A peeling multi-material additive powder spreading system and powder spreading method based on mesh screen

Abstract

The present invention discloses a peeling-type multi-material additive powder spreading system and a powder spreading method based on a mesh screen. The powder spreading system includes a forming chamber and a powder spreading device. The forming chamber is provided with a forming platform and a moving platform. The powder spreading device is installed on the moving platform. The powder spreading device includes a powder supply component, a powder suction component, a powder scraping component, a powder storage component and a powder stripping component. The powder suction component includes a rotating mesh screen and a vacuum pump. When the powder falls from the powder supply component, the suction action of the vacuum pump will adsorb the powder particles on the periphery of the mesh screen. During the rotation of the mesh screen and the movement of the moving platform, the powder scraping component scrapes some of the powder particles to the powder storage component to control the powder thickness. The powder stripping component peels the powder on the periphery of the mesh screen onto the forming platform for powder spreading, and finally realizes precise adjustment of the material type and the distribution form of the powder in the printing plane. While supplying powder, powder scraping and stripping can also be performed simultaneously, thereby greatly improving the printing speed and production efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a screen-based peeling multi-material additive powder spreading system and a powder spreading method. Background Art

[0002] Additive manufacturing is a new type of material forming process that accumulates from the bottom to the top. It builds a three-dimensional solid structure by stacking materials layer by layer. Metal parts formed using additive manufacturing technology can not only have complex and changeable structures, but also have high density and excellent mechanical properties. Furthermore, multi-material metal additive manufacturing combines the advantages of additive manufacturing technology and multi-material technology to obtain multi-material parts with excellent comprehensive service performance. This field has great potential and indicates a wide range of application prospects. Unlike the metal additive manufacturing method of directed energy deposition, powder bed fusion requires the metal powder to be laid on the forming platform first, and then the powder is melted by laser or electron beam and cooled to solidify. The existing powder spreading method can already stably realize the manufacturing of multi-material parts along a single forming direction. However, if we want to further realize true three-dimensional multi-material additive manufacturing, we face a major challenge: how to accurately adjust the type of material and the distribution form of the powder in the printing plane, which is a key problem that needs to be solved urgently. In addition, the existing powder spreading method generally provides powder first and then spreads powder, resulting in reduced powder spreading efficiency and production efficiency needs to be improved. Summary of the invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a mesh-based peeling multi-material additive powder laying system, which can accurately lay different powders in a layer, accurately adjust the material type and powder distribution pattern in the printing plane, realize three-dimensional multi-material additive manufacturing, and improve powder laying efficiency and production efficiency.

[0004] To solve the above problems, the technical solution adopted by the present invention is as follows: a peeling-type multi-material additive powder spreading system based on a mesh screen, comprising a forming chamber and a powder spreading device; a forming platform and a moving platform are provided in the forming chamber, and the moving platform can move above the forming platform to spread powder; the powder spreading device is installed on the moving platform, and there are multiple powder spreading devices, each of which includes a powder supply component, a powder suction component, a powder scraping component, a powder storage component and a powder peeling component; the powder supply component is installed on the moving platform and is located above the powder suction component, for providing powder material to the powder suction component; the powder suction component includes a mesh screen and a vacuum pump, the mesh screen is rotatably connected to the moving platform, the mesh screen has polygonal mesh holes distributed in a circular array, and the vacuum pump can pump powder from the mesh screen. The mesh screen is internally sucked to adsorb the powder particles falling from the powder supply component on the periphery of the mesh screen; the powder scraping component is installed on the mobile platform and is located on the first side of the powder suction component, and is used to scrape off part of the powder particles on the periphery of the mesh screen so that the powder thickness on the periphery of the mesh screen reaches the required thickness; the powder storage component is installed on the mobile platform and is located below the powder scraping component, and is used to store the powder particles scraped off by the powder scraping component; the powder stripping component is installed on the mobile platform and is located on the second side of the powder suction component, and the powder stripping component is used to peel off the powder particles on the periphery of the mesh screen from the mesh screen so that the powder particles fall on the forming platform; wherein the powder supply component, the powder scraping component, the powder storage component and the powder stripping component are distributed in sequence along the rotation direction of the mesh screen.

[0005] Compared with the prior art, the present invention has the following beneficial effects:

[0006] 1. The powder laying system is equipped with multiple powder laying devices, each of which can independently supply, absorb, scrape and peel powder, and can accurately lay different powders in one layer, meeting the needs of three-dimensional multi-material additive manufacturing, broadening the application scope of three-dimensional multi-material additive manufacturing, and improving production efficiency;

[0007] 2. The powder laying system is equipped with a powder scraping component, which can scrape off the powder particles on the periphery of the mesh screen so that the powder thickness on the periphery of the mesh screen reaches the required powder thickness. Combined with the movement of the mobile platform, the rotation of the mesh screen and the peeling of the powder stripping component, the thickness of the powder falling on the forming platform can be accurately controlled to ensure the quality and precision of multi-material additive manufacturing;

[0008] 3. The powder suction component in this powder spreading system adopts a mesh structure. The mesh has multiple polygonal mesh holes distributed in a circular array. When the powder falls from the powder supply component, the suction of the vacuum pump will adsorb the powder particles on the mesh, and the powder thickness on the periphery of the mesh is controlled by the powder scraping component. During the movement of the mobile platform, the powder on the periphery of the mesh is peeled off by the powder stripping component for powder spreading, ultimately achieving precise adjustment of the material type and powder distribution form in the printing plane;

[0009] 4. The powder spreading system installs the powder supply component, powder suction component, powder scraping component, powder storage component and powder stripping component on the mobile platform, which can move above the forming platform with the mobile platform. The powder supply component, powder scraping component, powder storage component and powder stripping component are sequentially distributed along the rotation direction of the mesh screen. After the powder supply component provides powder material, the powder suction component can absorb powder particles, and the powder scraping component scrapes part of the powder particles to the powder storage component to control the powder thickness, and then the powder stripping component peels the powder particles onto the forming platform. While supplying powder, powder scraping and stripping can be performed at the same time, thereby greatly improving the printing speed and production efficiency;

[0010] 5. This powder spreading system is equipped with a powder storage component under the powder scraping component, which can not only store the powder scraped by the powder scraping component to prevent the powder from falling on the forming platform and affecting the accuracy, but also realize the simultaneous powder supply and powder spreading, and can also realize the recycling of powder, reduce the waste of powder materials, and save manufacturing costs.

[0011] In the above-mentioned peeling-type multi-material additive powder laying system based on mesh screen, the inscribed circle diameter D1 of the polygonal mesh hole is less than the outer diameter d of the powder particles and less than the circumscribed circle diameter D2 of the polygonal mesh hole.

[0012] The above-mentioned mesh-based peeling multi-material additive powder spreading system also includes a control device, a gas circulation device and a laser device. The control device is used to control the operation of the powder spreading system and the operation of the powder spreading device. The gas circulation device is used to provide an inert gas environment in the forming chamber during operation. The laser device is arranged in the forming chamber and located above the forming platform, and is used to emit laser toward the forming platform to melt the powder on the forming platform.

