Powder spreading device for 3D printing

Abstract

The invention discloses a powder spreading device for 3D printing, relates to the technical field of 3D printing, and aims to solve the technical problem that two kinds of powder with large mass difference are insufficiently stirred, and the powder spreading device comprises a frame, a powder spreading mechanism, a stirring assembly, an opening and closing assembly and a material cavity assembly. The first one-way rotating structure and the second one-way rotating structure are reversely arranged, so that the stirring rod can be expanded or tightened as required; during expansion, the stirring rod is attached to the inner wall of the spherical stirring tank, heavy powder at the bottom is fully brought out, the dead angle problem of a traditional cylindrical stirring tank is solved, and the situation that the heavy powder precipitates and cannot be fully mixed is avoided; when tightened, the stirring device is spiral, so that powder with small mass difference can be efficiently stirred and diffused; in addition, the problem that a stirring cavity is incomplete due to the fact that a valve is assembled on a traditional pipeline is solved through the design of a blocking piece in the opening and closing assembly, and heavy powder is prevented from being gathered in the cylindrical channel; and the powder mixing uniformity is greatly improved, and the quality of 3D printing products is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and more specifically, to a powder spreading device for 3D printing. Background Art

[0002] In a 3D printing powder spreading device, dual-channel conveying refers to a technology that uses two independent channels to convey powder materials of different types or states; this conveying method has significant advantages in improving printing efficiency, enriching printing material combinations, etc.: enabling multi-material printing, optimizing powder mixing and distribution, and increasing printing efficiency. When dealing with powders with large quality differences in dual-channel conveying, there are many deficiencies in existing mixing tanks; common types of mixing tanks include cylindrical and spherical ones, etc.; there are dead corners at the bottom edge of the cylindrical mixing tank. When heavier powders precipitate in these dead corners, the mixing device is difficult to reach, and it is impossible to fully mix the heavier powders with other powders, thus affecting the overall uniformity of the powders; when using a spherical mixing tank with an arc-shaped inner wall of the mixing chamber and no dead corners, although the dead corner problem is avoided, if the mixing method is improper, the heavier powders will still precipitate at the bottom of the mixing chamber, resulting in uneven distribution of the two powders during subsequent powder spreading, and further affecting the quality of the printed product. In the case of a spherical mixing tank, if a valve assembled through a pipeline such as a solenoid valve is used, a cylindrical channel will be left between the pipeline and the spherical mixing tank, which will make the mixing chamber in the spherical mixing tank no longer a complete spherical cavity; this incomplete cavity structure will cause the heavier powders to easily accumulate inside the cylindrical channel when mixing two powders with large quality differences, further affecting the mixing effect of the two powders, and ultimately having an adverse impact on the quality of powder spreading and printing of the product. In view of this, we propose a powder spreading device for 3D printing. Summary of the Invention

[0003] The purpose of the present invention is to provide a powder spreading device for 3D printing to solve the technical problem of insufficient mixing of two powders with large quality differences.

[0004] To solve the above technical problems, the present invention provides the following technical solution: A powder spreading device for 3D printing, comprising a frame, a printing platform arranged inside the frame, a laser generator located above the printing platform, a powder spreading mechanism, a stirring assembly and an opening and closing assembly arranged above the printing platform, and a material cavity assembly arranged below the printing platform. The stirring assembly includes a spherical stirring tank located above the printing platform. A transmission rod is rotatably connected inside the spherical stirring tank. A plurality of stirring rods are annularly arrayed and hinged to the left end plate on the transmission rod. The other ends of the plurality of stirring rods are jointly hinged to a transmission cylinder. A first one-way rotation structure is arranged between the transmission cylinder and the stirring rods, and a second one-way rotation structure is arranged between the transmission cylinder and the spherical stirring tank. The first and second one-way rotation structures are arranged in opposite directions; the opening and closing assembly includes a blocking piece arranged inside the output end of the spherical stirring tank. The plurality of stirring rods can expand or contract through the first and second one-way rotation structures. When expanding, each stirring rod fits against the inner wall of the spherical stirring tank, causing the heavier powder deposited at the bottom of the spherical stirring tank to be removed and fully mixed with another powder; when contracting, the plurality of stirring rods are all in a spiral shape, capable of stirring two powders with relatively small mass differences, and causing the powder to accumulate on the inner wall of the spherical stirring cavity through the stirring rods and then spread around.

