Selective laser sintering 3D printer with precise powder supply and repeated powder laying functions

Abstract

The invention relates to a selective laser sintering 3D printer with precise powder supply and repeated powder laying functions. The selective laser sintering 3D printer comprises a rack, a laser scanning mechanism, a forming platform mechanism, a powder supply mechanism, a powder laying mechanism and a residual powder recycling mechanism. Compared with existing similar products in the market, the powder supply mechanism mainly has the following advantages that 1, the powder supply mechanism which is exquisite in design can achieve single-time quantitative accurate powder supply, it is guaranteed that powder evenly flows out of the powder outlet, and therefore a foundation is laid for providing an excellent powder laying effect for the powder laying mechanism; 2, the powder spreading mode that the powder spreading mechanism drops powder and scrapes the powder at the same time and secondary compensation spreading and scraping operation can ensure that all parts of the powder spread on the forming table are very uniform and flat every time, so that the sintering effect of laser beams on the powder is greatly improved, and the precision quality of a final model is improved; and thirdly, the powder falling from the forming table can be more effectively and conveniently collected and recycled through the residual powder recycling mechanism, so that the cleanness in the machine is ensured, the operation fault is reduced, and the powder is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printer manufacturing, and particularly to a selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions. Background Art

[0002] SLS (Selective Laser Sintering) is an advanced 3D printing technology. It uses an infrared laser as a heat source to perform high-temperature sintering on powder materials (mainly plastic powder, wax powder, metal powder, coated ceramic powder with a binder on the surface, coated metal powder, and coated sand, etc.), and stacks them layer by layer to form a three-dimensional part.

[0003] The working principle and process of current SLS 3D printers are generally as follows: Powder particles are stored in a powder supply bin. During printing, the lifting platform of the powder supply bin rises, and the powder above the printing plane is pushed onto the printing platform (forming table) through a powder spreading roller to form a very thin powder layer; at this time, the laser beam scanning system will selectively scan on the powder layer according to the two-dimensional CAD path of the slice. The scanned powder particles will be sintered together due to the high temperature of the laser focus, thus generating a solid thin slice with a certain thickness. The unscanned area remains in the original loose powder state; after one layer of sintering is completed, the printing platform descends by a layer thickness (usually 0.1 mm) according to the slice height, the powder spreading roller levels the powder again, and then starts a new layer of sintering. At this time, the layers are also sintered together synchronously; this process is repeated until all layers are sintered; the unsintered powder is removed and recycled, and then the printed solid model can be taken out. Subsequently, fine processing such as cleaning and polishing is performed on the model.