[0013] The above-mentioned peeling-type multi-material additive powder laying system based on mesh screen also includes a powder adding device, which includes multiple powder adding funnels. The feeding port of the powder adding funnel penetrates into the forming chamber. A solenoid valve is provided at the feeding port. The mobile platform can drive the powder supply assembly to move below the feeding port, and the solenoid valve can open the feeding port to add powder material into the powder supply assembly.

[0014] The above-mentioned peeling multi-material additive powder spreading system based on mesh screen, the powder supply component includes a powder supply cylinder, a first pressure sensor, a first electromagnet, a first reset member and a first powder blocking block; the powder supply cylinder is installed on the mobile platform and is located above the powder suction component, and is used to receive the powder material from the powder adding funnel; the first pressure sensor is installed in the powder supply cylinder, and is used to judge whether the amount of powder in the powder supply cylinder is sufficient; a powder outlet is opened at the bottom of the powder supply cylinder, the first electromagnet, the first reset member and the first powder blocking block are all installed at the powder outlet, and the first A reset member connects the first electromagnet and the first powder blocking block; when powder supply is required and the first pressure sensor determines that the amount of powder in the powder supply cylinder is sufficient, the first electromagnet is energized to attract the first powder blocking block to move in the direction of the first electromagnet, thereby opening the powder outlet of the powder supply cylinder to provide powder material to the powder suction component, and the first reset member is compressed to store elastic potential energy; when powder supply is not required, the first electromagnet is de-energized, and the first reset member releases the stored elastic potential energy, pushing the first powder blocking block away from the first electromagnet and back to its original position, thereby blocking the powder outlet of the powder supply cylinder.

[0015] The above-mentioned mesh-based peeling multi-material additive powder laying system, the powder suction component also includes a powder suction bracket, the powder suction bracket is installed on the mobile platform, and the powder suction bracket is a hollow structure, one end of the powder suction bracket is connected to the vacuum pump, and the other end is provided with a plurality of air holes distributed in a circular array, the mesh is coaxially sleeved on the outer periphery of the powder suction bracket, and when the vacuum pump is sucking, the inert gas flows through in sequence: the forming chamber, the polygonal mesh, the air holes, the inside of the powder suction bracket and the vacuum pump.

[0016] The above-mentioned screen-based peeling multi-material additive powder laying system, the powder scraping assembly includes a slide, a powder scraping bracket, a powder scraping strip and a cover plate, the slide can be slidably connected to the mobile platform, and can slide relative to the mobile platform along the X-axis, Y-axis and Z-axis directions, the powder scraping bracket is installed on the slide, the cover plate is installed on the powder scraping bracket, the powder scraping strip is installed between the powder scraping bracket and the cover plate, and the cover plate is provided with a chamfer.

[0017] The above-mentioned peeling multi-material additive powder spreading system based on mesh screen, the powder storage component includes a powder storage cylinder, a second powder blocking block, a second reset member, a second electromagnet and a second pressure sensor, the second pressure sensor is installed in the powder storage cylinder, and is used to judge whether the powder storage cylinder needs to be poured; a powder outlet is opened below the powder storage cylinder, the second reset member and the second electromagnet are both installed at the powder outlet, and the second reset member is connected to the second powder blocking block and the second electromagnet; a powder collecting bin is also provided in the forming chamber, and when the weight of the powder stored in the powder storage cylinder is too large, the mobile platform belt The powder storage assembly is moved to the top of the powder collecting bin, and the second electromagnet is energized to attract the second powder blocking block to move toward the second electromagnet, thereby opening the powder outlet of the powder storage cylinder to pour the powder in the powder storage cylinder into the powder collecting bin. At this time, the second reset member is compressed to store elastic potential energy; when the second pressure sensor determines that the powder in the powder storage cylinder has been poured out, the second electromagnet is de-energized, and the second reset member releases the stored elastic potential energy, pushing the second powder blocking block away from the second electromagnet and back to its original position, thereby blocking the powder outlet of the powder storage cylinder.

[0018] The above-mentioned peeling-type multi-material additive powder laying system based on mesh screen, the powder stripping component includes an electrostrictive element and an ejector pin, and the electrostrictive element and the ejector pin are provided in multiple and the number is the same, and the multiple ejector pins are correspondingly connected to the multiple electrostrictive elements; when powder stripping is required, the electrostrictive element can drive the ejector pin to move toward the mesh screen so that the ejector pin contacts the powder particles on the periphery of the mesh screen and pushes the powder particles away from the polygonal mesh, and the working end of the ejector pin can change the airflow state of the polygonal mesh close to it to change the force condition of the powder particles, so that the powder particles fall to the forming platform under the action of gravity, and when powder stripping is not required, the ejector pin can move away from the mesh screen.

[0019] In the above-mentioned mesh-based peeling multi-material additive powder laying system, the working end of the ejector pin is a sphere, the sphere is made of a soft material, and the diameter of the sphere is comparable to the diameter of the powder particles.

[0020] The present invention also provides a mesh-based peeling multi-material additive powder spreading method, which is performed using the mesh-based peeling multi-material additive powder spreading system, and includes the following steps:

[0021] Step S1, according to the number of materials required for the multi-material product, a corresponding number of powder spreading devices are installed on the mobile platform, different powder materials are added to the powder supply component in each powder spreading device, the distance between the powder scraping component and the mesh screen is adjusted, the power of the powder spreading system is turned on, and each device returns to the origin;

[0022] Step S2: judging whether it is necessary to add powder to the powder supply cylinder of the powder supply assembly through the powder adding device according to the data of the first pressure sensor, importing the data of the multi-material product that has been sliced, turning on the gas circulation device, until the oxygen content in the forming chamber reaches the working level, and preparing for printing;

[0023] Step S3, start the vacuum pump to form a relative negative pressure inside the mesh screen, the control device energizes the first electromagnet to make the first powder blocking block leave the powder outlet of the powder supply cylinder, start the rotary motor, the powder is adsorbed on the surface of the mesh screen, and the powder scraping assembly scrapes the powder, and the obtained powder layer thickness is the printed layer thickness;

[0024] Step S4, while performing step S3, the moving motor is started, and the moving motor and the rotating motor move in coordination. According to the slicing data, during the powder spreading process, if the area needs to be powdered, the control device energizes the electrostrictive element to make the ejector pin slide out of the groove, and the ball of the ejector pin touches the powder particles on the periphery of the mesh screen, so that the powder particles are peeled off and fall into the area, and the powder spreading is completed;

[0025] Step S5, after the powder spreading of the area is completed, if the next area still needs to be spread with powder, the power-on state of the electrostrictive element remains unchanged, the ball of the ejector pin remains in the same position, and the powder particles it touches are continuously peeled off to achieve continuous powder spreading; if the next area does not need to be spread with powder, the control device turns off the power of the electrostrictive element, the third reset member drives the reset plate to retract the ejector pin into the groove, and the ball of the ejector pin no longer touches the powder particles on the periphery of the mesh screen, thereby stopping the powder spreading;

