wherein the layers of a printing body are connected in a melting mode, and further extremely high structural strength is obtained.

Another object of the present invention is to provide a three-dimensional printing method capable of adjusting interlayer bonding force of a printed body, in which a region with low interlayer bonding force can be used as an auxiliary support to realize printing with a complex structure.

It is still another object of the present invention to provide a three-dimensional printing method, particularly a three-dimensional printing method of a metal material, which can use a conductive material as a printing raw material.

In order to achieve the above purpose, the invention adopts the technical scheme that: a three-dimensional printing method mainly comprises the following steps: placing the molten raw materials into a forming area used by the three-dimensional printing equipment, accumulating the molten raw materials in the forming area and converting the molten raw materials into a printing body, and accumulating the molten raw materials on the basis of the printing body until an object to be printed is formed; wherein: the position at which the molten raw material is placed during the accumulation of the molten raw material is determined by the shape and structure of the object to be printed, or by computer model data corresponding to the object to be printed; the forming area used by the three-dimensional printing equipment refers to a space used by the three-dimensional printing equipment when printing an object; the molten raw material accumulates in the forming zone and is converted into a print because of the temperature decrease;

the method is characterized in that:

in the process of accumulating the molten raw materials, the position of the printing body, at which the molten raw materials are to be accumulated, is melted or softened by means of electromagnetic induction heating, and/or the position of the printing body, at which the molten raw materials are being accumulated, is melted or softened.

Optionally: melting the position of the print body where the molten raw material is accumulating as described above, it is possible to achieve fusion bonding between the newly accumulated molten raw material and the print body (the print body is formed by the previously accumulated molten raw material as the temperature is lowered and changed into a solid state), thereby achieving high-strength interlayer bonding.

Optionally: the induction magnetic field used when the printing body is subjected to electromagnetic induction heating has a controlled range of action of induction heating and/or has a controlled heating intensity of the induction magnetic field to the printing body.

Optionally: the range of action of the induction heating includes an action area, a shape of a heating region of the magnetic field on the print body, and the like. The heating intensity of the induction magnetic field is determined by parameters such as magnetic field intensity, heating time, magnetic field frequency and the like.

Optionally: an induction magnetic field used when electromagnetic induction heating is performed on a print body, the state of the area and/or shape of a heating region of the print body can be adjusted. The state of the shape mainly includes a shape type, a direction of the shape, a layout of the shape, and a dynamic change of the shape.

Optionally: the molten raw material is obtained by heating and melting a solid raw material by using an electromagnetic induction heating mode.

Optionally: the above-mentioned method of heating and melting a solid raw material by using electromagnetic induction heating to obtain a molten raw material is produced by: when the solid raw material passes through or passes through the electromagnetic induction heating magnetic field, the electromagnetic induction heating magnetic field induces eddy current on the solid raw material to heat and melt the solid raw material;

or the electromagnetic induction heating magnetic field induces eddy current heating on the solid raw material and induces eddy current heating on a structure in contact with the solid raw material and conducts heat to the solid raw material to melt the solid raw material together;

alternatively, the electromagnetic induction heating magnetic field induces eddy current heat in a structure in contact with the solid raw material and conducts the heat to the solid raw material to melt the solid raw material.

Optionally: the above-mentioned molten raw material obtained by heating and melting a solid raw material by means of electromagnetic induction heating is not in contact with any other structure except the printed body or in contact with the printed body or the solid raw material during the accumulation of the molten raw material on the basis of the printed body.

Optionally: the molten raw material is obtained by heating and melting a solid raw material by electromagnetic induction heating, wherein the solid raw material is a linear solid raw material, a powdery solid raw material, a rod-shaped solid raw material, or a granular solid raw material.

Optionally:

the electromagnetic induction heating magnetic field used for heating the solid raw material to be converted into the molten raw material and the electromagnetic induction heating magnetic field used for heating the printing body are both generated by the same magnetic field generating device;

or the electromagnetic induction heating magnetic field used for heating the solid raw material to be converted into the molten raw material and the electromagnetic induction heating magnetic field used for heating the printing body are respectively generated by different magnetic field generating devices;

or the electromagnetic induction heating magnetic field used for heating the solid raw material to be converted into the molten raw material and the electromagnetic induction heating magnetic field used for heating the printing body are the same magnetic field;

alternatively, the electromagnetic induction heating magnetic field used for heating the solid raw material to melt the raw material and the electromagnetic induction heating magnetic field used for heating the print body are independent magnetic fields.

Optionally: the moving path of the solid raw material is guided by the guiding device in the process of entering the electromagnetic induction heating magnetic field.

Optionally: the molten raw material is obtained by heating a solid raw material, and the heating method at least comprises one of resistance heating, electromagnetic induction heating, arc heating, plasma heating, laser heating, electron beam heating and microwave heating. These heating means directly heat the solid feedstock and/or heat a structure or medium in contact with the solid feedstock and then transfer the heat to the solid feedstock by thermal conduction (i.e., indirect heating).

Optionally: the molten raw material is obtained by heating a solid raw material, and the heating method at least comprises one of resistance heating, electromagnetic induction heating, arc heating, plasma heating, laser heating, electron beam heating and microwave heating. When two or more of the heating patterns are used, different heating patterns may be switched, for example: in some cases, a resistance heating method is used, and in some cases, an electromagnetic induction heating method is used.

Optionally: the printing body is melted or softened by an electromagnetic induction heating mode, namely the surface of the printing body is heated and melted or softened.

