CN111873414A

CN111873414A - Special slit self-sealing powder spreading device for three-dimensional printer

Info

Publication number: CN111873414A
Application number: CN202010331480.5A
Authority: CN
Inventors: 吴小平; 罗天珍
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-05-03
Filing date: 2020-04-24
Publication date: 2020-11-03

Abstract

A slit self-sealing powder spreading device special for a three-dimensional printer belongs to the field of machinery. The main structure comprises: the device comprises a forming cylinder, a powder spreading device, an electronic module, a mechanical system, a shell, a touch display screen, a printing platform, an ink jet head or a laser scanning device; the method is characterized in that: the powder spreading device comprises a slit funnel and a seam edge scraper; in the powder spreading process, the forming cylinder and the powder spreading device are kept in a controlled relative motion state, wherein the relative motion state comprises that the forming cylinder moves while the powder spreading device is not moved, or the forming cylinder is not moved while the powder spreading device moves, or both the forming cylinder and the powder spreading device move; the basic construction of a slit funnel comprises: the device consists of 2 side plates with the distance of 0.2-10 mm, and 1 long and narrow rectangular slit opening is formed when being observed from the direction right below the slit funnel opening; defining a distance between the slit opening and the forming cylinder so that the slit opening directly touches the powder layer surface of the forming cylinder; the invention has simple structure, has the most important advantage of high efficiency which can be improved by more than 2-3 times, and has popularization and application values.

Description

Special slit self-sealing powder spreading device for three-dimensional printer

[ technical field ]

The invention belongs to the technical field of machinery, and particularly relates to a method for quickly spreading powder layer by layer, which is special for laser sintering and spray-bonding type 3D printing.

[ background art ]

At present, a 3D printer for sintering powder layer by layer and bonding powder layer by layer is increasingly used as an important means for industrial processing, and a powder laying technology and a powder laying device directly affect the printing speed and the printing quality of a workpiece, most of powder laying devices of the existing powder 3D printer are piston bin type powder storage and powder up-down type powder supply devices capable of lifting, the powder is collected or dropped in front of a flat powder scraping sheet by the powder laying devices to be piled into a hill-shaped strip-shaped powder pile with the thickness of dozens of layers, then the powder scraping sheet (also called a scraper) is required to push the powder pile horizontally to lay the powder evenly, and because the structure of a printed (sintered or bonded) formed object on the upper layer cannot be disturbed absolutely, a tiny forming structure without a firm root base of a shallow part of a forming bin can be displaced when the powder pile is too high or the powder laying speed is too high, the scraper speed has to be reduced, relatively thin fine printing is more severe, and for medium-sized printing rulers, the process takes as long as even 40 seconds to 2 minutes, resulting in extremely slow powder spreading speed and low efficiency.

Detailed technical background: the Three-dimensional printing technology (3DP, Three-dimensional printing) is mainly powder binding molding. The specific process of 3DP is: after each layer is bonded, the piston of the forming cylinder descends for a distance (equal to the layer thickness), the powder supply cylinder ascends for a certain height, a certain amount of powder is pushed out, the powder is pushed to the forming cylinder by the powder paving roller, and the powder is paved and compacted. The nozzle moves under the control of computer according to the two-dimensional geometrical information of the next section, and the adhesive is selectively sprayed to finally form a layer. The principle is very similar to that of a printer, namely, the source of the name of three-dimensional printing. And when the powder spreading roller spreads the powder, the redundant powder is collected by the powder collecting device. The powder is fed, spread and sprayed with the binder repeatedly, and finally the three-dimensional powder is bonded, so that the product is produced.

