A powder spreading system and powder spreading method for multi-material additive manufacturing

Abstract

The present invention relates to the field of additive manufacturing technology, and specifically to a powder spreading system and powder spreading method for multi-material additive manufacturing. The system is modified on the basis of existing additive manufacturing, and a forming cylinder is arranged in an airtight molding chamber. The forming cylinder is used to cooperate with the bottom of the airtight molding chamber to form a powder bed area, which is conducive to the powder spreading device to spread powder; a micro-electromechanical structure is arranged on the powder spreading device, and the micro-electromechanical structure can absorb or release material powder, so that uniform powder spreading can be achieved, and the powder spreading thickness is conducive to control. Moreover, the characteristics of the micro-electromechanical structure can achieve the simultaneous laying of multiple materials, and the laying area is precisely controllable. The micro-electromechanical structure can realize single-cylinder molding, which not only saves space and reduces the weight of the entire equipment, but also reduces the complexity of the entire processing equipment.

Description

Technical Field

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

[0002] Powder bed fusion (LPBF) technology is an additive manufacturing technology that selectively melts / sinters powder bed areas through thermal energy, including powder bed laser melting technology. In the past two decades, LPBF technology has continued to develop. Compared with traditional additive manufacturing technology, LPBF can not only use different types of materials in the manufacturing process, but also form specific structures in different parts of the parts, so as to accurately make the target part of the part obtain excellent properties such as high hardness, high wear resistance, high corrosion resistance, and reduce production costs.

[0003] Functionally gradient composite (FGM) is a composite material with a special structure. It is different from the traditional way of uniformly mixing composite materials, nor is it a direct splicing of multiple materials. FGM has no clear material boundary, and the content of different materials at the junction changes continuously. Therefore, FGM can not only have different performances in different parts of the parts, but also avoid the mismatch of thermodynamic properties at the junction of different materials, which leads to damage under great thermal stress. Therefore, the excellent properties of FGM make it widely used in the aerospace field, which is generally achieved through LPBF technology.

[0004] Conventional LPBF technology is generally used to manufacture metal parts of a single material, and the powder spreading mechanism used is a scraper or roller. However, when manufacturing parts with multiple materials and special distributions, especially when FGM needs to be processed, the existing blade-type and ultrasonic powder supply mechanisms obviously cannot meet the above-mentioned working requirements. In response to such a situation, the patent with publication number CN113290849B discloses an additive manufacturing method of powder spreading printing and molding. The invention prints powder and melts it by spreading powder, which solves the problem that the traditional powder printing process relies on the point-by-point solidification molding principle of scanning devices or trajectory control. It has high molding efficiency, high material utilization, a large number of applicable raw materials, and low cost. Although the powder printing linear array module in this patent provides two linear array modules that can manipulate powder particles, and the two linear array modules correspondingly print out the powder material A pattern and the powder material B pattern, it is still linear powder spreading, and its powder spreading thickness depends entirely on the linear motion rate of the linear motion module and the discharge speed of the linear array module. Therefore, the control system has high requirements, and the vibration of the linear motion module and the linear array module during the movement process can easily affect the quality of the powder spreading, directly affecting the quality of the later parts. Summary of the invention

[0005] To achieve the above objectives, the present invention provides a powder spreading system and a powder spreading method for multi-material additive manufacturing, which can not only improve the powder spreading accuracy and better control the performance of parts, but also improve efficiency and reduce production costs.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A powder laying system for multi-material additive manufacturing, comprising:

[0008] Airtight molding chamber;

[0009] A molding cylinder, which is installed at the bottom of the airtight molding chamber in a manner that it can be lifted and lowered, and the molding cylinder cooperates with the bottom of the airtight molding chamber to form a powder bed area;

[0010] A powder spreading device is installed in the airtight molding chamber, the powder spreading device can realize spatial displacement in the airtight molding chamber, and the spatial displacement area of ​​the powder spreading device in the airtight molding chamber covers all areas of the molding cylinder opening; a micro-electromechanical structure is arranged on the powder spreading end of the powder spreading device, and the micro-electromechanical structure can absorb the material powder in the powder spreading device and transfer and roll print on the powder bed area;

[0011] A feeding mechanism, which is installed on the airtight molding chamber, and the feeding mechanism can supply powders of various materials to the powder spreading device;

[0012] A laser system, which is installed on the airtight molding chamber, and the laser system can melt and mold the material powder falling into the powder bed area;

[0013] A gas circulation system is communicated with the airtight molding chamber.

