A multi-material powder spreading assembly based on SLM additive manufacturing and a powder spreading method thereof

Abstract

The application discloses a multi-material powder laying assembly based on SLM additive manufacturing and a powder laying method thereof, which comprises a forming chamber, a powder supply device, a powder laying device and a laser device, the forming chamber is internally provided with a forming platform, the forming platform can move up and down in the forming chamber under the action of a motor, the powder supply device is multiple and can be uniformly fixed on the two sides of the forming chamber, an electromagnetic valve is arranged below the powder supply device, the powder laying device is multiple, the powder laying device is correspondingly connected below the powder supply device, the powder laying device comprises a powder storage cylinder, a moving mechanism, an ultrasonic transducer, a rotating mechanism and a steel coil sheet, the powder storage cylinder is connected with the moving mechanism, the ultrasonic transducer is located in the powder storage cylinder, the rotating mechanism is installed on the two sides of the powder storage cylinder, the steel coil sheet is fixed below the powder laying device, a pressure sensor is arranged above the steel coil sheet, and the laser device is located above the forming platform and is used for melting powder and forming a required part.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of additive manufacturing, and particularly relates to a multi-material powder laying assembly based on SLM additive manufacturing and a powder laying method thereof. BACKGROUND

[0002] Selective Laser Melting (SLM) technology is an additive manufacturing technology suitable for metal materials. It irradiates metal powder in different areas to a molten state by controlling high-intensity laser generated by a laser system, so that the powder is combined with the substrate or the base metal, and after cooling and solidification, the parts are formed layer by layer. With the development of high-tech industries, single-material products cannot meet the needs of complex working environments, so multi-material additive manufacturing technology has received more and more attention. In the field of multi-material additive manufacturing, it is mainly divided into two categories: Powder Bed Fusion (PBF) and Directed Energy Deposition (DED). For DED, multi-material product manufacturing can be easily achieved by changing the proportion of powder feeding or the speed of wire feeding. For PBF, it is relatively easy to change the type of powder between layers, only a plurality of powder supply cylinders containing different materials are needed, and the powder laying mechanism can lay the powder material in the corresponding powder supply cylinder on the corresponding layer. However, how to lay different powders in one layer, how to achieve reasonable and efficient powder recycling, and how to solve the mutual contamination between powders are urgent problems to be solved. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a multi-material powder laying assembly based on SLM additive manufacturing and a powder laying method thereof, so as to solve the problems of laying different powders in one layer, powder recycling and contamination, and improve production efficiency.

[0004] To solve the above problems, the technical scheme adopted by the present application is as follows: a multi-material powder laying assembly based on SLM additive manufacturing, comprising:

[0005] a forming chamber, a forming platform is arranged in the forming chamber, and the forming platform can move up and down in the forming chamber under the action of a motor;

[0006] a powder supply device, the powder supply device is multiple and can be uniformly fixed on both sides of the forming chamber, and an electromagnetic valve is arranged below the powder supply device;

[0007] The powder laying device is multiple, and is correspondingly connected below the powder supply device, and comprises a powder storage cylinder, a moving mechanism, an ultrasonic transducer, a rotating mechanism and a steel coil sheet.

[0008] The laser device is located above the forming platform.

[0009] Compared with the prior art, the beneficial effects of the present application are that the cooperation between the rotating steel coil and the telescopic sheet can accurately control the powder to fall in the desired powder laying area, and since the powder falling can be accurately controlled, the falling of useless powder can be reduced, the utilization rate of the powder is improved, and since the powder can be accurately controlled to fall in the respective powder laying area, the pollution between different powders can be reduced, and the production efficiency is improved since the powder laying device can complete the printing of two layers of materials at one time under the driving of the moving mechanism.

[0010] The multi-material powder laying assembly, the powder laying device further comprises an induction head, an induction device and a sealing gasket, the induction head and the induction device are connected with the steel coil sheet and the powder storage cylinder respectively, and the sealing gasket is located between the powder storage cylinder and the steel coil sheet.

[0011] The multi-material powder laying assembly, the powder laying device further comprises an induction head, an induction device and a sealing gasket, the induction head and the induction device are connected with the steel coil sheet and the powder storage cylinder respectively, and the sealing gasket is located between the powder storage cylinder and the steel coil sheet.

[0012] The multi-material powder laying assembly, the powder laying device further comprises an induction head, an induction device and a sealing gasket, the induction head and the induction device are connected with the steel coil sheet and the powder storage cylinder respectively, and the sealing gasket is located between the powder storage cylinder and the steel coil sheet.

[0013] The multi-material powder laying assembly, the powder laying device further comprises an induction head, an induction device and a sealing gasket, the induction head and the induction device are connected with the steel coil sheet and the powder storage cylinder respectively, and the sealing gasket is located between the powder storage cylinder and the steel coil sheet.

[0014] The multi-material powder laying assembly further comprises a fixing plate for supporting the powder storage cylinder to enable the powder storage cylinder to move linearly in a horizontal direction within a rectangular channel of the fixing plate, and the moving mechanism comprises a motor, a coupling, a ball screw, a linear guide rail, an inductor and an induction device, the ball screw and the linear guide rail are parallel to each other and are both fixed to the fixing plate, one side of the powder storage cylinder is installed on the ball screw through a nut, and the other side of the powder storage cylinder is installed on the linear guide rail through a sliding block.

[0015] The multi-material powder laying assembly further comprises a rotating mechanism, the rotating mechanism comprises a stepped shaft, a pinion, a rotating motor and a large gear, a motor base is fixed below the powder storage cylinder, the rotating motor is fixed to the motor base and is keyed connected with the large gear, the pinion is keyed connected with the stepped shaft, the large gear can drive the pinion to rotate, and the steel sheet thin plate can be fixed to the stepped shaft, when the rotating motor works, the steel sheet thin plate can be driven to rotate through meshing of the gears, the top end of the telescopic thin plate is provided with a guide part, a guide groove is arranged in the sliding groove, and the guide part can move in cooperation with the guide groove.

