A powder spreading device for additive manufacturing

Abstract

The present invention discloses a powder spreading device for additive manufacturing, comprising a reciprocating mechanism, a powder feeding funnel and a scraper, wherein the reciprocating mechanism drives the powder feeding funnel to reciprocate above a forming substrate in a forming chamber, and the bottom of the powder feeding funnel is provided with a narrow powder outlet, and a powder spreading mechanism is provided at the powder outlet, and the powder spreading mechanism comprises a metering gear and a drive assembly, wherein the metering gear is arranged along the length direction of the powder outlet, and the lower part of the metering gear protrudes to the outside of the powder feeding funnel, and the drive assembly drives the metering gear to spread the powder in the powder feeding funnel onto the forming substrate, and the scraper is used to level the spread powder. During the powder spreading process, the powder follows the rotation of the metering gear, and the powder is gradually spread and leveled, so that the powder has better fluidity, improves the uniformity of the powder spreading, and is more conducive to rapid powder spreading, thereby improving the powder spreading efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a powder spreading device on additive manufacturing forming equipment. Background Art

[0002] With the development of the additive manufacturing industry, more and more stringent requirements are placed on forming speed and size. Additive manufacturing equipment is constantly optimized and upgraded to meet customer needs. Among them, the powder spreading device is an important part of the selective melting forming equipment. Currently, the upper powder feeding and lower powder feeding types are more widely used. The powder cabin of the upper powder feeding type is generally located above the scraper. The outflow of powder in each pass is controlled by the quantitative powder feeding mechanism. A certain amount of powder is first accumulated at the starting position, and then the scraper is swept back and forth to level it. The thickness of the forming layer is controlled by adjusting the distance between the scraper and the substrate surface. However, the powder is easily affected by the ambient humidity and temperature, causing changes in fluidity, which makes the powder spreadability worse, resulting in powder sticking or agglomeration, and affecting the performance stability of the formed part. The powder chamber of the bottom-feed powder type is generally located below the scraper, and the powder chamber and the forming chamber are located on the same plane. The powder in the powder chamber is pushed out by the stepper piston, and then the scraper collects the powder on the powder chamber surface and evenly spreads it on the forming layer. This method can more accurately control the amount of powder output per pass and has relatively low requirements for powder fluidity. However, because the powder chamber and the forming chamber are on the same plane, the flying residue and scraper carryback during the forming process will cause contamination of the powder raw material. The existing powder spreading method of additive manufacturing equipment can ensure the thickness of each layer of powder is uniform and flat, but it has high requirements for powder fluidity and particle size distribution. It cannot continuously maintain the stability of the powder spreading, and it is difficult to control the powder delivery volume, resulting in waste.

[0003] Among them, the Chinese utility model patent with application number 201920445863.8 discloses a selective laser sintering powder spreading device, which adopts a mobile hopper combined with a scraper and a powder spreading roller to spread powder, but the powder feeding method of the mobile hopper vibrating and breaking the arch cannot quantify the powder feeding amount evenly; the Chinese utility model patent with application number 201520953986.4 discloses a powder-based additive manufacturing equipment with two-way powder spreading, which realizes two-way powder spreading and improves efficiency. However, it is found through application that the uniformity of the powder spreading is insufficient. The main reason is that the powder currently spread has different particle sizes. In this case, the particle size of the powder used is within a range, that is, the powder particle size is uneven. If a powder compacting roller is used, the smaller particles will flow to both sides during the compaction of the loose powder, and the larger particles will be concentrated and compacted in the middle, resulting in uneven distribution of the particle size of the spread powder. Moreover, the powder measured by the quantitative powder feeding gear of this structure must pass through the powder outlet below before it can be discharged. The discharged powder is easy to accumulate and is not conducive to the flow of powder during the spread powder process. Moreover, when using the above two powder spreading methods, the powder is easy to adhere to the roller surface during the compaction process, affecting the flatness of the spread powder and thus affecting the molding quality. Therefore, a new powder spreading device is needed to solve the above problems. Summary of the Invention

[0004] The present invention addresses the shortcomings of existing technologies and provides a powder spreading device for additive manufacturing. This device addresses issues such as powder sticking, uneven spreading, and agglomeration, which can occur during the selective forming process of additive manufacturing, often due to the influence of the raw material powder's particle size distribution, fluidity, and working environment. This effectively improves forming efficiency and part stability, while reducing costs.