[0014] In some embodiments, the powder spreading device includes a spatial displacement mechanism, a plurality of powder bins and a plurality of powder spreading rollers. The spatial displacement mechanism is installed in the airtight molding chamber. All the powder bins are installed on the working end of the spatial displacement mechanism and can receive the material powder delivered by the feeding mechanism. Each of the powder spreading rollers can be rotatably installed on the lower end discharge port of a corresponding powder bin. The outer surface of each of the powder spreading rollers can be in rolling contact with the powder bed area in the powder bed area, and the outer surface of the powder spreading roller is coated with the micro-electromechanical structure.

[0015] In some embodiments, the micro-electromechanical structure includes an electrostrictive material layer and a controller, wherein the electrostrictive material layer is coated on the outer surface of the powder spreading roller, and a plurality of holes are provided on the electrostrictive material layer. The controller is mounted on the outer wall of the powder bin or the end of the powder spreading roller, and the controller controls the voltage at both ends of any region of the electrostrictive material layer to force the electrostrictive material layer to contract or expand, so that the holes can attach or release material powder.

[0016] In some embodiments, the electrostrictive material layer is composed of a plurality of electrostrictive units, all of the electrostrictive units are sequentially arranged and coated on the outer surface of the powder spreading roller, and all of the electrostrictive units are electrically connected to the controller.

[0017] In some embodiments, the spatial displacement mechanism includes an electric slide rail and a mounting seat mounted on the electric slide rail, the electric slide rail is mounted on the inner wall of the airtight molding chamber, all the powder bins are mounted on the mounting seat, and the electric slide rail can drive all the powder bins to reciprocate in the area between the discharge end of the feeding mechanism and the powder bed area away from the side of the feeding mechanism.

[0018] In some embodiments, all the powder bins are provided with a driver for driving the powder spreading roller to rotate.

[0019] In some embodiments, the feeding mechanism includes a plurality of powder bottles and powder feeding pipelines matched with the powder bottles, all of the powder bottles are installed on the airtight molding chamber, the output ends of all of the powder feeding pipelines pass through the side wall of the airtight molding chamber and are placed inside the airtight molding chamber, each of the powder feeding pipelines is adapted to one of the powder bins, and each of the powder feeding pipelines is provided with a control valve in the area outside the airtight molding chamber.

[0020] In some embodiments, the laser system includes a laser, a beam expander collimator, a scanning galvanometer and an optical lens. The beam expander collimator is arranged on the outer wall of the airtight molding chamber, and the scanning galvanometer is installed on the top of the airtight molding chamber. The laser emitted by the laser can enter the scanning galvanometer through the beam expander collimator. The optical lens is installed on the inner wall of the top of the airtight molding chamber and is located directly above the molding cylinder. The optical lens can receive the laser emitted by the scanning galvanometer and irradiate the laser on the material powder in the powder bed area to heat and melt it.

[0021] In some embodiments, the gas circulation system includes a nitrogen generating device, a vacuum pumping device, an oxygen content monitoring device and a gas circulation purification device. The gas circulation purification device, the nitrogen generating device and the vacuum pumping device are all connected to the airtight molding chamber, and the oxygen content monitoring device is installed in the airtight molding chamber.

[0022] A powder laying method for multi-material additive manufacturing comprises the following steps:

[0023] Step S100, digitize the part to be processed in three dimensions and obtain a three-dimensional CAD model; select a suitable processing layer thickness according to the processing accuracy requirements and the maximum processing accuracy of the equipment; use slicing software to perform layered slicing and slice data packaging, perform scanning path planning according to the slice contour of each package, and import it into the processing system after completion, ready for processing;

[0024] Step S200, start the vacuum pumping device, use the vacuum pumping device to vacuum and deoxygenate the airtight molding chamber, when the pressure in the airtight molding chamber is -10 to -15 KPa, start the nitrogen generating device and fill it with nitrogen, when the air pressure in the airtight molding chamber reaches 15 to 22 KPa, turn off the nitrogen generating device, continue to start the vacuum pumping device to vacuum, repeat the above operation several times until the oxygen content monitoring device detects that the oxygen content in the airtight molding chamber is lower than 0.1% and the air pressure reaches 15 to 22 KPa; turn off the nitrogen generating device and the vacuum pumping device, and start the gas circulation purification device to realize the separate circulation of gas in the airtight molding chamber;

[0025] Step S300, the feeding mechanism conveys the corresponding material powder into the corresponding powder bin, and after all the powder bins have finished adding the material powder, the powder spreading mechanism is turned on; the spatial displacement mechanism in the powder spreading mechanism drives all the powder bins to move from one side of the powder bed area to the other side thereof, and the driver drives the powder spreading roller to rotate following the movement of the spatial displacement mechanism, and the linear speed of the powder spreading roller is the same as the horizontal displacement rate of the spatial displacement mechanism; the controller controls the electrostrictive unit on the side of the corresponding powder spreading roller close to the powder bin outlet to selectively adsorb the material powder discharged from the corresponding powder bin according to the material distribution information data provided by the slicing software, and at the same time controls the electrostrictive unit on the bottom side of the corresponding powder spreading roller to release the adsorbed material powder, so that the fallen material powder falls into the powder bed area; after the spatial displacement mechanism moves to the limit away from the feeding mechanism, the driver stops working, and the spatial displacement mechanism drives the powder bin to reset, and prepares for printing the next layer;