[0016] The multi-material powder laying assembly further comprises a rotating mechanism, the rotating mechanism comprises a stepped shaft, a pinion, a rotating motor and a large gear, a motor base is fixed below the powder storage cylinder, the rotating motor is fixed to the motor base and is keyed connected with the large gear, the pinion is keyed connected with the stepped shaft, the large gear can drive the pinion to rotate, and the steel sheet thin plate can be fixed to the stepped shaft, when the rotating motor works, the steel sheet thin plate can be driven to rotate through meshing of the gears, the top end of the telescopic thin plate is provided with a guide part, a guide groove is arranged in the sliding groove, and the guide part can move in cooperation with the guide groove.

[0017] The multi-material powder laying assembly further comprises a rotating mechanism, the rotating mechanism comprises a stepped shaft, a pinion, a rotating motor and a large gear, a motor base is fixed below the powder storage cylinder, the rotating motor is fixed to the motor base and is keyed connected with the large gear, the pinion is keyed connected with the stepped shaft, the large gear can drive the pinion to rotate, and the steel sheet thin plate can be fixed to the stepped shaft, when the rotating motor works, the steel sheet thin plate can be driven to rotate through meshing of the gears, the top end of the telescopic thin plate is provided with a guide part, a guide groove is arranged in the sliding groove, and the guide part can move in cooperation with the guide groove.

[0018] The application further provides a multi-material powder laying method based on SLM additive manufacturing, which is performed by using the multi-material powder laying assembly and comprises the following steps.

[0019] S1: install a corresponding number of powder laying devices, turn on the system power supply, introduce a multi-material product after slicing is completed, determine whether powder needs to be added according to data of the pressure sensor, determine to perform vacuumization on the forming chamber after adding, and prepare for printing;

[0020] S2: According to the slice data, the computer sends the positions of different materials to the corresponding powder laying device. The moving mechanism drives the powder laying device to move in the positive direction, and the rotating mechanism drives the steel coil sheet to work;

[0021] S3: When the powder laying device reaches the required powder laying area, the steel coil sheet cooperates with the ultrasonic transducer to make the powder fall continuously and accurately in the powder laying area. During the powder laying process, the rotating steel coil and the telescopic sheet cooperate with the movement to control the length and position of the powder outlet, so that the powder fills the powder laying area;

[0022] S4: When the powder laying device leaves the powder laying area, the rotating steel coil and the telescopic sheet are advanced to close and stop powdering to prevent pollution of other areas. When the powder laying device reaches the powder laying area, the rotating steel coil and the telescopic sheet are opened in advance to realize accurate powder laying;

[0023] S5: The laser device irradiates and melts the laid powder, and after cooling, it is combined on the substrate or base material;

[0024] S6: Determine whether the multi-material product is completed, if yes, end; if not, execute step S7;

[0025] S7: Lower the forming platform by a layer thickness;

[0026] S8: The moving mechanism drives the powder laying device to move in the reverse direction, and the powder laying process in steps S3 and S4 is repeated to complete the powder laying of this layer by the powder laying device;

[0027] S9: Execute step S5, and then determine whether the product is completed, if yes, end; if not, execute S7 first, and then return to step S3 and continue to execute the steps. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The structure diagram of the multi-material powder laying device of the embodiment of the present application;

[0029] Figure 2 The enlarged schematic view of the embodiment of the present application Figure 1

[0030] Figure 3 The overall schematic view (top surface) of the powder laying device and the horizontal motion mechanism of the embodiment of the present application;

[0031] Figure 4 The overall schematic view (bottom surface) of the powder laying device and the rotating mechanism of the embodiment of the present application;

[0032] Figure 5 The enlarged schematic view of the embodiment of the present application Figure 4 ​Enlarged view of the middle II;

[0033] Figure 6 Steel sheet structure schematic diagram of multi-material powder laying device of the embodiment of the present application;

[0034] Figure 7 Material distribution diagram of one layer of the multi-material product of the embodiment of the present application;

[0035] Figure 8 Material distribution diagram of the next layer adjacent to the material layer in the multi-material product of the embodiment of the present application; Figure 7 Material distribution diagram of the next layer adjacent to the material layer in the multi-material product of the embodiment of the present application;

[0036] Figure 9 Material distribution diagram of the next layer adjacent to the material layer in the multi-material product of the embodiment of the present application; Figure 8 Material distribution diagram of the next layer adjacent to the material layer in the multi-material product of the embodiment of the present application;

[0037] Figure 10 Schematic diagram of the slice of the material layer after computer processing of the embodiment of the present application; Figure 7

[0038] Schematic diagram of the slice of the material layer after computer processing of the embodiment of the present application; Figure 11 Figure 8 Schematic diagram of the slice of the material layer after computer processing of the embodiment of the present application;

[0039] Figure 12 Schematic diagram of the slice of the material layer after computer processing of the embodiment of the present application Figure 9

[0040] BRIEF DESCRIPTION OF THE DRAWINGS: 1 forming chamber, 2 laser device, 3 first powder feeding hopper, 4 second powder feeding hopper, 5 third powder feeding hopper, 6 threaded hole, 7 first powder laying device, 8 second powder laying device, 9 third powder laying device, 10 forming platform, 11 multi-material product, 12 moving mechanism, 13 fourth powder feeding hopper, 14 fifth powder feeding hopper, 15 sixth powder feeding hopper, 16 pressure sensor, 17 ultrasonic transducer, 18 steel sheet, 19 sealing gasket, 20 inductive head, 21 inductive device, 22 linear motor, 23 coupling, 24 ball screw, 25 linear guide rail, 26 inductive iron, 27 inductive device, 28 fixed plate, 29 first stepped shaft, 30 first steel sheet, 31 first pinion, 32 first rotary motor, 33 first gear, 34 second steel sheet, 35 second pinion, 36 second gear, 37 second rotary motor, 38 second stepped shaft, 39 powder storage cylinder, 40 motor base, 41 first bearing seat, 42 first sealing gasket, 43 second bearing seat, 44 rotary steel sheet, 45 telescopic sheet, 46 first printing layer, 47 second printing layer, 48 third printing layer. DETAILED DESCRIPTION

