Powder laying structure and multi-material 3D printing system

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to a powder spreading structure and a multi-material 3D printing system.The powder spreading structure mainly comprises a control module, a powder discharging assembly, a freeze-frame assembly and a recycling assembly, the freeze-frame assembly comprises a plurality of freeze-frame units, the freeze-frame units are arranged side by side, and each freeze-frame unit comprises a freeze-frame base, a freeze-frame arm and a driver; the freeze-frame arm is rotationally connected into the freeze-frame seat, a notch is formed in the end, away from the freeze-frame seat, of the freeze-frame arm, the driver drives the freeze-frame arm to rotate in the freeze-frame seat, and a shielding part is arranged on the side edge of the notch. The powder outlet assembly comprises a powder storage bin and a powder outlet nozzle, the powder outlet nozzle is communicated with the powder storage bin, and the powder outlet nozzle is used for conveying powder stored in the powder storage bin to the notch in the freeze-frame arm; the control module is in signal connection with the driver and controls the driver to adjust the rotation angle of the freeze-frame arm; and the recycling assembly is used for recycling the powder material retained on the freeze-frame assembly. The problem that parts needing to be formed by printing multiple metal materials are difficult to manufacture is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a powder spreading structure and a multi-material 3D printing system. Background Art

[0002] Common 3D printing systems based on laser melting technology (SLM) can usually only use one type of powder for printing, and can only spread the same type of metal powder. The overall stiffness and strength of the printed parts are also evenly distributed. However, for some parts, the stiffness and strength of their own structure may not be evenly distributed. For example, the piston is a key component of the engine, and its quality directly affects the performance of the engine. The top of the piston contacts the combustion chamber, so it is required to be resistant to high temperature and high pressure, and has higher requirements for stiffness and strength. The skirt of the piston has relatively lower strength and stiffness in terms of mechanical structure, so its top and skirt can be made of different alloys. For metal parts that need to be printed with different metal powders in different parts, the existing 3D printing system is limited by its own powder spreading structure and can only complete the powder spreading of one type of metal powder, making it difficult to manufacture parts that need to be printed from multiple metal materials. Summary of the invention

[0003] The present invention is intended to provide a powder spreading structure and a multi-material 3D printing system to solve the problem of difficulty in manufacturing parts that need to be printed from multiple metal materials.

[0004] In order to achieve the above object, one aspect of the present invention is to provide a powder spreading structure, including a control module, a powder outlet component, a freeze component and a recovery component:

[0005] The freeze assembly includes a plurality of freeze units, which are arranged side by side. The freeze units include a freeze seat, a freeze arm and a driver. The freeze arm is rotatably connected to the freeze seat. A notch is provided at one end of the freeze arm away from the freeze seat. The driver drives the freeze arm to rotate in the freeze seat. A shielding portion is provided on the side of the notch.

[0006] The powder discharging assembly includes a powder storage bin and a powder discharging nozzle, the powder discharging nozzle is connected to the powder storage bin, and the powder discharging nozzle is used to transport the powder stored in the powder storage bin to the notch on the freezer arm;

[0007] The control module is connected with the driver signal and controls the driver to adjust the rotation angle of the freeze arm;

[0008] The recovery component is used to recover the powder material retained on the fixed component.

[0009] The working principle and beneficial effects of this solution are:

[0010] The control module controls the rotation stroke of the freeze arm in the freeze seat by controlling each driver of the freeze component, so that the end of the freeze part rotates so that the notch faces upward, and the notch is combined into a certain shape, and then the powder material is released from the notch by the powder discharge component to complete the powder spreading. The excess powder material that falls and stays on the freeze component is recovered by the recovery component. Each freeze unit can form a notch individually, and multiple freeze units can be controlled by the control module through stroke control to control the position and size of the notch, so that multiple notches can form a complex pattern. Therefore, this solution is also suitable for 3D printing parts with complex cross-sectional structures.

[0011] This solution is used when spreading multiple powder materials: 1. Multiple powder output components correspond to one fixed-frame component: each fixed-frame unit of the fixed-frame component can control the gap individually, so the gaps of multiple fixed-frame units can be controlled to form a pattern, and then different powder materials are released in the gaps of the fixed-frame units through the nozzles of different powder output components, thereby realizing the printing of multiple metal materials; 2. Multiple powder output components correspond one-to-one to multiple fixed-frame components: each fixed-frame component controls its own gap to form a pattern, and then different powder materials are released in the gaps of each fixed-frame component through the nozzles of their corresponding powder output components, thereby realizing the printing of multiple metal materials, and it is more efficient than the aforementioned many-to-one solution.