[0026] Step S400: After the powder spreading mechanism completes the powder spreading work of a sheet layer, the laser system performs material contour scanning on the material powder on the powder bed area according to the material distribution information data provided by the slicing software to achieve material powder melting. After the laser system completes the melting of the material powder of the corresponding sheet layer, it stops working and waits for the next round of melting work;

[0027] Step S500, after the material in the powder bed area is cold cut and melted, repeat steps S300 and S400 multiple times; after completing the powder spreading and laser melting of a preset number of sheets, control the forming cylinder to descend to a preset height; then repeat steps S300 and S400 multiple times until the powder spreading and laser melting of all sheets are completed.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The powder spreading system for multi-material additive manufacturing of the present invention is modified on the basis of existing additive manufacturing. A forming cylinder is arranged in an airtight molding chamber, and a powder bed area is formed by the forming cylinder and the bottom of the airtight molding chamber, which is conducive to the powder spreading device to spread powder; a micro-electromechanical structure is arranged on the powder spreading device, and the micro-electromechanical structure can absorb or release material powder, so that uniform powder spreading can be achieved, and the thickness of the powder spreading can be controlled. Moreover, the characteristics of the micro-electromechanical structure can realize the laying of multiple materials at the same time, and the laying area can be precisely controlled. The micro-electromechanical structure can realize single-cylinder molding, which not only saves space and reduces the weight of the entire equipment, but also reduces the complexity of the entire processing equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 is a schematic diagram of the internal structure of an embodiment of the present invention;

[0032] Figure 2 is a schematic structural diagram of a gas circulation system in an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of the structure of a powder bin in an embodiment of the present invention;

[0034] Figure 4 It is a schematic diagram of the structure of the powder bin and the powder spreading roller cooperating to feed the material in an embodiment of the present invention;

[0035] Figure 5 It is a schematic diagram of the structure of the powder bin and the powder spreading roller cooperating in feeding the material in an embodiment of the present invention.

[0036] Description of Figure Numbers:

[0037] Airtight molding chamber 10;

[0038] Forming cylinder 20, powder bed area 21;

[0039] Powder spreading device 30, powder bin 31, powder spreading roller 32, electrostrictive material layer 33, controller 34, hole 35, electrostrictive unit 36, electric slide rail 37, mounting seat 38, driver 39;

[0040] Feeding mechanism 40, powder bottle 41, powder feeding pipeline 42, control valve 43;

[0041] Laser system 50, laser 51, beam expander collimator 52, scanning galvanometer 53, optical lens 54;

[0042] Gas circulation system 60, nitrogen generating device 61, vacuum pumping device 62, oxygen content monitoring device 63, gas circulation purification device 64. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Reference Figures 1 to 5 The powder spreading system for multi-material additive manufacturing shown in the figure includes an airtight molding chamber 10, a molding cylinder 20, a powder spreading device 30, a feeding mechanism 40, a laser system 50 and a gas circulation system 60. The molding cylinder 20 can be installed at the bottom of the airtight molding chamber 10 in a liftable manner. The molding cylinder 20 cooperates with the bottom of the airtight molding chamber 10 to form a powder bed area 21; the powder spreading device 30 is installed in the airtight molding chamber 10, and the powder spreading device 30 can realize spatial displacement in the airtight molding chamber 10. The powder spreading device 30 is in the spatial displacement area of ​​the airtight molding chamber 10. The domain covers all areas of the opening of the forming cylinder 20; a micro-electromechanical structure is arranged on the powder spreading end of the powder spreading device 30, and the micro-electromechanical structure can absorb the material powder in the powder spreading device 30 and transfer and roll it on the powder bed area 21; the feeding mechanism 40 is installed on the airtight molding chamber 10, and the feeding mechanism 40 can supply a variety of material powders to the powder spreading device 30; the laser system 50 is installed on the airtight molding chamber 10, and the laser system 50 can melt and mold the material powder falling into the powder bed area 21; the gas circulation system 60 is connected to the airtight molding chamber 10.