[0005] When the blocking piece moves upward inside the output end of the spherical stirring tank, the blocking piece forms a seal with the inner wall of the spherical stirring tank. When moving downward, the blocking piece forms a flow passage inside the output end of the spherical stirring tank. In the present invention, the first and second one-way rotation structures are arranged in opposite directions, so that the stirring rods can expand or contract as needed; when expanding, the stirring rods fit against the inner wall of the spherical stirring tank, fully bringing out the heavy powder at the bottom, solving the dead angle problem of the traditional cylindrical stirring tank and avoiding the precipitation of heavy powder and insufficient mixing; when contracting, they are in a spiral shape, capable of efficiently stirring and spreading powders with small mass differences; in addition, the design of the blocking piece in the opening and closing assembly avoids the problem of incomplete stirring cavity caused by the traditional pipeline assembly valve, preventing heavy powder from accumulating in the cylindrical passage; these innovative designs greatly improve the uniformity of powder mixing, ensure uniform distribution when laying powder subsequently, and thus significantly improve the quality of 3D printed products.

[0006] Preferably, a storage module is arranged outside the frame, and the laser generator is arranged on the top of the frame through a translation mechanism.

[0007] Two guide rails are symmetrically and fixedly connected to the inner walls on both sides of the frame. Each guide rail surface is slidably connected with a pneumatic slider.

[0008] Preferably, the powder spreading mechanism includes two sliding boxes, which are respectively fixedly connected between two pneumatic sliders. A scraper module is slidably connected between the two sliding boxes. A top cylinder is fixedly connected to the inner wall of the bottom of each sliding box, and the output end of the top cylinder is drivingly connected to the scraper module. A bracket is fixedly connected between the two sliding boxes, and the bottom of the scraper module passes through the bracket.

[0009] Preferably, the stirring assembly includes a fixing plate, which is fixedly connected to the inner wall of one side of the bracket. The spherical stirring tank is fixedly connected to the top of the fixing plate, and the spherical stirring tank is communicated with the storage module through a pipeline.

[0010] Preferably, a first motor is fixedly connected to one side of the top of the fixing plate. A first ratchet wheel is arranged on the surface of the output shaft of the first motor. The output shaft of the first motor is drivingly connected to a transmission rod. A groove is formed on one side of each stirring rod. A first ratchet gear is arranged on the inner wall of the transmission cylinder, and the first ratchet wheel is meshed with the first ratchet gear; Among them, the meshing connection or non-meshing sliding connection between the first ratchet wheel and the first ratchet gear is a first one-way rotation structure.

[0011] Preferably, a second ratchet wheel is fixedly connected to the side of the transmission cylinder close to the first motor. A fixing plate is fixedly connected to the left end of the spherical stirring tank. A plurality of waist-shaped holes are formed in an annular array on one side of the fixing plate. A plurality of fixing blocks are movably connected to one side of the fixing plate through inserting rods, and the inserting rods on the fixing blocks are inserted into the waist-shaped holes. The other ends of the inserting rods on the plurality of fixing blocks are movably connected to a movable plate through the inserting rods, and a plurality of inclined holes are formed on one side of the movable plate, and the other ends of the inserting rods on the movable plate are inserted into the inclined holes; Among them, the plurality of fixing blocks can be gathered or unfolded. When gathered, the plurality of fixing blocks are meshed with the second ratchet wheel to form a second one-way rotation structure. When the plurality of fixing blocks are unfolded, they are disconnected from the second ratchet wheel, providing convenience for the expansion of the stirring rods.

[0012] Preferably, an electric push rod is fixedly connected to the hole on the fixing plate, and the output shaft of the electric push rod is hinged to the surface of the movable plate.

[0013] Preferably, the opening and closing assembly includes a connecting pipe, which is fixedly communicated with the top of the scraper module. The connecting pipe is movably sleeved on the inner wall of the output end of the spherical stirring tank. A blocking piece is fixedly connected to the top of the connecting pipe, and a flow port is arranged between the blocking piece and the connecting pipe.

[0014] Preferably, the material cavity assembly includes a transmission frame, which is fixedly connected to the inner wall of the bottom of the frame. Two servo motors are symmetrically fixedly connected to the inner wall of the bottom of the transmission frame. The output ends of the two servo motors are both fixedly connected with a first gear. Two second gears are rotatably connected to the top of the transmission frame.