Optionally:

in a part of printing area, closing an electromagnetic induction heating magnetic field which generates heating action on the printing body, so that the printing body in the area is not heated and melted or softened by electromagnetic induction;

or, in a part of the printing area, adjusting the action area and/or the shape state of an electromagnetic induction heating magnetic field which generates heating action on the printing body, so that the printing body in the area is not melted or softened by electromagnetic induction heating; and/or in a part of the printing area, reducing the heating intensity of the electromagnetic induction heating magnetic field which generates heating action on the printing body so as to prevent the printing body in the area from being heated and melted or softened by electromagnetic induction;

the state of the shape mainly comprises shape type, shape direction, shape layout/distribution mode and shape dynamic change;

the partial printing area refers to a part of the space occupied by the molten raw material and the printing body in the process of printing the object. The partial print area may also be understood as: the object to be printed is mapped to a portion of a mapping space formed by a molding zone used by the three-dimensional printing apparatus. The partial print area may also be understood as: dividing the space occupied by the object to be printed in the future in advance to form a virtual object which is in a mapping relation with the object to be printed, gradually converting the virtual object into a real object which is finally printed and molded, wherein the process of converting the virtual object into the real object is a three-dimensional printing and molding process; dividing the virtual object into a plurality of areas, wherein the partial area is the partial printing area.

Optionally: the heating intensity of the electromagnetic induction heating magnetic field on the printing body is controlled to control the melting state of the area of the printing body, which is in contact with the melting raw material, and further control the connection mode between the printing body and the melting raw material. The molten state includes molten, non-molten, semi-molten, softened and the like states. The connection mode can be divided into two types of fusion connection and non-fusion connection. When the area of the printing body in contact with the molten raw material is in a molten state, fusion in a molten connection manner is realized between the molten raw material and the printing body, so that high-strength connection is realized (in the case of printing a metal material, metallurgical-grade connection is also realized). When the region of the print body in contact with the molten raw material is in a non-molten state, the molten raw material and the print body are connected to each other in a non-molten state, and the lower the temperature of the region of the print body in contact with the molten raw material is, the lower the connection strength therebetween is. The structural strength of the printing area generated by accumulating the melted raw materials/voxels (i.e., three-dimensional pixel points) in a non-melting connection manner is low, so that the printing area with low structural strength can be used as a detachable auxiliary support/bracket to realize three-dimensional printing of a complex structure.

Optionally: during the accumulation of the molten raw material, an electrical connection is established between the print body and the molten raw material.

Optionally: in the process of accumulating the molten raw material, an electric current is applied between the molten raw material and the print body. Applying an electric current between the molten raw material and the print can obtain a number of benefits, such as: the temperature of the molten raw material and the temperature of the contact part of the printing body and the molten raw material can be adjusted through the current, and the contact state between the molten raw material and the printing body can be monitored by monitoring the current.

Optionally: an electrical connection is established between the print body and the molten raw material, and the state of contact between the print body and the molten raw material is determined by determining the state of electrical connection between the print body and the molten raw material. For example, whether contact occurs and the degree of contact are judged through the resistance value or the capacitance value between the two, and the accumulation position of the molten raw material is changed on the premise of ensuring the contact between the two, so that the effective accumulation of each voxel (namely, pixel point) in the three-dimensional forming process is ensured.

Optionally: the method comprises the steps of establishing electrical connection between a printing body and solid raw materials, applying current between the printing body and the solid raw materials, and melting the solid raw materials in a resistance heating/resistance heating mode or melting the solid raw materials by resistance heating/resistance heating and electromagnetic induction heating together. For example: by using a metal wire (linear solid raw material), after the molten raw material is contacted with the printing body, the metal wire and the printing body are connected through the molten raw material, and electrical connection can be established between the metal wire and the printing body. Another example is: the metal wire is adopted, the metal wire is directly contacted with the printing body, and the electrical connection can be established between the metal wire and the printing body; the contact part of the metal wire and the printing body has larger resistance, a larger partial pressure is obtained in a larger resistance area, the heating value of a larger partial pressure area is larger, the resistance is larger when the temperature is higher, and finally the contact part of the metal wire and the printing body is melted.

Optionally: an electrical connection is established between the print body and the molten and/or solid feedstock, namely: an electrical connection is established between the print body and the molten feedstock, and/or an electrical connection is established between the print body and the solid feedstock.

Optionally: the position and/or structure of the induction magnetic field generating device can be adjusted by the induction magnetic field used when the printing body is heated by electromagnetic induction. The position state mainly refers to the position of the induction magnetic field generating device and the position change caused by the motion modes of movement, rotation, lifting, descending, swinging, vibration and the like. The structural state mainly refers to the shape, structural composition, structural combination and change of the induction magnetic field generating device.

Optionally: the operating state of the induction magnetic field generating device can be adjusted by the induction magnetic field used when the printing body is heated by electromagnetic induction. The working state of the induction magnetic field generating device mainly refers to the working or non-working of the device, the working mode and mode switching of the device, the intensity of output energy, the frequency, the structure and the composition of the output energy, the starting and the closing of different functional components, the alternation of the different functional components and the like.

Optionally: the temperature of the molding area used by the three-dimensional printing equipment is adjustable, namely the temperature of the molding environment is adjustable. The adjustment of the state of the print body can be obtained by adjusting the temperature of the molding environment, for example: by raising the temperature of the forming environment, the internal stress of the printing body is reduced (for example, the titanium metal part is three-dimensionally printed in the environment of 900 ℃, most of the internal stress of the part can be eliminated), and the environmental temperatures required by printing different materials are different.

Optionally: in the process of accumulating the molten raw materials, the printed body which is printed and formed is heated integrally, and the temperature is adjustable. For example: the temperature of the printing body is increased to reduce the stress in the printing body (for example, the titanium metal part generated by maintaining the whole printing body at 900 ℃ in the process of accumulating the molten raw materials can eliminate most of the stress in the part), and the heating temperature required by printing of different materials is different.

Optionally: the printing body is melted or softened by an electromagnetic induction heating mode, and a magnetic field generating an electromagnetic induction heating effect is generated by the induction coil.

Optionally: and adjusting the distance between the induction coil and the surface of the printing body, or adjusting the intensity of current flowing through the induction coil, or adjusting the on-off frequency of the current flowing through the induction coil, or adjusting the oscillation frequency of the current flowing through the induction coil so as to realize the adjustment of the intensity of the heating action of the magnetic field on the surface of the printing body.

Optionally: the energizing area of the induction coil is adjustable. For example: the induction coil is composed of different sections, and certain sections can be controlled to pass current, and certain sections can be controlled to not pass current.

