CN111873414A - A special slit self-sealing powder spreading device for three-dimensional printers - Google Patents

Abstract

A special slit self-sealing powder spreading device for a three-dimensional printer belongs to the field of machinery. Its main structure includes: forming cylinder, powder spreading device, electronic module, mechanical system, shell, touch display screen, printing platform, inkjet head or laser scanning device; it is characterized in that: the powder spreading device includes a slot funnel and a Seam edge scraper; during the powder spreading process, a controlled relative motion is maintained between the forming cylinder and the powder spreading device, including movement of the forming cylinder without movement of the powder spreading device, or movement of the forming cylinder and movement of the powder spreading device, or Both the forming cylinder and the powder spreading device move; the basic structure of the slot funnel includes: it consists of 2 side plates with a spacing of 0.2-10 mm, which form a long and narrow rectangle when viewed from directly below the opening of the slot funnel. The slit opening is limited; the distance between the slit opening and the forming cylinder is limited, so that the slit opening directly touches the powder layer surface of the forming cylinder; the structure of the invention is simple, and the most important advantage is that the efficiency is fast, which can improve the 2- More than 3 times, it has the value of promotion and application.

Description

A special slit self-sealing powder spreading device for three-dimensional printers

[Technical field]

The invention belongs to the technical field of machinery, and specifically relates to a rapid layer-by-layer powder coating method specially used for laser sintering and spray-stick 3D printing.

[Background technique]

At present, powder laser sintering and powder layer-by-layer 3D printers are increasingly used as an important means of industrial processing, and the powder coating technology and devices directly affect the printing speed and printing quality of the workpiece. The existing powder 3D printers Most of the powder spreading devices are equipped with piston bin-type powder storage and up-and-down powder supply devices that can be lifted up and down. Such powder spreading devices collect or drop powder in front of the straight powder scraping sheet, and accumulate them into dozens of powders. A mound-shaped strip of powder pile with a layer thickness of layers, and then a scraper (also called a scraper) is required to push the powder pile to spread the powder evenly, because the previous layer has been printed (sintered or bonded) must not be disturbed. When the powder pile is too high or the powder spreading speed is too fast, the small molding structure without a solid foundation in the shallow part of the molding bin may be displaced, and the scraper speed has to be reduced, which is more serious for relatively thin fine printing. , For a molding machine with a medium-sized printing surface, this process takes as long as 40 seconds to 2 minutes, resulting in extremely slow powder spreading speed and low efficiency.

Detailed description of technical background: Three-dimensional printing technology (3DP, Three-Dimensional Printing) is mainly powder bonding molding. The specific process of 3DP is: after each layer is bonded, the piston of the forming cylinder drops a distance (equal to the layer thickness), the powder supply cylinder rises a certain height, pushes out a certain amount of powder, and is pushed to the forming cylinder by the powder spreading roller. , the powder is flattened and compacted. Under the control of the computer, the nozzle moves according to the two-dimensional geometric information of the next section, selectively sprays the adhesive, and finally forms the layer. The principle is very similar to that of the printer, which is the origin of the name of 3D printing. The excess powder is collected by the powder collecting device when the powder is spread by the powder roller. In this way, powder feeding, powder spreading and binder spraying are carried out over and over again, and finally a three-dimensional powder bonding is completed to produce products.

3DP technology is relatively mature. In 1989, Emanual Sachs et al. of the Massachusetts Institute of Technology applied for the 3DP patent, which is one of the core patents in the field of non-forming material droplet spray forming. Manufacturers using 3DP technology are mainly ZCorporation (acquired by 3DSystems in 2011), Ex-One and Japan's RikonInstituto, mainly zprinter and R series 3D printers. In 2000, Israel's ObjectGeometries (acquired by Stratasys in 2012) launched Quadra, a printing equipment based on a combination of 3Dink-Jet and SLA processes. 3DP printing equipment can use many materials, including plaster, plastic, ceramics and metal, etc., and can also print color parts, which can form parts with complex shapes inside. This type of printer increases speed with multiple bumps and nozzles. Domestically, Tsinghua University, Xi'an Jiaotong University, Shanghai University, etc. are also actively researching and developing. 3DP has a fast forming speed and can do color prototypes. 3DP technology has fast forming speed and low price of forming materials, which is suitable for desktop rapid prototyping equipment. At the same time, thanks to the addition of pigments to the binder, colorful prototypes can be made, which is one of the most competitive features of the process. The entire molding process does not require support, and it is convenient to remove excess powder, especially suitable for prototypes with complex inner cavities. Of course, due to the low strength of 3DP molded parts, only conceptual models can be made, but functional test parts cannot be made. 3DP technology has been widely used in foreign appliances, automobiles, aerospace, ships, industrial design, medical and other fields. At present, the mainstream full-color 3D portrait printing on the market mostly adopts 3DP technology.