[0004] Summarizing the performance characteristics of current SLS 3D printers on the market, there are generally the following relatively prominent disadvantages: First, for the powder supply bin of the powder supply mechanism, either the lifting type with upward powder output or the powder output through an electromagnetic valve controlling the lower powder outlet is used for powder supply, and neither can achieve single-time quantitative and precise powder output, resulting in unstable powder output each time. Moreover, the powder accumulates in the powder supply bin, and due to the combined action and influence of the fluidity and viscosity of the powder during powder output, it is more likely to cause uneven powder output each time and uneven powder output at each part of the powder outlet, thus comprehensively affecting the powder spreading effect of the powder spreading mechanism; Second, the powder spreading mechanism spreads powder on the forming table by pushing the powder with a roller or a scraper, and each powder spreading operation only pushes once, making it difficult to ensure excellent uniformity and flatness at each part of the powder surface, thus extremely affecting the scanning and sintering effect of the laser beam on the powder, resulting in a decline in the final model accuracy and quality; Third, due to the structural design, the collection and recycling operations of the powder flowing down from the forming table are relatively inconvenient, and the processing efficiency is low. It not only easily causes powder pollution inside the machine, leading to operation failures, but also causes powder waste (because the recycled powder can be reused). Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions, so as to overcome the defects and deficiencies existing in the existing similar technologies and products as described in the background art.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows: A selective laser sintering 3D printer with precise powder supply and multiple powder spreading functions, including a frame, a laser scanning mechanism, a forming platform mechanism, a powder supply mechanism, a powder spreading mechanism, and a residual powder recovery mechanism. The forming platform mechanism includes a forming table, and is characterized in that: The powder supply mechanism includes a powder storage tank, in which a powder stirring device and a precise powder dropping hopper are arranged. The powder stirring device is composed of a rotating shaft and powder stirring blades fixed on the rotating shaft. The two ends of the rotating shaft are positioned by the powder storage tank, and one end of the rotating shaft is driven by a motor; The precise powder dropping hopper is located below the powder stirring device and at the powder outlet of the powder storage tank. The precise powder dropping hopper has a powder dropping cavity that is wider at the top and narrower at the bottom. The wider opening at the top is the powder inlet, and the narrower opening at the bottom is the powder dropping outlet. At the powder dropping outlet, a powder guiding trough is arranged. A partition is formed in the powder dropping cavity, and the partition evenly divides the powder dropping cavity into several powder dropping channels. At a position close to the powder dropping outlet in the powder dropping cavity, a powder control shaft along the length direction of the powder dropping outlet is arranged. The shaft diameter and length of the powder control shaft are precisely adapted to the width and length of the powder dropping outlet. A number of axial V-shaped powder grooves are evenly formed on the surface of the powder control shaft. The two ends of the powder control shaft are positioned by the precise powder dropping hopper, and one end of the powder control shaft is driven by a motor; The powder spreading mechanism includes a powder spreader. The powder spreader is horizontally movably mounted above the forming table through a set of linear sliding rails arranged at both ends thereof. At both ends of the powder spreader, a set of traction pulley groups are also arranged respectively. The sliders of the linear sliding rails are respectively fixed to the belts of the traction pulley groups on the same side. The driving wheels of the two sets of traction pulley groups are uniformly driven by a forward and reverse rotation motor at the same time; A powder loading through groove adapted to the width dimension of the forming table is formed in the powder spreader, and the lower groove opening of the powder loading through groove is smooth and flat; At one end of the forming table, a powder spreader initial state powder supporting plate and a powder spreader residual powder dropping opening are arranged in sequence. The powder spreader initial state powder supporting plate is in contact with the lower groove edge of the powder loading through groove of the powder spreader and can completely cover the lower groove edge of the powder loading through groove. When the powder spreader is directly above the powder spreader initial state powder supporting plate, the outlet of the powder guiding trough just aligns with the upper groove opening of the powder loading through groove of the powder spreader; The forward and reverse rotation motor is controlled by a programming controller to operate. Under the forward rotation drive of the forward and reverse rotation motor, when the powder spreader linearly translates from above the powder spreader initial state powder supporting plate to above the other end of the forming table, the programming controller commands the forward and reverse rotation motor to reverse, and the powder spreader returns along the original path until it reaches above the powder spreader residual powder dropping opening, and then the programming controller commands the forward and reverse rotation motor to rotate forward again to make the powder spreader return to directly above the powder spreader initial state powder supporting plate to wait for powder to be loaded into its powder loading through groove again; The residual powder recovery mechanism includes a residual powder collection bin. The residual powder collection bin is located below the forming table. The residual powder collection bin has two powder receiving hoppers. The two powder receiving hoppers are respectively located below the two ends of the forming table along the translation direction of the powder spreader. The inner cavities of the two powder receiving hoppers are communicated through a communicating part. At a position near the bottom in the residual powder collection bin, a negative pressure powder suction pipe is arranged. The negative pressure powder suction pipe penetrates through the two powder receiving hoppers and the communicating part of the residual powder collection bin, and a plurality of powder suction holes are opened on the pipe wall. The outlet end of the negative pressure powder suction pipe penetrates through the wall of the residual powder collection bin and extends outside the frame to be connected to an external negative pressure air suction machine.

[0007] Further, an elastic shock sheet is provided in each powder dropping channel of the precise powder dropping hopper. The upper edges of the elastic shock sheets are uniformly positioned through a shock sheet positioning plate mounted on the precise powder dropping hopper. Each elastic shock sheet is located above the powder control shaft. When the powder control shaft rotates driven by a motor, the walls of the V-shaped powder grooves of the powder control shaft will alternately and intermittently press against the lower edges of the elastic shock sheets, causing the elastic shock sheets to deform. During the rapid reset process of the elastic shock sheets, impacts and vibrations are caused to the powder control shaft.