Optionally: after the molten raw material is accumulated on the printing body, heating the newly formed voxel (namely, the pixel point) and the adjacent area thereof for a set time length and a set intensity is continuously carried out so as to control the cooling rate (namely, the annealing rate) of the newly formed voxel and the adjacent area thereof.

Optionally: the forming area used by the three-dimensional printing equipment is filled with vacuum or protective atmosphere.

Optionally: and a gas removing device is arranged in the forming area used by the three-dimensional printing equipment, and specific gas is removed in a chemical reaction mode. For example: an unsealed high-temperature heating container is arranged in a closed forming area, active metal powder (such as iron powder with the particle size of 10 microns) is placed in the container, after vacuum pumping (such as the air pressure is reduced to below 10 Pa), the powder is heated to 600 ℃, the iron powder and residual oxygen in the forming area are subjected to chemical reaction, and the oxygen is removed, so that the oxidation of the oxygen to high-temperature molten raw materials in the three-dimensional printing process is avoided.

Optionally: in the three-dimensional forming process, the printed body is processed by using a numerical control processing technology. For example: milling the edge of the newly formed layer using a milling cutter after each layer of print has been accumulated; alternatively, after the three-dimensional printing is completed, the print body is processed by a milling cutter as set. It can integrate traditional CNC (numerically controlled machine tool) and three-dimensional printing equipment into one set of equipment.

Optionally: the main steps of three-dimensional printing include:

step S1 of accumulating the molten raw material on the XY plane to generate a first layer printed body;

step S2, accumulating the melting raw material (n is more than or equal to 1) on the nth layer of printing body, and starting the molding of the first voxel of the voxel data chain of the (n + 1) th layer; the magnetic field heating the print body at an intensity insufficient to melt a region of the print body where molten material is about to accumulate and is accumulating;

step S3, according to the property of the computer model data, judging whether the formed voxel and the print body are connected in a melting mode; if the connection in the melting mode is needed, the step S4 is proceeded, otherwise, the step S6 is proceeded;

step S4 of melting a region of the upper surface of the print body which is in contact with the molten raw material; melting the area of the printing body by enhancing the heating intensity of the magnetic field to the printing body and/or applying current auxiliary heating between the melting raw material and the printing body;

step S5, the heating intensity of the printing body by the magnetic field is adjusted to the previous state, and the heating current applied between the melting raw material and the printing body is closed;

step S6, the heating intensity of the printing body by the magnetic field is kept unchanged, and no heating current is applied between the melting raw material and the printing body;

step S7, judging whether the forming of the current layer is finished; if not, go to step S8, otherwise go to S9;

step S8, the next voxel is formed, and the process advances to step S3;

step S9, determining whether three-dimensional printing has been completed; if not, the induction coil and the molten material generating apparatus are moved away from the newly formed layer of the print body (i.e., moved in the Z direction) by a distance of one layer height or thickness, and then the process proceeds to step S2 to form a new layer; if it is completed, proceed to step S10;

step S10, terminating the generation of the molten raw material and closing the magnetic field;

the XY plane refers to a molding reference plane of the three-dimensional printing equipment, and the Z direction refers to a direction perpendicular to the XY plane. For example: when a horizontal plane is taken as a forming reference plane, each layer of the printing body is a parallel plane of the horizontal plane, and the Z direction is a vertical direction.

Optionally: the main steps of three-dimensional printing include:

step S2, accumulating the melting raw material (n is more than or equal to 1) on the nth layer of printing body, and starting the molding of the (n + 1) th layer; the magnetic field heating the print body at an intensity insufficient to melt a region of the print body where molten material is about to accumulate and is accumulating;

step S3 of accumulating the molten raw material in a region where the voxel and the print body are not connected in a molten manner according to the properties of the computer model data, keeping the heating intensity of the magnetic field to the print body constant, and not applying a heating current between the molten raw material and the print body; until all the zones that do not need to be joined in a molten manner have accumulated molten raw material;

step S4, accumulating molten raw material in a region where voxels and print bodies need to be connected in a molten manner according to the properties of the computer model data; melting a region of the upper surface of the print body, which is in contact with the molten raw material, during the accumulation of the molten raw material; melting the area of the printing body by enhancing the heating intensity of the magnetic field to the printing body and/or applying current auxiliary heating between the melting raw material and the printing body; until all the areas to be joined in a molten manner have accumulated molten raw material;

step S6, determining whether three-dimensional printing has been completed; if not, the induction coil and the molten material generating apparatus are moved away from the newly formed layer of the print body (i.e., moved in the Z direction) by a distance of one layer height or thickness, and then the process proceeds to step S2 to form a new layer; if it is completed, proceed to step S7;

step S7, terminating the generation of the molten raw material and closing the magnetic field;

The invention has the following beneficial effects:

(1) the invention realizes the connection between the melting raw material and the printing body in a melting way by melting the position of the printing body, which is to accumulate the melting raw material, and/or melting the position of the printing body, which is accumulating the melting raw material, in an electromagnetic induction heating way, thereby obtaining extremely high interlayer bonding force and extremely high structural strength.

(2) The invention controls whether the contact part of the printing body and the melting raw material is melted or not by adjusting the heating intensity of the induction magnetic field to the printing body which is printed and formed and/or applying current between the melting raw material and the printing body to assist in heating, and further controls whether the layers of the specific area of the printing body are connected in a melting way or not; the interlayer bonding force of the regions connected in a non-melting mode is low, the regions with the low interlayer bonding force can be used as auxiliary supporting bodies and can be detached, and printing of complex structures can be achieved.

(3) The invention can adopt linear solid raw materials (such as metal wires), and compared with powdery raw materials adopted by the existing mainstream technology, the cost of the linear raw materials is low; when the solid raw material is metal, the metal three-dimensional printing can be realized, and compared with the existing metal three-dimensional printing technology, the metal three-dimensional printing method is low in cost.