[0045] Among them, the airtight molding chamber 10, the powder spreading device 30 and the laser system 50 actually constitute a 3D printing structure, and the purpose of the gas circulation system 60 is to protect the material powder so that the material powder does not react with oxygen when melted by the laser emitted by the laser system 50, thereby ensuring the molding quality of the later products. In addition, the airtight molding chamber 10 is a closed space container, and the molding cylinder 20 is located in the airtight molding chamber 10, and the two are closedly connected, and the molding cylinder 20 extends downward as a whole, which is conducive to the operation of the powder spreading device 30 and avoids the movement interference between the two. The actual structure of the molding cylinder 20 includes a cylinder body and a piston seat that can be lifted and lowered. The piston seat is movably inserted in the cylinder body, and the powder bed area 21 is actually located in the opening area of ​​the cylinder body. The piston seat can be installed on an external driving structure, such as a linear telescopic motor, a lifting structure driven by a screw rod, etc. Its main purpose is to prevent the material area that has been laid in the powder bed area 21 from being damaged by the moving powder spreading device 30 after the powder spreading device 30 performs several powder spreading operations, and thus affecting the quality of the later product molding.

[0046] It should be noted that in this application, the internal structure of the MEMS structure is generally at the micron or even nanometer level, and it is an independent intelligent system. The MEMS structure has a conventional mechanical system structure, but the size is at the micron or even nanometer level. For this reason, this application mainly uses its micron or even nanometer mechanical system structure to achieve the adsorption and release of material powder, and then realize the transfer of materials. Compared with the traditional adhesion transfer and direct movement transfer methods, the thickness of each layer laid by the powder laying device 30 is thinner, which can make the manufacturing accuracy of the entire component higher and the internal material distribution more uniform, greatly ensuring the quality of the later molded products.

[0047] The powder spreading system for multi-material additive manufacturing is modified on the basis of the existing additive manufacturing. A forming cylinder 20 is arranged in the airtight molding chamber 10. The forming cylinder 20 cooperates with the bottom of the airtight molding chamber 10 to form a powder bed area 21, which is conducive to the powder spreading device 30 to spread powder; a micro-electromechanical structure is arranged on the powder spreading device 30, and the micro-electromechanical structure can absorb or release material powder, so that uniform powder spreading can be achieved, and the powder spreading thickness is conducive to control. Moreover, the characteristics of the micro-electromechanical structure can achieve the laying of multiple materials at the same time, and the laying area can be precisely controlled. The use of the micro-electromechanical structure can realize single-cylinder molding, which not only saves space and reduces the weight of the entire equipment, but also reduces the complexity of the entire processing equipment.

[0048] To illustrate how the MEMS structure can achieve uniform laying of material powder, refer to Figure 1 to Figure 2As shown, the powder spreading device 30 includes a spatial displacement mechanism, a plurality of powder bins 31 and a plurality of powder spreading rollers 32. The spatial displacement mechanism is installed in the airtight molding chamber 10. All powder bins 31 are installed on the working end of the spatial displacement mechanism and can receive the material powder delivered by the feeding mechanism 40. Each powder spreading roller 32 can be rotatably installed on the lower end discharge port of a corresponding powder bin 31, and the outer surface of the powder spreading roller 32 is coated with a micro-electromechanical structure.

[0049] Among them, the main purpose of the spatial displacement mechanism is to drive the powder bin 31 and the powder spreading roller 32 to reciprocate between the initial position and the working position, that is, to reciprocate between the feeding mechanism 40 and the powder bed area 21. The number of powder bins 31 is the same as the number of materials required for the required processing parts. The bottom of the powder bin 31 is provided with a discharge slit, and the powder spreading roller 32 is correspondingly installed at the bottom of the powder bin 31 and blocked directly below the discharge slit. In order to facilitate the transfer of material powder, there is a certain gap between the outer wall of the powder spreading roller 32 and the discharge slit. In fact, the powder spreading roller 32 and the powder bin 31 cooperate to form a conventional laser printer, so its specific working principle is not described in detail in this application. In fact, the powder spreading roller 32 transfers the material powder in the powder bin 31 to the powder bed area 21 according to a specific arrangement. In the above embodiment, all the powder bins 31 are arranged side by side, and the length direction is perpendicular to the horizontal displacement direction of the spatial displacement mechanism, so that the material powder transferred by the powder spreading roller 32 corresponding to all the powder bins 31 can be completely spread on the powder bed area 21.

[0050] In order to ensure that the powder spreading roller 32 rotates evenly and spreads the powder evenly, refer to Figures 3 to 5 As shown, all powder bins 31 are provided with a driver 39 for driving the powder spreading roller 32 to rotate, wherein the driver 39 is an electric motor. Of course, in some embodiments, the outer surface of each powder spreading roller 32 can be in rolling contact with the material powder bed in the powder bed area 21, and the powder spreading roller 32 is driven to roll by friction with the structures on both sides of the powder bed area 21, so that the powder spreading roller 32 will not damage the material powder bed that has been laid in the powder bed area 21. However, using friction to drive the powder spreading roller 32 to rotate will cause the powder spreading roller 32 to wear, and the uniformity of the powder spreading cannot be guaranteed. For this reason, this application does not adopt this technical solution.