[0005] A powder spreading device for additive manufacturing includes a reciprocating motion mechanism, a powder feeding funnel and a scraper. The reciprocating motion mechanism drives the powder feeding funnel to reciprocate above a forming substrate in a forming bin. A narrow and long powder outlet is provided at the bottom of the powder feeding funnel. A powder spreading mechanism is provided at the powder outlet. The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet, and the lower part of the metering gear protrudes to the outside of the powder feeding funnel. The drive assembly drives the metering gear to spread the powder in the powder feeding funnel onto the forming substrate. The scraper is used to level the spread powder.

[0006] Furthermore, it also includes a powder adding mechanism, which is connected to the powder feeding funnel and is used to add powder into the powder feeding funnel.

[0007] Specifically, the powder adding mechanism includes a powder storage cabin provided in the forming bin, and the powder storage cabin is provided with a powder discharge mechanism. When the powder feeding funnel moves to the bottom of the powder storage cabin through the reciprocating motion mechanism, the powder in the powder storage cabin is transferred to the powder feeding funnel through the powder discharge mechanism.

[0008] Specifically, the powder storage cabin is shaped to be upward and downward sloping, and the powder feeding funnel is shaped to be wide at the top and narrow at the bottom.

[0009] Furthermore, a powder amount detection sensor is provided in the powder feeding funnel.

[0010] Further preferably, there are two powder storage compartments, which are respectively arranged on the first side wall and the second side wall of the forming bin that are parallel and opposite to each other, and the powder discharge mechanism is a spring switch.

[0011] Furthermore, there are two scrapers, which are respectively installed below the powder feeding funnel and located on both sides of the powder outlet along the length direction. The transverse section of the scraper includes an inclined structure or an arc structure.

[0012] Preferably, the transverse section of the scraper is an arc-shaped structure.

[0013] Furthermore, the scraper and the powder feeding funnel are detachably mounted.

[0014] More specifically, metering gear shafts are provided at both ends of the metering gear, and the metering gear shafts are installed on two parallel and opposite side surfaces of the powder feeding funnel. The transverse section of the metering gear is a gear structure, and the tooth top of the metering gear is tangent to the edge of the powder outlet along the length direction. The driving assembly drives the metering gear shaft to rotate synchronously or rotate with the track.

[0015] Optionally, the drive assembly includes a transmission shaft, a coupling transmission belt and a metering gear drive motor, the transmission shaft is installed on one side of the powder feeding funnel, the metering gear drive motor is connected to the transmission shaft, the transmission shaft is connected to the metering gear shaft through the coupling transmission belt, and the metering gear drive motor drives the metering gear shaft to rotate synchronously.

[0016] Further preferably, the drive assembly includes a multi-stage gear and a plurality of racks arranged side by side, the multi-stage gear is mounted on the metering gear shaft, the multi-stage gear is composed of a combination of two or more gears with different numbers of teeth, the multiple racks are arranged along the direction of the reciprocating motion of the powder feeding funnel, and are located on one side of the forming substrate, and a lifting mechanism is provided under the multiple racks, the lifting mechanism lifts any one of the multiple racks to engage with the corresponding gear in the multi-stage gear, and drives the metering gear shaft to rotate with the rail.

[0017] Specifically, the length of the rack is equal to the side length of the base plate, and the number of gears in the multi-stage gear is not less than 2.

[0018] Furthermore, the number of gears in the multi-stage gear is 3-5.

[0019] Furthermore, the reciprocating motion mechanism includes a slide rail assembly, which includes a reciprocating driver, a slider and a slide rail. The slider and the slide rail are slidably connected, the slider is fixedly connected to the powder feeding funnel, and the reciprocating driver drives the slider to reciprocate along the slide rail.

[0020] Furthermore, it also includes a powder recovery system, which includes two residual powder collection chambers and one waste powder collection chamber. The residual powder collection chambers are respectively arranged on two parallel and opposite sides of the forming substrate and perpendicular to the length direction of the rack. The waste powder collection chamber is arranged between the rack and the forming substrate.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. During the powder spreading process, the powder follows the rotation of the metering gear and is gradually spread flat. The powder has better fluidity, which improves the uniformity of the powder spreading and is more conducive to rapid powder spreading and improved powder spreading efficiency.