Metal 3D printing SLS technology is the most cutting-edge and potential technology in the 3D printing system. With the development of science and technology and the needs of popularization and application, the use of rapid prototyping to directly manufacture metal functional parts has become the main development direction of rapid prototyping. At present, the rapid prototyping methods that can be used to directly manufacture metal functional parts mainly include: laser net shaping (LENS, LaserEngineeredNetShaping), selective laser sintering (SLS, SelectiveLaserSintering) and selective laser melting (SLM, SelectiveLaserMelting, SLM), direct metal laser sintering (DMLS, DirectMetalLaserSintering) and electron beam melting technology (EBM, ElectronBeamMelting) and so on. SLS technology uses the laser as the energy source, and the powder is uniformly sintered on the processing plane by the laser beam. A very thin layer of powder (sub-millimeter level) is evenly spread on the worktable as a raw material, and the laser beam is controlled by a computer and scanned by a scanner at a certain speed and energy density according to the layered two-dimensional data. After being scanned by the laser beam, the powder at the corresponding position is sintered into a solid sheet with a certain thickness, and the unscanned areas remain loose powder. After this layer is scanned, the next layer needs to be scanned. Repeat this until all layers are scanned. Parts are obtained by removing excess powder and subjecting them to appropriate post-processing such as grinding, drying, etc. SLS technology is suitable for complex parts manufacturing. SLS technology was first proposed in 1989 by Carl Deckard and Joe Beaman of the University of Texas at Austin. Later, the two established the DTM company, and in 1992 began the SLS commercial product SinterSation. In 2001, 3DSystems acquired DTM, completing the technical integration. The raw materials that can be processed by SLS include plastic powder (nylon, polystyrene, polycarbonate, etc., direct laser sintering), metal powder (the process is divided into direct method, indirect method and double-member method), ceramic powder (binder needs to be used) , including inorganic binders, organic binders and metal binders). SLS has been successfully used in many industries such as automotive, shipbuilding, aerospace and aviation. In addition to DTM company, German EOS company has also developed a corresponding series of molding equipment. In China, such as Huazhong University of Science and Technology, Nanjing University of Aeronautics and Astronautics, Northwestern Polytechnical University, North China Institute of Technology and Beijing Longyuan Automatic Forming Co., Ltd., etc., have also achieved many major achievements, such as the RAP-I laser sintering developed by Nanjing University of Aeronautics and Astronautics Rapid prototyping system, AFS-300 laser rapid prototyping equipment developed by Beijing Longyuan Automatic Prototyping Co., Ltd., etc. SLS has been successfully used in many industries such as automotive, shipbuilding, aerospace and aviation, mainly involving rapid prototyping, rapid mold and tool manufacturing, and small batch production.

Defects of the current powder spreading technology: The current powder spreading technology includes double-cylinder and single-cylinder powder dropping methods, scraper or rolling compaction technology, and has strict requirements on powder; at the same time, the powder spreading device itself has high requirements; resulting in Not only is the equipment expensive, but the cost of consumables is also high, often hundreds of yuan or even thousands of yuan per KG, which seriously hinders the promotion of powder-based 3D printing technology. Another major factor affecting the promotion is that in addition to SLM technology, the density of printed objects with SLS and 3DP technology cannot increase the density, resulting in the inability to guarantee the strength of printed objects of metal and ceramics.

[Content of the Invention]

Purpose of the present invention:

It is to solve the defects of traditional powder spreading technology such as slow spreading speed, complex structure and too high requirements for powder performance.

The present invention has the advantages of simple structure, high powder spreading efficiency and low requirements on the performance of powder.

Technical scheme of the present invention:

The main structure includes: forming cylinder, powder spreading device, electronic module, mechanical system, casing, touch display screen, printing platform, inkjet head or laser scanning device; forming cylinder, including cylinder block, piston and guiding structure, laying The powder device includes a slot funnel and a slot edge scraper, the mechanical system includes a guide motor that drives the molding cylinder and the funnel movement, and the electronic module includes control, motion drive and data interaction; in the process of powder spreading, between the molding cylinder and the powder spreading device A controlled relative motion is maintained, including movement of the forming cylinder while the powder spreading device does not move, or the forming cylinder does not move and the powder spreading device moves, or both the forming cylinder and the powder spreading device move.