[0008] Preferably, the above-mentioned elastic shock sheet is made of spring steel.

[0009] Still further, the rotating shaft of the powder stirrer and the powder control shaft are uniformly driven by the same motor through a pulley group.

[0010] Preferably, the powder stirring blades of the powder stirrer are spiral-shaped.

[0011] Preferably, the forward and reverse motor adopts a double-output shaft motor, and its two output shafts synchronously drive the driving wheels of one side of the traction pulley group respectively.

[0012] The beneficial effects of the present invention are as follows: Compared with the existing similar products on the market, the selective laser sintering 3D printer with precise powder supply and multiple powder spreading functions mainly has the following advantages: First, its exquisitely designed powder supply mechanism can achieve single-time quantitative and precise powder supply, and ensure that the powder flows out evenly at the powder outlet, thus laying a foundation for providing excellent powder spreading effect for the powder spreading mechanism; Second, the powder spreading mechanism receives the powder quantitatively input by the powder supply mechanism, and with the exquisitely designed powder spreading method of dropping powder while scraping flat and the secondary supplementary scraping operation, it ensures that the powder laid on the forming table each time is very uniform and flat everywhere, which greatly helps to improve the scanning and sintering effect of the laser beam on the powder and improve the precision quality of the final model; Third, through the residual powder recovery mechanism, the powder flowing from the forming table can be collected and recycled more effectively and conveniently, thus ensuring the cleanliness inside the machine, reducing operation failures, and saving powder (because the recycled powder can be reused). BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be further described below with reference to the drawings and embodiments.

[0014] Figure 1 It is a three-dimensional structure schematic diagram of the present invention (in order to clearly show the internal structure, some of the frame shells are removed, omitted or sectioned);

[0015] Figure 2 、 Figure 3 They are respectively the front view and rear view structure schematic diagrams of the present invention (in order to clearly show the internal structure, some of the frame shells are removed, omitted or sectioned);

[0016] Figure 4 It is a schematic three-dimensional structure diagram of the powder supply mechanism in the present invention (the front panel of the powder storage box is removed and omitted for clearly showing its internal structure);

[0017] Figure 5 、 Figure 6 They are all schematic three-dimensional structure diagrams of the precise powder dropping hopper in the powder supply mechanism (different perspectives; including the powder control shaft and the elastic vibration sheet, etc.);

[0018] Figure 7 It is a schematic three-dimensional structure diagram of the cooperation between the powder control shaft and the elastic vibration sheet in the powder supply mechanism;

[0019] Figure 8 、 Figure 9 They are all schematic three-dimensional structure diagrams of the powder spreading mechanism in the present invention (different perspectives; when the powder spreader is above the powder supporting plate in the initial state of the powder spreader (initial powder loading state of the powder spreader));

[0020] Figure 10 It is also a schematic three-dimensional structure diagram of the powder spreading mechanism (when the powder spreader travels back and forth above the forming table (powder spreading working state of the powder spreader));

[0021] Figure 11 It is also a schematic three-dimensional structure diagram of the powder spreading mechanism (when the powder spreader is above the remaining powder dropping port of the powder spreader (state of the powder spreader discharging the remaining powder));

[0022] Figure 12 、 Figure 13 、 Figure 14 They are respectively the front view, top view and schematic three-dimensional structure diagrams of the powder spreader in the powder spreading mechanism;

[0023] Figure 15 、 Figure 18 They are all schematic three-dimensional structure diagrams of the remaining powder recovery mechanism in the present invention (different perspectives);

[0024] Figure 16 、 Figure 19 、 Figure 22 They are respectively the rear view, front view and top view structure diagrams of the remaining powder collection bin in the remaining powder recovery mechanism;

[0025] Figure 17 、 Figure 20 、 Figure 21 They are all schematic three-dimensional structure diagrams of the remaining powder collection bin (different perspectives).

