Powder spreading structure and 3D printing system

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly relates to a powder spreading structure and a 3D printing system.The powder spreading structure 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, each freeze-frame unit comprises a freeze-frame base, a freeze-frame arm and a driver, one end of the freeze-frame arm is slidably connected into the freeze-frame base, and the other end of the freeze-frame arm is slidably connected into the freeze-frame base; the driver drives the freeze-frame arm to slide in the freeze-frame seat, and a notch is formed in the end, away from the freeze-frame seat, of the freeze-frame arm. 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 a notch formed in the freeze-frame arm; the control module is in signal connection with the driver and controls the driver to adjust the displacement stroke 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 when an SLM printing system prints parts formed by printing multiple metal materials, powder materials are wasted 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 3D printing system. Background Art

[0002] Common 3D printing systems based on laser melting technology (SLM) include a machine body, a powder laying component, a laser sintering component, a power supply module, and a controllable lifting table. The lifting table moves up and down precisely inside the machine body. Every time the lifting table descends, the powder laying component is covered with a layer of powder material, and then the laser component sintered into a corresponding shape according to the cross-sectional shape of the printed part. This process is repeated to complete the printing of the part. After printing, the part is removed through vibration, powder removal and other processes to recycle the unused powder material. However, most of the existing powder laying components can only release one type of powder material required for printing parts. For metal parts that need to be printed with different metal powders for different parts, even if the powder material is constantly changed when the powder laying component is laying powder, different powder materials will inevitably mix together, resulting in a large amount of powder material waste. Summary of the invention

[0003] The present invention aims to provide a powder spreading structure and a 3D printing system to solve the problem of powder waste when the SLM printing system prints parts made of various 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. One end of the freeze arm is slidably connected to the freeze seat. The driver drives the freeze arm to slide in the freeze seat and form a gap at one end of the freeze arm away from the freeze seat.

[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 formed on the freezer arm;

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

[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 sliding stroke of the freeze arm in the freeze seat by controlling the various drivers of the freeze component, so that the end of the freeze part is displaced 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 or stays on the freeze component is recovered by the recovery component. Each freeze unit can form a relative notch individually, and multiple freeze units can control the displacement stroke size through the control module to control the size of the notch, so that a complex pattern is formed with multiple notches. Therefore, this solution is also suitable for 3D printing parts with complex cross-sectional structures.

[0011] This solution is first applicable to the laying of a single powder material, that is, the powder discharge component only includes a powder storage bin and a powder discharge nozzle. Since the size of the gap is controllable, the size of the gap can be increased when laying the lower layer of powder material, and gradually reduced from bottom to top. And each layer is backfilled through complementary gaps, that is, after each layer is sintered, the fixed unit that did not form a gap before forms a gap again and releases powder material, and the unsintered area of ​​the layer is filled with powder material.

[0012] In addition to being applicable to the laying of a single powder material, this solution is also applicable to the laying of multiple powder materials: 1. Multiple powder output components correspond to one fixed-frame component: each fixed-frame unit of the fixed-frame component can independently control the position of the notch, so the notches of multiple fixed-frame units can be controlled to form a pattern, and then different powder materials are released in the notches of the fixed-frame units through the nozzles of different powder output components, thereby achieving 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 notch to form a pattern, and then different powder materials are released in the notches of its own fixed-frame component through the nozzles of its corresponding powder output components, thereby achieving the printing of multiple metal materials, and it is more efficient than the aforementioned many-to-one solution. When laying powder with the above two methods, excess powder will be retained on the fixed-frame arm where no notch is formed, which is convenient for recycling by the recycling component, thereby reducing the waste of powder.

[0013] 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.

[0014] 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, greatly reduce the waste of powder materials, and can greatly reduce production costs.

[0015] 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 slide 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.