The 3DP technique is mature. In 1989, EmanualSachs et al, Massachusetts, USA, filed the 3DP patent, which is one of the core patents in the domain of droplet ejection forming of non-forming materials. Manufacturers using 3DP technology, mainly Zcorporation (3 DSsystems, 2011), Ex-One, Rikon institutto, Japan, and others, mainly zprinter, R series three-dimensional printers. The ObjectGeometries (acquired 2012 by Stratasys) in Israel 2000 introduced a printing device Quadra based on a combination of 3Dink-Jet and SLA processes. The 3DP printing equipment can be used with a large number of materials, including plaster, plastic, ceramic, metal, etc., and can also print colored parts, and parts with complex shapes inside can be formed. Such printers increase speed by multiple impact heads and nozzles. In China, the Qinghua university, the SiAn transportation university, the Shanghai university and the like are also actively researched and developed at present. 3DP shaping speed is fast, can make the colored prototype. The 3DP technology has high forming speed and low forming material price, and is suitable for being used as desktop type rapid forming equipment. Meanwhile, due to the addition of pigment in the binder, a color prototype can be made, which is one of the most competitive features of the process. The whole forming process does not need to be supported, the removal of redundant powder is convenient, and the method is particularly suitable for making prototypes with complicated inner cavities. Of course, the 3DP formed part has low strength, so that only a conceptual model can be made, and a functional test part cannot be made. The 3DP technology has been widely used in the fields of foreign home appliances, automobiles, aerospace, ships, industrial design, medical treatment, and the like. The 3DP technology is mostly adopted for the mainstream full-color 3D portrait printing in the current market.

The metal 3D printing SLS technology is the most advanced and potential technology in the 3D printing system. With the requirements of scientific and technological development and popularization and application, the main development direction of rapid prototyping is to directly manufacture metal functional parts by rapid prototyping. The main fast forming methods which can be used for directly manufacturing metal functional parts at present are: laser net shape forming (LENS), Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Direct Metal Laser Sintering (DMLS), and Electron Beam Melting (EBM), among others. The SLS technique uses a laser as an energy source to uniformly sinter a powder on a processing plane by a laser beam. A layer of very thin (submillimeter-level) powder is uniformly spread on a workbench to serve as a raw material, and a laser beam is scanned by a scanner at a certain speed and energy density according to two-dimensional data of a layered surface under the control of a computer. After the laser beam is scanned, the powder at the corresponding position is sintered into a solid sheet layer with a certain thickness, and the non-scanned position still keeps loose powder. This layer is scanned and the next layer is scanned. Repeating the steps until all layers are scanned. Removing the redundant powder, and carrying out appropriate post-treatment such as grinding, drying and the like to obtain the part. SLS techniques are suitable for complex part manufacturing. The SLS technology was first proposed in 1989 by carldecgard and JoeBeaman distributed in ostun, university of texas, and later two established the DTM corporation and began the SLS commercial product sintersarion in 1992. In 2001, DTM was purchased from 3D systems, Inc., completing the technology integration. SLS processable raw materials include plastic powders (nylon, polystyrene, polycarbonate, etc., direct laser sintering), metal powders (direct, indirect and two-component processes), ceramic powders (requiring the use of binders including inorganic, organic and metallic binders). SLS has been successfully applied in many industries, such as automotive, shipbuilding, aerospace, and aviation. In addition to the company DTM, the company EOS in germany also developed a corresponding series of molding apparatuses. In China, such as the university of science and technology in Huazhong, the university of Nanjing aerospace, the university of northwest industry, the North China institute of Industrial science, and Beijing Longyuan automatic molding Co., Ltd, and the like, a lot of important achievements are also obtained, such as RAP-I type laser sintering rapid molding system developed by the university of Nanjing aerospace, AFS-300 laser rapid molding equipment developed by the Beijing Longyuan automatic molding Co., Ltd, and the like. SLS has been successfully applied to various industries such as automobile, shipbuilding, aerospace, aviation, and the like, and mainly relates to links such as rapid prototyping, rapid mold and tool manufacturing, small-batch production, and the like.

The prior powder laying technology has the following defects: the existing powder laying technology comprises a double-cylinder and single-cylinder powder up-falling mode and a scraper or rolling compaction technology, and has strict requirements on powder; meanwhile, the powder paving device has high requirements; the equipment is expensive, the cost of the consumable is high, hundreds yuan or even thousands yuan/KG is often generated; the popularization of the powder 3D printing technology is seriously hindered. Another significant factor affecting popularization is that, in addition to the SLM technology, the density of printed objects of the SLS and 3DP technologies cannot be increased, so that the strength of printed objects of metal and ceramic cannot be guaranteed.