[0026] In the figure: 1. Frame; 2. Molding table; 3. Powder storage box; 4. Powder stirrer; 5. Precision powder dropping hopper; 6. Powder guiding trough; 7. Powder control shaft; 7-1. V-shaped powder trough; 8. Elastic shaking plate; 9. Shaking plate positioning plate; 10. Powder spreading device; 10-1. Powder carrying through groove; 11. Linear slide rail; 12. Traction pulley group; 13. Forward and reverse motor; 14. Powder supporting plate in the initial state of the powder spreading device; 15. Remaining powder dropping port of the powder spreading device; 16. Remaining powder collection bin; 16-1. Powder receiving hopper; 16-2. Connecting part; 17. Negative pressure powder suction pipe; 17-1. Powder suction hole. Detailed implementation manner

[0027] A selective laser sintering 3D printer with precise powder supply and multiple powder spreading functions, as Figures 1 to 3 shown, which includes a frame 1, a laser scanning mechanism, a molding platform mechanism, a powder supply mechanism, a powder spreading mechanism, and a remaining powder recovery mechanism. The molding platform mechanism includes a molding table 2, as Figures 4 to 6 shown. The powder supply mechanism includes a powder storage box 3, in which a powder stirrer 4 and a precision powder dropping hopper 5 are arranged. The powder stirrer 4 is composed of a rotating shaft and powder stirring blades fixed on the rotating shaft. Both ends of the rotating shaft are positioned by the powder storage box 3, and one end of the rotating shaft is driven by a motor; the precision powder dropping hopper 5 is located below the powder stirrer 4 and at the powder outlet of the powder storage box 3. The precision powder dropping hopper 5 has a powder dropping cavity with a wider upper part and a narrower lower part. The wider upper opening is the powder inlet, and the narrower lower opening is the powder dropping port. A powder guiding trough 6 is arranged at the powder dropping port. A partition 5-1 is formed in the powder dropping cavity. The partition 5-1 evenly divides the powder dropping cavity into several powder dropping channels. A powder control shaft 7 along the length direction of the powder dropping port is arranged close to the powder dropping port in the powder dropping cavity. The shaft diameter and length of the powder control shaft 7 are precisely adapted to the width and length of the powder dropping port. A number of axial V-shaped powder troughs 7-1 are evenly formed on the surface of the powder control shaft 7. Both ends of the powder control shaft 7 are positioned by the precision powder dropping hopper 5, and one end of the powder control shaft 7 is driven by a motor.

[0028] The stirring action of the powder stirrer 4 in the powder storage box 3 can ensure that the powder with a certain viscosity maintains good and stable fluidity in the powder storage box 3, ensuring that the powder can flow smoothly and evenly into each powder dropping channel of the lower precision powder dropping hopper 5; the powder flows out evenly through each powder dropping channel of the precision powder dropping hopper 5, laying a foundation for the uniform powder spreading operation of the subsequent powder spreading mechanism; the presence of the powder control shaft 7 in the precision powder dropping hopper 5 realizes the precise control of the single powder output: the powder loading capacity of a single V-shaped powder trough 7-1 of the powder control shaft 7 is pre-designed. Under the control of the motor, the rotation angle of the powder control shaft 7 is constant each time. Each time, a predetermined number (such as 3) of V-shaped powder troughs 7-1 are rotated to face downwards with the trough openings, so that the powder carried in the troughs drops, thereby realizing a constant powder amount dropped from the precision powder dropping hopper 5 each time, which is beneficial to the effect of the powder spreading operation of the subsequent powder spreading mechanism.

[0029] See Figures 5 to 7, in this example, an elastic shock sheet 8 is provided in each powder dropping channel of the precise powder dropping hopper 5. The upper edges of the elastic shock sheets 8 are uniformly positioned by a shock sheet positioning plate 9 mounted on the precise powder dropping hopper 5. Each elastic shock sheet 8 is located above the powder control shaft 7. When the powder control shaft 7 rotates driven by a motor, the groove walls of the V-shaped powder grooves 7-1 of the powder control shaft 7 will alternately and intermittently press against the lower edges of the elastic shock sheets 8, causing the elastic shock sheets 8 to deform. During the rapid reset process of the elastic shock sheets 8, impacts and vibrations are caused to the powder control shaft 7. The purpose of this solution is that since the powder has a certain viscosity, in order to prevent a small amount of the powder falling into the V-shaped powder grooves 7-1 of the powder control shaft 7 from adhering to the grooves and not falling out when dropping powder as the powder control shaft 7 rotates, by providing the elastic shock sheets 8 beside the powder control shaft 7, when the powder control shaft 7 rotates, the elastic shock sheets 8 are pressed, and the resulting vibrations can prompt all the powder adhering to the grooves to be shaken off, thus more ensuring the accuracy of the powder feeding amount.