[0016] Optionally, the driver includes a rotating shaft, a driver motor, and an electromagnetic clutch pin corresponding to the number of freeze arms, the rotating shaft is connected to the output end of the driver motor, the electromagnetic clutch pin includes an electromagnetic induction part, a fixed pin and a movable pin, the electromagnetic induction part is distributed on the side of the rotating shaft along the axial direction of the rotating shaft, the fixed pin is fixed in the rotating shaft along the radial direction of the rotating shaft, one end of each fixed pin is correspondingly connected to an electromagnetic induction part, one end of each fixed pin is provided with a matching hole matched with the movable pin, each freeze arm is provided with a connecting hole corresponding to the connecting hole, each connecting hole is slidably connected with a movable pin, the fixed pin is made of a magnetic conductive material, the movable pin is made of a soft magnetic material, and the electromagnetic induction part is controlled by a control module whether to generate a magnetic field. The control module accurately controls certain electromagnetic induction parts to generate a magnetic field, and the magnetic force is conducted through the fixed pin and then adsorbs the movable pin, so that the movable pin is inserted into the matching hole. When the driver motor rotates a certain angle, the freeze arm corresponding to the electromagnetic induction part can be driven to move, and a gap can be generated at the other end of the freeze arm, thereby accurately controlling the position where the gap is generated to accurately spread the powder. The driver motor can be reversed to a corresponding angle to reset the freeze arm. The gap is created and reset very quickly. Together with the powder outlet assembly, it can achieve the rapid powder spreading required by the 3D printer.

[0017] Optionally, the driver includes a high-pressure pump, a vacuum pump, and valve bodies corresponding to the number of freeze arms, the valve body is provided with an air inlet and an air extraction port, the air inlet and the air extraction port are both provided with a solenoid valve, the high-pressure pump is connected to the solenoid valve on the air inlet, the vacuum pump is connected to the solenoid valve on the air extraction pump, and the control module controls the solenoid valve; each freeze arm forms a separate cavity with the freeze seat and the freeze arm is slidably connected with the freeze seat, and each valve body is correspondingly installed on each cavity. By filling or extracting gas into the cavity, the freeze arm slides on the freeze seat, thereby controlling the freeze arm to form a gap at its end. And the size of the gap can also be controlled by controlling the amount of gas in the cavity.

[0018] Optionally, the powder outlet includes a nozzle, and the nozzle is used to spray the powder in a cone shape when releasing the powder.

[0019] 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 slidably connected to the two ends of the powder storage tube. The adjustment assembly connects 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.

[0020] Optionally, the recovery assembly includes a brush assembly or a vacuum cleaner.

[0021] 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.

[0022] 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.

[0023] 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

[0024] Figure 1 This is a schematic diagram of the structure of the powder spreading structure in the first embodiment of the present invention;

[0025] Figure 2A cross-sectional view of a driver of a powder spreading structure in Embodiment 1 of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure of the powder spreading structure in the second embodiment of the present invention;

[0027] Figure 4 It is a cross-sectional view of a powder discharging component of the powder spreading structure in the second embodiment of the present invention;

[0028] Figure 5 It is a structural schematic diagram of three fixed-frame units of the powder spreading structure in the third embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following is further described in detail through specific implementation methods:

[0030] The marks in the drawings of the specification include: a fixing seat 1, a fixing arm 2, a driver 3, a rotating shaft 301, a driver motor 302, an electromagnetic induction part 303, a fixed pin 304, a movable pin 305, a connecting hole 306, 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 assisting seam 905, a linear motor 10, a baffle 11, a brush shaft 12, bristles 13, a collecting trough 14, a powder guide plate 15, a negative pressure pipe 16, an electromagnetic valve 17, a valve body 18, an air inlet 19, and an air exhaust port 20.

[0031] Embodiment 1

[0032] The 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:

[0033] As attached Figure 1 As shown, in this embodiment, the freeze assembly includes 32 freeze units, and the freeze units 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 slidably connected to the freeze seat 1. The driver 3 drives one or some of the freeze arms 2 to slide in the freeze seat 1 toward the freeze seat 1, and a gap 4 is formed at the end of the freeze arm 2 away from the freeze seat 1. The gaps 4 of multiple freeze arms 2 can be connected together. 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 gap 4. Part of the powder material is accumulated on the workbench through the gap 4, and part of the powder material is blocked by the end 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 neater after the gap 4 releases the powder, a baffle 11 is also provided at the end of the gap 4 of the freeze arm 2. More specifically, as shown in the attached Figure 2As shown, the driver 3 includes a rotating shaft 301, a driver motor 302, and electromagnetic clutch pins corresponding to the number of freeze arms 2, and the rotating shaft 301 is connected to the output end of the driver motor 302. By controlling the freeze arms 2 of multiple freeze units simultaneously through one driver motor 302, the control structure and control logic are simplified, and the reliability of the powder spreading mechanism is also ensured. The method of controlling a single freeze unit is that: the electromagnetic clutch pin includes an electromagnetic induction part 303, a fixed pin 304 and a movable pin 305, the electromagnetic induction part 303 is distributed on the side of the rotating shaft 301 along the axial direction of the rotating shaft 301, the fixed pin 304 is fixed in the rotating shaft 301 along the radial direction of the rotating shaft 301, one end of each fixed pin 304 is correspondingly connected to an electromagnetic induction part 303, one end of each fixed pin 304 is provided with a matching hole matched with the movable pin 305, each freeze arm 2 is provided with a connecting hole 306 corresponding to the connecting hole 306, each connecting hole 306 is slidably connected with a movable pin 305, the fixed pin 304 is made of magnetic conductive material, the movable pin 305 is made of soft magnetic material, and the electromagnetic induction part 303 is controlled by the control module whether to generate a magnetic field. In this embodiment, the main structure of the electromagnetic induction part 303 is a conductive coil, and a part of the end of the fixed pin 304 is inserted into the conductive coil. The control module precisely controls certain electromagnetic induction parts 303 to generate a magnetic field, and the magnetic force is conducted through the fixed pin 304 to adsorb the movable pin 305, so that the movable pin 305 is inserted into the matching hole. In the present embodiment, the matching hole is a hole formed by the fixed pin 304 being shorter than the diameter of the rotating shaft 301. In other embodiments, it can be a hole separately opened on the end of the fixed pin 304. When the driver motor 302 rotates a certain angle, the freeze arm 2 corresponding to the electromagnetic induction part 303 can be driven to move, and a gap 4 can be generated at the other end of the freeze arm 2, thereby accurately controlling the position where the gap 4 is generated to accurately spread the powder. The driver motor 302 reverses the corresponding angle, and after the electromagnetic induction part 303 is powered off, the soft magnetic movable pin 305 automatically loses its magnetism and falls, so that the freeze arm 2 can be reset. The gap 4 and reset are very fast, and the cooperation with the powder outlet component 9 can realize the fast powder spreading required by the 3D printer.

[0034] The powder discharge assembly 9 includes a powder storage bin 5 and a powder discharge nozzle, the powder discharge nozzle is connected to the powder storage bin 5, and the powder discharge nozzle is used to transport the powder stored in the powder storage bin 5 to the gap 4 formed on the freeze arm 2. However, in this embodiment, three sets of powder storage bins 5 and powder discharge nozzles are included, two sets of powder storage bins 5 are used to store two different metal powder materials, and the other set of powder storage bins 5 is used to store auxiliary powder materials, which are cheaper and are not used for part molding but are used to fill the gaps generated after each layer of powder laying, and are used to support the parts to be molded and the unsintered powder materials.

[0035] The powder discharging assembly 9 also includes three sets of conveying pipes 6 and a turntable 7. The conveying pipes 6 are provided with a nozzle 8 with a strip on the side. 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 to complete the powder spreading. The three conveying pipes 6 are installed on the turntable 7, which is located above the gap 4 formed by the fixed assembly. The turntable 7 is driven to rotate by a servo motor and controlled by a control module. When a certain powder needs to be sprayed, the conveying pipe 6 of that powder is rotated to the top of the gap 4.

[0036] The control module is connected to the driver 3 signal and controls the driver 3 to adjust the displacement stroke 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 notch 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 notch 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 notch 4 (the position where the powder material required for part molding is not laid).

[0037] 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 12, bristles 13 and a collection trough 14. The bristles 13 are distributed in a row on the side of the brush shaft 12. The brush shaft 12 is driven by a servo motor, and the servo motor is controlled by the control module; the collection trough 14 is located below the brush shaft 12 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 13 to sweep the powder material retained on the freeze arm 2 into the collection trough 14 below. In order to prevent the powder material from being recycled more smoothly, a powder guide plate 15 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 14 better.