[0026] Step S6: During the whole powder spreading process, the second pressure sensor keeps working, and judges whether the powder in the powder storage cylinder needs to be cleaned according to the pressure value. If necessary, after the printing work of the current layer is completed, the powder spreading device returns to the origin, the second electromagnet is energized, the second powder blocking block leaves the powder outlet of the powder storage cylinder, and the powder is poured into the powder collecting bin. If not necessary, the current working state is not interrupted;

[0027] Step S7, multiple powder spreading devices work simultaneously, and driven by the moving mechanism, a layer of multi-material powder spreading of parts is achieved;

[0028] Step S8, the laser device irradiates and melts the laid powder to complete the manufacturing of a layer of parts;

[0029] Step S9, determining whether the multi-material product has been manufactured, if it has been manufactured, then the process ends; if it has not been manufactured, then executing step S10;

[0030] Step S10, lowering the forming platform by a layer thickness;

[0031] Step S11, the moving mechanism drives the powder spreading device to move in the opposite direction, repeating the powder spreading process in step S4 to step S7, and completing the powder spreading of this layer through the powder spreading device;

[0032] Step S12: determine whether the product has been manufactured. If it has been manufactured, the process ends. If it has not been manufactured, the process returns to step S10 and the subsequent steps are executed in sequence.

[0033] The present method adopts the above-mentioned powder spreading system for powder spreading, and it has at least all the beneficial effects that the above-mentioned powder spreading system can bring. In addition, during the powder spreading process, it can be judged whether it is necessary to add powder to the powder supply cylinder based on the data of the first pressure sensor, and the amount of powder in the powder supply cylinder can be monitored in real time to avoid the situation of empty spreading due to insufficient powder. During the powder spreading process, it can also be judged whether it is necessary to clean the powder in the powder storage cylinder based on the data of the second pressure sensor, and the amount of powder in the powder storage cylinder can be monitored in real time to avoid excessive powder overflowing onto the forming platform. The present method adopts multiple powder spreading devices to work simultaneously, which can realize multi-material additive manufacturing in the XY plane, and then through the vertical movement of the forming platform, it can realize multi-material additive manufacturing in the Z direction, and finally it can realize the manufacturing of parts with fully optimized performance.

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of a powder spreading system according to an embodiment of the present invention;

[0036] Figure 2 for Figure 1 A partial enlarged view of point I in the middle;

[0037] Figure 3 It is a structural schematic diagram of a mobile platform, a mobile mechanism and a powder spreading device according to an embodiment of the present invention;

[0038] Figure 4 for Figure 3 A partial enlarged view of position II in the middle;

[0039] Figure 5 A partial cross-sectional view of a powder spreading system according to an embodiment of the present invention;

[0040] Figure 6 A schematic diagram of the working principle of the powder spreading device according to an embodiment of the present invention;

[0041] Figure 7 It is a schematic structural diagram of a powder scraping assembly according to an embodiment of the present invention;

[0042] Figure 8 It is a schematic diagram of the principle of laying powder by the powder laying system according to an embodiment of the present invention.

[0043] Description of the accompanying drawings: 1 forming chamber, 2 laser device, 3 moving mechanism, 4 first powder adding funnel, 5 first powder spreading device, 6 second powder adding funnel, 7 second powder spreading device, 8 third powder adding funnel, 9 third powder spreading device, 10 third powder collecting bin, 11 second powder collecting bin, 12 first powder collecting bin, 13 multi-material product, 14 forming platform, 15 fourth powder adding funnel, 16 fifth powder adding funnel, 17 sixth powder adding funnel, 18 moving platform, 19 top screw, 20 sleeve, 21 fixed seat, 22 bearing, 23 rotating shaft, 24 first bearing seat, 25 first coupling, 26 rotating motor, 31 moving motor, 32 second coupling, 33 ball screw, 34 second bearing seat, 35 linear guide, 36 linear Slider, 37 fixed platform, 51 powder supply assembly, 511 powder supply cylinder, 512 first pressure sensor, 513 first electromagnet, 514 first reset member, 515 first powder stop block, 52 powder suction assembly, 521 powder suction bracket, 522 mesh screen, 523 vacuum pump, 53 powder stripping assembly, 531 groove, 532 electrostrictive element, 533 third reset member, 534 ejector pin, 535 reset plate, 54 powder storage assembly, 541 powder storage cylinder, 542 second powder stop block, 543 second reset member, 544 second electromagnet, 545 second pressure sensor, 55 powder scraping assembly, 551 powder scraping strip, 553 powder scraping bracket, 552 cover plate, 554 slide, 60 control device, 70 gas circulation device. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below. Figures 1 to 8 An embodiment of the present invention provides a mesh-based peeling multi-material additive powder spreading system, including a forming chamber 1, a laser device 2, a powder adding device, a powder spreading device, a control device 60 and a gas circulation device 70.

[0045] A forming platform 14 is provided inside the forming chamber 1. The forming platform 14 can be moved up and down in the forming chamber 1 under the drive of the lifting device to adjust the height of the forming platform 14 so as to realize multi-layer printing. The lifting device can adopt conventional motors, electric cylinders and other structures as long as the forming platform 14 can be lifted and lowered. A moving platform 18 is also provided in the forming chamber 1. The moving platform 18 can move above the forming platform 14 to spread powder. The movement of the moving platform 18 is driven by the moving mechanism 3.

[0046] The laser device 2 is arranged in the forming chamber 1 and is located above the forming platform 14. A conventional laser scanning galvanometer device can be used. The laser emitted by the laser device can reach any position on the surface directly above the forming platform 14, ensuring that the powder at any position on the forming platform 14 can be melted by the laser.

[0047] The control device 60 is used to control the movement of various components of the powder spreading system, such as the lifting and lowering of the forming platform 14, the opening and closing of the laser device 2, the movement of the mobile platform 18, the opening and closing of various components in the powder spreading device, and the opening and closing of the gas circulation device 70.

[0048] The gas circulation device 70 is used to provide an inert gas environment in the forming chamber 1 during operation.

[0049] Further, refer to Figure 1 The powder adding device includes a plurality of powder adding funnels for adding different powder materials into each powder supply component 51. For example, in the present embodiment, there are six powder adding funnels, namely, the first powder adding funnel 4, the second powder adding funnel 6, the third powder adding funnel 8, the fourth powder adding funnel 15, the fifth powder adding funnel 16 and the sixth powder adding funnel 17, wherein the first powder adding funnel 4, the second powder adding funnel 6, the third powder adding funnel 8 and the sixth powder adding funnel 17, the fifth powder adding funnel 16 and the fourth powder adding funnel 15 are symmetrically arranged on both sides of the forming chamber 1. The bottoms of the first powder adding funnel 4, the second powder adding funnel 6, the third powder adding funnel 8, the fourth powder adding funnel 15, the fifth powder adding funnel 16 and the sixth powder adding funnel 17 are all provided with a feeding port, and the feeding port penetrates into the forming chamber 1. A solenoid valve is provided at the feeding port. After the solenoid valve is opened, the feeding port can be opened for feeding.