[0051] In order to better absorb the material powder and absorb the powder material at any position as needed to control the quality of the subsequent transfer, the micro-electromechanical structure includes an electrostrictive material layer 33 and a controller 34. The electrostrictive material layer 33 is coated on the outer surface of the powder spreading roller 32. A plurality of holes 35 are provided on the electrostrictive material layer 33. The controller 34 is installed on the outer wall of the powder bin 31 or the end of the powder spreading roller 32. The controller 34 controls the voltage at both ends of any area of ​​the electrostrictive material layer 33 to force the electrostrictive material layer 33 to contract or open, so that the holes 35 can attach or release the material powder. The electrostrictive material layer 33 is composed of an electrostrictive material. The working principle of the electrostrictive material layer is to control the voltage at both ends of the electrostrictive material so that the electrostrictive material contracts or relaxes, thereby changing the air pressure in the cavity of the hole 35, and finally achieving the purpose of adsorbing and releasing the material powder. The electrostrictive material is a conventional material, and the present application does not describe its specific components in detail. The electrostrictive material can be a conventional ferroelectric material and a ceramic material containing any one of lead magnesium niobate, lead magnesium niobate-lead titanate, lead lanthanum zirconate titanate, and barium zirconate titanate. In the above embodiment, the controller 34 of the present application is connected to an external power source or a battery. At the same time, since the voltage change at both ends of the electrostrictive material layer 33 is very small, for the sake of simplicity of structure, it can be powered by a battery; and the controller 34 can be connected to an external central control system through a wireless communication module, which is conducive to realizing external remote control.

[0052] In order to achieve that the voltage at both ends of any region of the electrostrictive material layer 33 can be accurately controlled, refer to Figures 1 to 5 As shown, the electrostrictive material layer 33 is composed of a plurality of electrostrictive units 36, all of which are arranged in sequence and coated on the outer surface of the powder spreading roller 32, and all of which are electrically connected to the controller 34. In fact, for the sake of easy control, the electrostrictive units 36 in each area have corresponding numbers, and the controller 34 can realize that a plurality of electrostrictive units 36 are composed of corresponding graphic areas by controlling the electrostrictive units 36 in the corresponding numbered areas, so as to adapt to the cross-sectional contour shapes of components of different layers.

[0053] In order to better realize the reciprocating motion of the powder bin 31 between the feeding mechanism 40 and the powder bed area 21, refer to Figure 1As shown, the spatial displacement mechanism includes an electric slide rail 37 and a mounting seat 38 mounted on the electric slide rail 37. The electric slide rail 37 is mounted on the inner wall of the airtight molding chamber 10. All powder bins 31 are mounted on the mounting seat 38. The electric slide rail 37 can drive all powder bins 31 to reciprocate between the discharge end of the feeding mechanism 40 and the powder bed area 21 away from the feeding mechanism 40. Of course, in some embodiments, the electric slide rail 37 in the present application can be replaced by a combination of a synchronous belt and a motor, the synchronous belt is driven to rotate by the motor, and the mounting seat 38 is mounted on the synchronous belt. Of course, in order to stabilize the displacement, a slide rail can also be provided on the airtight molding chamber 10 in this embodiment, and the mounting seat 38 slides on the slide rail, and then driven to slide by the synchronous belt.

[0054] In order to facilitate the replenishment of material powder to the powder bin 31, refer to Figure 1 As shown, the feeding mechanism 40 includes a plurality of powder bottles 41 and a powder feeding pipeline 42 matched with the powder bottles 41, all of which are installed on the airtight molding chamber 10, and the output ends of all of the powder feeding pipelines 42 pass through the side wall of the airtight molding chamber 10 and are placed in the airtight molding chamber 10, each of which is adapted to a powder bin 31, and each of which is located outside the airtight molding chamber 10. The area of ​​the powder feeding pipeline 42 is provided with a control valve 43. Among them, the control valve 43 can be a manual valve or a conventional electromagnetic control valve, which is selected according to demand. In the above-mentioned embodiment, the number of powder bottles 41 is set according to the type of material powder. In fact, the number of powder bottles 41 is adapted to the number of powder bins 31, and each powder bottle 41 supplies powder material to each powder bin 31, so that different materials can be prevented from mixing and causing quality defects in parts processed later.