[0041] The embodiments of the present application are described in detail below with reference to the drawings. Figures 1 to 12 ​​The embodiment of the application provides a multi-material powder laying assembly based on SLM additive manufacturing and a powder laying method thereof, which comprises a forming chamber 1, a powder supply device, a powder laying device and a laser device 2, the forming chamber 1 is internally provided with a forming platform 10, the forming platform 10 can move up and down in the forming chamber 1 under the action of a motor; the powder supply device is multiple and can be uniformly fixed on two sides of the forming chamber 1, the powder supply device is provided below with an electromagnetic valve; the powder laying device is multiple, the powder laying device is correspondingly connected below the powder supply device, the powder laying device comprises a powder storage cylinder 39, a moving mechanism 12, an ultrasonic transducer 17, a rotating mechanism and a steel coil sheet 18, the powder storage cylinder 39 is connected with the moving mechanism 12, the ultrasonic transducer 17 is located in the powder storage cylinder 39, and more further, the powder outlet width of the powder storage cylinder 39 is greater than the diameter of the metal powder, of course, the diameter of the metal powder is not limited in the application, preferably, the powder outlet width of the powder storage cylinder 39 is greater than the maximum metal powder diameter, the powder outlet width direction of the powder storage cylinder 39 is provided with chamfers on both sides, and the chamfers are used for compacting the powder. The rotating mechanism is installed on both sides of the powder storage cylinder 39, the steel coil sheet 18 is fixed below the powder laying device, the steel coil sheet 18 is provided above with a pressure sensor 16, the steel coil sheet 18 comprises a rotating steel coil 44 and an extension sheet 45, the rotating steel coil 44 is connected with the rotating mechanism, and the extension sheet 45 can move in cooperation with a sliding groove below the powder storage cylinder 39; the laser device 2 is located above the forming platform 10 and is used for melting the powder and forming a required part, the laser device 2 can adjust the power and the scanning speed according to the needs, so as to adapt to the melting characteristics of different materials. When the multi-material powder laying assembly based on SLM additive manufacturing works, referring to Figure 1 The moving mechanism 12 can drive the powder laying device to move forward, when the powder laying device moves to a region needing powder laying, referring to Figure 2 and Figure 6, the rotating steel roll 44 and the telescopic sheet 45 of the steel roll sheet 18 are matched in advance, the rotating steel roll 44 and the telescopic sheet 45 are elongated and shortened respectively, the opening is moved to the center position of the powder laying area under the condition of ensuring that no powder is leaked, since there is still a certain height from the powder outlet to the surface of the forming area, the steel roll sheet 18 opens the powder outlet in advance, cooperates with the ultrasonic transducer 17, and powder can be continuously and accurately laid on the powder laying area, the steel roll sheet 18 is used for controlling the laying thickness and flatness of the powder, a pressure sensor 16 is arranged above the steel roll sheet 18 to monitor the pressure change on the steel roll sheet 18, so as to ensure the quality of powder laying and detect the amount of powder remaining in the powder storage cylinder to determine whether to add powder, the rotating steel roll 44 is connected with the rotating mechanism and controls the position of the powder outlet through rotation, the telescopic sheet 45 can be matched and moved with the sliding groove below the powder storage cylinder 39 to control the length of the powder outlet, in the process of laying powder, the rotating steel roll 44 and the telescopic sheet 45 still move cooperatively to control the length and position of the powder outlet, so that the powder can be laid on the powder laying area, since the powder outlet can accumulate a part of the powder, the rotating steel roll 44 and the telescopic sheet 45 will be in advance before leaving the powder laying area, so as to stop powdering and prevent pollution of other areas, when the powder laying device reaches the powder laying area, the rotating steel roll 44 and the telescopic sheet 45 are opened in advance to realize accurate powder laying; each powder laying device moves independently and interferes complementarily to complete the powder laying of a layer of multi-material powder, through the cooperative movement between the rotating steel roll 44 and the telescopic sheet 45, the powder can be accurately controlled to fall on the area where the powder is desired to be laid, since the falling of the powder can be accurately controlled, the falling of useless powder can be reduced, the utilization rate of the powder is improved, and since the powder can be accurately controlled to fall on the respective powder laying area, the pollution between different powders can be reduced, and the powder laying device can complete the printing of two layers of materials every time it is in place under the driving of the moving mechanism 12, so that the production efficiency is improved.

[0042] Further, referring to Figure 1 , the forming chamber 1 comprises a forming platform 10 capable of moving up and down, the forming platform 10 is driven by a motor, the powder supply device is a plurality of groups, the plurality of groups of powder supply devices are evenly arranged on both sides of the forming chamber 1, of course, the specific number and specific structure of the powder supply device are not limited in the present application, preferably, the powder supply device is a powder supply hopper, the number of the powder supply hoppers is six, further, referring to Figure 1 and Figure 4 , each powder supply hopper is provided with a powder laying device below, the powder laying device comprises a powder storage cylinder 39, a moving mechanism 12, an ultrasonic transducer 17, a rotating mechanism and a steel roll sheet 18, wherein the powder storage cylinder 39 is connected with the moving mechanism 12, of course, the specific structure and movement direction of the moving mechanism 12 are not limited in the present application, preferably, referring to Figure 3The moving mechanism 12 comprises a linear motor 22, a coupling 23, a ball screw 24, a linear guide rail 25, an inductor 26 and an inductor device 21, the ball screw 24 and the linear guide rail 25 are parallel to each other and are fixed on a fixed plate 28, one side of the powder storage cylinder 39 is installed on the ball screw 24 through a nut, the other side of the powder storage cylinder 39 is installed on the linear guide rail 25 through a sliding block, the moving mechanism 12 is used for ensuring the stable movement of the powder storage cylinder 39, further, the ultrasonic transducer 17 is installed inside the powder storage cylinder 39, which is used for improving the powder flowability and distribution uniformity, and still further, the rotating steel roll 44 is fixed on the rotating mechanism, referring to Figure 5 The rotating mechanism comprises a stepped shaft, a pinion, a rotating motor and a large gear, the motor base 40 is fixed below the powder storage cylinder 39, the rotating motor is fixed on the motor base 40 and the rotating motor 32 is key-connected with the large gear, the pinion is key-connected with the stepped shaft, the large gear can drive the pinion to rotate, the steel roll sheet 18 can be fixed with the stepped shaft, when the rotating motor works, the steel roll sheet 18 can be driven to rotate through the meshing of the gears, the top end of the telescopic sheet is provided with a guide part, the sliding groove of the powder storage cylinder is provided with a guide groove, the guide part can move in cooperation with the guide groove, the rotating mechanism is installed on both sides of the powder storage cylinder 39, of course, the specific installation position of the rotating mechanism is not limited in the present application, preferably, the rotating mechanism is installed on both sides of the length direction of the powder storage cylinder 39, each powder storage cylinder 39 corresponds to two rotating mechanisms, each rotating mechanism corresponds to one steel roll sheet 18, the rotating mechanism drives the rotating steel roll 44 of the steel roll sheet 18 to rotate, so as to drive the telescopic side sheet 45 to extend and retract.