[0050] Furthermore, there are multiple powder spreading devices for spreading different powder materials. For example, in this embodiment, on one side of the forming chamber 1, there are three powder spreading devices, namely, a first powder spreading device 5, a second powder spreading device 7 and a third powder spreading device 9. The positions of the first powder spreading device 5, the second powder spreading device 7 and the third powder spreading device 9 during feeding correspond to the positions below the first powder adding funnel 4, the second powder adding funnel 6 and the third powder adding funnel 8 respectively. When a certain powder material needs to be added, the solenoid valve of the corresponding powder adding funnel is opened to add the corresponding powder material to the corresponding powder spreading device. Multiple powder spreading devices are arranged on the mobile platform 18, refer to Figure 3 A plurality of powder spreading windows are provided on the mobile platform 18, and a plurality of powder spreading devices are respectively installed at the positions of the plurality of powder spreading windows.

[0051] Further, refer to Figure 2 Each powder spreading device includes a powder supply component 51, a powder suction component 52, a powder scraping component 55, a powder storage component 54 and a powder stripping component 53. Figure 2As shown, the powder supply component 51 is located above the powder suction component 52, the powder scraping component 55 and the powder storage component 54 are located on the left side of the powder suction component 52, and the powder storage component 54 is located below the powder scraping component 55, and the powder stripping component 53 is located on the right side and lower part of the powder suction component 52. The powder spreading system is provided with a plurality of powder spreading devices, each of which can realize independent powder supply, powder suction, powder scraping and powder stripping, and can realize accurate laying of different powders in one layer, meet the needs of three-dimensional multi-material additive manufacturing, broaden the application scope of three-dimensional multi-material additive manufacturing, and improve production efficiency.

[0052] Reference Figures 1 to 4 The powder supply assembly 51 includes a powder supply cylinder 511, a first pressure sensor 512, a first electromagnet 513, a first reset member 514 and a first powder stop block 515. The powder supply cylinder 511 is used to receive the powder material added from the feeding funnel. The first pressure sensor 512 is installed in the powder supply cylinder 511 to determine whether the amount of powder in the powder supply cylinder 511 is sufficient. A powder outlet is provided at the bottom of the powder supply cylinder 511. The first electromagnet 513, the first reset member 514 and the first powder stop block 515 are all installed at the powder outlet. The first reset member 514 connects the first electromagnet 513 and the first powder stop block 515. When powder supply is required and the first pressure sensor 512 determines that the amount of powder in the powder supply cylinder 511 is sufficient, the first electromagnet 513 is energized to attract the first powder blocking block 515 to move in the direction of the first electromagnet 513, thereby opening the powder outlet of the powder supply cylinder 511 and providing powder material to the powder suction assembly 52. ​​At this time, the first reset member 514 is compressed to store elastic potential energy. When powder supply is not required, the first electromagnet 513 is de-energized, and the first reset member 514 releases the stored elastic potential energy, pushing the first powder blocking block 515 away from the first electromagnet 513 and back to its original position, thereby blocking the powder outlet of the powder supply cylinder 511. The control device 60 can control the power-on state of the first electromagnet 513 according to the signal of the first pressure sensor 512. When the first pressure sensor 512 determines that the amount of powder in the powder supply cylinder 511 is insufficient, the control device 60 will temporarily interrupt the printing work after completing the powder laying of the current layer, control the powder laying device to return to its original position, open the solenoid valve of the corresponding powder adding funnel, and add powder material to the powder supply cylinder 511. After the first pressure sensor 512 determines that the material has been added, it will return to the working state before the interruption.

[0053] Reference Figures 2 to 5The powder suction component 52 includes a powder suction bracket 521, a mesh screen 522 and a vacuum pump 523. The powder spreading device also includes a top screw 19, a sleeve 20, a fixed seat 21, a bearing 22, a rotating shaft 23, a first bearing seat 24, a first coupling 25 and a rotating motor 26. The fixed seat 21, the first bearing seat 24 and the rotating motor 26 are all installed on the mobile platform 18. The powder suction bracket 521 is connected to the fixed seat 21 through the top screw 19, and the mesh screen 522 can be fixedly connected to the sleeve 20 and the rotating shaft 23 by screw connection or the like. The rotating shaft 23 is installed on the first bearing seat 24, and the rotating shaft 23 is connected to the output end of the rotating motor 26 through the first coupling 25. When the rotating motor 26 is turned on, it can drive the rotating shaft 23, the sleeve 20 and the mesh screen 522 to rotate together, and the bearing 22 is installed between the sleeve 20 and the rotating powder suction bracket 521, isolating the movement transmission between the sleeve 20 and the powder suction bracket 521, and the top screw 19 can fix the powder suction bracket 521 on the fixed seat 21, so that when the mesh screen 522 is driven to rotate relative to the moving platform 18, the powder suction bracket 521 can be kept in a stationary state. Figure 2 and Figure 5 As shown, the mesh screen 522 has a plurality of polygonal meshes distributed in a circumferential array, the powder suction bracket 521 is a hollow structure, one end of the powder suction bracket 521 is connected to the vacuum pump 523, and the other end is provided with a plurality of air holes distributed in a circumferential array, such as Figure 6 As shown, when the vacuum pump 523 sucks, the inert gas flows through the forming chamber 1, the polygonal mesh, the inside of the mesh 522, the pores on the powder suction bracket 521, the inside of the powder suction bracket 521, and the vacuum pump 523 in sequence. The mesh 522 is coaxially sleeved on the outside of the powder suction bracket 521, and the powder suction bracket 521 is provided with evenly distributed pores, which can ensure the uniformity of the air pressure inside the mesh 522, that is, the air pressure is consistent on the side surfaces of each concentric cylinder of the mesh 522. Finally, by controlling the powder supply rate of the powder supply component 51 and the flow rate sucked by the vacuum pump 523, it is possible to avoid the generation of invalid powder that is not adsorbed, and to avoid these invalid powders from falling directly onto the forming platform 14 and affecting the powder spreading accuracy.

[0054] Furthermore, the inscribed circle diameter D1 of the polygonal mesh is less than the outer diameter d of the powder particles and less than the circumscribed circle diameter D2 of the polygonal mesh. When the powder falls from the powder supply assembly 51, the suction action of the vacuum pump 523 will adsorb the powder particles on the mesh 522, and the powder particles will not be sucked into the mesh 522, and will not completely cover the polygonal mesh, so that the airflow can still pass through the gap between the polygonal mesh and the powder particles, thereby maintaining the pressure difference between the inside and outside of the mesh 522, continuing to adsorb more powder particles, and controlling the powder thickness on the periphery of the mesh 522 through the powder scraping assembly 55. During the movement of the mobile platform 18, the powder on the periphery of the mesh 522 is stripped off by the powder stripping assembly 53 for spreading the powder, and finally achieving precise adjustment of the material type and the distribution form of the powder in the printing plane. It can be understood that the polygonal mesh is a polygonal mesh with a circumscribed circle, such as a regular polygonal mesh. Furthermore, the polygonal mesh is a square hole, and the side length of the square hole is less than the diameter of the smallest powder particle, thereby ensuring that the powder will not be sucked into the mesh 522.