[0023] 2. The powder is quantitatively spread onto the forming substrate through the metering gear, and the scraper flattens the spread powder. The scraper only moves in parallel. During the leveling process, powders of different particle sizes are more evenly distributed, and the arc structure of the scraper is used to achieve the compaction function. The powder outlet is equipped with a metering gear and double scrapers, which move in coordination. The rotation of the metering gear can bring out the powder in the powder feeding funnel more evenly, and cooperate with the scraper to complete the leveling of the powder. The excess powder can be recovered into the powder feeding funnel as the metering gear rotates, saving powder and avoiding waste. At the same time, since the powder is brought out in the form of rotation of the metering gear, the fluidity requirements of the powder are lower, and powder with a wider range of particle size distribution can be used.

[0024] 3. The powder spreading device of the present invention integrates the functions of powder feeding and powder spreading. The powder feeding funnel can transfer the powder in the powder storage chamber to the powder feeding funnel by impacting the powder discharge mechanism, and the powder loading is controlled by the impact spring stroke. For powder with good fluidity, a small impact stroke and a small flow rate can be used to avoid powder splashing and save back-and-forth loading time. For powder with poor fluidity, a deeper impact is required to make the powder flow out more stably. At the same time, the impact stroke can be controlled to control the amount of powder transferred in a single time. Different powder loading amounts can be selected for different powders to ensure stable outflow of powder during the powder spreading process. Two powder storage chambers are provided to facilitate the filling of powder when the powder feeding funnel moves back and forth, thereby improving operating efficiency.

[0025] 4. The scraper in the present invention is arranged at the bottom of the powder feeding funnel, which simplifies the structure of the device; the metering gear can be driven by the transmission component to realize synchronous rotation powder feeding or track-following powder feeding. Track-following powder feeding can control the powder to be evenly spread on the substrate plane, and can realize multi-level regulation. The metering gear and the multi-stage gear are connected through the metering gear shaft, and the multi-stage gear and the rack move in coordination to control the rotation rate of the metering gear, thereby achieving the effect of adjustable powder delivery amount; when multi-stage powder feeding is not required, synchronous powder feeding can be adopted to improve the efficiency of powder spreading while ensuring stable powder output.

[0026] 5. The excess powder scraped back and forth by the powder feeding funnel is collected through two residual powder collection chambers, and the smoke, impurities and powder splashed during the forming process are collected through a waste powder collection chamber, which further saves powder and purifies the powder spreading environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the front structure of the powder spreading device for additive manufacturing in Example 1;

[0028] Figure 2 for Figure 1 A-direction schematic diagram;

[0029] Figure 3 Schematic diagram of the connection structure between the powder feeding funnel and the metering gear in Example 1;

[0030] Figure 4 Schematic diagram of the structure of the driving assembly in Example 1;

[0031] Figure 5 Schematic diagram of the structure of the driving component in Example 2.

[0032] Among them, 1-powder storage cabin, 2-reciprocating motion mechanism, 3-powder feeding funnel, 4-scraper, 5-powder discharge mechanism, 6-powder outlet, 7-powder spreading mechanism, 8-forming bin, 9-forming base plate, 10-first side wall, 11-second side wall, 12-metering gear, 13-metering gear shaft, 14-gear, 15-slide rail assembly, 16-transmission shaft, 17-coupling transmission belt, 18-drive assembly, 19-slider, 20-slide rail, 21-multi-stage gear, 22-rack, 23-lifting mechanism, 24-powder recovery system, 25-residual powder collection cabin, 26-waste powder collection cabin. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 、 Figure 2 As shown, a powder spreading device for additive manufacturing includes a reciprocating motion mechanism, a powder feeding funnel and a scraper. The reciprocating motion mechanism drives the powder feeding funnel to reciprocate above the forming substrate in the forming bin. The bottom of the powder feeding funnel is provided with a narrow and long powder outlet. The powder outlet is provided with a powder spreading mechanism. The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet, and the lower part of the metering gear protrudes to the outside of the powder feeding funnel. The drive assembly drives the metering gear to spread the powder in the powder feeding funnel onto the forming substrate, and the scraper is used to level the spread powder.