[0015] Preferably, the first gear and the second gear are connected by a transmission belt. A lead screw is threadedly connected to the inner wall of each second gear, and the two lead screws are inserted into the holes on the transmission frame. The surface of the end of the lead screw is square. A bearing plate is fixedly connected to the tops of the two lead screws, and the bearing plate is slidably sleeved inside the powder spreading cavity of the printing platform.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the present invention, the first and second one-way rotation structures are arranged in the reverse direction, so that the stirring rod can be expanded or tightened as required; when expanded, the stirring rod fits against the inner wall of the spherical stirring tank, and the heavy powder at the bottom is fully carried out, solving the dead angle problem of the traditional cylindrical stirring tank and avoiding the precipitation of heavy powder and insufficient mixing; when tightened, it is in a spiral shape, which can efficiently stir and disperse powders with small quality differences; in addition, the plug design in the opening and closing assembly avoids the problem of incomplete stirring cavity caused by the traditional pipeline assembly valve, preventing heavy powder from accumulating in the cylindrical passage; these innovative designs greatly improve the uniformity of powder mixing, ensure uniform distribution when laying powder subsequently, and thus significantly improve the quality of 3D printing products.

[0017] 2. The present invention innovatively designs a double one-way rotation structure and a variable-form stirring rod for powders with different quality differences in double-channel transportation; when dealing with powders with small quality differences, the stirring rod rotates in a spiral shape to realize the cyclic mixing of powder accumulation and diffusion; when dealing with powders with large quality differences, the stirring rod expands and fits against the tank wall, and the heavy powder at the bottom is carried out by the grooves and mixed orderly through axial rotation, effectively solving the problem that the traditional stirring tank cannot be fully mixed and improving the powder uniformity.

[0018] 3. The present invention adopts a unique opening and closing assembly to replace the traditional pipeline assembly valve, avoiding the formation of a cylindrical passage in the spherical stirring tank, ensuring that the stirring cavity is a complete sphere, eliminating the dead angle of powder accumulation, ensuring full stirring of two powders with large quality differences, improving the stirring effect and the quality of printing products, and at the same time, preventing the blockage of the valve structure and improving the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a three-dimensional structural schematic diagram of the present invention.

[0020] Figure 2 is a schematic cross-sectional view of the overall structure of the present invention.

[0021] Figure 3 is a three-dimensional structural schematic diagram of the powder spreading mechanism of the present invention.

[0022] Figure 4 is a three-dimensional exploded structural schematic diagram of the powder spreading mechanism of the present invention.

[0023] Figure 5Schematic diagram of the three-dimensional exploded structure of the stirring component of the present invention.

[0024] Figure 6 Schematic diagram of the cross-section of the three-dimensional structure of the stirring component of the present invention.

[0025] Figure 7 Schematic diagram of the three-dimensional exploded structure of the stirring component of the present invention.

[0026] Figure 8 For the present invention Figure 7 Enlarged structure schematic diagram at position A in

[0027] Figure 9 Schematic diagram of the three-dimensional exploded structure of the opening and closing component of the present invention.

[0028] Figure 10 Schematic diagram of the cross-section of the structure of the stirring rod in the tightened state of use of the present invention.

[0029] Figure 11 Schematic diagram of the cross-section of the structure of the stirring rod in the expanded state of use of the present invention.

[0030] Figure 12 Schematic diagram of a physical object of the prior art.

[0031] Description of the reference numerals in the figure: 1. Frame; 11. Printing platform; 12. Laser generator; 13. Storage module; 2. Translation mechanism; 3. Guide rail; 31. Pneumatic slider; 4. Powder spreading mechanism; 41. Sliding box; 42. Scraper module; 43. Top cylinder; 44. Bracket; 5. Stirring component; 51. Fixed plate; 52. Spherical stirring tank; 53. First motor; 531. First ratchet wheel; 54. Transmission rod; 55. Stirring rod; 551. Groove; 56. Transmission cylinder; 561. First ratchet gear; 562. Second ratchet wheel; 57. Fixed disk; 571. Waist-shaped hole; 58. Fixed block; 59. Movable disk; 591. Tilted hole; 510. Electric push rod; 6. Opening and closing component; 61. Connecting pipe; 62. Plug piece; 7. Material cavity component; 71. Transmission frame; 72. Servo motor; 73. First gear; 74. Second gear; 75. Transmission belt; 76. Lead screw; 77. Carrier plate. Detailed implementation manners

[0032] Example 1, as Figures 1 - 4 shown, a powder spreading device for 3D printing according to the present invention includes a frame 1, a printing platform 11 and a laser generator 12 arranged inside the frame 1, and a storage module 13 arranged outside the frame 1. The laser generator 12 is arranged on the top of the frame 1 through a translation mechanism 2.