[0055] In order to melt the material powder on the powder bed area 21, the laser system 50 may be a conventional laser generator, as shown in FIG. Figure 1 As shown, in one embodiment of the present application, the laser system 50 includes a laser 51, a beam expander collimator 52, a scanning galvanometer 53 and an optical lens 54. The beam expander collimator 52 is arranged on the outer wall of the airtight molding chamber 10, and the scanning galvanometer 53 is installed on the top of the airtight molding chamber 10. The laser emitted by the laser 51 can enter the scanning galvanometer 53 through the beam expander collimator 52. The optical lens 54 is installed on the inner wall of the top of the airtight molding chamber 10 and is located directly above the molding cylinder 20. The optical lens 54 can receive the laser emitted by the scanning galvanometer 53 and irradiate the laser on the material powder in the powder bed area 21 to heat and melt. In fact, the adjustment working range of the scanning galvanometer 53 can fully cover the powder bed area 21 and adapt to the entire working area.

[0056] In order to prevent the material powder from reacting with oxygen in the air during the melting process and to ensure the quality of the parts, refer to Figure 1 and Figure 2 As shown, the gas circulation system 60 includes a nitrogen generator 61, a vacuum device 62, an oxygen content monitoring device 63 and a gas circulation purification device 64. The gas circulation purification device 64, the nitrogen generator 61 and the vacuum device 62 are all connected to the airtight molding chamber 10, and the oxygen content monitoring device 63 is installed in the airtight molding chamber 10. Among them, the nitrogen generator 61 can adopt the technical solution disclosed in the patent CN204939624U-nitrogen generator, which is not described in detail in this application. The vacuum device 62 can be a conventional vacuum equipment, such as a vacuum pump and other supporting pipelines and valve bodies, and the oxygen content monitoring device 63 can be a conventional oxygen content sensor. The gas circulation purification device 64 is a fan and a supporting pipeline, wherein the inlet and outlet of the pipeline are connected to the airtight molding chamber 10, and the fan is installed on the pipeline. Among them, the main purpose of the nitrogen generating device 61 is to generate protective gas nitrogen, and the vacuum device 62 is to remove oxygen in the airtight molding chamber 10; the main purpose of the gas circulation purification device 64 is to better circulate the nitrogen in the airtight molding chamber 10, which is beneficial to heat dissipation.

[0057] Reference Figure 4 and Figure 5 As shown, the present invention also provides a powder laying method for multi-material additive manufacturing, comprising the following steps:

[0058] Step S100, digitize the part to be processed in three dimensions and obtain a three-dimensional CAD model; select a suitable processing layer thickness according to the processing accuracy requirements and the maximum processing accuracy of the equipment; use slicing software to perform layered slicing and slice data packaging, perform scanning path planning according to the slice contour of each package, and import it into the processing system after completion, ready for processing;

[0059] Step S200, start the vacuum pumping device 62, use the vacuum pumping device 62 to vacuum and deoxygenate the airtight molding chamber 10, when the pressure in the airtight molding chamber 10 is -10 to -15 KPa, start the nitrogen generating device 61 and fill it with nitrogen, when the air pressure in the airtight molding chamber 10 reaches 15 to 22 KPa, turn off the nitrogen generating device 61, continue to start the vacuum pumping device 62 to vacuum, repeat the above operation several times until the oxygen content monitoring device 63 detects that the oxygen content in the airtight molding chamber 10 is lower than 0.1% and the air pressure reaches 15 to 22 KPa; turn off the nitrogen generating device 61 and the vacuum pumping device 62, and start the gas circulation purification device 64 to realize the separate circulation of the gas in the airtight molding chamber 10;

[0060] Step S300, the feeding mechanism 40 conveys the corresponding material powder into the corresponding powder bin 31, and after all the powder bins 31 have finished adding the material powder, the powder spreading mechanism is turned on; the spatial displacement mechanism in the powder spreading mechanism drives all the powder bins 31 to move from one side of the powder bed area 21 to the other side thereof, and the driver 39 drives the powder spreading roller 32 to rotate following the movement of the spatial displacement mechanism, and the linear speed of the powder spreading roller 32 is the same as the horizontal displacement rate of the spatial displacement mechanism; the controller 34 controls the electrostrictive unit 36 ​​on the side of the corresponding powder spreading roller 32 close to the outlet of the powder bin 31 to selectively adsorb the material powder discharged from the corresponding powder bin 31 according to the material distribution information data provided by the slicing software, and at the same time controls the electrostrictive unit 36 ​​on the bottom side of the corresponding powder spreading roller 32 to release the adsorbed material powder, so that the fallen material powder falls into the powder bed area 21; after the spatial displacement mechanism moves to the limit away from the feeding mechanism 40, the driver 39 stops working, and the spatial displacement mechanism drives the powder bin 31 to reset, and prepares for the printing of the next slice layer;

[0061] Step S400: After the powder spreading mechanism completes the powder spreading work of a sheet layer, the laser system 50 performs material contour scanning on the material powder on the powder bed area 21 according to the material distribution information data provided by the slicing software to achieve material powder melting. After the laser system 50 completes the melting of the material powder of the corresponding sheet layer, it stops working and waits for the next round of melting work;

[0062] Step S500, after the material in the powder bed area 21 is cold cut and melted, repeat steps S300 and S400 multiple times; after completing the powder spreading and laser melting of a preset number of sheets, control the forming cylinder 20 to descend to a preset height; then repeat steps S300 and S400 multiple times until the powder spreading and laser melting of all sheets are completed.