The powder spreading device of the present invention is a slit self-sealing (powder-falling) powder spreading scheme with a slit funnel as the main body. The necessary conditions for the slit self-sealing powder spreading technical scheme are: it is necessary to maintain the correctness of the powder during the process of powder falling from the slit. The impact force on the surface of the laid powder layer is limited to a certain extent, which requires the control of the following parameters: the width of the slit, the height of the buffered powder in the buffered powder bin, the vibration intensity of the oscillator on the wall of the slotted funnel, the The distance between the mouth of the funnel and the surface of the powder layer of the forming cylinder; the basic composition of the slot funnel includes: it consists of two side plates and end plates with a spacing of 0.2-10 mm. When viewed from directly below the opening of the slot funnel, it forms a 1 long and narrow rectangular slit opening; the distance between the slit opening and the forming cylinder is limited, so that the slit opening directly touches the powder layer surface of the forming cylinder.

From the point of view of mathematical and physical principles: the closer the distance between the funnel mouth of the slot funnel and the surface of the powder layer of the molding cylinder (the smaller: that is, the smaller the layer height), the worse the powder fluidity, and the smaller the height of the buffer powder. , The weaker the vibration of the auxiliary oscillator, the more difficult it is for the powder in the slit funnel to flow out, or even completely self-sealing (cannot flow out); that is, when the buffer powder is resisted by the container wall, the support force of the lower powder layer surface, When the frictional resistance between the particles and the flow trend caused by the accumulation of powder gravity cancel each other, the powder in the slot funnel will not flow out naturally (this is the concept of self-styled). When the slot funnel is moved horizontally, Since the surface of the front powder layer is lower than the plane of the powder outlet of the slot funnel, the powder inside will flow out naturally under the action of gravity to fill the space between the surface of the front powder layer and the slot funnel, and the surface of the pavement forming cylinder will create a new powder layer.

*Further: The shape of the slit edge of the powder outlet plane of the slit funnel is a flat shape or a bell mouth shape. The shape of the bell mouth just meets the characteristics of the conventional SLS and 3DP flat powder scrapers. The slope towards the powder can compact and smooth the powder surface well, but the excessive viscous force is easy to cause cracks on the surface of the powder layer. , is often necessary to avoid these shocks.

*Further: The plane of the powder outlet at the edge of the slit of the slot funnel directly touches the surface of the new powder layer of the molding cylinder, or a powder pressing roller (cylindrical, whose cylindrical surface contacts the surface of the new powder layer) is installed horizontally. The straight line of the cylindrical edge at the lowest position of the powder roller is parallel to the surface of the powder layer, and is lower than the plane of the powder outlet at the edge of the slit, so as to extend the height of the slit funnel, and the straight line of the cylindrical edge of the lowest position of the powder roller Parallel to the surface of the powder layer; that is to say: the powder from the edge of the slit of the slot funnel continues to fall to, and is discharged from the opening composed of one (the other side is a fixed wall) or two powder pressing rollers, and is laid into a new The powder layer; in which the rolling of the powder roller is responsible for the compaction and paving work.

The beneficial effects of the present invention are:

The powder spreading method and the simplified powder spreading device reduce the requirement on the precision of the equipment. Compared with the prior art, the present invention has a simple structure, and the powder spreading speed is greatly accelerated, which can be increased by more than 2-3 times, and has the advantages of popularization and application. the value of.

[Description of drawings]

Below in conjunction with accompanying drawing, the present invention is further described with respect to preferred embodiment:

Figure 1. Schematic diagram of the self-sealing principle of the original slit funnel.

Figure 2 Schematic diagram of the principle of powder spreading in the slot funnel.

Figures 3 and 4 are schematic diagrams of the special slit self-sealing powder spreading device for 3D printers.