[0036] The device further includes a powder adding mechanism, which is connected to the powder feeding funnel and is used to add powder to the powder feeding funnel. The powder adding mechanism includes a powder storage compartment provided in the forming chamber, and a powder discharge mechanism is provided on the powder storage compartment. When the powder feeding funnel is moved to the bottom of the powder storage compartment by the reciprocating motion mechanism, the powder in the powder storage compartment is transferred to the powder feeding funnel by the powder discharge mechanism.

[0037] The powder storage cabin is shaped to be upward and downward sloping, and the powder feeding funnel is shaped to be wide at the top and narrow at the bottom, which is conducive to the flow of powder while ensuring a sufficiently large loading capacity.

[0038] The powder feeding funnel is provided with a powder amount detection sensor for monitoring the powder loading amount in the powder feeding funnel. When the powder is less, the funnel moves to the end of the stroke to transfer the powder in the powder storage cabin.

[0039] There are two powder storage chambers, which are respectively arranged on the first side wall and the second side wall of the forming bin that are parallel to each other. The bottom of the powder storage chamber is provided with two rows of circular holes of different diameters. The powder discharge mechanism is a spring switch, which includes an L-shaped covering plate. The top surface of the covering plate blocks the circular holes, and the side surface of the covering plate elastically fits the spring. When the reciprocating motion mechanism drives the powder feeding funnel to contact the side surface of the covering plate, the spring is compressed, the circular holes are opened, and powder falls into the powder feeding funnel from the circular holes; when the powder feeding funnel moves in the opposite direction, the covering plate automatically resets under the action of the spring, and the circular holes are blocked; the powder transfer amount can be controlled by controlling the stroke of the powder feeding funnel hitting the spring switch. According to the fluidity of the powder, different impact strokes are selected so that the powder in the powder storage chamber can flow out stably and be transferred to the powder feeding funnel. At the same time, the impact stroke can be controlled to control the transfer amount of single powder. Different powder loading amounts can be selected for different powders to ensure stable outflow of powder during the powder spreading process.

[0040] like Figure 3 As shown, there are two scrapers, which are respectively installed below the powder feeding funnel and located on both sides of the powder outlet along the length direction. The transverse section of the scraper is an arc structure.

[0041] The scraper and the powder feeding funnel are detachable and installable. The scraper and the powder feeding funnel are a dovetail connection structure. After the connection is completed, they are further fastened by fastening nails. The disassembly structure can replace scrapers of different heights. By adjusting the lifting height, the metering gear can be replaced with different specifications. Different specifications correspond to different tooth sizes. The scraper is replaced synchronously when the metering gear is replaced. It is used to cooperate with the lowest position of the metering gear to control the powder spreading state and level the powder sent out of the powder feeding funnel. Two scrapers are provided to move back and forth to avoid wasting time in air transportation and improve the efficiency of powder spreading.

[0042] The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet. Metering gear shafts are provided at both ends of the metering gear. The metering gear shafts are installed on two parallel and opposite side surfaces of the powder feeding funnel. The transverse section of the metering gear is a gear structure, and the tooth top of the metering gear is tangent to the edge of the powder outlet along the length direction.

[0043] like Figure 4As shown, the drive assembly includes a multi-stage gear and multiple racks arranged side by side. The multi-stage gear is installed on the metering gear shaft. The multi-stage gear is composed of two or more gears with different numbers of teeth. The multiple racks are arranged along the direction of reciprocating motion of the powder feeding funnel and are located on one side of the forming base plate. A lifting mechanism is provided below the multiple racks. The lifting mechanism lifts any one of the multiple racks to engage with the corresponding gear in the multi-stage gear, driving the metering gear shaft to rotate along the rail. The length of the rack is equal to the side length of the base plate. The number of gears in the multi-stage gear is 3, of which the smallest gear has 20 teeth, and the number of teeth of the remaining two gears increases by 5 in sequence. By meshing with the racks with different numbers of teeth, the metering gears produce different rotation rates when the powder feeding funnel moves at the same speed, thereby adjusting the amount of powder spread. This structure has good stability and does not require an additional power source. The lifting mechanism includes guide rails at both ends of the rack. The rack can move vertically along the guide rails. A cylinder is provided under each rack to lift the rack and engage with the corresponding gear through the cylinder.