[0055] Furthermore, if Figure 6 and Figure 7 As shown, when the powder supply component 51 continues to supply powder, due to too many factors of real environment change, the thickness of the powder layer adsorbed on the periphery of the mesh 522 is often variable and uncontrollable, but the general powder thickness will be greater than the set printing layer thickness. Therefore, the present invention adopts a powder scraping component 55 to control the thickness of the powder on the periphery of the mesh. The powder scraping component 55 is installed on the mobile platform 18 and is located on the first side of the powder suction component 52. It is used to scrape off some powder particles on the periphery of the mesh 522 so that the powder thickness on the periphery of the mesh 522 reaches the required thickness. Further, referring to Figure 4 and Figure 7The powder scraper assembly 55 includes a slide 554, a powder scraper bracket 553, a powder scraper strip 551 and a cover plate 552. The slide 554 can be slidably connected to the mobile platform 18 and can slide relative to the mobile platform 18 along the X-axis, Y-axis and Z-axis directions. The powder scraper bracket 553 is installed on the slide 554, the cover plate 552 is installed on the upper side of the end of the powder scraper bracket 553, and the powder scraper strip 551 is installed between the powder scraper bracket 553 and the cover plate 552 and is located at the front end of the powder scraper bracket 553. During installation, after installing the powder scraping bracket 553, the cover plate 552 and the powder scraping strip 551 on the slide 554, first adjust the Z axis of the slide 554 so that the axis of the powder scraping strip 551 is at the same height as the axis of the mesh 522, and then adjust the X axis of the slide 554 so that the working surface of the powder scraping strip 551 is aligned with the working surface of the mesh 522, that is, the powder scraping strip 551 can completely scrape all the powder on the outer surface of the mesh 522, and finally adjust the Y axis of the slide 554 to change the distance between the powder scraping strip 551 and the axis of the mesh 522. The difference obtained by subtracting the outer surface radius of the mesh 522 and the outer surface radius of the powder scraping strip 551 from this distance is the required powder thickness, that is, the printing layer thickness. The cover plate 552 is provided with a chamfer, which can be used to control the flow direction of the scraped powder to ensure that the powder can accurately fall into the powder storage component 54. The powder scraping assembly 55 of the present invention can scrape the powder particles on the periphery of the mesh 522 so that the powder thickness on the periphery of the mesh 522 reaches the required powder thickness, and combined with the movement of the mobile platform 18, the rotation of the mesh 522 and the stripping of the powder stripping assembly 53, the thickness of the powder falling on the forming platform 14 can be accurately controlled to ensure the quality and accuracy of multi-material additive manufacturing. Furthermore, the slide 554 is a precision slide.

[0056] Furthermore, if Figure 2 and Figure 6As shown, the powder storage assembly 54 is installed on the mobile platform 18 and is located below the powder scraping assembly 55, and is used to store the powder particles scraped by the powder scraping assembly 55. The powder storage assembly 54 includes a powder storage cylinder 541, a second powder blocking block 542, a second reset member 543, a second electromagnet 544 and a second pressure sensor 545. The second pressure sensor 545 is installed in the powder storage cylinder 541. A powder outlet is provided below the powder storage cylinder 541. The second reset member 543 and the second electromagnet 544 are both installed at the powder outlet, and the second reset member 543 is connected to the second powder blocking block 542 and the second electromagnet 544. A powder collecting bin is also provided in the forming chamber 1. When the weight of the powder stored in the powder storage cylinder 541 is too large, the mobile platform 18 drives the powder storage assembly 54 to move to the top of the powder collecting bin, and the second pressure sensor 545 sends a signal to the control device 60 to control the second electromagnet 544 to be powered on, attracting the second powder blocking block 542 to move toward the second electromagnet 544, thereby opening the powder outlet of the powder storage cylinder 541 to pour the powder in the powder storage cylinder 541 into the powder collecting bin. At this time, the second reset member 543 is compressed to store elastic potential energy. When the second pressure sensor 545 determines that the powder in the powder storage cylinder 541 has been poured out, the second electromagnet 544 is powered off, and the second reset member 543 releases the stored elastic potential energy, pushing the second powder blocking block 542 away from the second electromagnet 544 and returning to its original position, thereby blocking the powder outlet of the powder storage cylinder 541. Furthermore, there are multiple powder collecting bins. For example, in the present embodiment, there are three powder collecting bins, namely the first powder collecting bin 12, the second powder collecting bin 11 and the third powder collecting bin 10. When pouring powder, the first powder collecting bin 12, the second powder collecting bin 11 and the third powder collecting bin 10 are respectively located below the first powder spreading device 5, the second powder spreading device 7 and the third powder spreading device 9. The powder storage component 54 of the present invention can not only store the powder scraped off by the powder scraping component 55 to prevent the powder from falling on the forming platform 14 and affecting the accuracy, and realize the simultaneous powder supply and powder spreading, but also can realize the recycling of powder, reduce the waste of powder materials, and save manufacturing costs. Further, referring to Figure 2 The side of the powder storage cylinder 541 close to the powder suction component 52 is tilted along the contour of the mesh screen 522 , and combined with the cover plate 552 in the powder scraping component 55 , it can be ensured that the scraped powder can completely fall into the powder storage cylinder 541 .

[0057] Further, refer to Figure 2 and Figure 6The powder stripping assembly 53 includes an electrostrictive element 532, a third reset member 533, a pin 534 and a reset plate 535. A groove 531 is provided on the mobile platform 18. The third reset member 533 is installed in the groove 531 and connected to the reset plate 535. The reset plate 535 is installed on the mobile platform 18. There are multiple electrostrictive elements 532 and the same number of pins 534. One pin 534 is correspondingly connected to one electrostrictive element 532. The multiple pins 534 are distributed along the axial direction of the mesh 522. The electrostrictive element 532 is electrically connected to the control device 60. When powder needs to be spread, the control device 60 sends an electrical signal to the electrostrictive element 532, so that the electrostrictive element 532 extends outward, pushes the pin 534 to move outward, and stretches the third reset member 533 to push the reset plate 535 to move. When the ejector pin 534 moves toward the mesh 522, the ejector pin 534 can contact the powder particles on the periphery of the mesh 522, and the generated force can push the powder particles away from the polygonal mesh. At the same time, the working end of the ejector pin 534 can also change the airflow state of the polygonal mesh close to it, specifically, at the position close to the polygonal mesh, it blocks part of the space corresponding to the polygonal mesh, thereby reducing the cross-sectional area of ​​the airflow passage there, thereby changing the airflow state there, so that the adsorption force on the powder particles is reduced, destroying the original force of the powder particles, and finally under the action of gravity, the powder particles fall toward the forming platform 14 to achieve powder spreading. At this time, the powder particles at other positions can still be adsorbed on the surface of the mesh 522 under the action of the pressure difference and will not fall on the forming platform 14. The working end of the ejector pin 534 is a sphere, and the diameter of the sphere is equivalent to the diameter of the powder particles. When the ejector pin 534 pushes the powder particles away from the polygonal mesh, the sphere can block a part of the polygonal mesh, so that the powder particles fall on the forming platform 14 under the action of gravity. Further, the working end of the ejector pin 534 does not contact the mesh 522, but changes the airflow state of the polygonal mesh at a position close to the polygonal mesh, so that the powder particles fall onto the forming platform 14 more smoothly. The ejector pin 534 does not interfere with the mesh 522 and does not affect the rotation of the mesh 522. During the continuous powder spreading process, the ejector pin 534 can always remain in the extended state, constantly changing the force of the powder particles transported by the mesh 522, so as to better achieve continuous powder spreading. When powder spreading is not required, the ejector pin 534 can move away from the mesh 522 without affecting the airflow state of the polygonal mesh, so that the powder particles can remain adsorbed on the periphery of the mesh 522. The ejector pin 534 can be fixedly connected to the end of the electrostrictive element 532. When the electrostrictive element 532 retracts, the ejector pin 534 retracts together and moves away from the mesh 522. In one embodiment of the present invention, the retraction of the ejector pin 534 is achieved by the cooperation of the third reset member 533 and the reset plate 535. In some other embodiments, the ejector pin 534 may also be retracted in other ways.