[0033] On both inner walls of the frame 1, two guide rails 3 are fixedly connected in a symmetric structure. On the surface of each guide rail 3, a pneumatic slider 31 is slidably connected. Between the two pneumatic sliders 31, a powder spreading mechanism 4, a stirring assembly 5, an opening and closing assembly 6, and a powder chamber assembly 7 are arranged.

[0034] The powder spreading mechanism 4 includes two sliding boxes 41 which are respectively fixedly connected between the two pneumatic sliders 31. A scraper module 42 is slidably connected between the two sliding boxes 41. On the inner bottom wall of each sliding box 41, a top cylinder 43 is fixedly connected, and the output end of the top cylinder 43 is in transmission connection with the scraper module 42. A bracket 44 is fixedly connected between the two sliding boxes 41, and the bottom of the scraper module 42 passes through the bracket 44.

[0035] It should be noted that the laser generator 12 precisely scans each layer of powder with a high-energy laser beam, completely melting and solidifying the metal powder to form a dense metal structure.

[0036] It should be noted that the translation mechanism 2 in the present invention is a motor-driven movable lead screw sliding platform. The motor-driven lead screw sliding platform is an existing conventional technology and will not be described in detail here. Using the lead screw sliding platform to realize the translation movement of the laser generator 12 not only has precise movement but also is beneficial to improving the printing efficiency.

[0037] It should be noted that the scraper module 42 in the present invention has the functions of scraping and leveling the powder, and after the powder is stirred, it evenly flows into the powder spreading chamber from it. This module is an existing conventional technology and will not be described in detail here.

[0038] Specifically, the scraper module 42 moves up or down through the top cylinder 43. When moving down, the output end of the scraper module 42 is flush with the edge of the powder spreading chamber. When moving up, the output end of the scraper module 42 is located above the edge of the powder spreading chamber.

[0039] Such as Figures 4 - 11As shown in the figure, the stirring assembly 5 includes a fixing plate 51, which is fixedly connected to the inner wall of one side of the bracket 44. A spherical stirring tank 52 is fixedly connected to the top of the fixing plate 51, and the spherical stirring tank 52 is communicated with the storage module 13 through a pipeline. A first motor 53 is fixedly connected to one side of the top of the fixing plate 51. A first ratchet wheel 531 is arranged on the surface of the output shaft of the first motor 53. The output shaft of the first motor 53 is fixedly connected to a transmission rod 54. A plurality of stirring rods 55 are hinged in an annular array on the left end plate of the transmission rod 54. A groove 551 is formed on one side of each stirring rod 55. The other ends of the plurality of stirring rods 55 are jointly hinged to a transmission cylinder 56. A first ratchet gear 561 is arranged on the inner wall of the transmission cylinder 56, and the first ratchet wheel 531 is meshed with the first ratchet gear 561. A second ratchet wheel 562 is fixedly connected to one side of the transmission cylinder 56 close to the first motor 53. A fixing disk 57 is fixedly connected to the left end of the spherical stirring tank 52. A plurality of waist-shaped holes 571 are formed in an annular array on one side of the fixing disk 57. A plurality of fixing blocks 58 are movably connected to one side of the fixing disk 57 through inserting rods, and the inserting rods on the fixing blocks 58 are inserted into the waist-shaped holes 571. The other ends of the inserting rods on the plurality of fixing blocks 58 are movably connected to a movable disk 59. A plurality of inclined holes 591 are formed on one side of the movable disk 59, and the other ends of the inserting rods on the movable disk 59 are inserted into the inclined holes 591. An electric push rod 510 is fixedly connected to the hole on the fixing plate 51, and the output shaft of the electric push rod 510 is hinged to the surface of the movable disk 59.