[0044] The reciprocating motion mechanism includes a slide rail assembly, and the slide rail assembly includes a reciprocating drive (not shown in the figure), a slider and a slide rail. The slider and the slide rail are slidably connected, and the slider is fixedly connected to the powder feeding funnel. The reciprocating drive drives the slider to reciprocate along the slide rail. In this embodiment, the slider and the slide rail are two groups, which are arranged in parallel along the reciprocating motion direction and located on both sides of the powder feeding funnel to ensure the stability of the powder feeding funnel during the reciprocating motion. The reciprocating drive is an electric push rod, which is controlled by a PLC servo. When the powder amount detection sensor detects that there is less powder, it feeds back to the PLC controller, and the powder feeding funnel moves to the end of the stroke to transfer the powder in the powder storage cabin.

[0045] It also includes a powder recovery system, which includes two residual powder collection chambers and one waste powder collection chamber. The residual powder collection chambers are respectively arranged on two parallel and opposite sides of the forming substrate and perpendicular to the length direction of the rack. The waste powder collection chamber is arranged between the rack and the forming substrate.

[0046] Example 2

[0047] A powder spreading device for additive manufacturing includes a reciprocating motion mechanism, a powder feeding funnel and a scraper. The reciprocating motion mechanism drives the powder feeding funnel to reciprocate above a forming substrate in a forming bin. A narrow and long powder outlet is provided at the bottom of the powder feeding funnel. A powder spreading mechanism is provided at the powder outlet. The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet, and the lower part of the metering gear protrudes to the outside of the powder feeding funnel. The drive assembly drives the metering gear to spread the powder in the powder feeding funnel onto the forming substrate. The scraper is used to level the spread powder.

[0048] The powder feeding mechanism is also included, which is connected to the powder feeding funnel and is used to add powder to the powder feeding funnel. In this embodiment, the powder feeding mechanism is a metered powder feeding pipeline that can feed powder to the powder feeding funnel under the protection of inert gas. The pipeline extends to the outside of the forming chamber to facilitate powder feeding operations during the powder spreading process.

[0049] The powder storage compartment is sloping downward from the top, while the powder feeding hopper is wide at the top and narrow at the bottom. A powder level sensor is installed within the powder feeding hopper to monitor the powder loading within. There are two powder storage compartments, located on the first and second parallel side walls of the forming chamber. The powder discharge mechanism is a spring-loaded switch.

[0050] There are two scrapers, which are respectively installed below the powder feeding funnel and located on both sides of the powder outlet along the length direction. The transverse section of the scraper is an inclined structure.

[0051] The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet. Metering gear shafts are provided at both ends of the metering gear. The metering gear shafts are installed on two parallel and opposite side surfaces of the powder feeding funnel. The transverse section of the metering gear is a gear structure. The tooth top of the metering gear is tangent to the edge of the powder outlet along the length direction. The drive assembly drives the metering gear shaft to rotate synchronously or rotate with the track.

[0052] like Figure 5 As shown, the drive assembly includes a transmission shaft, a coupling transmission belt and a metering gear drive motor. The transmission shaft is installed on one side of the powder feeding funnel. The metering gear drive motor is connected to the transmission shaft. The transmission shaft is connected to the metering gear shaft through the coupling transmission belt. The metering gear drive motor drives the metering gear shaft to rotate synchronously.

[0053] The reciprocating mechanism includes a slide rail assembly, which includes a reciprocating driver, a slider, and a slide rail. The slider and the slide rail are slidably connected, and the slider is fixedly connected to the powder feeding funnel. The reciprocating driver drives the slider to reciprocate along the slide rail. The reciprocating mechanism causes the powder feeding funnel to reciprocate to spread the powder, which provides good stability.