[ summary of the invention ]

The purpose of the invention is as follows:

the powder paving device aims to overcome the defects of low powder paving speed, complex structure, high requirement on the performance of powder and the like of the traditional powder paving technology.

The invention has the characteristics that: simple structure, high powder spreading efficiency, low requirement on the performance of the powder and the like.

The technical scheme of the invention is as follows:

the main structure is as follows: the device comprises a forming cylinder, a powder spreading device, an electronic module, a mechanical system, a shell, a touch display screen, a printing platform, an ink jet head or a laser scanning device; the powder spreading device comprises a slit funnel and a slit edge scraper, the mechanical system comprises a guide rail motor for driving the forming cylinder and the funnel to move, and the electronic module comprises control, motion drive and data interaction; in the powder spreading process, the forming cylinder and the powder spreading device are kept in a controlled relative motion state, and the controlled relative motion state comprises that the forming cylinder moves while the powder spreading device is not moved, or the forming cylinder is not moved while the powder spreading device moves, or both the forming cylinder and the powder spreading device move.

The powder spreading device adopts a slit self-sealing (powder falling) powder spreading scheme taking a slit funnel as a main body, and the necessary conditions of the slit self-sealing powder spreading technical scheme are as follows: the impact force on the surface of the laid powder layer during the slit powder falling process must be kept limited to a certain extent, which requires controlling the following parameters: the width of the slit, the height of the cache powder in the cache powder bin, the oscillation strength of an oscillator on the wall of the slit funnel, and the distance between the funnel opening of the slit funnel and the surface of the powder layer of the forming cylinder; the basic construction of a slit funnel comprises: the slit funnel consists of 2 side plates, end plates and the like with the distance of 0.2-10 mm, and 1 long and narrow rectangular slit opening is formed when being observed from the direction right below the slit funnel opening; a distance between the slit opening and the forming cylinder is defined such that the slit opening directly touches a powder layer surface of the forming cylinder.

From the mathematical, physical principle point of view: the closer the distance between the funnel opening of the slit funnel and the surface of the powder layer of the forming cylinder is (the smaller the distance is, namely the layer height is smaller), the poorer the flowability of the powder is, the smaller the height of the buffer powder is, and the weaker the vibration of the auxiliary oscillator is, the harder the powder in the slit funnel flows out, and even the powder is completely self-sealed (cannot flow out); that is, when the buffer powder is subjected to the resistance of the container wall, the supporting force of the surface of the lower powder layer, the frictional resistance between powder particles and the flowing trend caused by the accumulation of the powder gravity, the powder in the slit funnel cannot naturally flow out (which is the concept of self-sealing), when the slit funnel is moved horizontally, because the surface of the front powder layer is lower than the powder outlet plane of the slit funnel, the powder in the slit funnel can naturally flow out under the action of gravity to fill the space between the surface of the front powder layer and the slit funnel, and a new powder layer is established on the surface of the surfacing forming cylinder.

Further: the shape of the slit edge of the powder outlet plane of the slit funnel is a plane shape or a horn mouth shape. The shape of the bell mouth just meets the characteristics of the conventional SLS and 3DP powder leveling scraper, the slope part facing the powder can well compact and level the powder surface, but the excessive viscous force is easy to cause the surface of the powder layer to generate cracks, and is often necessary for avoiding the vibration.

Further: the powder outlet plane at the edge of the slit funnel directly touches the surface of a new powder layer of the forming cylinder, or a powder pressing roller (cylindrical, the cylindrical surface of the powder pressing roller contacts the surface of the new powder layer) is horizontally arranged, the edge of the lowest cylindrical surface of the powder pressing roller is linearly parallel to the surface of the powder layer and is lower than the powder outlet plane at the edge of the slit, so that the height of the slit funnel is prolonged by the powder pressing roller, and the edge of the lowest cylindrical surface of the powder pressing roller is linearly parallel to the surface of the powder layer; that is to say: the powder from the slit edge of the slit funnel continuously falls to an opening formed by one (the other side is a fixed wall) or two powder pressing rollers for discharging, and a new powder layer is laid; wherein the rolling of the powder compaction roller is used for burdening the compaction and the paving work.