[0040] Specifically, the first ratchet wheel 531 and the first ratchet gear 561 are of a first one-way rotation structure, the second ratchet wheel 562 and the gathered fixing blocks 58 are of a second one-way rotation structure, and the meshing connection and non-meshing sliding connection directions of the first and second one-way rotation structures are opposite.

[0041] Specifically, the plurality of stirring rods 55 expand or contract. When expanding, each stirring rod 55 fits against the inner wall of the spherical stirring tank 52, causing the heavier powder deposited at the bottom of the spherical stirring tank 52 to be removed and fully mixed with another powder. When contracting, the plurality of stirring rods 55 are all in a spiral shape, capable of stirring two powders with relatively small mass differences, and the powder can accumulate on the inner wall of one side of the spherical stirring tank 52 through the spiral stirring rods 55 and then spread around.

[0042] The present invention innovatively designs a double one-way rotation structure and a variable-form stirring rod 55 for powders with different mass differences in double-channel transportation; when processing powders with small mass differences, the stirring rod 55 rotates in a spiral shape to realize the cyclic mixing of powder accumulation and diffusion; when processing powders with large mass differences, the stirring rod 55 expands and fits against the tank wall, and the groove 551 is used to bring out the heavy powder at the bottom, and the powders are orderly mixed through axial rotation, effectively solving the problem that traditional stirring tanks cannot be fully mixed and improving the powder uniformity.

[0043] Example 2, as Figure 9As shown, the opening and closing assembly 6 includes a connecting pipe 61. The connecting pipe 61 is fixedly connected and communicated with the top of the scraper module 42, and the connecting pipe 61 is movably sleeved on the inner wall of the output end of the spherical stirring tank 52. A blocking piece 62 is fixedly connected to the top of the connecting pipe 61. The blocking piece 62 is hermetically adapted to the inner wall of the spherical stirring tank 52, and a circulation port is arranged between the blocking piece 62 and the connecting pipe 61.

[0044] Specifically, when the scraper module 42 moves upward, the blocking piece 62 forms a seal with the inner wall of the spherical stirring tank 52. When moving downward, the blocking piece 62 moves and is located inside the output end of the spherical stirring tank 52, and there is a circulation passageway left between them.

[0045] Compared with other valves, such as solenoid valves and other valves assembled through pipelines used on the spherical stirring tank 52, there is a cylindrical passageway left between the pipeline and the spherical stirring tank 52, resulting in an incomplete spherical cavity in the stirring cavity of the spherical stirring tank 52. When stirring two kinds of powders with large mass differences, the heavier powders gather inside the cylindrical passageway, which not only affects the stirring of the two kinds of powders with large mass differences, but also affects the quality of product powder spreading and printing.

[0046] The present invention adopts a unique opening and closing assembly 6 to replace the traditional pipeline-assembled valve, avoiding the formation of a cylindrical passageway inside the spherical stirring tank 52, ensuring that the stirring cavity is a complete sphere, eliminating the dead corners of powder accumulation, ensuring the full stirring of two kinds of powders with large mass differences, improving the stirring effect and the quality of printed products. At the same time, it prevents the blockage of the valve structure and improves the service life.

[0047] As Figure 2 shown, the material cavity assembly 7 includes a transmission frame 71. The transmission frame 71 is fixedly connected to the inner wall of the bottom of the frame 1. Two servo motors 72 are symmetrically fixedly connected to the inner wall of the bottom of the transmission frame 71. The output ends of the two servo motors 72 are fixedly connected with first gears 73. Two second gears 74 are rotatably connected to the top of the transmission frame 71. The first gears 73 and the second gears 74 are connected by a transmission belt 75. The inner wall of each second gear 74 is threadedly connected with a lead screw 76, and the two lead screws 76 are inserted into the holes on the transmission frame 71. The surface of the end of the lead screw 76 is square. The two lead screws 76 are commonly fixedly connected to a bearing plate 77 at the top, and the bearing plate 77 is slidably sleeved inside the powder spreading cavity on the printing platform 11.

[0048] It is worth noting that by arranging a square on the surface of the end of the lead screw 76, the lead screw 76 can move upward or downward during the rotation of the second gear 74 and cannot rotate.