[0058] Furthermore, the powder stripping assembly 53 is installed below the second side of the mesh 522, rather than directly below it, so as to prevent the ejector pin 534 from interfering with the powder particles at other polygonal mesh positions on the mesh 522 during movement, thereby avoiding spreading powder on areas that do not need to be spread. Since there is a certain height between the powder stripping position and the forming platform 14, in order to reduce the error caused by the horizontal speed of the powder particles, this height can be reduced, preferably to 8mm~10mm. Furthermore, the sphere at the working end of the ejector pin 534 is made of soft material, and when colliding with the powder particles, it can absorb part of the kinetic energy of the powder, thereby reducing the speed of the powder in the horizontal direction, thereby reducing the error. In addition, this error can also be eliminated by compensating the slicing data of the multi-material product 13. The horizontal movement distance of the powder during the falling process can be calculated, and this value can be imported into the horizontal compensation module of the path planning software. When the area where powder is to be spread reaches the designated position, the powder stripping component 53 can strip off the powder on the mesh screen 522 in advance. During the falling process of the powder, its horizontal component velocity continues to move the powder a certain distance in the horizontal direction. When the powder falls on the forming platform 14, the horizontal distance moved is equal to the distance compensated in the software, so that the powder falls exactly on the powder spreading area, achieving precise powder spreading.

[0059] In the present invention, the powder supply component 51, the powder suction component 52, the powder scraping component 55, the powder storage component 54 and the powder stripping component 53 are all installed on the mobile platform 18, and can move above the forming platform 14 with the mobile platform 18, and the powder supply component 51, the powder scraping component 55, the powder storage component 54 and the powder stripping component 53 are distributed in sequence along the rotation direction of the mesh screen 522. After the powder supply component 51 provides powder material, the powder suction component 52 can absorb powder particles, and the powder scraping component 55 can scrape part of the powder particles to the powder storage component 54 to control the powder thickness, and then the powder stripping component 53 can peel the powder particles onto the forming platform 14. While supplying powder, powder scraping and stripping can be performed at the same time, thereby greatly improving the printing speed and improving production efficiency.

[0060] Further, refer to Figure 3, the horizontal movement of the mobile platform 18 is driven by the mobile mechanism 3, and the mobile mechanism 3 includes a mobile motor 31, a second coupling 32, a ball screw 33, a second bearing seat 34, a linear guide 35 and a linear slider 36. A fixed platform 37 is provided in the forming chamber 1, and the mobile motor 31 and the second bearing seat 34 are installed on the fixed platform 37. One end of the ball screw 33 is connected to the second bearing seat 34, and the other end is connected to the mobile motor 31 through the second coupling 32. The mobile platform 18 is connected to the nut seat of the ball screw 33, and is connected to the linear guide 35 through the linear slider 36. When the mobile motor 31 is started, it can drive the ball screw 33 to rotate, and then drive the nut seat to slide on the ball screw 33, and finally drive the horizontal movement of the mobile platform 18. The powder spreading device is installed on the mobile platform 18. When the mobile platform 18 is translated, it can drive the powder spreading device to translate together.

[0061] Furthermore, if Figure 8 As shown, the control device 60 is connected to the electrostrictive element 532 via a signal line, and the control device 60 can independently control the power-on state of each electrostrictive element 532, thereby controlling whether each ejector pin 534 peels off powder. Each time the control device 60 sends a signal, all ejector pins 534 in the state of "1" peel off the corresponding powder, and all ejector pins 534 in the state of "0" do not peel off powder, thereby completing the powder laying on the forming platform 14 corresponding to this straight line. Subsequently, the moving motor 31 moves forward one step, and the rotating motor 26 rotates one step in coordination. The corresponding relationship can be derived from parameters such as the diameter of the mesh screen 522, the lead of the ball screw 33, and the transmission ratio of the mechanism. Then, the control device 60 sends a signal again to complete the powder laying on the next straight line, for example Figure 8 The fifth powder spreading is to spread the powder in the fifth straight line area on the forming platform 14. Repeating this process several times, the powder spreading in the working area of ​​the entire forming platform 14 can be completed.

[0062] The embodiment of the present invention further provides a screen-based peeling multi-material additive powder spreading method, which is performed using the above-mentioned multi-material additive powder spreading system and includes the following steps:

[0063] Step S1, according to the amount of materials required for the multi-material product 13, a corresponding number of powder spreading devices are installed on the mobile platform 18, different powder materials are added to the powder supply component 51 in each powder spreading device, the distance between the powder scraping component 55 and the mesh screen 522 is adjusted, the power of the powder spreading system is turned on, and each device returns to the origin;

[0064] Step S2: according to the data of the first pressure sensor 512, it is determined whether it is necessary to add powder to the powder supply cylinder 511 of the powder supply assembly 51 through the powder adding device, the data of the multi-material product 13 that has been sliced ​​is imported, and the gas circulation device 70 is turned on until the oxygen content in the forming chamber 1 reaches the working level, and the printing is prepared;

[0065] Step S3, start the vacuum pump 523 to form a relative negative pressure inside the mesh 522, the control device 60 energizes the first electromagnet 513 to make the first powder blocking block 515 leave the powder outlet of the powder supply cylinder 511, start the rotary motor 26, the powder is adsorbed on the surface of the mesh 522, the powder scraping assembly 55 scrapes the powder, and the obtained powder layer thickness is the printed layer thickness;

[0066] Step S4: while performing step S3, the moving motor 31 is started, and the moving motor 31 and the rotating motor 26 move in coordination. According to the slice data, during the powder spreading process, if the area needs to be powdered, the control device 60 energizes the electrostrictive element 532 to make the ejector pin 534 slide out of the groove 531, and the ball of the ejector pin 534 touches the powder particles on the periphery of the mesh 522, so that the powder particles are peeled off and fall into the area, and the powder spreading is completed;

[0067] Step S5, after the powder spreading of the area is completed, if the next area still needs to be spread with powder, the power-on state of the electrostrictive element 532 remains unchanged, the ball of the ejector pin 534 remains in the same position, and the powder particles it touches are continuously peeled off to achieve continuous powder spreading; if the next area does not need to be spread with powder, the control device 60 turns off the power of the electrostrictive element 532, the third reset member 533 drives the reset plate 535 to retract the ejector pin 534 into the groove 531, and the ball of the ejector pin 534 no longer touches the powder particles on the periphery of the mesh 522, thereby stopping the powder spreading;

[0068] Step S6: During the whole powder spreading process, the second pressure sensor 545 keeps working, and judges whether the powder in the powder storage cylinder 541 needs to be cleaned according to the pressure value. If necessary, after the printing of the current layer is completed, the powder spreading device returns to the origin, the second electromagnet 544 is energized, the second powder blocking block 542 leaves the powder outlet of the powder storage cylinder 541, and the powder is poured into the powder collecting bin. If not necessary, the current working state is not interrupted.