Label description:

(1) Slit funnel

(1-1) Funnel end plate

(1-2) Funnel side plate

(1-3) Oscillator

(1-4) Seam edge scraper

(2) Self-sealing boundary of powder

(3) Impact strength of falling powder

(4) Powder supply roller

(5) Powder storage tank

(6) Powder roller shaft

(7) Powder supply motor

(8) Rails

(9) Slit area

(10) Funnel end face section

(12) Cache powder bin

(13) Forming cylinder

(13-1) Piston

(13-2) Guide post

(13-3) Cylinder block

(14) Main powder storage bin

(15) Waste powder tank

(16) Linear bearing

(17) Powder spreading motor

(18) Screw female

(19) Lead screw

(22) Bracket

(23) Electronic and laser scanning system

(24) Cache powder

(25) Main storage powder

(26) Local pressure

(27) Unfilled sand funnel

(28) Sand filling funnel

(29) Front powder layer

(30) The current powder layer

(31)Slit line

(32) Arrow

(33) Self-sealing overflow powder

(34) Horizontal impact force

[Example]

As shown in Figure 1 and Figure 2:

The figure is a section of the slot funnel (1) taken by a plane parallel to the end plate of the funnel; Figure 1 is a static self-sealing state diagram, and Figure 2 is a state diagram of translationally spreading powder.

The slot funnel (1) is a space surrounded by two funnel side plates (1-2) and two funnel end plates, and a plurality of oscillators (1-3) are attached to the funnel side plates (1-2). ), vibration is added during the powder spreading process to help the powder fall in the slit area (9), and the slit edge scraper (1-4) compacts the powder layer and smoothes the current powder layer (30). ); when advancing along the arrow (32), the current powder layer (30) is built on the front powder layer (29); the size of the horizontal impact force (34) depends on the vertical direction of the powder to the powder layer The magnitude of the force.

The slot funnel (1) is separated by a cylindrical powder supply roller (4) into a buffer powder storage bin (12) for storing the buffer powder (24) and a main powder storage bin (12) for storing the main storage powder (25). 14), the rotation of the powder supply roller (4) can make the powder stored in the powder storage tank (5) continuously fall into the powder storage bin (12). The motor drives the powder roller shaft (6) and changes the rotational speed of the powder supply roller (4) to achieve this; the self-sealing of the powder is determined by the difference in the fluidity of the powder, the geometrical parameters of the slit and the height of the powder in the powder storage bin. The shape of the border (2). The size of the powder falling impact force (3) depends on three factors: the height of the powder in the buffered powder bin, the height of the powder layer laid and the parameters of the powder.

As shown in Figure 3 and Figure 4:

The entire slit self-sealing powder spreading device is composed of: a slit funnel (1), a forming cylinder (13), a waste powder cylinder (15), a powder spreading motor (17), etc., wherein the slit funnel (1) is composed of: 2 A funnel end plate (1-1) and a funnel side plate (1-2), and the space surrounded by two funnel end plates, a plurality of oscillators (1-3) are attached to the funnel side plate (1-2) The addition of vibration during the powder laying process helps to drop the powder in the slit area (9), and the slit edge scraper (1-4) compacts the powder layer and flattens the current powder layer (30). ; When advancing along the arrow (32), the current powder layer (30) is established on the front powder layer (29); the size of the horizontal impact force (34) depends on the vertical effect of the powder on the powder layer Magnitude of the force.

Comparing the unfilled sand funnel (27) and the sand filled funnel (28), the internal structure can be seen clearly; then combined with Figure 1 and the funnel end section (10), it can be seen more clearly that the slot funnel (1) is surrounded by a cylindrical The powder supply roller (4) is separated into a buffer powder bin (12) for storing the powder (24) and a main powder storage bin (14) for storing the main powder (25). The powder supply roller (4) ) rotation can make the powder stored in the powder storage tank (5) continuously fall into the powder storage bin (12). The roller shaft (6) is realized by changing the rotational speed of the powder supply roller (4).

The bracket (22) represents the structure that supports various devices and components: such as shells, supports, mounts, bridges, etc.; the forming cylinder (13) is rigidly connected to the guide rail (8) and to the funnel end plate (1-1) Under the constraint of the linear bearing (16), the powder spreading motor (17) drives the lead screw (19) to drive the lead screw mother (18) fixed to the other side of the funnel end plate (1-1) to move, so that the slit The funnel (1) moves horizontally relative to the forming cylinder (13). From the partial enlarged view of FIG. 3, the position of the powder layer corresponding to the slit line (31) can be clearly seen; after each layer is printed, the piston (13-1) of the forming cylinder (13) needs to be relative to the cylinder (13-1). The cylinder (13-3) moves downward by the height of one layer under the constraint of the guide post (13-2), and the powder surface of the cylinder will reduce the height of one layer; the electronic and laser scanning system (23) will drive the corresponding the motor, so that the slot funnel (1) is moved, and the rotation of the powder supply roller (4) will provide continuous powder supply.

Claims (4)

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.

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