[0038] 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.

[0039] Embodiment 2

[0040] The difference between this embodiment and the first embodiment is that: Figure 3As 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 slide 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.

[0041] 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 4 As 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 slidably connected to the two ends of the powder storage pipe 901. The adjusting assembly connects the ends 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.

[0042] In this embodiment, the recovery component is a vacuum cleaner type recovery component, and the vacuum cleaner includes a negative pressure pipe 16 and an electromagnetic air valve 17. The negative pressure pipe 16 has 32 air holes on its side, and each air hole faces one end of a fixed frame arm 2 to form a gap. The electromagnetic air valve 17 is installed at one end of the negative pressure pipe 16, and the electromagnetic air valve 17 is connected to the vacuum pump, and the electromagnetic air valve 17 is controlled by the control module. After the powder is spread, the control module starts the electromagnetic air valve 17 and the vacuum pump, and the retained powder can be sucked away for recovery.

[0043] Embodiment 3

[0044] The difference between this embodiment and the second embodiment is that: Figure 5 It is a structural schematic diagram of three freeze units. The driver 3 includes a high-pressure pump, a vacuum pump and 32 valve bodies 18. The valve body 18 is provided with an air inlet 19 and an air extraction port 20. The air inlet 19 and the air extraction port 20 are both provided with a solenoid valve. The high-pressure pump is connected to the solenoid valve on the air inlet 19, and the vacuum pump is connected to the solenoid valve on the air extraction pump. The control module controls the solenoid valve; each freeze arm 2 forms a separate cavity with the freeze seat 1 and the freeze arm 2 is slidably connected with the freeze seat 1, and each valve body 18 is correspondingly installed on each cavity. The control module controls the solenoid valve of each freeze unit to control the filling or extraction of gas into the cavity, so that the freeze arm 2 slides on the freeze seat 1, thereby controlling the freeze arm 2 to form a gap 4 at its end. And the size of the gap 4 can also be controlled by controlling the amount of gas in the cavity.

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. One end of the freeze arm is slidably connected to the freeze seat. The driver drives the freeze arm to slide in the freeze seat and form a gap at one end of the freeze arm away from the freeze seat. 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 formed on the freezer arm; The control module is connected with the driver signal and controls the driver to adjust the stroke of the freeze arm displacement; 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 slide 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 includes a rotating shaft, a driver motor and electromagnetic clutch pins whose number corresponds to the number of freeze arms. The rotating shaft is connected to the output end of the driver motor. The electromagnetic clutch pin includes an electromagnetic induction part, a fixed pin and a movable pin. The electromagnetic induction part is distributed on the side of the rotating shaft along the axial direction of the rotating shaft. The fixed pin is fixed in the rotating shaft along the radial direction of the rotating shaft. One end of each fixed pin is correspondingly connected to an electromagnetic induction part. A matching hole matching with the movable pin is provided on one end of each fixed pin. Each freeze arm is provided with a connecting hole corresponding to the connecting hole. A movable pin is slidably connected in each connecting hole. The fixed pin is made of magnetically conductive material, and the movable pin is made of soft magnetic material. Whether the electromagnetic induction part generates a magnetic field is controlled by a control module.

4. The powder spreading structure according to claim 2, characterized in that: The driver includes a high-pressure pump, a vacuum pump and valve bodies corresponding to the number of freeze arms. The valve body is provided with an air inlet and an air exhaust port. The air inlet and the air exhaust port are both provided with solenoid valves. The high-pressure pump is connected to the solenoid valve on the air inlet, the vacuum pump is connected to the solenoid valve on the air exhaust pump, and the control module controls the solenoid valve; each freeze arm forms a separate cavity with the freeze seat and the freeze arm is slidably connected with the freeze seat, and each valve body is correspondingly installed on each cavity.

5. The powder spreading structure according to any one of claims 1 to 4, 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 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 slidably 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 7, 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 7, 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 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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