[0069] Step S7, multiple powder spreading devices work simultaneously, and driven by the moving mechanism 3, a multi-material powder spreading of a layer of parts is realized;

[0070] Step S8, the laser device 2 irradiates and melts the laid powder to complete the manufacturing of one layer of parts;

[0071] Step S9, determining whether the multi-material product 13 has been manufactured, if it has been manufactured, then the process ends, if it has not been manufactured, then executing step S10;

[0072] Step S10, lowering the forming platform 14 by a layer thickness;

[0073] Step S11, the moving mechanism 3 drives the powder spreading device to move in the opposite direction, repeating the powder spreading process in step S4 to step S7, and completing the powder spreading of this layer through the powder spreading device;

[0074] Step S12, execute step S8, and then determine whether the product has been manufactured. If it is completed, end; if not, return to step S10 and execute the subsequent steps in sequence.

[0075] It should be noted that in step S2, although the gas circulation device 70 provides inert gas to the forming chamber 1, in actual circumstances, whether printing can be started is determined based on the oxygen content to prevent oxidation of the material during the printing process, and the oxygen content can also be directly detected and displayed using corresponding measuring instruments. Therefore, in step S2, after turning on the gas circulation device 70, the oxygen content in the forming chamber 1 is monitored in real time until the oxygen content in the forming chamber 1 reaches the working level before preparing for printing.

[0076] It should be noted that in the description of the present invention, if there are any orientation descriptions, such as up, down, front, back, left, right, etc., the orientations or positional relationships indicated are all based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and cannot be understood as a limitation on the present invention.

[0077] In the description of the present invention, the first restoring member 514, the second restoring member 543 and the third restoring member 533 may adopt structures such as restoring springs.

[0078] In the description of the present invention, "several" means one or more, "more" means two or more, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0079] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0080] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A screen-based peeling multi-material additive powder laying system, characterized in that: It comprises a forming chamber (1) and a powder spreading device; A forming platform (14) and a moving platform (18) are provided in the forming chamber (1), and the moving platform (18) is capable of moving above the forming platform (14) to spread powder; The powder spreading device is installed on the mobile platform (18), and a plurality of the powder spreading devices are provided, each of the powder spreading devices comprising a powder supply component (51), a powder suction component (52), a powder scraping component (55), a powder storage component (54), and a powder stripping component (53); The powder supply component (51) is mounted on the mobile platform (18) and is located above the powder suction component (52), and is used to provide powder material to the powder suction component (52); The powder suction component (52) comprises a mesh screen (522) and a vacuum pump (523); the mesh screen (522) is rotatably connected to the mobile platform (18); the mesh screen (522) has polygonal mesh holes distributed in a circumferential array; the vacuum pump (523) is capable of suction from the inside of the mesh screen (522) to absorb powder particles falling from the powder supply component (51) onto the periphery of the mesh screen (522); The powder scraping assembly (55) is mounted on the mobile platform (18) and is located on the first side of the powder suction assembly (52), and is used to scrape off some powder particles on the periphery of the mesh screen (522) so that the powder thickness on the periphery of the mesh screen (522) reaches a desired thickness. The powder scraping assembly (55) comprises a slide table (554), a powder scraping bracket (553), a powder scraping strip (551) and a cover plate (552). The slide table (554) is slidably connected to the mobile platform (18) and can slide relative to the mobile platform (18) along the X-axis, Y-axis and Z-axis directions. The powder scraping bracket (553) is mounted on the slide table (554), the cover plate (552) is mounted on the powder scraping bracket (553), the powder scraping strip (551) is mounted between the powder scraping bracket (553) and the cover plate (552), and the cover plate (552) is provided with a chamfer. The powder storage component (54) is installed on the mobile platform (18) and is located below the powder scraping component (55), and is used to store powder particles scraped off by the powder scraping component (55); The powder stripping assembly (53) is installed on the moving platform (18) and is located on the second side of the powder suction assembly (52), and the powder stripping assembly (53) is used to strip powder particles on the periphery of the mesh screen (522) from the mesh screen (522) so that the powder particles fall onto the forming platform (14); The powder supply component (51), the powder scraping component (55), the powder storage component (54), and the powder stripping component (53) are sequentially distributed along the rotation direction of the mesh screen (522).

2. The screen-based peeling multi-material additive powder laying system according to claim 1, characterized in that: The inscribed circle diameter D1 of the polygonal mesh is less than the outer diameter d of the powder particles and less than the circumscribed circle diameter D2 of the polygonal mesh.

3. The screen-based peeling multi-material additive powder laying system according to claim 2, characterized in that: It also includes a powder adding device, which includes a plurality of powder adding funnels, the feeding ports of the powder adding funnels penetrate into the forming chamber (1), an electromagnetic valve is provided at the feeding port, the movable platform (18) can drive the powder supply component (51) to move below the feeding port, and the electromagnetic valve can open the feeding port to add powder material into the powder supply component (51).

4. The screen-based peeling multi-material additive powder laying system according to claim 3, characterized in that: The powder supply assembly (51) comprises a powder supply cylinder (511), a first pressure sensor (512), a first electromagnet (513), a first reset member (514) and a first powder blocking block (515); The powder supply cylinder (511) is installed on the mobile platform (18) and is located above the powder suction component (52), and is used to receive powder material from the powder adding funnel; The first pressure sensor (512) is installed in the powder supply cylinder (511) and is used to determine whether the amount of powder in the powder supply cylinder (511) is sufficient; A powder outlet is provided at the bottom of the powder supply cylinder (511); the first electromagnet (513), the first reset member (514) and the first powder blocking block (515) are all installed at the powder outlet; the first reset member (514) connects the first electromagnet (513) and the first powder blocking block (515); When powder supply is required and the first pressure sensor (512) determines that the amount of powder in the powder supply cylinder (511) is sufficient, the first electromagnet (513) is energized to attract the first powder blocking block (515) to move in the direction of the first electromagnet (513), thereby opening the powder outlet of the powder supply cylinder (511) to supply powder material to the powder suction component (52), and the first reset member (514) is compressed to store elastic potential energy; When powder supply is not required, the first electromagnet (513) is powered off, and the first reset element (514) releases stored elastic potential energy to push the first powder blocking block (515) away from the first electromagnet (513) and back to its original position, thereby blocking the powder outlet of the powder supply cylinder (511).