The invention has the beneficial effects that:

compared with the prior art, the invention has simple structure, greatly quickens the powder spreading speed, can improve the powder spreading speed by more than 2-3 times, and has popularization and application values.

[ description of the drawings ]

The invention is further described in the following preferred embodiments with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of the self-sealing principle of a slit funnel.

Fig. 2 is a schematic diagram of the principle of powder spreading by a slit funnel.

Fig. 3 and 4 are schematic diagrams of a special slit self-sealing powder spreading device for the three-dimensional printer.

Description of reference numerals:

(1) slit funnel

(1-1) funnel end plate

(1-2) funnel side plate

(1-3) Oscillator

(1-4) edge-sewing scraper

(2) Self-sealing boundary of powder

(3) Impact strength of powder falling

(4) Powder supply roller

(5) Powder storage tank

(6) Powder roller shaft

(7) Powder supply motor

(8) Guide rail

(9) Slit region

(10) Cross section of funnel end face

(12) Caching powder bin

(13) Forming cylinder

(13-1) piston

(13-2) guide post

(13-3) Cylinder body

(14) Main powder storage bin

(15) Waste powder jar

(16) Linear bearing

(17) Powder paving motor

(18) Lead screw nut

(19) Screw rod

(22) Support frame

(23) Electron and laser scanning system

(24) Cache powder

(25) Main storage powder

(26) Local pressure intensity

(27) Non-filled sand funnel

(28) Sand filling funnel

(29) Front powder layer

(30) Currently laying the powder layer

(31) Slit mouth line

(32) Arrow head

(33) Self-sealing overflow powder

(34) Horizontal impact force

[ examples of embodiment ]

As shown in fig. 1 and 2:

the figure is a section of a slit funnel (1) taken by a plane parallel to its funnel end plate; fig. 1 is a static self-sealing state diagram, and fig. 2 is a state diagram of translational powder spreading.

The slit funnel (1) is composed of: 2 funnel side plates (1-2) and 2 funnel end plates, wherein a plurality of oscillators (1-3) are attached to the funnel side plates (1-2), the oscillators are added in the powder laying process to facilitate the falling of powder in a slit area (9), and a slit edge scraper (1-4) compacts a powder laying layer and lays a current powder laying layer (30); the current powder layer (30) is built on the previous powder layer (29) when advancing along the arrow (32); the magnitude of the horizontal impact force (34) depends on the magnitude of the vertical force of the powder on the powder layer.

The slit funnel (1) is separated into a cache powder bin (12) used for storing cache powder (24) and a main human powder storage bin (14) used for storing main powder storage (25) by a cylindrical powder supply roller (4), the rotation of the powder supply roller (4) can enable the stored powder in the powder storage tank (5) to continuously fall into the cache powder bin (12), the higher the rotation speed is, the faster the powder falling speed is, and the powder quantity can be realized by driving a powder roller shaft (6) by a motor and changing the rotation speed of the powder supply roller (4); the shape of the self-sealing boundary (2) of the powder is determined by the flowability of the powder, the geometric parameters of the slit and the height of the powder in the buffer powder bin. The powder falling impact strength (3) depends on 3 factors: caching the height of powder in the powder bin, the height of the laid powder layer and the powder quality parameters.

As shown in fig. 3 and 4:

the whole slit self-sealing powder spreading device comprises: slit funnel (1), shaping jar (13), useless powder jar (15), shop powder motor (17) etc. constitute, wherein slit funnel (1) is by: 2 funnel end plates (1-1), funnel side plates (1-2) and a space surrounded by the 2 funnel end plates, wherein a plurality of oscillators (1-3) are attached to the funnel side plates (1-2), oscillation is added in the powder laying process to facilitate the falling of powder in a slit area (9), and a seam edge scraper (1-4) compacts powder laying layers and lays a current powder laying layer (30); the current powder layer (30) is built on the previous powder layer (29) when advancing along the arrow (32); the magnitude of the horizontal impact force (34) depends on the magnitude of the vertical force of the powder on the powder layer.