[0012] In this solution, when releasing powder material, it can be released to multiple gaps at the same time to spread the powder, and the powder spreading efficiency is high, so the 3D printing system using this solution has higher printing efficiency. More importantly, the powder discharge component does not need positioning control, which can greatly reduce the control difficulty of the powder discharge component and make the powder discharge structure simpler and more reliable.

[0013] Compared with the traditional powder laying structure, this solution has the ability to lay multiple powder materials locally. Therefore, not only can a part of the fixing components and the powder outlet components be used to accurately lay multiple metal powder materials that need to be sintered on the sintering position, but the remaining fixing components and the powder outlet components can lay cheaper powder materials that are not used for part molding on the remaining positions to form support for the metal powder materials of the parts. Compared with the solution of laying a whole layer of powder materials to form parts in the prior art, the recovery component can also recycle the powder materials retained on the fixing components, which can greatly reduce the consumption of metal powder materials for forming parts and can greatly reduce production costs.

[0014] Optionally, a walking assembly is also included, the walking assembly includes a walking driver, a walking seat and a guide rail, the walking driver is installed on the walking seat and drives the walking seat to rotate along the guide rail, the freeze assembly is installed on the walking seat, and the walking driver is connected to the control module signal. When the walking assembly is not included, it is more suitable for printing sheet metal (or shell) parts. After combining with the walking assembly, it is widely applicable to 3D printing of various parts.

[0015] Optionally, the driver includes servo motors corresponding to the number of freeze arms, the output end of each servo motor is connected to a freeze arm, and the servo motors are controlled by a control module. The rotation angle of the freeze arm is controlled by the servo motors.

[0016] Optionally, the driver includes a gear rack mechanism, a driver motor and an electromagnetic clutch pin whose number corresponds to the number of the freeze arms, the gear rack structure includes a rack and a driven gear whose number corresponds to the freeze arms, a driving gear is installed on the output end of the driver motor, and the driving gear and the driven gear are both engaged with the rack; the electromagnetic clutch pin includes an electromagnetic induction part and a latch, the freeze arm includes a connecting part and a rotating part, the rotating part is rotatably connected to the freeze seat, one end of each connecting part is coaxially connected to a driven gear, the other end of each connecting part is equipped with an electromagnetic induction part and is provided with a slot corresponding to the latch, one end of the rotating part is provided with a connecting groove corresponding to the slot, the latch is rotatably connected in the connecting groove, the latch is made of a permanent magnet and the two poles of magnetism are located at both ends of the latch, and the other end of the rotating part is provided with a notch groove in the radial direction. The control module precisely controls certain electromagnetic induction parts to generate magnetic fields, and controls the magnetism of the side of the magnetic field facing the latch. When the magnetism of the magnetic field is different from the magnetism of the end close to the latch, the latch is attracted and inserted into the connection slot, and the driver motor drives the rack to translate for a certain distance. During the translation of the second rack, the drive latch connects the connection part and the rotating part to the fixed arm to rotate a certain angle until the notch is facing the powder outlet, and the powder material can be released. After the powder material is released, the driver motor reverses again, the notch is reset, and the direction of the notch changes and is no longer exposed. The control module controls the electromagnetic induction part corresponding to the fixed arm of the latch connecting the connection part and the rotating part to generate an opposite magnetic field, repel the latch and reset the latch.

[0017] Optionally, the powder outlet includes a nozzle, and the nozzle is used to spray the powder in a cone shape when releasing the powder, so as to avoid a powder spreading dead angle caused by the shielding part when the shielding part rotates and the gap is exposed, thereby ensuring uniform and continuous powder spreading.

