A powder collecting device and 3D printer for laser powder bed melting

Abstract

The present invention relates to a powder collecting device and a 3D printer for laser powder bed melting. The powder collecting device comprises a powder bed and a powder collecting mechanism, and also comprises a visual sensing module and a control module. The visual sensing module, the control module and the powder collecting mechanism are electrically connected in sequence. The visual sensing module is used to take pictures and analyze the amount of powder shortage or excess powder on the powder bed and determine the appropriate amount of powder to be collected accordingly. The control module is used to control the powder collecting mechanism to collect powder according to the appropriate amount of powder to be collected. Compared with the powder collecting device in the prior art, which cannot automatically adjust in real time to obtain the appropriate amount of powder to be collected, resulting in too little or too much powder to be collected, resulting in the problem of over-melting defects or waste of powder in printing, the present invention can automatically adjust in real time during the printing process and obtain an appropriate amount of powder to be collected, thereby preventing over-melting defects or waste of powder in printing. The 3D printer has a powder collecting device with the aforementioned structure and has the same technical effect.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a powder collecting device and a 3D printer for laser powder bed melting. Background Art

[0002] Additive manufacturing, also known as 3D printing, refers to an emerging manufacturing technology that uses digital models as the basis to stack materials layer by layer to create physical objects. Additive manufacturing equipment can directly build physical parts "from scratch" without following the traditional process of roughing, rough processing, and finishing, nor relying on special forming molds. It has the advantages of design freedom, manufacturing flexibility, low cost, and short cycle. Additive manufacturing technology has been widely used in aerospace, automotive, machinery, energy, medical and other industries for rapid development, rapid manufacturing, and rapid repair.

[0003] Laser Powder Bed Fusion (LPBF) is one of the most common technologies in metal additive manufacturing. It uses a laser energy source to selectively fuse granular materials such as metals, ceramics or polymers together according to a model to form a three-dimensional object. First, a layer of powder material is laid on the powder bed through the powder collection and laying mechanism. The laser energy source selectively melts and sinters the current layer of powder material together according to the model. Then the substrate drops a layer thickness, and the powder is evenly and flatly laid on the powder bed. The laser then selectively melts and sinters again, and repeats this process to print the three-dimensional object layer by layer.

[0004] A powder bed with uniform layer thickness and smooth surface is crucial to the printing quality. The uniform powder layer thickness keeps the laser energy density stable and forms a dense and defect-free solid material. To ensure uniform powder spreading, the appropriate amount of powder is the key. When insufficient powder is taken, the local energy density will be too high, forming over-melting defects. When too much powder is taken, a large amount of powder will remain in the powder spreading mechanism after spreading, and the remaining powder will directly enter the overflow powder tank. This situation not only wastes powder, but also requires frequent replacement of the overflow powder tank and addition of powder, which wastes time and manpower.

[0005] In the prior art, two solutions are often used to control the amount of powder taken. The first solution is to manually adjust the amount of powder to adapt to the printing process, material and layer thickness through theoretical calculation or trial and error, and then fix the amount of powder for each layer. However, due to the influence of powder splashing and airflow, the theoretically calculated powder value is inaccurate. There are three disadvantages to determining the amount of powder taken by trial and error. First, it is time-consuming and labor-intensive; second, after changing the material, layer thickness, and printing model, the amount of powder taken needs to be readjusted and adapted; third, the fixed amount of powder cannot handle unexpected situations in the printing process in real time. For example, when new powder is added during the printing process, the powder fluidity changes due to differences in powder batches, differences in recycling times, or changes in humidity, causing fluctuations in the amount of powder taken; the second solution is to take more powder than needed to accommodate the influence of various factors. This solution causes waste of powder and requires frequent replacement of the overflow powder tank, which not only increases costs, but also interrupts the continuity of production and affects quality (replacement of the overflow powder tank may cause an increase in the oxygen content in the molding chamber). Summary of the invention

[0006] The first purpose of the present invention is to provide a powder collecting device for laser powder bed melting to address the problem that the powder collecting device in the prior art cannot automatically adjust in real time to obtain an appropriate amount of powder, resulting in too little or too much powder, which leads to over-melting defects or waste of powder during printing; the second purpose of the present invention is to provide a 3D printer.

[0007] In order to achieve the above first purpose, the technical solution adopted by the present invention is:

[0008] A powder collection device for laser powder bed melting includes a powder bed and a powder collection mechanism, and also includes a visual sensing module and a control module. The visual sensing module, the control module and the powder collection mechanism are electrically connected in sequence. The visual sensing module is used to take pictures and analyze the amount of missing or excess powder on the powder bed and determine the appropriate amount of powder to be collected accordingly. The control module is used to control the powder collection mechanism to collect powder according to the appropriate amount of powder to be collected.