[0054] Example 3

[0055] This embodiment differs from embodiment 2 in that:

[0056] The drive assembly also includes a multi-stage gear and multiple racks arranged side by side. The multi-stage gear is mounted on the metering gear shaft. The multi-stage gear is composed of two or more gears with different numbers of teeth. The racks are arranged along the reciprocating direction of the powder feeding funnel and are located on one side of the forming base. A lifting mechanism is located below the racks. This lifting mechanism lifts any one of the multiple racks to engage with the corresponding gear in the multi-stage gear, driving the metering gear shaft to rotate with the track. The multi-stage gear has five gears and five racks. The smallest gear has 18 teeth, and the remaining gears have teeth increasing by three.

[0057] The powder spreading device can deliver powder synchronously or along the track. When one of them is selected, the other is in an empty state. The device is more flexible to use and can adapt to different powder spreading needs.

[0058] The rest of the content is the same as Example 2.

Claims

1. A powder spreading device for additive manufacturing, comprising a reciprocating mechanism, a powder feeding funnel and a scraper, wherein the reciprocating mechanism drives the powder feeding funnel to reciprocate above a forming substrate in a forming chamber, characterized in that The bottom of the powder feeding funnel is provided with a narrow and long powder outlet, and a powder spreading mechanism is provided at the powder outlet. The powder spreading mechanism includes a metering gear and a drive assembly. The metering gear is arranged along the length direction of the powder outlet, and the lower part of the metering gear protrudes to the outside of the powder feeding funnel. The drive assembly drives the metering gear to spread the powder in the powder feeding funnel onto the forming substrate, and the scraper is used to level the spread powder. The invention also includes a powder adding mechanism connected to the powder feeding funnel, wherein the powder adding mechanism is used to add powder into the powder feeding funnel; The powder adding mechanism includes a powder storage cabin provided in the forming bin, and the powder storage cabin is provided with a powder discharge mechanism. When the powder feeding funnel moves to the bottom of the powder storage cabin through the reciprocating motion mechanism, the powder in the powder storage cabin is transferred to the powder feeding funnel through the powder discharge mechanism. There are two powder storage compartments, which are respectively arranged on the first side wall and the second side wall of the forming chamber, which are parallel and opposite to each other. The powder discharge mechanism is a spring switch. Both ends of the metering gear are provided with metering gear shafts, which are installed on two parallel and opposite sides of the powder feeding funnel. The transverse section of the metering gear is a gear structure, and the tooth top of the metering gear is tangent to the edge of the powder outlet along the length direction. The driving assembly drives the metering gear shaft to rotate synchronously or rotate with the track; The reciprocating motion mechanism includes a slide rail assembly, which includes a reciprocating drive, a slider and a slide rail. The slider and the slide rail are slidably connected, the slider is fixedly connected to the powder feeding funnel, and the reciprocating drive drives the slider to reciprocate along the slide rail. The drive assembly includes a transmission shaft, a coupling transmission belt and a metering gear drive motor. The transmission shaft is installed on one side of the powder feeding funnel. The metering gear drive motor is connected to the transmission shaft. The transmission shaft is connected to the metering gear shaft through the coupling transmission belt. The metering gear drive motor drives the metering gear shaft to rotate synchronously.

2. The powder spreading device for additive manufacturing according to claim 1, characterized in that There are two scrapers, which are respectively installed below the powder feeding funnel and located on both sides of the powder outlet along the length direction. The transverse section of the scraper includes an inclined structure or an arc structure.

3. The powder spreading device for additive manufacturing according to claim 1, characterized in that The driving assembly includes a multi-stage gear and a plurality of racks arranged side by side. The multi-stage gear is installed on the metering gear shaft. The multi-stage gear is composed of two or more gears with different numbers of teeth. The multiple racks are arranged along the direction of the reciprocating motion of the powder feeding funnel and are located on one side of the forming base plate. A lifting mechanism is provided under the multiple racks. The lifting mechanism lifts any one of the multiple racks to engage with the corresponding gear in the multi-stage gear, driving the metering gear shaft to rotate with the rail.

4. The powder spreading device for additive manufacturing according to any one of claims 1 to 3, characterized in that It also includes a powder recovery system, which includes two residual powder collection chambers and one waste powder collection chamber. The residual powder collection chambers are respectively arranged on two parallel and opposite sides of the forming substrate and perpendicular to the length direction of the rack. The waste powder collection chamber is arranged between the rack and the forming substrate.

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