[0043] Further, the stepped shafts include first stepped shaft 29 and second stepped shaft 38, the pinions include first pinion 31 and second pinion 35, the rotary motors include first rotary motor 32 and second rotary motor 37, the gearwheels include first gearwheel 33 and second gearwheel 36, the steel sheet rolls 18 include first steel sheet roll 30 and second steel sheet roll 34, the first stepped shaft 29, the first pinion 31, the first rotary motor 32, the first gearwheel 33 and the first steel sheet roll 30 are located on one side of the fixed plate 28, the second stepped shaft 38, the second pinion 35, the second rotary motor 37, the second gearwheel 36 and the second steel sheet roll 34 are located on the other side of the fixed plate 28, the first rotary motor 32 is fixed on the motor base 40 and connected with the first gearwheel 33 through key connection. The first gearwheel 33 drives the first pinion 31 to rotate through meshing, the first pinion 31 is also connected with the first stepped shaft 29 through key connection, and the first steel sheet roll 30 can be fixed on the first stepped shaft 29 through screw connection. Thus, the power generated by the first rotary motor 32 can be transmitted to the first steel sheet roll 30 through the meshing of the gearwheels, the key connection and the screw connection, i.e. the first steel sheet roll 30 is driven to rotate. Further, the first steel sheet roll 30 is provided with first bearing seat 41 and second bearing seat 43 at two ends thereof, and the first steel sheet roll 30 is also provided with first sealing gasket 42 on one side thereof.

[0044] Further, referring to Figure 2 , the powder spreading device further includes inductive head 20 and induction device 21, which are connected with the telescopic sheet 45 of the steel sheet roll 18 and the powder storage cylinder 39 respectively, so as to limit the minimum length of the telescopic sheet 45 and prevent the telescopic sheet 45 from being separated from the sliding groove of the powder storage cylinder 39. Further, the powder spreading device further includes sealing gasket 19, which is located between the powder storage cylinder 39 and the steel sheet roll 18, is installed on the powder storage cylinder 39 and acts between the powder storage cylinder 39 and the telescopic sheet 45 of the steel sheet roll 18. Since the metal powder has a very small diameter and is easy to invade into the sliding groove and the guide groove of the powder storage cylinder 39, thereby affecting the telescoping of the telescopic sheet 45, the sealing gasket 19 needs to have a certain elasticity. When the telescopic sheet 45 is between the upper and lower sealing gaskets 19, the sealing gaskets 19 can be closely attached to the telescopic sheet 45; when the telescopic sheet 45 is not between the upper and lower sealing gaskets 19, the two sealing gaskets 19 can still be closely attached to each other. Before each powder spreading, the sealing gasket 19 ensures that the inert atmosphere in the forming chamber 1 is not destroyed and prevents oxygen from entering, thereby affecting the melting quality of the material. During the powder spreading process, the sealing gasket 19 effectively prevents the powder from leaking out of the powder storage cylinder 39 and ensures that the powder is laid only in the required area. During the entire manufacturing process, the sealing gasket 19 continuously maintains a good environment in the forming chamber 1, which helps to improve the quality of the finished product.

[0045] Further, referring to Figure 1The powder laying device includes a first powder laying device 7, a second powder laying device 8 and a third powder laying device 9, which are respectively installed below the first powder supply funnel 3, the second powder supply funnel 4 and the third powder supply funnel 5. The number of the powder laying devices can be increased or decreased through the threaded holes 6 on the powder storage cylinder 39. The powder laying device is used to lay the powder in the powder supply funnel on the forming platform 10. The connection between the powder laying device and the powder supply funnel needs to have good sealing measures to prevent powder leakage. The powder laying device is connected with the powder supply funnel through bolts or buckles to ensure that the powder can flow smoothly from the powder supply funnel into the powder laying device. Each powder laying device contains a powder storage cylinder 39 for temporarily storing the powder falling from the powder supply funnel. Further, the powder supply device includes a first powder supply funnel 3, a second powder supply funnel 4, a third powder supply funnel 5, a fourth powder supply funnel 13, a fifth powder supply funnel 14 and a sixth powder supply funnel 15, which are located on one side of the forming chamber 1, and the fourth powder supply funnel 13, the fifth powder supply funnel 14 and the sixth powder supply funnel 15 are located on the other side of the forming chamber 1. The powder supply funnel is used to store powder of different materials. Of course, the specific structure of the powder supply funnel is not limited in the present application, and preferably, the powder supply funnel is designed as a conical structure, which is wide at the top for easy feeding and gradually narrows at the bottom for facilitating powder flow. An electromagnetic valve is arranged below the powder supply funnel for controlling the supply of powder. The opening and closing of the electromagnetic valve can be accurately controlled by the computer system. The powder supply funnel is connected with the powder laying device through a connecting pipe or directly connected to ensure that the powder can flow smoothly from the powder supply funnel into the powder laying device. Of course, the specific number of the powder supply funnel is not limited in the present application, and by using independent powder supply funnels, the powder of different materials can be effectively separated to avoid mixing.

[0046] Further, with reference to Figure 3The multi-material powder laying assembly based on SLM additive manufacturing provided by the application further comprises a fixing plate 28, which is used for supporting a powder storage cylinder 39 so that the powder storage cylinder 39 can move linearly in a horizontal direction in a rectangular channel of the fixing plate 28. The moving mechanism 12 comprises a motor 22, a coupling 23, a ball screw 24, a linear guide rail 25, an inductor 26 and an inductive device 27, the ball screw 24 and the linear guide rail 25 are parallel to each other and are both fixed on the fixing plate 28. One side of the powder storage cylinder 39 is installed on the ball screw 24 through a nut, and the other side of the powder storage cylinder 39 is installed on the linear guide rail 25 through a sliding block. The ball screw 24 and the linear guide rail 25 are parallel to each other and are both installed on the fixing plate 28. The linear motor 22 drives the ball screw 24 to rotate through the coupling 23, the nut seat converts the rotary motion into linear motion, and the guiding action of the linear guide rail 25 enables the powder storage cylinder 39 to move linearly in a horizontal direction in the rectangular channel of the fixing plate 28. The inductor 26 is installed on the powder storage cylinder 39, and the inductive device 27 is installed on the fixing plate 28. Through the action of the inductor 26 and the inductive device 27, the working distance of the horizontal moving mechanism is limited, and structural interference is prevented. The inductor 26 is used in cooperation with the inductive device 27 to detect the position of the powder storage cylinder 39. The inductive device 27 is used to sense the position of the inductor 26 to control the movement of the powder storage cylinder 39.