(4) If the linear solid raw material is adopted, the movement of the solid linear raw material drives the movement of the molten raw material, the molten raw material is contacted with the formed printing body, mechanical acting force exists in the contact process, gas between pixel points and between the forming layer and the formed layer before is driven away, gaps are filled, and a 'gap network' between the pixel points and between the layers is few (the 'gap network' structure is generally existed in the existing selective laser melting technology SLM and electron beam melting technology EBM which adopts a mode of spreading a metal powder layer); thus, the density of the parts printed using the techniques of the present invention is high. The forming accuracy of the present invention depends mainly on the volume or granularity of the accumulated molten raw material, and the droplet size of the accumulated molten raw material can be controlled to achieve three-dimensional printing with a desired accuracy.

(5) The invention can control the accumulation position of the melting raw material through a three-dimensional or multi-axis motion mechanism to realize large-format three-dimensional printing and forming (for example, 5m multiplied by 5m), which is difficult to realize by the prior SLM/EBM and other technologies.

(6) When the conductive material is used for three-dimensional printing, a high-power laser system (the high-power laser system is expensive, and the service life of a laser is generally within ten thousand hours) is not needed, the implementation cost is low, and the production cost and the use cost are low; the printing and forming can be carried out under vacuum and non-vacuum environments without a complex electron beam system, and the printing and forming device can also be applied to space environments.

(7) The material used by the invention has wide selection range, and the solid material which can induce eddy current under the action of a magnetic field can be used for the specific embodiment of the invention, so that the problem of narrow material selection range caused by the fact that the raw material reflects heating energy or the heating energy absorption rate is low in the existing mainstream technology (such as SLM/EBM/LENS) is solved; common materials (e.g., aluminum, copper, iron, stainless steel, nickel-base superalloys, titanium, rhenium, molybdenum, tungsten, cermets) are suitable for use in embodiments of the present invention.

(8) In the process of accumulating the molten raw materials on the basis of the printing body, the molten raw materials only contact with the unmelted solid raw materials and the printing body, and do not contact with any other structures. The heat carried by the molten feedstock does not damage other structures and therefore the present invention can be used with very high melting point conductive materials such as tungsten (melting point about 3400 c). Compared with the prior three-dimensional printing technology adopting a micro smelting furnace to melt printing raw materials, the three-dimensional printing technology can use the printing raw materials which are limited by the performance of the micro smelting furnace and cannot print high-temperature materials such as molybdenum and tungsten.

(9) In the process of accumulating the molten raw materials on the basis of the printing body, the electrical connection is established between the molten raw materials and the printing body, and the forming process of each voxel (three-dimensional pixel point) can be monitored.

In conclusion, the invention has the beneficial effects that: the interlayer bonding force of the printing body is high, and the structural strength of the printing body is high; the detachable auxiliary supporting body can be synchronously generated to realize the printing of a complex structure; the structure is simple, and large components can be printed; the moulding process of each voxel is monitored; the three-dimensional printing of conductive materials such as metal, metal ceramic, plastic mixed with metal powder and the like can be realized by using various types of applicable materials; the cost is low. The invention has substantial progress.

Drawings

FIG. 1 is a schematic diagram illustrating the magnetic field generated by an induction coil, wherein the induction coil is shown in cross-section;

FIG. 2 is a schematic diagram illustrating the principles of a first embodiment of the present invention, wherein arrow D1 indicates the direction of movement of the solid feedstock and arrow D2 indicates the movement of the induction coil for induction heating with the solid feedstock relative to the print body;

FIG. 3 is a perspective three-dimensional view illustrating an induction coil used in the first embodiment of the present invention;

FIG. 4 is a top view of the induction coil shown in FIG. 3;

FIG. 5 is a perspective three-dimensional view illustrating an induction coil and a solid feedstock guiding apparatus used in a second embodiment of the present invention;

FIG. 6 is a side view of the device shown in FIG. 5;

FIG. 7 is a top view of the device shown in FIG. 5;

fig. 8 and 9 are schematic views for explaining the position state of the induction coil, in which arrows D3 and D4 indicate the moving direction;

FIG. 10 is a schematic diagram illustrating a third embodiment of the present invention using powdered solid material, wherein arrow D5 indicates the direction of movement of the powdered solid material and arrow D6 indicates the movement of the induction coil for induction heating together with the solid material relative to the print body;

wherein the reference numbers: 1-magnetic field, 2-coil one, 3-linear solid raw material one, 4-printing body one, 5-molten raw material, 6-melting zone one of printing body, 7-coil three, 8-coil electrode one, 9-coil electrode two, 10-coil electrode three, 11-coil electrode four, 12-coil two, 13-solid raw material guiding device, 14-cooling interface, 15-linear solid raw material two, 16-nozzle, 17-powdery solid raw material, 18-molten liquid drop raw material, 19-melting zone two, 20-molten raw material deposited on printing body, 21-printing body two.

Detailed Description

The following describes three preferred embodiments of a three-dimensional printing method according to the present invention in detail with reference to the accompanying drawings.

Fig. 1 to 4 show a first preferred embodiment of a three-dimensional printing method according to the present invention: a three-dimensional printing method mainly comprises the following steps: placing molten raw materials (namely, molten raw materials 5) into a forming area used by a three-dimensional printing device, accumulating the molten raw materials in the forming area to be converted into a printing body, accumulating the molten raw materials on the basis of the printing body (namely, the printing body-4) until an object to be printed is formed, and forming the object to be printed by the accumulated printing body; wherein: 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, that is, by the computer model data corresponding to the object to be printed; the forming area used by the three-dimensional printing equipment refers to a space used by the three-dimensional printing equipment when printing an object; the molten raw material accumulates in the molding zone and is converted into a print body due to the temperature decrease;

the key technology is as follows:

in the process of accumulating the molten raw material, the position of the printing body where the molten raw material is to be accumulated is melted or softened by means of electromagnetic induction heating, and the position of the printing body where the molten raw material is being accumulated is melted or softened.

Melting the position of the print body where the molten raw material is accumulating as described above, it is possible to achieve fusion bonding between the newly accumulated molten raw material and the print body (the print body is formed by the previously accumulated molten raw material as the temperature is lowered and changed into a solid state), thereby achieving high-strength interlayer bonding.