[0063] Among them, the processing system in step S100 is the powder spreading system of the present invention; in step S200, as the molding proceeds, the oxygen content in the molding chamber may fluctuate. During the start-up of the gas circulation purification device 64, that is, during the gas circulation, if the oxygen content monitoring device 63 detects that the oxygen content in the airtight molding chamber 10 is higher than 0.1%, the entire central control system shuts down the gas circulation purification device 64 system, and controls the vacuum pumping device 62 to perform vacuum pumping and the nitrogen generator 61 at the same time, so that on the one hand, the air pressure in the airtight molding chamber 10 can be reduced, and on the other hand, protective gas can be introduced, and such cooperation can minimize the oxygen content in the airtight molding chamber 10. After the oxygen content monitoring device 63 detects that the oxygen content in the airtight molding chamber 10 meets the preset standard, the vacuum pumping device 62 and the nitrogen generator 61 are shut down at the same time, and then the gas circulation purification device 64 is turned on again for gas circulation.

[0064] In step S300, the material distribution information data provided by the slicing software actually includes the contour information of the parts in each layer sliced ​​by the slicing software in step S100, the occupied area and position of the parts in the entire layer, etc. This is conducive to distinguishing that different powder spreading rollers 32 evenly distribute the material powder in the corresponding powder bin 31 on the entire powder bed in the powder bed area 21 according to the preset distribution. The controller 34 is electrically connected to the entire central control system, which is conducive to remote control by the staff and understanding the powder spreading situation at any time.

[0065] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A powder spreading system for multi-material additive manufacturing, characterized in that: include: Airtight molding chamber; A molding cylinder, which is installed at the bottom of the airtight molding chamber in a manner that it can be lifted and lowered, and the molding cylinder cooperates with the bottom of the airtight molding chamber to form a powder bed area; A powder spreading device is installed in the airtight molding chamber, the powder spreading device can achieve spatial displacement in the airtight molding chamber, and the spatial displacement area of ​​the powder spreading device in the airtight molding chamber covers all areas of the molding cylinder opening; a micro-electromechanical structure is arranged on the powder spreading end of the powder spreading device, and the micro-electromechanical structure can absorb the material powder in the powder spreading device and transfer and roll-print it on the powder bed area; A feeding mechanism, which is installed on the airtight molding chamber, and the feeding mechanism can supply powders of various materials to the powder spreading device; A laser system, which is installed on the airtight molding chamber, and the laser system can melt and mold the material powder falling into the powder bed area; a gas circulation system, which is in communication with the airtight molding chamber; The powder spreading device comprises a spatial displacement mechanism, a plurality of powder bins and a plurality of powder spreading rollers, wherein the spatial displacement mechanism is installed in the airtight molding chamber, all the powder bins are installed on the working end of the spatial displacement mechanism and can receive the material powder sent by the feeding mechanism, each of the powder spreading rollers can be rotatably installed on the lower end discharge port of a corresponding powder bin, the outer surface of each of the powder spreading rollers can be in rolling contact with the powder bed area in the powder bed area, and the outer surface of the powder spreading roller is coated with the micro-electromechanical structure; The micro-electromechanical structure includes an electrostrictive material layer and a controller, wherein the electrostrictive material layer is coated on the outer surface of the powder spreading roller, and a plurality of holes are provided on the electrostrictive material layer. The controller is mounted on the outer wall of the powder bin or the end of the powder spreading roller, and the controller controls the voltage at both ends of any area of ​​the electrostrictive material layer to force the electrostrictive material layer to contract or expand, so that the holes can absorb or release material powder.

2. A powder spreading system for multi-material additive manufacturing according to claim 1, characterized in that: The electrostrictive material layer is composed of a plurality of electrostrictive units, all of which are arranged in sequence and coated on the outer surface of the powder spreading roller, and all of which are electrically connected to the controller.

3. A powder spreading system for multi-material additive manufacturing according to claim 1, characterized in that: The spatial displacement mechanism includes an electric slide rail and a mounting seat mounted on the electric slide rail. The electric slide rail is mounted on the inner wall of the airtight molding chamber. All the powder bins are mounted on the mounting seat. The electric slide rail can drive all the powder bins to reciprocate in the area between the discharge end of the feeding mechanism and the powder bed area away from the side of the feeding mechanism.