[0047] Further, the application further discloses a multi-material powder laying method based on SLM additive manufacturing, which is performed by using the multi-material powder laying assembly and comprises the following steps.

[0048] S1: install a corresponding number of powder laying devices, turn on the system power, introduce a multi-material product 11 which has been sliced, determine whether to add powder according to the data of the pressure sensor 16, determine to vacuum the forming chamber 1 after adding, and prepare for printing;

[0049] S2: according to the slicing data, the computer sends the positions of different materials to the corresponding powder laying devices, the moving mechanism 12 drives the powder laying devices to move in the positive direction, and the rotating mechanism drives the steel roll sheet 18 to work;

[0050] S3: when the powder laying device reaches the required powder laying area, the steel roll sheet 18 cooperates with the ultrasonic transducer 17 to make the powder continuously and accurately fall in the powder laying area; during the powder laying process, the rotating steel roll 44 and the telescopic sheet 45 cooperate to move, control the length and position of the powder outlet, and make the powder cover the powder laying area;

[0051] S4: when the powder laying device leaves the powder laying area, the rotating steel roll 44 and the telescopic sheet 45 are in advance in close contact to stop powder from being discharged, so as to prevent other areas from being polluted; when the powder laying device reaches the powder laying area, the rotating steel roll and the telescopic sheet are in advance opened to realize accurate powder laying;

[0052] S5: the laser device 2 irradiates and melts the laid powder, and after cooling, the powder is combined on the substrate or base material;

[0053] S6: it is judged whether the multi-material product 11 is completed, if yes, the process is ended, if not, step S7 is executed;

[0054] S7: the forming platform 10 is lowered by a layer thickness;

[0055] S8: the powder laying device is moved in the opposite direction by the moving mechanism 12, and the powder laying process in steps S3 and S4 is repeated, so that the powder laying of the layer is completed by the powder laying device;

[0056] S9: step S5 is executed, and it is judged whether the product is completed, if yes, the process is ended, if not, step S7 is executed first, and then the process returns to step S3 and continues.

[0057] According to the above steps, the multi-material product 11 with three materials is printed by SLM technology, and the specific implementation is as follows: assuming that each layer of the multi-material product 11 is composed of two or more materials, through computer processing, each layer can be divided into multiple printing areas according to the types of materials, and all the printing areas with the same material will form a material model with the same material, for example, in this example, the multi-material product 11 model can be composed of a first material, a second material and a third material, assuming that the first material is 316L stainless steel powder, which is loaded in the first powder laying device 7 before printing, the second material is chromium-nickel-iron alloy 625 powder, which is loaded in the second powder laying device 8 before printing, and the third material is CuSn10 powder, which is loaded in the third powder laying device 9 before printing, assuming that the powder layer thickness is 30 , the computer is set to lower the forming platform 10 by 30 μm after completing the printing of each layer. Figure 7 Since the price of the 316L stainless steel powder is the lowest among the three metal powders, the powder is used as the filling material of the filling area. Assuming that the next three printing layers of the multi-material product 11 are as shown in Figure 8 , Figure 9 and Figure 10 , Figure 11 and Figure 12As shown, 461 in the first printing layer 46 is divided into an area 4611, and 462 is divided into an area 4621. 463 is divided into two areas, namely 4631 and 4632, and the remaining areas are filling areas, namely 4641, 4642 and 4643; in the second printing layer 47, 471 is divided into one area 4711, 472 is divided into three areas, namely 4721, 4722 and 4723, and 473 is also divided into three areas, namely 4731, 4732 and 4733, and the remaining areas are filling areas, namely 4741, 4742 and 4743; in the third printing layer 48, 481 is divided into two areas, namely 4811 and 4812, 482 is divided into two areas, namely 4821 and 4822, 483 is divided into two areas, namely 4831 and 4832, and the remaining areas are filling areas, namely 4841, 4842 and 4843. According to the divided areas, the computer can obtain the scanning path of each area. Obviously, the powder materials used in the 4X1Y area and the 4X4Z area are the same, both of which are 316L stainless steel powder in the first powder spreading device 7. After completing the powder spreading of each small area, the computer will control the two rotating motors of the powder spreading device to close the powder outlet.

[0058] Furthermore, assuming that the forming platform 10 has been lowered to the specified height, for the first printing layer 46, the powder spreading device performs powder spreading from bottom to top. During the horizontal movement of the powder spreading device, the two rotating motors of the first powder spreading device 7 will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and first complete the powder spreading in area 4641. Then, the first powder spreading device 7 goes to area 4642 and area 4611 along the powder spreading direction, and at the same time moves the position of the powder outlet to area 46421 on one side of area 4642, first completes the powder spreading on the straight line where the powder outlet is located, and then, while keeping the powder outlet closed, moves the position of the powder outlet along this straight line to area 4611, and completes the powder spreading of this area on this straight line, and then, while keeping the powder outlet closed, moves the position of the powder outlet along this straight line to area 46422 on the other side of area 4642, and completes the powder spreading of this area on this straight line. Then the first powder spreading device 7 moves forward in the powder spreading direction, and the two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, first completing the powder spreading on the straight line where the powder outlet of area 46422 is located, and then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to area 4611, and the powder spreading of this area on this straight line is completed, and then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to area 46421, and the powder spreading of this area on this straight line is completed. Repeat this process until the powder spreading of areas 4642 and 4611 is completed, and then the first powder spreading device 7 moves to area 4643 along the powder spreading direction, and the two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading of area 4643. While the first powder spreading device 7 is spreading powder, the two rotating motors of the second powder spreading device 8 will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading in the 4621 area. While the first and second powder spreading devices 7 and 8 are spreading powder, the two rotating motors of the third powder spreading device 9 will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, first completing the powder spreading on the straight line where the powder outlet of area 46311 on one side of area 4631 is located, then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to area 46312 on the other side of area 4631, and the powder spreading of this area on this straight line is completed. Then, the third powder spreading device 9 moves one step in the powder spreading direction, and the two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, first completing the powder spreading on the straight line where the powder outlet of area 46312 is located, then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to area 46311, and the powder spreading of this area on this straight line is completed. Repeat this process until the powder spreading of area 4631 is completed.Then the third powder spreading device 9 comes to the 4632 area along the powder spreading direction. The two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer. First, the powder spreading on the straight line where the powder outlet of the 46321 area on one side of the 4632 area is located is completed. Then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to the 46322 area on the other side of the 4632 area, and the powder spreading of this area on this straight line is completed. Then the third powder spreading device 9 moves one step forward along the powder spreading direction. The two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer. First, the powder spreading on the straight line where the powder outlet of the 46322 area is located is completed. Then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to the 46321 area, and the powder spreading of this area on this straight line is completed. Repeat this process until the powder spreading of the 4632 area is completed. The computer determines that the first printing layer 46 has completed powder coating in all areas. Under computer control, the laser device 2 completes powder melting in areas 4611, 4621, 4631, and 4632. The computer determines that the first printing layer 46 is not the final layer, so the build platform 10 descends 30°. .