In this particular embodiment: an induction magnetic field used in electromagnetic induction heating of a print body, the range of action of the induction heating thereof is controlled and the heating intensity of the induction magnetic field is controlled. The range of action of the induction heating includes an action area, a shape of a heating region of the magnetic field on the print body, and the like. The heating intensity of the induction magnetic field is determined by parameters such as magnetic field intensity, heating time, magnetic field frequency and the like.

In this particular embodiment: the induction magnetic field used when the print body is electromagnetically induction heated can be adjusted in the state of the area and/or shape of the heating region of the print body in the molten material accumulation path. The state of the shape mainly includes a shape type, a direction of the shape, a layout/distribution manner of the shape, and a dynamic change of the shape.

In this particular embodiment: the molten raw material is obtained by heating and melting a solid raw material by means of electromagnetic induction heating, as shown in fig. 2.

In this particular embodiment: the above-mentioned method of heating and melting a solid raw material by using electromagnetic induction heating to obtain a molten raw material is produced by: when the solid raw material passes through or passes through the electromagnetic induction heating magnetic field, the electromagnetic induction heating magnetic field induces eddy current on the solid raw material to heat and melt the solid raw material.

In this particular embodiment: the above-mentioned molten raw material obtained by heating and melting the solid raw material by means of electromagnetic induction heating is not in contact with any other structure except the printed body and the solid raw material in the process of accumulating the molten raw material on the basis of the printed body, as shown in fig. 2.

In this particular embodiment: the molten raw material is obtained by heating and melting a solid raw material, which is a linear solid raw material (e.g., a wire), by using an electromagnetic induction heating method.

In this particular embodiment: the electromagnetic induction heating magnetic field used for heating the solid raw material to be converted into the molten raw material and the electromagnetic induction heating magnetic field used for heating the printing body are both generated by the same magnetic field generating device.

In this particular embodiment: the printing body is melted or softened by an electromagnetic induction heating mode, namely the surface of the printing body is heated and melted or softened.

In this particular embodiment: adjusting the action area and/or shape state of an electromagnetic induction heating magnetic field which generates heating action on the printing body in a part of printing area, so that the printing body in the area distributed on the accumulation path of the melting raw material is not melted or softened by electromagnetic induction heating; in addition, the heating intensity of the electromagnetic induction heating magnetic field to the printing body can be adjusted. The partial printing area refers to a part of the space occupied by the molten raw material and the printing body in the process of printing the object. The partial print area may also be understood as: the object to be printed is mapped to a portion of a mapping space formed by a molding zone used by the three-dimensional printing apparatus. The partial print area may also be understood as: dividing the space occupied by the object to be printed in the future in advance to form a virtual object which is in a mapping relation with the object to be printed, gradually converting the virtual object into a real object which is finally printed and molded, wherein the process of converting the virtual object into the real object is a three-dimensional printing and molding process; dividing the virtual object into a plurality of areas, wherein the partial area is the partial printing area. The state of the shape mainly includes a shape type, a direction of the shape, a layout/distribution manner of the shape, and a dynamic change of the shape.

In this particular embodiment: the heating intensity of the electromagnetic induction heating magnetic field on the printing body is controlled to control the melting state of the area of the printing body, which is in contact with the melting raw material, and further control the connection mode between the printing body and the melting raw material. The molten state includes molten, non-molten, semi-molten, softened and the like states. The connection mode can be divided into two types of fusion connection and non-fusion connection. When the area of the printing body in contact with the molten raw material is in a molten state, fusion in a molten connection manner is realized between the molten raw material and the printing body, so that high-strength connection is realized (in the case of printing a metal material, metallurgical-grade connection is also realized). When the region of the print body in contact with the molten raw material is in a non-molten state, the molten raw material and the print body are connected to each other in a non-molten state, and the lower the temperature of the region of the print body in contact with the molten raw material is, the lower the connection strength therebetween is. The structural strength of the printing area generated by accumulating the molten raw materials in a non-molten connection mode (the molten raw materials in unit volume form voxel/three-dimensional pixel points) is low, so that the printing area with low structural strength can be used as a detachable auxiliary support (bracket) to realize three-dimensional printing of a complex structure.

In this particular embodiment: in the process of accumulating the molten raw material, the molten raw material and the print body are connected to a control circuit, and an electric current is applied between the molten raw material and the print body. Applying an electric current between the molten raw material and the print can obtain a number of benefits, such as: the temperature of the molten raw material and the temperature of the part of the printing body, which is in contact with the molten raw material, can be adjusted through the current, and the contact state between the molten raw material and the printing body can be monitored by monitoring the current.

In this particular embodiment: an electrical connection is established between the print body and the molten raw material, and the state of contact between the print body and the molten raw material is determined by determining the state of electrical connection between the print body and the molten raw material. For example: whether contact occurs or not and the degree of the contact are judged through the resistance value or the capacitance value between the two, and the accumulated position of the molten raw material is changed on the premise of ensuring the contact between the two, so that the effective accumulation of each voxel (namely pixel point) in the three-dimensional forming process is ensured. During three-dimensional printing, a first layer of the printed body is accumulated on a conductive support platform (not shown in the figures). The conductive support platform and the linear solid material (using metal wires) are connected to the control circuit, and electrical connection is established between the print body and the molten material because the print body is in contact with the conductive support platform and the molten material is in contact with the solid material.

In this particular embodiment: the position and/or structure of the induction magnetic field generating device can be adjusted by the induction magnetic field used when the printing body is heated by electromagnetic induction. The position state mainly refers to the position of the induction magnetic field generating device and the position change caused by the motion modes of movement, rotation, lifting, descending, swinging, vibration and the like. The structural state mainly refers to the shape, structural composition, structural combination and change of the induction magnetic field generating device.

In this particular embodiment: the printing body is melted or softened by an electromagnetic induction heating mode, a magnetic field generating an electromagnetic induction heating effect is generated by an induction coil (namely, the coil I2), and current in the induction coil is driven by an oscillating circuit.