[0018] Optionally, the powder outlet assembly includes a powder storage tube, an inner nozzle and an adjustment assembly. The powder storage tube is provided with a feed port. The nozzle is arranged on the side of the powder storage tube in a direction parallel to the axis of the powder storage tube. The nozzle is a strip-shaped through hole. The inner nozzle is sleeved in the powder storage tube. The side wall of the inner tube is provided with a power-assisting seam that matches the nozzle. The two ends of the inner nozzle are rotatably connected to the two ends of the powder storage tube. The adjustment assembly is connected to the end of the inner nozzle and is used to adjust the distance between the power-assisting seam and the nozzle. The inner nozzle is connected with an air filling nozzle. The air filling nozzle is filled with pressurized gas. After the powder enters the powder storage tube, it is carried out from the nozzle by the gas rushed out of the power-assisting seam and can remain in a cone shape. The amount of powder sprayed is controlled by adjusting the distance between the power-assisting seam and the nozzle through the adjustment assembly. The larger the distance, the larger the amount of powder sprayed and the greater the thickness of the single layer of powder. Conversely, the smaller and thinner it is.

[0019] Optionally, the recovery component includes a brush or a vacuum cleaner.

[0020] Optionally, the brush assembly includes a brush shaft, bristles and a collecting groove, the bristles are distributed on the side of the brush shaft, the brush shaft is driven by a servo motor, and the servo motor is controlled by a control module; the collecting groove is located below the brush shaft and the freezer arm.

[0021] Optionally, the vacuum cleaner includes a negative pressure pipe and an electromagnetic air valve. A plurality of air holes are opened on the side of the negative pressure pipe, and the air holes face one end of the notch formed by the freeze arm. The electromagnetic air valve is installed at one end of the negative pressure pipe, and the electromagnetic air valve is connected to the vacuum pump and controlled by the control module.

[0022] Another aspect of the present invention is to provide a 3D printing system, including a machine body, a laser sintering component, a power supply module and a workbench with controllable lifting and lowering, and adopts the aforementioned powder spreading structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the powder spreading mechanism in the first embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of the powder spreading structure in the second embodiment of the present invention;

[0025] Figure 3 It is a cross-sectional view of a powder discharging component of the powder spreading structure in the second embodiment of the present invention;

[0026] Figure 4 It is a structural schematic diagram of a fixed-frame unit of the powder spreading structure in the third embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following is further described in detail through specific implementation methods:

[0028] The marks in the drawings of the specification include: a freezer seat 1, a freezer arm 2, a servo motor 3, a notch 4, a powder storage bin 5, a conveying pipe 6, a turntable 7, a nozzle 8, a powder outlet assembly 9, a powder storage pipe 901, an inner nozzle 902, a push plate 903, a feed port 904, a power assist seam 905, a linear motor 10, a powder guide plate 11, an electromagnetic induction part 12, a connecting part 13, a rotating part 14, a slot 15, a latch 16, a brush shaft 17, a baffle 18, a driven gear 19, a baffle 20, bristles 21, a collecting trough 22, and a negative pressure pipe 23.

[0029] Embodiment 1

[0030] The multi-material 3D printing system in this example includes a machine body, a laser sintering component, a power supply module and a controllable lifting table. The above components are all mature existing technologies and are not described here or shown in the figure. The system includes a set of powder spreading structure, which includes a control module, a powder outlet component 9, a freeze component and a recycling component:

[0031] As attached Figure 1 As shown, in this embodiment, the freeze assembly includes 32 freeze units, which are arranged side by side. The freeze units include a freeze seat 1, a freeze arm 2 and a driver 3. One end of the freeze arm 2 is rotatably connected to the freeze seat 1. The servo motor 3 drives one or some freeze arms 2 to rotate 90° in the freeze seat 1. The shielding plate 18 turns to a vertical state, and the notch 4 faces upward. The powder outlet of the powder outlet assembly 9 only needs to uniformly release the powder material to the end of the freeze arm 2 with the notch 4. Part of the powder material is accumulated on the workbench through the notch 4, and part of the powder material is blocked by the end shielding plate 18 of the freeze arm 2 and retained on the freeze arm 2, and finally recovered by the recovery assembly. In this embodiment, in order to ensure that the edge of the powder accumulation is more neat after the notch 4 releases the powder, a baffle 20 is also provided at the notch 4 end of the freeze arm 2. The servo motor 3 is reversed 90° to reset.