[0059] Further, the computer controls the first powder spreading device 7, the second powder spreading device 8 and the third powder spreading device 9 to complete the powder spreading of the second printing layer 47. For the second printing layer 47, the powder spreading device performs powder spreading from top to bottom, and in the process of horizontal movement of the powder spreading device, the two rotating motors of the first powder spreading device 7 control the matching movement of the steel roll sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading of the 4741 region first. Further, the first powder spreading device 7 reaches the 4742 region and the 4711 region along the powder spreading direction, and at the same time, the position of the powder outlet is moved to one side 47421 region of the 4742 region, the powder spreading on the straight line where the powder outlet is located is completed first, then under the condition of keeping the powder outlet closed, the position of the powder outlet is moved to the other side 47422 region of the 4742 region along the straight line, and the powder spreading of the region on the straight line is completed, then the first powder spreading device 7 further moves along the powder spreading direction, the two rotating motors control the matching movement of the steel roll sheet 18 according to the instructions transmitted by the computer, complete the powder spreading on the straight line where the powder outlet of the 47422 region is located first, then under the condition of keeping the powder outlet closed, the position of the powder outlet is moved to the 47421 region along the straight line, and the powder spreading of the region on the straight line is completed, if the first powder spreading device 7 moves from one side region of the 4742 region to the other side region, passes through the 4711 region, then the first powder spreading device 7 also completes the powder spreading on the straight line where the powder outlet of the 4711 region is located. Repeat the process until the powder spreading of the 4742 region and the 4711 region is completed. Then the first powder spreading device 7 reaches the 4743 region along the powder spreading direction, and the two rotating motors control the matching movement of the steel roll sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading of the 4743 region.

[0060] Further, while the first powdering device 7 is powdering, the two rotary motors of the second powdering device 8 control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powdering of the 4721 area first. Subsequently, the second powdering device 8 moves to the 4722 area along the powdering direction, and at the same time, the position of the powder outlet is moved to one side of the 4722 area, i.e., the 47221 area. The powdering on the straight line where the powder outlet is located is completed first. Then, while keeping the powder outlet closed, the position of the powder outlet is moved to the other side of the 4722 area, i.e., the 47222 area, along the straight line, and the powdering on the straight line in the 47222 area is completed. Subsequently, the second powdering device 8 moves further along the powdering direction, and the two rotary motors control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, complete the powdering on the straight line where the powder outlet in the 47222 area is located first, and then, while keeping the powder outlet closed, the position of the powder outlet is moved to the 47221 area along the straight line, and the powdering on the straight line in the 47221 area is completed. This process is repeated until the powdering of the 4722 area is completed. Further, the second powdering device 8 moves to the 4723 area along the powdering direction, and the two rotary motors control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powdering of the 4723 area.

[0061] Furthermore, while the first powder spreading device 7 and the second powder spreading device 8 are spreading powder, the two rotating motors of the third powder spreading device 9 will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and first complete the powder spreading in area 4731. Then, the third powder spreading device 9 comes to area 4732 along the powder spreading direction, and at the same time moves the position of the powder outlet to area 47321 on one side of area 4732, first completing the powder spreading on the straight line where the powder outlet is located, and then, while keeping the powder outlet closed, move the position of the powder outlet along this straight line to area 47322 on the other side of area 4732, and complete the powder spreading of this area on this straight line. Then the third powder spreading device 9 moves forward in the powder spreading direction, and the two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, first completing the powder spreading on the straight line where the powder outlet of area 47322 is located, and then, while keeping the powder outlet closed, the position of the powder outlet is moved along this straight line to area 47321, and the powder spreading of this area on this straight line is completed. Repeat this process until the powder spreading of area 4732 is completed. Then the third powder spreading device 9 moves to area 4733 along the powder spreading direction, and the two rotating motors will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading of area 4733. The computer determines that the second printing layer 47 has completed the powder spreading of all areas, and the laser device 2, under the control of the computer instructions, completes the powder melting of areas 4711, 4721, 4722, 4723, 4731, 4732 and 4733. The computer determines that the second printing layer 47 is not the last layer, so the forming platform 10 drops 30 .