In this particular embodiment: and adjusting the distance between the induction coil and the surface of the printing body, or adjusting the intensity of current flowing through the induction coil, or adjusting the on-off frequency of the current flowing through the induction coil, or adjusting the oscillation frequency of the current flowing through the induction coil so as to realize the adjustment of the heating action intensity of the magnetic field on the surface of the printing body.

In this particular embodiment: the energizing area of the induction coil is adjustable. The induction coil is composed of different sections, and certain sections can be controlled to pass current, and certain sections can be controlled to not pass current. The induction coil (i.e., coil one 2) shown in fig. 3 and 4 is formed by connecting 3 segments.

In this particular embodiment: the forming area used by the three-dimensional printing device is vacuumized, and a protective atmosphere (such as inert gas) can be filled in the forming area.

In this particular embodiment: and a gas removing device is arranged in the forming area used by the three-dimensional printing equipment, and specific gas is removed in a chemical reaction mode. For example: arranging an unsealed high-temperature heating container in the sealed forming area, and placing active metal powder (such as iron powder with the particle size of 10 microns) in the container; after the forming area is vacuumized (for example, the air pressure is reduced to below 10 Pa), the powder is heated to 600 ℃, the iron powder and the residual oxygen in the forming area are subjected to chemical reaction to generate iron oxide, and the oxygen is removed, so that the oxidation of the oxygen to the high-temperature molten raw material in the three-dimensional printing process is avoided. Another example is: pure aluminum metal is placed in a high-temperature heating container, the high-temperature heating container is heated to be more than 800 ℃, aluminum reacts with nitrogen and oxygen in a forming area to generate aluminum nitride and aluminum oxide, and therefore nitrogen and oxygen are removed.

In this particular embodiment: the main steps of three-dimensional printing include:

step S4, accumulating molten raw material in a region where voxels and print bodies need to be connected in a molten manner according to the properties of the computer model data; melting a region of the upper surface of the print body, which is in contact with the molten raw material, during the accumulation of the molten raw material; melting the area of the printing body by enhancing the heating intensity of the magnetic field to the printing body and applying current to assist heating between the melting raw material and the printing body; until all the areas to be joined in a molten manner have accumulated molten raw material;

the XY plane refers to a molding reference plane of the three-dimensional printing equipment, and the Z direction refers to a direction perpendicular to the XY plane. For example: when a horizontal plane is taken as a forming reference plane, each layer of the printing body is a parallel plane of the horizontal plane, and the Z direction is a direction perpendicular to the horizontal plane.

In this particular embodiment: the moving path of the solid raw material is guided by a guiding device (not shown in the drawing) in the process of entering the electromagnetic induction heating magnetic field.

The specific application scheme is as follows:

fig. 1 illustrates a schematic form of a high-frequency magnetic field (i.e., magnetic field 1) generated by an induction coil (i.e., coil one 2) used in the present embodiment. The conductive material induces eddy currents in a high frequency alternating magnetic field. The eddy current forms a loop inside the conductive material and causes resistive heating inside the material. The higher the frequency of the magnetic field is, the more significant the skin effect it produces when heating the conductive material, namely: the higher the frequency of the magnetic field, the more the heated region of the conductive material tends toward the surface of the conductive material; even when the heating power is sufficiently high, the surface of the conductive material has been melted, but its internal center temperature is still close to the ambient temperature for a short time.

Fig. 2 illustrates the basic principle of this embodiment: the solid raw material is a linear conductive material (i.e. linear solid raw material one 3), for example, a titanium metal wire with a wire diameter of 0.1mm is used; the induction coil (i.e., the coil one 2) and the solid raw material (i.e., the linear solid raw material one 3) are driven to move (e.g., a moving direction shown by an arrow D2) by a position control subsystem of the three-dimensional printing apparatus, and the solid raw material (i.e., the linear solid raw material one 3) is driven to move in a vertical direction (e.g., a moving direction shown by an arrow D1) by a raw material conveying device (not shown in the drawings); when the solid raw material (i.e. the linear solid raw material one 3) passes through the center of the induction coil (i.e. the coil one 2), the magnetic field 1 induces eddy current on the solid raw material, and the eddy current generates heat to melt the section of the solid raw material passing through the magnetic field to generate molten raw material (i.e. the molten raw material 5); as the solid raw material moves along the moving direction indicated by the arrow D1, the melting section is pushed away from the induction coil by the unmelted section, and the subsequent solid raw material is melted while passing through the magnetic field to continuously generate new molten raw material, so as to visually form a 'molten raw material flow'; the molten raw material (i.e., the molten raw material 5) is joined with the unmelted solid raw material (i.e., the linear solid raw material one 3); the molten raw material is accumulated in the moving direction indicated by the arrow D2 by the unmelted solid raw material, and the induction coil (i.e., coil one 2) is moved up by one layer after each layer is accumulated (the height or thickness of the layer is set by the user); the accumulated molten raw material becomes a solid state after the temperature is reduced and is converted into a printing body (i.e., printing body one 4), and the newly generated molten raw material continues to be accumulated on the previously formed layer of the printing body to form a new layer until the three-dimensional printing is finished; in the area needing to be connected in a melting mode, the high-frequency magnetic field generated by the induction coil (namely, the coil one 2) melts the position, on the upper surface of the printing body (namely, the printing body one 4), where the molten raw materials are to be accumulated and the position, where the molten raw materials are accumulated, of the upper surface of the printing body, the position, where the molten raw materials are accumulated, is also heated by the current applied between the molten raw materials and the printing body (optional, determined by parameters set by a user of the three-dimensional printing device), a melting area one 6 of the printing body is formed, and the molten raw materials are accumulated on the melting area one 6 of the printing body, so that the molten; after the magnetic field is removed or turned off, the melted region one 6 of the print body and the molten material accumulated thereon are solidified by the heat conducted away.