[0032] The powder discharging assembly 9 also includes three sets of conveying pipes 6 and a turntable 7. The conveying pipes 6 are provided with nozzles 8 with strips on the side. The nozzles 8 are installed at the powder discharging hole, and the nozzles 8 are always facing downward. The powder material is pumped out from the powder storage bin 5 by a pumping device, and then filled into the conveying pipe 6. The pumped powder material is sprayed out from the nozzle 8 at the same pressure to ensure uniform powder spreading. A main solenoid valve and 32 conduits are provided at the outlet of the pumping device. The control module controls the main solenoid valve to control the opening and closing of the powder delivery and the delivery amount. The 32 conduits are connected to each nozzle 8 respectively. The three conveying pipes 6 are installed on the turntable 7. The turntable 7 is located above the gap 4 formed by the fixed assembly. The turntable 7 is driven to rotate by another servo motor and controlled by the control module. When a certain powder needs to be sprayed, the conveying pipe 6 of that powder is turned to the top of the gap 4.

[0033] The control module is connected to the driver 3 signal and controls the driver 3 to adjust the rotation angle of the freeze arm 2. In this embodiment, the control module is a computer with input, output, calculation, storage and other functions. After inputting the model information of the part, the control module can automatically slice according to the model of the part, and parse to obtain the corresponding distribution position of the gap 4 when each layer of the part is printed, and control the freeze component to cooperate with the lifting workbench to give a signal to the driver 3 when printing to the layer, simulate the gap 4 there, and control the corresponding powder output component 9 and the turntable 7 to spray the corresponding powder material to complete the powder laying, and then lay the auxiliary powder material at the complementary position of each layer of the gap 4 (the position where the powder material required for part molding is not laid).

[0034] The recovery component is used to recover the powder material retained on the freeze component. In this embodiment, the brush component includes a brush shaft 17, bristles 21 and a collection trough 22. The bristles 21 are distributed in a row on the side of the brush shaft 17. The brush shaft 17 is driven by a servo motor, and the servo motor is controlled by the control module; the collection trough is located below the brush shaft 17 and the freeze arm 2. When the freeze arm 2 is reset after the powder material is laid, the control module starts the servo motor to rotate the bristles 21 to sweep the powder material retained on the freeze arm 2 into the collection trough 22 below. In order to prevent the powder material from being recycled more smoothly, a powder guide plate 11 is also provided above the freeze arm to block the powder material and cooperate with the brush component to allow the powder material to fall into the collection trough 22 better.

[0035] In this embodiment, since no walking assembly is used, 3D printing can only be completed by raising and lowering the workbench, so it is more suitable for printing sheet metal (or shell) parts with linear cross-sections.

[0036] Embodiment 2

[0037] The difference between this embodiment and the first embodiment is that: Figure 2 As shown, it also includes a walking component, so that the freeze component can generate movement perpendicular to the lifting direction of the workbench as a whole. The walking component includes a walking driver 3, a walking seat and a guide rail. The walking driver 3 is installed on the walking seat and drives the walking seat to rotate along the guide rail. The freeze component is installed on the walking seat, and the walking driver 3 is connected to the control module signal. In this embodiment, the combination of the walking driver 3 and the guide rail is a linear motor 10, which is controlled by the control module. The walking seat is installed on the output end of the linear motor 10, so as to accurately control the displacement of the freeze component perpendicular to the lifting direction. In combination with the constantly changing notch 4 of the freeze component, 3D printing of parts with more complex cross-sections can be produced.