[0049] Working principle: This embodiment provides a powder spreading device for 3D printing. When powders with relatively small mass differences are conveyed through a double-channel, the powders flow into the interior of the spherical stirring tank 52 from the storage module 13 through a pipeline. At this time, the external control system is used to drive the movable disk 59 to rotate by the electric push rod 510. The fixed block 58 expands through the insertion rod and disconnects from the second ratchet wheel 562, and the first one-way structure is meshed and connected. Then, the first motor 53 is operated through the external circuit system. The first motor 53 drives the transmission rod 54 to rotate. The first one-way structure is in a non-meshing sliding connection, so that the left end of the stirring rod 55 rotates first, causing the entire stirring rod 55 to form a spiral shape and rotate through torque, stirring two powders with relatively small mass differences. For the powders located in the middle of the spherical stirring tank 52, through the spiral stirring rod 55, they are piled up to one side and diffused around through the spherical stirring cavity, forming a cyclic mixing effect; When powders with relatively large mass differences are conveyed through a double-channel: The powders flow into the interior of the spherical stirring tank 52 from the storage module 13 through a pipeline. At this time, the external control system is used to drive the movable disk 59 to rotate by the electric push rod 510. The fixed block 58 gathers through the insertion rod to form ratchet teeth and meshes with the second ratchet wheel 562 to form a second one-way rotation structure. Then, the first motor 53 drives the transmission rod 54 to rotate, so that the first one-way rotation structure is in a meshing connection and the second one-way rotation structure is in a non-meshing sliding connection, causing several stirring rods 55 to rotate synchronously. Among them, the powders with relatively large mass differences gather on the inner wall of the bottom of the spherical stirring tank 52, and the powders at the bottom are taken out through the grooves 551 on the stirring rod 55. During the upward rotation of the stirring rod 55 in the axial direction, the powders are discharged orderly; Powder spreading and printing: After the stirring is completed, the external control system is used to drive the scraper module 42 to move by the pneumatic slider 31. When the scraper module 42 moves to the edge of the powder spreading cavity, the scraper module 42 is moved downward by the top cylinder 43. At this time, the blocking piece 62 moves downward inside the output end of the spherical stirring tank 52 and flows out of the channel. The powders flow into the scraper module 42 through this channel, and then the powders are evenly distributed in each part through the scraper module 42 and then flow out from its output end. During the movement of the scraper module 42, the powders are filled and leveled. Then, the translation mechanism 2 is used to drive the laser generator 12 to move, adjust the position of the laser generator 12, and perform printing processing on the powders below. At the same time, during layer-by-layer printing, the servo motor 72 works, and the second gear 74 is driven to rotate by the transmission belt 75, causing the rod 76 threadedly connected thereto to drive the bearing plate 77 to move downward, providing sufficient space for printing and powder spreading.

[0050] The embodiments disclosed in this invention are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of this invention based on the above embodiments and make different extensions and changes. However, as long as they do not depart from the spirit of this invention, they are within the protection scope of this invention.

Claims

1. A powder spreading device for 3D printing, comprising a frame, a printing platform arranged inside the frame, a laser generator located above the printing platform, a powder spreading mechanism, a stirring assembly and an opening and closing assembly arranged above the printing platform, and a material cavity assembly arranged below the printing platform, characterized in that, The stirring assembly includes a spherical stirring tank located above the printing platform. A transmission rod is rotatably connected inside the spherical stirring tank. A plurality of stirring rods are annularly arrayed and hinged to the left end plate on the transmission rod. The other ends of the plurality of stirring rods are commonly hinged to a transmission cylinder. A first one-way rotation structure is arranged between the transmission cylinder and the stirring rods, and a second one-way rotation structure is arranged between the transmission cylinder and the spherical stirring tank. The first and second one-way rotation structures are arranged in opposite directions. The opening and closing assembly includes a blocking piece arranged inside the output end of the spherical stirring tank. The plurality of stirring rods can expand or contract through the first and second one-way rotation structures. When expanding, each stirring rod fits against the inner wall of the spherical stirring tank, causing the heavier powder deposited at the bottom of the spherical stirring tank to be removed and fully mixed with another powder. When contracting, the plurality of stirring rods are all in a spiral shape, capable of stirring two powders with relatively small mass differences, and causing the powder to accumulate on the inner wall of the spherical stirring cavity through the stirring rods and then spread around. When the blocking piece moves upward inside the output end of the spherical stirring tank, the blocking piece forms a seal with the inner wall of the spherical stirring tank. When moving downward, the blocking piece forms a flow channel inside the output end of the spherical stirring tank.