During the process of accumulating the molten raw material (i.e., the molten raw material 5) on the basis of the print body (i.e., the print body one 4), the molten raw material comes into contact with only the unmelted solid raw material (i.e., the linear solid raw material one 3), the print body, and does not come into contact with any other structure. The heat carried by the molten feedstock does not damage other structures, so this embodiment may use a very high melting point conductive material such as tungsten (melting point about 3400 ℃). Compared with the three-dimensional printing technology adopting the micro smelting furnace to melt the printing raw materials, the three-dimensional printing technology can use the printing raw materials which are limited by the performance (such as temperature resistance) of the micro smelting furnace, and high-temperature materials such as molybdenum and tungsten cannot be printed.

In this particular embodiment, the induction coil is made up of 3 sections (coil one 2 as shown in fig. 3 and 4), namely: the coil I2 is divided into 3 sections which are connected in sequence by a coil electrode I8, a coil electrode II 9, a coil electrode III 10 and a coil electrode IV 11; the coil electrode I8 and the coil electrode II 9 control the innermost circle of the coil I2, the coil electrode I8 and the coil electrode III 10 control the inner circle of the coil I1.5, and the coil electrode I8 and the coil electrode IV 11 control the whole of the coil I2. The first coil 2 is made of a metal tube. The coil-2 generates heat in the operating state, and cooling liquid needs to be communicated with the internal channel of the coil-2 to cool the coil-2. The area of action of the induced magnetic field (i.e., the magnetic field 1) on the printing body one 4 is adjusted by changing the operating section of the coil one 2.

In the present embodiment, the heating time period of the same area of the surface of the printing body by the induction magnetic field (i.e., the magnetic field 1) is adjusted by changing the action area of the induction magnetic field on the printing body (i.e., the printing body one 4) and controlling the moving rate of the induction coil (i.e., the coil one 2), that is: when the moving speed of the magnetic field is not changed, the larger the action area is, the longer the time that the same area is covered by the magnetic field is; the slower the field movement rate, the longer the same area is covered by the field. The longer the surface of the print body is heated by the magnetic field, the higher the temperature of the heated area, provided that the magnetic field strength and frequency are constant. The temperature and the melting state of the surface of the printing body in a specific printing area are controlled by regulating the heating time of the induction magnetic field on the printing body and regulating the magnetic field intensity. The corresponding parameters may take the form of empirical values: empirical values were obtained and formed by multiple trials.

In this embodiment, when the layers of some printed areas need to be connected in a fusion manner, the surface of the printed body is melted during the molding of the printed areas to obtain extremely high structural strength. When a low strength connection is required between layers of some printing areas (even loose connection), the surface of the printing body is not melted during the molding process of the printing areas, and the temperature difference between the surface of the printing body and the molten raw material is larger, and the bonding force between the surface of the printing body and the molten raw material is lower; can regard as supplementary support/support with the printing body or the printing region of low joint strength, demolish supplementary support/support after three-dimensional printing finishes, can realize the printing of complicated structure like this.

Because the volume of the section of the solid raw material (i.e., the linear solid raw material one 3) located in the induction magnetic field is small, the volume of the printing body (i.e., the printing body one 4) is large, so that the heat quantity required when the solid raw material and the printing body are melted is large, and therefore, the solid raw material can be melted without melting the printing body. The corresponding parameters may take the form of empirical values: empirical values were obtained and formed by multiple trials.

In this embodiment, both the solid feed and the print are connected to the control circuit. When the molten material contacts the print body, the control circuit monitors that the molten material contacts the print body, and then moves the molten material to form the next location or voxel. In the embodiment, when the layers of some printing areas need to be connected in a melting mode, a current with specific intensity is applied between the melting raw material and the printing body in the forming process of the printing areas so as to enhance the melting of the surface of the printing body, and therefore more flexible control is achieved compared with the mode of simply using a magnetic field heating mode. The boiling point of most metallic materials is much higher than the melting point (e.g., titanium metal has a melting point of about 1660 c and a boiling point of about 3290 c). During the formation of each voxel (three-dimensional pixel), a large current (e.g., 50 amperes/0.1 mm diameter of molten raw material) can be applied in a very short time (e.g., 1 microsecond) to assist the magnetic field heating to instantaneously melt the region of the print body in contact with the molten raw material. The corresponding parameters may take the form of empirical values: empirical values were obtained and formed by multiple trials.

In this embodiment, after the molten material is accumulated on the print body, because the molten material moves from the central position of the induction coil to the print body and accumulates, the newly formed voxel (i.e., pixel point) and its neighboring area are still within the coverage of the induction magnetic field for a certain period of time; thus, the rate of movement of the induction coil can be controlled to control the rate of cooling (i.e. the annealing rate) of the newly formed voxel and its adjacent regions. Since the molten raw material moves from the center position of the induction coil toward the print body and accumulates, a region of the upper surface of the print body where the molten raw material is to accumulate is preheated in advance.

The embodiment can be used for three-dimensionally printing common parts made of conductive solid materials, such as tungsten (melting point 3400 ℃), stainless steel, titanium alloy, aluminum alloy and copper. The problem that the existing mainstream metal three-dimensional printing technology (such as SLM/EBM/LENS) chooses materials (namely, the raw materials have the problems of low reflection or absorptivity on heating energy, and the like, so that the usable material types are limited) does not exist.

The second preferred embodiment of a three-dimensional printing method according to the present invention as shown in fig. 5 to 9 is mainly different from the first embodiment of the present invention in that: the area of the action region of the induction magnetic field on the printing body is unchanged, but the distribution mode of the action region of the induction magnetic field on the printing body can be adjusted by rotating the induction coil (namely, the second coil 12); the heating time of the printing body distributed in the area where the molten raw material is to be accumulated on the molten raw material accumulation path is adjusted by adjusting the distribution manner of the action area of the induction magnetic field on the printing body (under the condition that the moving speed of the induction coil is not changed), so that the melting state of the area where the molten raw material is accumulated is adjusted. The second coil 12 is also made of a metal tube, and the inner passage is used for passing cooling liquid.