Comparing the sand-unfilled funnel (27) with the sand-filled funnel (28), so that the internal structure can be seen clearly; as can be seen more clearly by combining fig. 1 with the funnel end section (10): slit funnel (1) is kept apart into by cylindric confession powder roller (4) and is used for saving the buffer memory powder storehouse (12) of buffer memory powder (24) and is used for saving the main people who stores up powder (25) and mainly stores up powder storehouse (14), the rotation that supplies powder roller (4) just can make the powder of the storage in storage tank (5) constantly fall in buffer memory powder storehouse (12), the higher speed that falls the powder is faster for the rotational speed, such powder volume can be realized through supplying the rotational speed that powder motor (7) drive powder roller axle (6), change the powder roller that supplies (4).

The support (22) represents the structure supporting the various devices, components: such as housings, supports, mounts, bridges, and the like; under the restraint of a guide rail (8) and a linear bearing (16) rigidly connected to the funnel end plate (1-1), the forming cylinder (13) is driven by a powder laying motor (17) to drive a screw rod (19) to drive a screw rod nut (18) fixed with the funnel end plate (1-1) on the other side to move, so that the slit funnel (1) horizontally moves relative to the forming cylinder (13). From the enlarged partial view of fig. 3, the corresponding powder layer position of the slit line (31) can be clearly seen; after each layer is printed, a piston (13-1) of the forming cylinder (13) moves downwards by one layer of height relative to a cylinder body (13-3) under the constraint of a guide pillar (13-2), and the powder surface of the cylinder body is lowered by one layer of height; the electronic and laser scanning system (23) will drive the respective motors so that the slit funnel (1) is moved while the rotation of the powder supply roller (4) will provide a continuous supply of powder.

Claims

1. A special slit self-sealing powder spreading device for a three-dimensional printer mainly comprises the following components: the device comprises a forming cylinder, a powder spreading device, an electronic module, a mechanical system, a shell, a touch display screen, a printing platform, an ink jet head or a laser scanning device; the method is characterized in that: the powder spreading device comprises a slit funnel and a seam edge scraper; in the powder spreading process, the forming cylinder and the powder spreading device are kept in a controlled relative motion state, wherein the relative motion state comprises that the forming cylinder moves while the powder spreading device is not moved, or the forming cylinder is not moved while the powder spreading device moves, or both the forming cylinder and the powder spreading device move; the basic construction of a slit funnel comprises: the device consists of 2 side plates with the distance of 0.2-10 mm, and 1 long and narrow rectangular slit opening is formed when being observed from the direction right below the slit funnel opening; a distance between the slit opening and the forming cylinder is defined such that the slit opening directly touches a powder layer surface of the forming cylinder.

2. The slit edge scraper of the slit funnel of the slit self-sealing powder-spreading device special for the three-dimensional printer according to claim 1 is characterized in that: the shape of the slit edge scraper of the slit edge of the powder outlet plane of the slit funnel is a plane shape or a bell mouth shape.

3. The slit edge powder outlet plane of the slit funnel of the slit self-sealing powder spreading device special for the three-dimensional printer according to claim 1 is characterized in that: the powder outlet plane at the edge of the slit funnel directly touches the surface of a new powder layer of the forming cylinder, or a powder pressing roller is horizontally arranged to prolong the height of the slit funnel, and the edge of the cylinder surface at the lowest part of the powder pressing roller is in a straight line parallel to the surface of the powder layer and is lower than the powder outlet plane at the edge of the slit; that is to say: the powder discharged from the slit edge of the slit funnel continuously falls to an opening formed by one or two powder pressing rollers to be discharged, and a new powder layer is laid; wherein the rolling of the powder compaction roller is used for burdening the compaction and the paving work.

4. The side plate of the slit funnel of the special slit self-sealing powder spreading device for the three-dimensional printer according to claim 1 is characterized in that: the side plate is kept in a static state or is provided with an oscillator, the side plate keeps in a vibration state when powder spreading translation is carried out, and the type of the oscillator is a mechanical oscillator or a piezoelectric ceramic oscillator; and (4) mounting position.