[0038] In other embodiments, the travel driver 3 may be an electric cylinder, an oil cylinder, an air cylinder, an electric lead screw, etc. In this embodiment, two sets of fixed frame components are included, each set of fixed frame components corresponds to a set of powder outlet components 9, which are respectively used to lay two different metal powder materials for forming parts. Figure 3As shown, the powder discharging assembly 9 includes a powder storage pipe 901, an inner nozzle 902 and an adjusting assembly. The powder storage pipe 901 is provided with a feed port 904. In this embodiment, the feed port 904 is a strip-shaped through port. The feed port 904 is located below the powder storage bin 5 and is directly connected to the powder storage bin 5. The nozzle 8 is arranged on the side of the powder storage pipe 901 in a direction parallel to the axis of the powder storage pipe 901. The nozzle 8 is a strip-shaped through hole. The inner nozzle 902 is sleeved in the powder storage pipe 901. The side wall of the inner pipe is provided with a power-assisting seam 905 matched with the nozzle 8. The two ends of the inner nozzle 902 are rotatably connected to the two ends of the powder storage pipe 901. The adjusting assembly is connected to the end of the inner nozzle 902 and is used to adjust the distance between the power-assisting seam 905 and the nozzle 8. The inner nozzle 902 is connected with an air filling nozzle. Since the feed port 904 in the present embodiment is directly connected to the storage bin, a push plate 903 is installed at the feed port 904. The push plate 903 is wedge-shaped and controlled by a micro electric cylinder (connected to the end of the material withdrawal plate, and its end extends outside the powder storage bin 5, and a slide groove is provided on the side wall of the powder storage bin 5). The electric cylinder is controlled by a control module and is used to push the powder in the storage bin into the powder storage tube 901 and block the feed port 904 when the powder storage tube 901 is inflated. When the inflation nozzle is filled with pressurized gas, the powder enters the powder storage tube 901 and is taken out of the nozzle 8 by the gas rushing out of the power-assisting seam 905, and can remain in a cone shape. The amount of powder sprayed is controlled by adjusting the distance between the power-assisting seam 905 and the nozzle 8 by the adjustment component. The larger the distance, the larger the amount of powder sprayed and the greater the thickness of the single layer of powder. Conversely, the smaller and thinner it is.

[0039] In this embodiment, the recovery component is a vacuum cleaner type recovery component, and the vacuum cleaner includes a negative pressure pipe 23 and an electromagnetic air valve. The negative pressure pipe has 32 air holes on the side, and each air hole faces one end of a fixed frame arm 2 to form a gap. The electromagnetic air valve is installed at one end of the negative pressure pipe 23, and the electromagnetic air valve is connected to the vacuum pump. The electromagnetic air valve is controlled by the control module. After the powder is spread, the control module starts the electromagnetic air valve and the vacuum pump, and the retained powder can be sucked away for recovery.

[0040] Embodiment 3

[0041] The difference between this embodiment and the second embodiment is that the driver 3 includes a gear rack mechanism, a driver motor and 32 electromagnetic clutch pins, the gear rack structure includes a rack and 32 driven gears 19, a driving gear is installed on the output end of the driver motor, and the driving gear and the driven gear 19 are both meshed with the rack; the electromagnetic clutch pin includes an electromagnetic induction part 12 and a latch 16, and the cross section of the latch 16 is square. In this embodiment, the main structure of the electromagnetic induction part 12 is a conductive coil. As shown in the attached figure Figure 4As shown, the freeze arm 2 includes a connecting portion 13 and a rotating portion 14, the rotating portion 14 is rotatably connected to the freeze seat 1, one end of each connecting portion 13 is coaxially connected to a driven gear 19, the other end of each connecting portion 13 is equipped with an electromagnetic induction portion 12 and has a slot 15 corresponding to the latch 16, the slot 15 is square, one end of the rotating portion 14 has a connecting groove corresponding to the slot 15, the connecting groove is also in the direction, the latch 16 is rotatably connected in the connecting groove, the latch 16 is made of a permanent magnet and the two poles of magnetism are located at both ends of the latch 16, and the other end of the rotating portion 14 has a notch groove 17 along the radial direction. The control module precisely controls certain electromagnetic induction parts 12 to generate a magnetic field, and controls the magnetism of the magnetic field toward the side of the latch 16. When the magnetic field magnetism is different from the magnetism of the end close to the latch 16, the latch 16 is attracted and inserted into the connection slot, and the driver motor drives the rack to translate for a distance. During the second translation of the rack, the latch 16 is driven to connect the freeze arm 2 of the connection part 13 and the rotating part 14 to rotate 90° until the notch 17 faces the powder outlet nozzle, and the powder can be released. In this embodiment, the nozzle 8 is used to release the powder material in a cone shape, so that the powder material can pass through the notch 4 smoothly, and avoid the lack of powder material caused by the dead angle. After the powder is released, the driver motor is reversed again, the notch 17 is reset, and the notch 17 is changed in direction and no longer exposed. The control module controls the electromagnetic induction part corresponding to the freeze arm 2 of the latch 16 connected to the connection part 13 and the rotating part 14 to generate an opposite magnetic field, repel the latch 16 and reset the latch 16. In this embodiment, the notch groove 17 is composed of two parallel, eccentrically arranged shielding plates 18, which ensures that the notch 4 is large enough and that no gap is generated after the freeze arm 2 rotates 90 degrees.