4. A powder spreading system for multi-material additive manufacturing according to claim 1, characterized in that: All the powder bins are provided with a driver for driving the powder spreading roller to rotate.

5. A powder spreading system for multi-material additive manufacturing according to any one of claims 2 to 4, characterized in that: The feeding mechanism includes a plurality of powder bottles and powder feeding pipelines matched with the powder bottles, all of the powder bottles are installed on the airtight molding chamber, the output ends of all the powder feeding pipelines pass through the side wall of the airtight molding chamber and are placed inside the airtight molding chamber, each of the powder feeding pipelines is adapted to one of the powder bins, and a control valve is arranged on the area of ​​each of the powder feeding pipelines outside the airtight molding chamber.

6. A powder spreading system for multi-material additive manufacturing according to any one of claims 1 to 4, characterized in that: The laser system includes a laser, a beam expander collimator, a scanning galvanometer and an optical lens. The beam expander collimator is arranged on the outer wall of the airtight molding chamber, and the scanning galvanometer is installed on the top of the airtight molding chamber. The laser emitted by the laser can enter the scanning galvanometer through the beam expander collimator. The optical lens is installed on the inner wall of the top of the airtight molding chamber and is located directly above the molding cylinder. The optical lens can receive the laser emitted by the scanning galvanometer and irradiate the laser on the material powder in the powder bed area to heat and melt it.

7. A powder spreading system for multi-material additive manufacturing according to any one of claims 1 to 4, characterized in that: The gas circulation system includes a nitrogen generator, a vacuum pumping device, an oxygen content monitoring device and a gas circulation purification device. The gas circulation purification device, the nitrogen generator and the vacuum pumping device are all connected to the airtight molding chamber, and the oxygen content monitoring device is installed in the airtight molding chamber.

8. A powder spreading method for multi-material additive manufacturing, the powder spreading method being implemented on the powder spreading system for multi-material additive manufacturing as claimed in claim 2, characterized in that: The following steps are involved: Step S100, digitize the part to be processed in three dimensions and obtain a three-dimensional CAD model; select a suitable processing layer thickness according to the processing accuracy requirements and the maximum processing accuracy of the equipment; use slicing software to perform layered slicing and slice data packaging, perform scanning path planning according to the slice contour of each package, and import it into the processing system after completion, ready for processing; Step S200, start the vacuum pumping device, use the vacuum pumping device to vacuum and deoxygenate the airtight molding chamber, when the pressure in the airtight molding chamber is -10 to -15 KPa, start the nitrogen generating device and fill it with nitrogen, when the air pressure in the airtight molding chamber reaches 15 to 22 KPa, turn off the nitrogen generating device, continue to start the vacuum pumping device to vacuum, repeat the above operation several times until the oxygen content monitoring device detects that the oxygen content in the airtight molding chamber is lower than 0.1% and the air pressure reaches 15 to 22 KPa; turn off the nitrogen generating device and the vacuum pumping device, and start the gas circulation purification device to realize the separate circulation of gas in the airtight molding chamber; Step S300, the feeding mechanism conveys the corresponding material powder into the corresponding powder bin, and after all the powder bins have finished adding the material powder, the powder spreading mechanism is turned on; the spatial displacement mechanism in the powder spreading mechanism drives all the powder bins to move from one side of the powder bed area to the other side thereof, and the driver drives the powder spreading roller to rotate following the movement of the spatial displacement mechanism, and the linear speed of the powder spreading roller is the same as the horizontal displacement rate of the spatial displacement mechanism; the controller controls the electrostrictive unit on the side of the corresponding powder spreading roller close to the powder bin outlet to selectively adsorb the material powder discharged from the corresponding powder bin according to the material distribution information data provided by the slicing software, and at the same time controls the electrostrictive unit on the bottom side of the corresponding powder spreading roller to release the adsorbed material powder, so that the fallen material powder falls into the powder bed area; after the spatial displacement mechanism moves to the limit away from the feeding mechanism, the driver stops working, and the spatial displacement mechanism drives the powder bin to reset, and prepares for printing the next layer; Step S400: After the powder spreading mechanism completes the powder spreading work of a sheet layer, the laser system performs material contour scanning on the material powder on the powder bed area according to the material distribution information data provided by the slicing software to achieve material powder melting. After the laser system completes the melting of the material powder of the corresponding sheet layer, it stops working and waits for the next round of melting work; Step S500, after the material in the powder bed area is cold cut and melted, repeat steps S300 and S400 multiple times; after completing the powder spreading and laser melting of a preset number of sheets, control the forming cylinder to descend to a preset height; then repeat steps S300 and S400 multiple times until the powder spreading and laser melting of all sheets are completed.

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