[0030] In this example, the elastic shock sheet 8 is made of spring steel to ensure its use effect and service life.

[0031] In this example, to simplify the mechanical structure, the rotating shaft of the powder stirring device 4 and the powder control shaft 7 are uniformly driven by the same motor through a pulley set.

[0032] In this example, the powder stirring blades of the powder stirring device 4 are designed in a spiral shape, and the stirring effect on the powder is more excellent.

[0033] Such as Figures 8 to 14As shown in the figure, the powder spreading mechanism includes a powder spreader 10. The powder spreader 10 is horizontally movably mounted above the molding table 2 by means of a set of linear slide rails 11 provided at each of its two ends. A set of traction pulley groups 12 are also provided at each of the two ends of the powder spreader 10. The sliders of the linear slide rails 11 are fixedly connected to the belts of the traction pulley groups 12 on the same side. The driving wheels of the two sets of traction pulley groups 12 are uniformly driven by a forward and reverse motor 13 at the same time. A powder loading through groove 10-1 adapted to the width dimension of the molding table 2 is formed in the powder spreader 10. The lower notch of the powder loading through groove 10-1 is smooth and flat. A powder spreader initial state powder supporting plate 14 and a powder spreader residual powder dropping port 15 are sequentially arranged at one end of the molding table 2. The powder spreader initial state powder supporting plate 14 is in contact with the lower notch edge of the powder loading through groove 10-1 of the powder spreader 10 and can completely cover the lower notch of the powder loading through groove 10-1. When the powder spreader 10 is directly above the powder spreader initial state powder supporting plate 14, the outlet of the powder guiding trough 6 of the powder feeding mechanism is exactly aligned with the upper notch of the powder loading through groove 10-1 of the powder spreader 10. The forward and reverse motor 13 is controlled by a programming controller to operate. Under the forward drive of the forward and reverse motor 13, when the powder spreader 10 linearly translates from above the powder spreader initial state powder supporting plate 14 to above the other end of the molding table 2, the programming controller commands the forward and reverse motor 13 to reverse, and the powder spreader 10 returns along the original path until it reaches above the powder spreader residual powder dropping port 15. Then the programming controller commands the forward and reverse motor 13 to forward again, so that the powder spreader 10 returns to directly above the powder spreader initial state powder supporting plate 14 to wait for powder to be loaded into its powder loading through groove 10-1 again.

[0034] In this example, in order to simplify the mechanical structure, the forward and reverse motor 13 adopts a double-output shaft motor, and its two output shafts synchronously drive the driving wheels of the traction pulley groups 12 on one side respectively. The two ends of the powder spreader 10 are synchronously pulled and translated, which can ensure that there will be no mechanical jamming or stalling caused by unilateral force.

[0035] When the powder spreading device 10 is directly above the powder supporting plate 14 in the initial state of the powder spreading device, it receives the quantitative powder flowing out from the precision powder dropping hopper 5 through the powder guiding trough 6 of the powder feeding mechanism and stores it in its powder carrying through groove 10-1. Then, the powder spreading device 10 starts to translate above the forming platform 2 to spread the powder. The powder gradually falls out from the powder carrying through groove 10-1 of the powder spreading device 10 (but will not all fall out at once, because the gap between the lower side slot of the powder carrying through groove 10-1 of the powder spreading device 10 and the powder spreading surface is extremely small). The fallen powder is immediately scraped and leveled by the smooth and flat lower side slot edge of the powder carrying through groove 10-1 (leveling while the powder is falling). When the powder spreading device 10 translates to the other end of the forming platform 2, it returns along the original path (the height of the forming platform 2 remains unchanged), and starts to make up for the just first powder spreading process, filling and scraping the depressions and unevenness that may be left in the first powder spreading process, so as to ensure excellent powder spreading effect. After the secondary powder spreading is completed, the small amount of remaining powder in the powder carrying through groove 10-1 of the powder spreading device 10 is discharged through the powder remaining dropping port 15 of the powder spreading device, and is received by the powder remaining recovery mechanism.