Claims

1. Powder spreading structure, characterized by: Including control module, powder discharging component, freeze component and recycling component: The freeze assembly includes a plurality of freeze units, which are arranged side by side. The freeze units include a freeze seat, a freeze arm and a driver. The freeze arm is rotatably connected to the freeze seat. A notch is provided at one end of the freeze arm away from the freeze seat. The driver drives the freeze arm to rotate in the freeze seat. A shielding portion is provided on the side of the notch. The powder discharging assembly includes a powder storage bin and a powder discharging nozzle, the powder discharging nozzle is connected to the powder storage bin, and the powder discharging nozzle is used to transport the powder stored in the powder storage bin to the notch on the freezer arm; The control module is connected with the driver signal and controls the driver to adjust the rotation angle of the freeze arm; The recovery component is used to recover the powder material retained on the fixed component.

2. The powder spreading structure according to claim 1, characterized in that: It also includes a walking component, which includes a walking driver, a walking seat and a guide rail. The walking driver is installed on the walking seat and drives the walking seat to rotate along the guide rail. The freezing component is installed on the walking seat, and the walking driver is connected to the control module signal.

3. The powder spreading structure according to claim 2, characterized in that: The driver comprises servo motors whose number corresponds to the freeze arms, the output end of each servo motor is connected to a freeze arm, and the servo motors are controlled by a control module.

4. The powder spreading structure according to claim 2, characterized in that: The driver comprises a gear rack mechanism, a driver motor and an electromagnetic clutch pin whose number corresponds to the number of the freeze arms. The gear rack structure comprises a rack and a driven gear whose number corresponds to the number of the freeze arms. A driving gear is installed on the output end of the driver motor, and both the driving gear and the driven gear are meshed with the rack. The electromagnetic clutch pin comprises an electromagnetic induction part and a latch. The freeze arm comprises a connecting part and a rotating part. The rotating part is rotatably connected with the freeze seat. One end of each connecting part is coaxially connected with a driven gear. The other end of each connecting part is equipped with an electromagnetic induction part and is provided with a slot corresponding to the latch. One end of the rotating part is provided with a connecting slot corresponding to the slot. The latch is rotatably connected in the connecting slot. The latch is made of a permanent magnet and two poles of magnetism are located at both ends of the latch. A notch slot is provided at the other end of the rotating part in a radial direction.

5. The powder spreading structure according to claim 1, characterized in that: The powder outlet includes a nozzle, and the nozzle is used to spray the powder in a cone shape when releasing the powder.

6. The powder spreading structure according to any one of claim 5, characterized in that: The powder discharge assembly includes a powder storage tube, an inner nozzle and an adjustment assembly. The powder storage tube is provided with a feed port. The nozzle is arranged on the side of the powder storage tube along the axial direction parallel to the powder storage tube. The nozzle is a strip-shaped through hole. The inner nozzle is sleeved in the powder storage tube. The side wall of the inner tube is provided with a power-assisting seam matching with the nozzle. The two ends of the inner nozzle are rotatably connected to the two ends of the powder storage tube. The adjustment assembly is connected to the end of the inner nozzle and is used to adjust the distance between the power-assisting seam and the nozzle. The inner nozzle is connected with an inflation nozzle.

7. The powder spreading structure according to claim 6, characterized in that: The recycling kit includes a brush or a vacuum cleaner.

8. The powder spreading structure according to claim 6, characterized in that: The brush assembly includes a brush shaft, bristles and a collecting trough. The bristles are distributed on the side of the brush shaft. The brush shaft is driven by a servo motor which is controlled by a control module. The collecting trough is located below the brush shaft and the freezer arm.

9. The powder spreading structure according to claim 1, characterized in that: The vacuum cleaner includes a negative pressure pipe and an electromagnetic air valve. A plurality of air holes are opened on the side of the negative pressure pipe, and the air holes face the end of the notch formed by the freeze arm. The electromagnetic air valve is installed at one end of the negative pressure pipe, connected to the vacuum pump, and controlled by the control module.

10. A multi-material 3D printing system, comprising a machine body, a laser sintering assembly, a power supply module and a controllable lifting workbench, characterized in that: And adopt the powder spreading structure as described in any one of claims 1 to 9.

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