5. The screen-based peeling multi-material additive powder laying system according to claim 4, characterized in that: The powder suction component (52) further comprises a powder suction bracket (521), the powder suction bracket (521) being mounted on the mobile platform (18), and the powder suction bracket (521) being a hollow structure, one end of the powder suction bracket (521) being connected to the vacuum pump (523), and the other end being provided with a plurality of air holes distributed in a circular array, the mesh screen (522) being coaxially sleeved on the outer periphery of the powder suction bracket (521), and when the vacuum pump (523) is suctioning, the inert gas flows sequentially through: the forming chamber (1), the polygonal mesh, the air holes, the interior of the powder suction bracket (521), and the vacuum pump (523).

6. The screen-based peeling multi-material additive powder laying system according to claim 5, characterized in that: The powder storage assembly (54) comprises a powder storage cylinder (541), a second powder blocking block (542), a second reset member (543), a second electromagnet (544) and a second pressure sensor (545); the second pressure sensor (545) is installed in the powder storage cylinder (541) and is used to determine whether the powder storage cylinder (541) needs to be dumped; A powder outlet is provided below the powder storage cylinder (541); the second reset member (543) and the second electromagnet (544) are both installed at the powder outlet, and the second reset member (543) is connected to the second powder blocking block (542) and the second electromagnet (544); A powder collecting bin is also provided in the forming chamber (1). When the weight of the powder stored in the powder storage cylinder (541) is too large, the movable platform (18) drives the powder storage assembly (54) to move above the powder collecting bin, and the second electromagnet (544) is energized to attract the second powder blocking block (542) to move in the direction of the second electromagnet (544), thereby opening the powder outlet of the powder storage cylinder (541) to pour the powder in the powder storage cylinder (541) into the powder collecting bin. At this time, the second reset member (543) is compressed to store elastic potential energy. When the second pressure sensor (545) determines that the powder in the powder storage cylinder (541) has been poured out, the second electromagnet (544) is powered off, and the second reset member (543) releases the stored elastic potential energy to push the second powder blocking block (542) away from the second electromagnet (544) and back to its original position, thereby blocking the powder outlet of the powder storage cylinder (541).

7. The screen-based peeling multi-material additive powder laying system according to claim 6, characterized in that: The powder stripping assembly (53) comprises an electrostrictive element (532) and an ejector pin (534); the electrostrictive element (532) and the ejector pin (534) are both provided in plurality and in the same number; the plurality of ejector pins (534) are correspondingly connected to the plurality of electrostrictive elements (532); When powder stripping is required, the electrostrictive element (532) can drive the ejector pin (534) to move toward the mesh screen (522), so that the ejector pin (534) contacts the powder particles on the periphery of the mesh screen (522) and pushes the powder particles away from the polygonal mesh. The working end of the ejector pin (534) can change the airflow state of the polygonal mesh close to it, so as to change the force applied to the powder particles, so that the powder particles fall onto the forming platform (14) under the action of gravity. When powder stripping is not required, the ejector pin (534) can move away from the mesh screen (522).

8. The screen-based peeling multi-material additive powder laying system according to claim 7, characterized in that: The working end of the ejector pin (534) is a sphere, the sphere is made of a soft material, and the diameter of the sphere is comparable to the diameter of the powder particles.

9. A peeling multi-material additive powder laying method based on a mesh screen, characterized in that: The method is carried out using the screen-based peeling multi-material additive powder laying system as claimed in claim 8, comprising the following steps: Step S1, according to the quantity of materials required for the multi-material product (13), a corresponding number of powder spreading devices are installed on the mobile platform (18), different powder materials are added to the powder supply component (51) in each powder spreading device, the distance between the powder scraping component (55) and the mesh screen (522) is adjusted, the power of the powder spreading system is turned on, and each device returns to the origin; Step S2, judging whether it is necessary to add powder to the powder supply cylinder (511) of the powder supply assembly (51) through the powder adding device according to the data of the first pressure sensor (512), importing the data of the multi-material product (13) that has been sliced, turning on the gas circulation device (70), until the oxygen content in the forming chamber (1) reaches the working level, and preparing for printing; Step S3, turning on the vacuum pump (523) to form a relative negative pressure inside the mesh screen (522), the control device (60) energizes the first electromagnet (513), causing the first powder blocking block (515) to leave the powder outlet of the powder supply cylinder (511), starting the rotary motor (26), the powder being adsorbed on the surface of the mesh screen (522), the powder scraping assembly (55) scraping the powder, and the obtained powder layer thickness is the printed layer thickness; Step S4, while performing step S3, the moving motor (31) is started, and the moving motor (31) and the rotating motor (26) move in coordination. According to the slice data, during the powder spreading process, if the area needs to be powdered, the control device (60) energizes the electrostrictive element (532), so that the ejector pin (534) slides out of the groove (531), and the ball of the ejector pin (534) touches the powder particles on the periphery of the mesh screen (522), so that the powder particles are peeled off and fall into the area, and the powder spreading is completed; Step S5, after the powder spreading of the area is completed, if the next area still needs to be spread with powder, the power-on state of the electrostrictive element (532) remains unchanged, the ball of the ejector pin (534) remains in the same position, and the powder particles it touches are continuously peeled off to achieve continuous powder spreading; if the next area does not need to be spread with powder, the control device (60) turns off the power of the electrostrictive element (532), the third reset member (533) drives the reset plate (535) to retract the ejector pin (534) into the groove (531), and the ball of the ejector pin (534) no longer touches the powder particles on the periphery of the mesh screen (522), thereby stopping the powder spreading; Step S6: During the entire powder spreading process, the second pressure sensor (545) continues to work, and determines whether the powder in the powder storage cylinder (541) needs to be cleaned according to the pressure value. If necessary, after the printing work of the current layer is completed, the powder spreading device returns to the original point, the second electromagnet (544) is energized, and the second powder blocking block (542) leaves the powder outlet of the powder storage cylinder (541), and the powder is poured into the powder collecting bin. If not necessary, the current working state is not interrupted; Step S7, multiple powder spreading devices work simultaneously, and driven by the moving mechanism (3), a multi-material powder spreading of a layer of parts is achieved; Step S8, the laser device (2) irradiates and melts the laid powder to complete the manufacturing of a layer of parts; Step S9, determining whether the multi-material product (13) has been manufactured. If so, the process ends. If not, the process proceeds to step S10; Step S10, lowering the forming platform (14) by a layer thickness; Step S11, the moving mechanism (3) drives the powder spreading device to move in the opposite direction, repeating the powder spreading process in steps S4 to S7, and completing the powder spreading of this layer through the powder spreading device; Step S12, execute step S8, and then determine whether the product has been manufactured. If it is completed, end; if not, return to step S10 and execute the subsequent steps in sequence.

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