[0036] As Figures 15 to 21 shown, the powder remaining recovery mechanism includes a powder remaining collection bin 16. The powder remaining collection bin 16 is located below the forming platform 2. The powder remaining collection bin 16 has two powder receiving hoppers 16-1. The two powder receiving hoppers 16-1 are respectively located below the two ends of the forming platform 2 along the translation direction of the powder spreading device 10. The inner cavities of the two powder receiving hoppers 16-1 are connected through a communication part 16-2. A negative pressure powder suction pipe 17 is arranged at a position near the bottom in the powder remaining collection bin 16. The negative pressure powder suction pipe 17 penetrates through the two powder receiving hoppers 16-1 and the communication part 16-2 of the powder remaining collection bin 16, and a plurality of powder suction holes 17-1 are opened on the pipe wall. The outlet end of the negative pressure powder suction pipe 17 penetrates through the wall of the powder remaining collection bin 16 and extends outside the frame 1 for connecting an external negative pressure air suction machine.

[0037] In the forming platform mechanism, there are relatively large gaps between the two ends of the forming platform 2 along the translation direction of the powder spreading device 10 and the enclosure plates. Under the powder pushing action of the powder spreading device 10, the excess powder on the forming platform 2 will flow out from the gaps at these two ends. Therefore, it is necessary to focus on receiving the powder flowing down from the gaps at these two ends of the forming platform 2. So, the two powder receiving hoppers 16-1 of the powder remaining collection bin 16 respectively receive the powder. At the same time, the powder flowing down from the powder remaining dropping port 15 of the powder spreading device at one end of the forming platform 2 is also integrally received by the powder receiving hopper 16-1 of the powder remaining collection bin 16. When the powder collected in the powder remaining collection bin 16 reaches a certain amount, an external negative pressure air suction machine is connected to the outlet end of the negative pressure powder suction pipe 17. By using the negative pressure air suction machine, the powder accumulated in the powder remaining collection bin 16 can be conveniently and quickly sucked out without any disassembly and assembly operations on the machine body. The powder collected by the negative pressure air suction machine can be poured back into the powder storage tank 3 of the powder feeding mechanism for repeated use to save powder.

[0038] The above embodiments are only used to explain the present invention, rather than limiting the protection scope of the present invention. Any non-substantive modification made on the basis of the essential solution of the present invention shall fall within the protection scope of the present invention.