In the present embodiment, the solid raw material (i.e., the second linear solid raw material 15) is guided in its moving direction by the solid raw material guide device 13 before being heated and melted by the induction magnetic field, and the induction coil (i.e., the second coil 12) is rotated about the solid raw material guide passage of the solid raw material guide device 13. The solid raw material guide 13 is provided with a cooling passage for cooling the solid raw material guide 13. The cooling channel of the solid material guiding device 13 is connected to an external cooling system via a cooling connection 14. The induction coil (i.e., coil two 12) is approximately rectangular.

By rotating the induction coil, the heated time length of the printing body distributed in the area on the molten raw material accumulation path where the molten raw material is to be accumulated is adjusted, as shown in fig. 8 and 9: arrows D3 and D4 indicate the moving direction of the induction coil and the solid raw material in the XY plane (non-vertical direction), i.e., the accumulating direction of the molten raw material; when the long side of the induction coil (approximately rectangular) is parallel to the moving direction D3, the heated time period of the region where the molten raw material is accumulated is the largest (that is, the heating time period of the mapped region of the path where the molten raw material is accumulated on the upper surface of the print body is the longest); when the long side of the rectangular induction coil is perpendicular to the moving direction D4, the heated time period of the region where the molten raw material is accumulated is shortest (that is, the heating time period of the mapped region of the path where the molten raw material is accumulated on the upper surface of the print body is shortest).

In the process of accumulating the molten raw material on the basis of the printed body, the molten raw material is only contacted with the unmelted solid raw material (i.e. the linear solid raw material two 15) and the printed body, and is not contacted with any other structures. The heat carried by the molten feedstock does not damage other structures, such as the solid feedstock directing device 13, and therefore this embodiment may use a very high melting point conductive material, such as tungsten (melting point about 3400 ℃). Compared with the prior three-dimensional printing technology adopting a micro smelting furnace to melt printing raw materials, the three-dimensional printing technology can use the printing raw materials which are limited by the performance of the micro smelting furnace and cannot print high-temperature materials such as molybdenum and tungsten.

Fig. 10 shows a third preferred embodiment of a three-dimensional printing method according to the present invention: the solid raw material is a powdery raw material (i.e., powdery solid raw material 17); the powdery solid raw material 17 is ejected through the nozzle 16 (belonging to the solid raw material guide means) in the direction indicated by the arrow D5, and is heated by the magnetic field into a molten raw material (i.e., a molten droplet-like raw material 18) while passing through the central region of the induction coil (i.e., coil three 7); the surface of the printing body (namely, the second printing body 21) accumulating the melting raw materials is heated and melted by the magnetic field to form a second melting area 19 of the printing body; the melting raw material 20 deposited on the print body is solidified and then transformed into the print body; the molten raw material accumulates in the direction indicated by the arrow D6. The main differences between this embodiment and the first embodiment of the present invention are: the solid raw material adopts powdery raw material (namely, powdery solid raw material 17), and gas is used for pushing the powdery raw material to be sprayed; no current is applied between the molten feedstock and the print. This embodiment may use conductive powdered solid raw materials, such as: high melting point cermet powders, such as titanium carbide (melting point about 3000 ℃ C., useful in aerospace applications), are used to allow three-dimensional printing of parts of such materials. In this particular example, the molten feedstock is in contact with the print only.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and should not be taken as limiting the scope of the present invention, which is intended to be covered by the appended claims and equivalents thereof.

Claims

1. A three-dimensional printing method mainly comprises the following steps: placing the molten raw materials into a forming area used by the three-dimensional printing equipment, accumulating the molten raw materials in the forming area and converting the molten raw materials into a printing body, and accumulating the molten raw materials on the basis of the printing body until an object to be printed is formed; wherein: 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 equipment refers to a space used by the three-dimensional printing equipment when printing an object;

the method is characterized in that:

melting or softening the position of the printing body where the melting raw materials are accumulated in the process of accumulating the melting raw materials by an electromagnetic induction heating mode, and/or melting or softening the position of the printing body where the melting raw materials are accumulating;

in the process of accumulating the molten raw material on the basis of the printed body, the molten raw material is not in contact with any other structure except the printed body, or is not in contact with any other structure except the printed body and the solid raw material;

the molten raw material is obtained by heating and melting a solid raw material by using an electromagnetic induction heating mode;

when the solid raw material passes through or passes through the electromagnetic induction heating magnetic field, the electromagnetic induction heating magnetic field induces eddy current on the solid raw material to heat and melt the solid raw material; the solid raw material adopts a linear solid raw material, when the linear solid raw material passes through an electromagnetic induction heating magnetic field, the electromagnetic induction heating magnetic field leads the linear solid raw material to pass through a section of the electromagnetic induction heating magnetic field to be melted so as to generate a molten raw material, and the molten raw material is connected with the unmelted solid raw material; or, the solid raw material is a powdery solid raw material which is sprayed out through a nozzle and is heated into a molten raw material when passing through the electromagnetic induction heating magnetic field;

alternatively, the electromagnetic induction heating magnetic field used for heating the solid raw material to melt the raw material and the electromagnetic induction heating magnetic field used for heating the print body are the same magnetic field.

2. The three-dimensional printing method according to claim 1, characterized in that:

the partial printing area is a part of the space occupied by the molten raw material and the printing body in the process of printing the object; the partial print area may also be understood as: the object to be printed is mapped to a portion of a mapping space formed by a molding zone used by the three-dimensional printing apparatus.

3. The three-dimensional printing method according to claim 1, characterized in that:

an electrical connection is established between the print body and the molten feedstock, and/or an electrical connection is established between the print body and the solid feedstock.

4. The three-dimensional printing method according to claim 1, characterized in that:

the position and/or structure of the induction magnetic field generating device can be adjusted by the induction magnetic field used when the printing body is heated by electromagnetic induction.

5. The three-dimensional printing method according to claim 1, characterized in that:

and a gas removing device is arranged in the forming area used by the three-dimensional printing equipment, and specific gas is removed in a chemical reaction mode.

6. The three-dimensional printing method according to claim 1, characterized in that:

and establishing electrical connection between the printing body and the solid raw material, applying current between the printing body and the solid raw material, and melting the solid raw material through resistance heating and electromagnetic induction heating.