[0062] Furthermore, the computer controls the first powder spreading device 7, the second powder spreading device 8, and the third powder spreading device 9 to complete the powder spreading of the third printing layer 48. For the third printing layer 48, the powder spreading device spreads the powder from bottom to top. During the horizontal movement of the powder spreading device, the two rotating motors of the first powder spreading device 7 will control the coordinated movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder spreading of area 4841 first. Then the first powder spreading device 7 moves along the powder spreading direction to area 4811 and most of area 4842, as shown in FIG. Figure 12As shown, the 4842 region is divided into two parts by the dotted line. Since the 4811 region and most of the 4842 region are in contact, the computer will combine these two regions into one region during powdering. The two sides of this new region are recorded as the 48511 region and the 48512 region. During powdering, the first powdering device 7 moves the powder outlet to the 48511 region, first completes powdering on the straight line where the powder outlet is located, then moves the powder outlet to the 48512 region along this straight line while keeping the powder outlet closed, and completes powdering on this straight line in this region. Then the first powdering device 7 moves further along the powdering direction, and the two rotating motors control the coordinated movement of the steel roll sheet 18 according to the instructions transmitted by the computer, first complete powdering on the straight line where the powder outlet is located in the 48512 region, then move the powder outlet to the 48511 region along this straight line while keeping the powder outlet closed, and complete powdering on this straight line in this region. Repeat this process until the powdering of the 4811 region and part of the 4842 region is completed. Then the first powdering device 7 moves to the 4812 region, part of the 4842 region and the 4843 region along the powdering direction. Since the 4812 region, part of the 4842 region and the 4843 region are in contact, the computer will combine these three regions into one region during powdering. This new region is recorded as the 4852 region. During powdering, the two rotating motors of the first powdering device 7 control the coordinated movement of the steel roll sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powdering of the 4852 region, i.e. the 4812 region, part of the 4842 region and the 4843 region.

[0063] Further, while the first powdering device 7 is powdering, the two rotating motors of the second powdering device 8 control the coordinated movement of the steel roll sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and first complete the powdering of the 4821 region. Then the second powdering device 8 moves to the 4822 region along the powdering direction, and moves the powder outlet to one side of the 4822 region, i.e. the 48221 region. First complete powdering on the straight line where the powder outlet is located, then move the powder outlet to the other side of the 4822 region, i.e. the 48222 region along this straight line while keeping the powder outlet closed, and complete powdering on this straight line in this region. Then the second powdering device 8 moves further along the powdering direction, and the two rotating motors control the coordinated movement of the steel roll sheet 18 according to the instructions transmitted by the computer, first complete powdering on the straight line where the powder outlet is located in the 48222 region, then move the powder outlet to the 48221 region along this straight line while keeping the powder outlet closed, and complete powdering on this straight line in this region. Repeat this process until the powdering of the 4822 region is completed.

[0064] Further, while the first powder laying device 7 and the second powder laying device 8 are laying powder, the two rotating motors of the third powder laying device 9 control the matching movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, complete the powder laying in one side 48311 area of the 4831 area along the straight line where the powder outlet is located, then move the position of the powder outlet to the middle area 48312 area of the 4831 area along the straight line while keeping the powder outlet closed, and complete the powder laying in the area along the straight line. Then move the position of the powder outlet to the other side 48313 area of the 4831 area along the straight line while keeping the powder outlet closed, and complete the powder laying in the area along the straight line. Then the third powder laying device 9 moves forward along the powder laying direction, the two rotating motors control the matching movement of the steel coil sheet 18 according to the instructions transmitted by the computer, complete the powder laying in the 48313 area along the straight line where the powder outlet is located, then move the position of the powder outlet to the 48312 area along the straight line while keeping the powder outlet closed, and complete the powder laying in the area along the straight line. Then move the position of the powder outlet to the 48311 area along the straight line while keeping the powder outlet closed, and complete the powder laying in the area along the straight line. Repeat this process until the powder laying in the 4831 area is completed. Then the third powder laying device 9 moves to the 4832 area along the powder laying direction, the two rotating motors control the matching movement of the steel coil sheet 18 according to the instructions transmitted by the computer, adjust the size and position of the powder outlet, and complete the powder laying in the 4832 area. The computer determines that the third printing layer 48 has completed the powder laying in all areas, and the laser device 2 completes the powder melting in the 4811, 4812, 4821, 4822, 4831 and 4832 areas under the control of the computer instructions. If the third printing layer 48 is the last layer, the computer determines that the printing of the multi-material product 11 is completed. Otherwise, the forming platform 10 is lowered 30 for the next printing.

[0065] It should be noted that in the description of the present application, if there are orientation descriptions such as the orientation or position relationship indicated by the upper, lower, front, rear, left, right and the like, they are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and cannot be understood as indicating or implying that the devices or elements 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 application.

[0066] In the description of the present application, the meaning of one or more is one or more, the meaning of multiple is two or more, greater than, less than, more than, etc. is understood as not including the number, above, below, within, etc. is understood as including the number. If there is a description of first or second, etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the order of the indicated technical features.

[0067] In the description of the present application, unless otherwise expressly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and those skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical scheme.

[0068] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art on the basis of the present application are within the scope of protection of the present application.

Claims

1. A multi-material powder lay-up assembly for additive manufacturing based on SLM, characterized in that, The utility model relates to a multi -material powder laying device, including: The forming chamber (1) is equipped with the forming platform (10) in, the forming platform (10) can be under the action of motor and carry out the lifting movement in the forming chamber (1); The powder supply device is multiple and can be uniformly fixed to both sides of the forming chamber (1), and the lower part of the powder supply device is provided with a solenoid valve; The powder laying device is multiple, and the powder laying device is connected to the lower part of the powder supply device correspondingly, and the powder laying device includes a powder storage cylinder (39), a moving mechanism (12), an ultrasonic transducer (17), a rotating mechanism and a steel roll sheet (18), the powder storage cylinder (39) is connected with the moving mechanism (12), the ultrasonic transducer (17) is located in the powder storage cylinder (39), the rotating mechanism is installed on both sides of the powder storage cylinder (39), the steel roll sheet (18) is fixed to the lower part of the powder laying device, the upper part of the steel roll sheet (18) is provided with a pressure sensor (16), and the steel roll sheet (18) includes a rotating steel roll (44) and a telescopic sheet (45); The laser device (2) is located above the forming platform (10); The pressure sensor (16) monitors the pressure change on the steel roll sheet (18) to ensure the quality of powder laying, and the pressure sensor (16) can detect the amount of remaining powder in the powder storage cylinder (39) to determine whether to add powder, the rotating steel roll (44) is connected with the rotating mechanism, and the position of the powder outlet is controlled by rotating; the telescopic sheet (45) can move in cooperation with the chute below the powder storage cylinder (39) to control the length of the powder outlet, and in the process of laying powder, the rotating steel roll (44) and the telescopic sheet (45) still move in cooperation to control the length and position of the powder outlet, so that the powder is laid full in the powder laying area, since the powder outlet will accumulate a part of the powder, therefore, when leaving the powder laying area, the rotating steel roll (44) and the telescopic sheet (45) will be in advance and stop powdering to prevent pollution to other areas, when the powder laying device reaches the powder laying area, the rotating steel roll (44) and the telescopic sheet (45) are opened in advance to realize accurate powder laying, and each powder laying device moves independently and does not interfere with each other, so as to complete the powder laying of a layer of multi-material powder.