2. The powder spreading device for 3D printing according to claim 1, wherein A storage module is arranged outside the frame, and the laser generator is arranged at the top of the frame through a translation mechanism. Two guide rails are symmetrically fixed to the inner walls on both sides of the frame, and a pneumatic slider is slidably connected to the surface of each guide rail.

3. The powder spreading device for 3D printing according to claim 2, wherein The powder spreading mechanism includes two sliding boxes respectively fixedly connected between the two pneumatic sliders. A scraper module is slidably connected between the two sliding boxes. A top cylinder is fixedly connected to the inner wall of the bottom of each sliding box, and the output end of the top cylinder is in transmission connection with the scraper module. A bracket is fixedly connected between the two sliding boxes, and the bottom of the scraper module passes through the bracket.

4. A powder spreading device for 3D printing according to claim 3, characterized in that, The stirring assembly includes a fixing plate fixedly connected to the inner wall of one side of the bracket. The spherical stirring tank is fixedly connected to the top of the fixing plate, and the spherical stirring tank is communicated with the storage module through a pipeline.

5. The powder spreading device for 3D printing according to claim 4, characterized in that, A first motor is fixedly connected to one side of the top of the fixing plate. A first ratchet wheel is arranged on the surface of the output shaft of the first motor. The output shaft of the first motor is in transmission connection with the transmission rod. A groove is formed on one side of each stirring rod. A first ratchet gear is arranged on the inner wall of the transmission cylinder, and the first ratchet wheel is meshed with the first ratchet gear. Among them, the meshing connection or non-meshing sliding connection between the first ratchet wheel and the first ratchet gear is the first one-way rotation structure.

6. A powder spreading device for 3D printing according to claim 5, characterized in that, A second ratchet wheel is fixedly connected to the side of the transmission cylinder close to the first motor. A fixing disk is fixedly connected to the left end of the spherical stirring tank. A plurality of waist-shaped holes are annularly arrayed on one side of the fixing disk. A plurality of fixing blocks are movably connected to one side of the fixing disk through inserting rods, and the inserting rods on the fixing blocks are inserted into the waist-shaped holes. The other ends of the inserting rods on the plurality of fixing blocks are movably connected to a movable disk. A plurality of inclined holes are formed on one side of the movable disk, and the other ends of the inserting rods on the movable disk are inserted into the inclined holes. Among them, several fixed blocks can be gathered or unfolded. When gathered, the several fixed blocks are meshed and connected with the second ratchet wheel to form a second one-way rotation structure. When the several fixed blocks are unfolded, they are disconnected from the second ratchet wheel, providing convenience for the expansion of the stirring rod.

7. The powder spreading device for 3D printing according to claim 6, characterized in that, An electric push rod is fixedly connected in the hole of the fixed plate, and the output shaft of the electric push rod is hinged to the surface of the movable disc.

8. A powder spreading device for 3D printing according to claim 7, characterized in that, The opening and closing assembly includes a connecting pipe. The connecting pipe is fixedly communicated with the top of the scraper module. The connecting pipe is movably sleeved on the inner wall of the output end of the spherical stirring tank. The blocking piece is fixedly connected to the top of the connecting pipe, and a circulation port is arranged between the blocking piece and the connecting pipe.

9. The powder spreading device for 3D printing according to claim 8, characterized in that, The material cavity assembly includes a transmission frame. The transmission frame is fixedly connected to the inner wall of the bottom of the frame. Two servo motors are symmetrically fixedly connected to the inner wall of the bottom of the transmission frame. The output ends of the two servo motors are fixedly connected with first gears. Two second gears are rotatably connected to the top of the transmission frame.

10. A powder spreading device for 3D printing according to claim 9, characterized in that, The first gear and the second gear are connected by a transmission belt. A lead screw is threadedly connected to the inner wall of each second gear. The two lead screws are inserted into the holes on the transmission frame. The surface of the end of the lead screw is square. A bearing plate is fixedly connected to the tops of the two lead screws. The bearing plate is slidably sleeved inside the powder spreading cavity on the printing platform.

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