Claims

1. A selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions, comprising a frame (1), a laser scanning mechanism, a forming platform mechanism, a powder feeding mechanism, a powder spreading mechanism, and a residual powder recovery mechanism. The forming platform mechanism includes a forming table (2), and is characterized in that: The powder supply mechanism described above includes a powder storage tank (3). Inside the powder storage tank (3), there is a powder stirrer (4) and a precise powder dropping hopper (5). The powder stirrer (4) consists of a rotating shaft and powder stirring blades fixed on the rotating shaft. Both ends of the rotating shaft are positioned by the powder storage tank (3), and one end of the rotating shaft is driven by a motor. The precise powder dropping hopper (5) is located below the powder stirrer (4) and at the powder outlet of the powder storage tank (3). The precise powder dropping hopper (5) has a powder dropping cavity that is wider at the top and narrower at the bottom. The upper wide opening is the powder inlet, and the lower narrow opening is the powder dropping outlet. At the powder dropping outlet, there is a powder guiding chute (6). A partition (5-1) is formed in the powder dropping cavity. The partition (5-1) evenly divides the powder dropping cavity into several powder dropping channels. Near the powder dropping outlet in the powder dropping cavity, there is a powder control shaft (7) along the length direction of the powder dropping outlet. The shaft diameter and length of the powder control shaft (7) are precisely adapted to the width and length of the powder dropping outlet. On the surface of the powder control shaft (7), several axial V-shaped powder grooves (7-1) are evenly formed. Both ends of the powder control shaft (7) are positioned by the precise powder dropping hopper (5), and one end of the powder control shaft (7) is driven by a motor. The powder spreading mechanism described above includes a powder spreader (10). The powder spreader (10) is horizontally movably mounted above the molding table (2) through a set of linear slide rails (11) provided at each of its two ends. At each of the two ends of the powder spreader (10), there is also a set of traction pulley groups (12). The sliders of the linear slide rails (11) are respectively fixedly connected to the belts of the traction pulley groups (12) on the same side. The driving wheels of the two sets of traction pulley groups (12) are simultaneously driven by a forward and reverse motor (13). A powder loading through groove (10-1) adapted to the width dimension of the molding table (2) is formed in the powder spreader (10). The lower notch of the powder loading through groove (10-1) is smooth and flat. At one end of the molding table (2), there are successively arranged a powder spreader initial state powder supporting plate (14) and a powder spreader residual powder dropping opening (15). The powder spreader initial state powder supporting plate (14) is in contact with the lower notch edge of the powder loading through groove (10-1) of the powder spreader (10) and can completely cover the lower notch of the powder loading through groove (10-1). When the powder spreader (10) is directly above the powder spreader initial state powder supporting plate (14), the outlet of the powder guiding chute (6) just aligns with the upper notch of the powder loading through groove (10-1) of the powder spreader (10). The forward and reverse motor (13) is controlled by a programming controller to operate. Under the forward drive of the forward and reverse motor (13), when the powder spreader (10) linearly translates from above the powder spreader initial state powder supporting plate (14) to above the other end of the molding table (2), the programming controller commands the forward and reverse motor (13) to reverse. The powder spreader (10) returns along the original path until it reaches above the powder spreader residual powder dropping opening (15). Then the programming controller commands the forward and reverse motor (13) to forward again, so that the powder spreader (10) returns to directly above the powder spreader initial state powder supporting plate (14) to wait for powder to be loaded into its powder loading through groove (10-1) again. The described residual powder recovery mechanism includes a residual powder collection bin (16). The residual powder collection bin (16) is located below the molding table (2). The residual powder collection bin (16) has two powder receiving hoppers (16-1). The two powder receiving hoppers (16-1) are respectively located below the two ends of the molding table (2) along the translation direction of the powder spreading device (10). The inner cavities of the two powder receiving hoppers (16-1) are connected through a connecting part (16-2). At a position near the bottom inside the residual powder collection bin (16), a negative pressure powder suction pipe (17) is provided. The negative pressure powder suction pipe (17) penetrates through the two powder receiving hoppers (16-1) and the connecting part (16-2) of the residual powder collection bin (16), and a plurality of powder suction holes (17-1) are opened on the pipe wall. The outlet end of the negative pressure powder suction pipe (17) penetrates through the wall of the residual powder collection bin (16) and extends outside the frame (1) for external connection to a negative pressure air suction machine.

2. The selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions according to claim 1, characterized in that: An elastic shaking piece (8) is provided in each powder falling channel of the described precise powder falling hopper (5). The upper edges of the elastic shaking pieces (8) are uniformly positioned through a shaking piece positioning plate (9) mounted on the precise powder falling hopper (5). The elastic shaking pieces (8) are located above the powder control shaft (7). When the powder control shaft (7) rotates driven by a motor, the walls of the V-shaped powder grooves (7-1) of the powder control shaft (7) will alternately and intermittently press against the lower edges of the elastic shaking pieces (8), causing the elastic shaking pieces (8) to deform. During the rapid reset process of the elastic shaking pieces (8), impacts and vibrations are caused to the powder control shaft (7).

3. The selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions according to claim 2, characterized in that: The described elastic shaking piece (8) is made of spring steel.

4. The selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions according to claim 1, characterized in that: The rotating shaft of the described powder stirring device (4) and the powder control shaft (7) are uniformly driven by the same motor through a pulley group.

5. The selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions according to claim 1, characterized in that: The powder stirring blades of the described powder stirring device (4) are spiral.

6. The selective laser sintering 3D printer with precise powder feeding and multiple powder spreading functions according to claim 1, characterized in that: The described forward and reverse motor (13) is a double output shaft motor, and its two output shafts synchronously drive the driving wheels of the traction pulley groups (12) on one side respectively.

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