2. The multi-material powder spreading assembly of claim 1, wherein, The powder laying device further includes an induction head (20), an induction device (21) and a sealing gasket (19), the induction head (20) is connected with the steel roll sheet (18), the induction device (21) is connected with the powder storage cylinder (39), and the sealing gasket (19) is located between the powder storage cylinder (39) and the steel roll sheet (18).

3. The multi-material powder laying assembly of claim 1, wherein, The width of the powder outlet of the powder storage cylinder (39) is greater than the diameter of the metal powder, and the two sides of the width direction of the powder outlet of the powder storage cylinder (39) are provided with chamfers, and the chamfers are used for compacting the powder.

4. The multi-material powder laying assembly of claim 1, wherein, The powder supply device includes a first powder supply hopper (3), a second powder supply hopper (4), a third powder supply hopper (5), a fourth powder supply hopper (13), a fifth powder supply hopper (14) and a sixth powder supply hopper (15), the first powder supply hopper (3), the second powder supply hopper (4) and the third powder supply hopper (5) are located on one side of the forming chamber (1), and the fourth powder supply hopper (13), the fifth powder supply hopper (14) and the sixth powder supply hopper (15) are located on the other side of the forming chamber (1).

5. The multi-material powder laying assembly of claim 1, wherein, The powder laying device includes a first powder laying device (7), a second powder laying device (8) and a third powder laying device (9), the first powder laying device (7), the second powder laying device (8) and the third powder laying device (9) are all correspondingly installed below the first powder supply hopper (3), the second powder supply hopper (4) and the third powder supply hopper (5), and the number of the powder laying device can be increased or reduced through the threaded holes (6) on the powder storage cylinder (39).

6. The multi-material powder laying assembly of claim 1, wherein, It also includes a fixed plate (28) for supporting the powder storage cylinder (39) so that the powder storage cylinder (39) can move linearly in the horizontal direction within the rectangular channel of the fixed plate (28), and the moving mechanism (12) includes a linear motor (22), a coupling (23), a ball screw (24), a linear guide rail (25), an induction iron (26) and an induction device (27), the ball screw (24) and the linear guide rail (25) are parallel to each other and are both fixed on the fixed plate (28), one side of the powder storage cylinder (39) is installed on the ball screw (24) through a nut, and the other side of the powder storage cylinder (39) is installed on the linear guide rail (25) through a sliding block.

7. The multi-material powder laying assembly of claim 1, wherein, The rotating mechanism includes a stepped shaft, a pinion, a rotating motor and a large gear, a motor base (40) is fixed below the powder storage cylinder (39), the rotating motor is fixed on the motor base (40) and is keyed connected with the large gear, the pinion is keyed connected with the stepped shaft, the large gear can drive the pinion to rotate, the steel coil sheet (18) can be fixed with the stepped shaft, when the rotating motor works, the steel coil sheet (18) can be driven to rotate through the meshing of the gears, the top end of the telescopic sheet (45) is provided with a guide part, the sliding groove is provided with a guide groove, and the guide part can move in cooperation with the guide groove.

8. The multi-material powder laying assembly of claim 7, wherein, The stepped shafts include first stepped shafts (29) and second stepped shafts (38), the pinions include first pinions (31) and second pinions (35), the rotary motors include first rotary motors (32) and second rotary motors (37), the gearwheels include first gearwheels (33) and second gearwheels (36), the steel sheet rolls (18) include the first steel sheet rolls (30) and the second steel sheet rolls (34), the first stepped shafts (29), the first pinions (31), the first rotary motors (32), the first gearwheels (33) and the first steel sheet rolls (30) are located on one side of the fixed plate (28), and the second stepped shafts (38), the second pinions (35), the second rotary motors (37), the second gearwheels (36) and the second steel sheet rolls (34) are located on the other side of the fixed plate (28).

9. The multi-material powder spreading assembly of claim 8, wherein, Both ends of the first steel sheet roll (30) are provided with first bearing seats (41) and second bearing seats (43), and one side of the first steel sheet roll (30) is further provided with a first sealing gasket (42).

10. A multi-material powder laying method for additive manufacturing based on SLM, characterized in that, The multi-material powder laying assembly according to any one of claims 1-9 is used, comprising the following steps: S1: install a corresponding number of the powder laying devices, turn on the system power, introduce a multi-material product (11) that has completed slicing, determine whether to add powder according to the data of the pressure sensor (16), determine to perform vacuumization on the forming chamber (1) after adding, and prepare for printing; S2: according to the slicing data, the computer sends the positions of different materials to the corresponding powder laying devices, the moving mechanism (12) drives the powder laying devices to move in the positive direction, and the rotating mechanism drives the steel sheet roll (18) to work; S3: when the powder laying devices reach the required powder laying area, the steel sheet roll (18) cooperates with the ultrasonic transducer (17) to make the powder continuously and accurately fall in the powder laying area; during the powder laying process, the rotating steel roll (44) and the telescopic sheet (45) cooperate to move, control the length and position of the powder outlet, and make the powder cover the powder laying area; S4: when the powder laying devices leave the powder laying area, the rotating steel roll (44) and the telescopic sheet (45) are stuck in advance to stop powdering to prevent pollution of other areas; when the powder laying devices reach the powder laying area, the rotating steel roll (44) and the telescopic sheet (45) are opened in advance to realize accurate powder laying; S5: the laser device (2) irradiates and melts the laid powder, and after cooling, the powder is combined on the substrate or base material; S6: determine whether the multi-material product (11) is completed, if yes, end; if not, execute step S7; S7: the forming platform (10) is lowered by a layer thickness; S8: the moving mechanism (12) drives the powder laying devices to move in the reverse direction, and the powder laying process in steps S3 and S4 is repeated to complete the powder laying of the layer by the powder laying devices; S9: execute step S5, and then determine whether the product is completed or not. If yes, the process is ended. If not, execute step S7 first, and then return to step S3 and continue the process.

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