[0009] The present invention adopts the above-mentioned technical solution, by setting a visual sensor module to take pictures of each layer of powder laid, and calculates the amount of powder shortage or excess on the powder bed through analysis of the photographic results, and transmits the appropriate powder collection amount determined thereby to the control module to control the powder collection mechanism to collect powder. Compared with the powder collection device in the prior art that cannot automatically adjust in real time to obtain the appropriate powder collection amount, resulting in too little or too much powder collection, leading to the problem of over-melting defects or waste of powder in printing, the present invention can automatically adjust in real time during the printing process and obtain an appropriate powder collection amount, thereby preventing over-melting defects or waste of powder in printing.

[0010] Furthermore, the powder taking mechanism includes a powder storage hopper, a powder lowering plate and a motor, the visual sensor module includes a high-definition camera and a visual control chip module, the powder lowering plate is provided with a powder lowering groove, the discharge port at the lower end of the powder storage hopper is connected with the powder lowering groove to form a powder lowering channel, the control module can control the motor to drive the powder lowering plate to move to adjust the size of the powder lowering channel, the high-definition camera is used to take full-frame photos of the powder bed, the visual control chip module can analyze the amount of powder shortage or excess on the powder bed through the photo results, and the size of the powder lowering channel is adjusted by driving the powder lowering plate through the motor so that the powder amount can be continuously adjusted to ensure that the powder taking amount is more accurate.

[0011] Furthermore, it also includes a protective cover arranged on the upper part of the powder bed, the powder bed and the protective cover form a box structure, the powder storage hopper and the lower powder plate are arranged inside the box, the motor is arranged on the outer side of the side panel of the box and is connected to the lower powder plate through the opening on the side panel, and the high-definition camera is arranged on the outer side of the top plate of the box. The protective cover not only protects the powder bed, but also can integrate the above-mentioned components together to save space.

[0012] Furthermore, a base plate which can move up and down is provided in the middle of the powder bed, and the laser selectively melts and sinters the powder in coordination with the movement of the base plate to realize layer-by-layer printing of a three-dimensional object.

[0013] Furthermore, the powder bed is provided with strip-shaped powder overflow ports on both sides of the substrate, and also includes a powder overflow tank arranged below the powder bed. The powder overflow port is connected to the powder overflow tank through a connecting pipe, and excess powder after spreading can enter the powder overflow tank through the powder overflow port and be collected.

[0014] Furthermore, the powder overflow port includes a first powder overflow port, the first powder overflow port is located below the powder storage hopper, and the first powder overflow port is used to collect powder leaked from the powder storage hopper during the powder taking process.

[0015] Furthermore, the powder overflow port also includes a second powder overflow port, and the second powder overflow port and the first powder overflow port are respectively arranged on both sides of the substrate. A long pendulum with a "+"-shaped cross-section is provided in the second powder overflow port, and both ends of the pendulum are hinged to the powder bed. When the pendulum is in a naturally drooping state, the second powder overflow port can be covered. If there is excess powder after spreading the powder, it will accumulate on one side of the pendulum, which is convenient for the high-definition camera to take pictures and determine the amount of excess powder. When too much powder is accumulated, the balance of the pendulum is destroyed, and the powder falls into the powder overflow tank from the second powder overflow port.

[0016] Furthermore, a powder spreading mechanism that can move along the surface of the powder bed is provided below the lower powder plate, and the powder spreading mechanism is used to spread the powder falling from the lower powder channel onto the surface of the powder bed to facilitate subsequent laser melting and sintering of the powder material.

[0017] Furthermore, it also includes a powder storage tank, which is arranged on the outside of the protective cover top plate, and the lower opening of the powder storage tank is connected to the feed port at the upper end of the powder storage hopper through the opening on the top plate. The powder storage tank is arranged outside the protective cover to facilitate the addition of raw material powder.

[0018] To achieve the second purpose, the present invention adopts the following technical solution:

[0019] A 3D printer comprises the above-mentioned powder collecting device for laser powder bed melting.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1) based on the closed-loop control of visual recognition, the powder taking amount can be automatically adjusted to achieve the optimization of the powder taking amount, while reducing the influence of frequent manual replacement of the overflow powder tank on the printing continuity, thereby improving the product quality; 2) powder can be taken in real time during the printing process to adapt to the printing process, material and layer thickness, without the need to determine the powder amount of each layer through offline trial and error, thereby improving the printing efficiency; 3) excess powder is reduced, powder waste and production costs caused by frequent manual replacement of the overflow powder tank are reduced; the 3D printer has the same technical effects as the aforementioned powder taking device. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention;

[0022] Figure 2 This is the exploded view of the powder extraction mechanism;

[0023] Figure 3 This is a cross-sectional view of the second powder overflow port.

[0024] Markings in the figure: 1-powder bed, 2-powder storage tank, 3-powder taking mechanism, 4-powder spreading mechanism, 5-high-definition camera, 6-overflow powder tank, 7-protective cover, 8-pendulum, 11-base plate, 12-overflow powder port, 31-powder storage hopper, 32-powder lower plate, 33-motor, 34-connecting seat, 35-fixing plate, 36-guide plate, 311-mounting plate, 321-powder lower trough, 341-connecting end, 351-positioning groove, 352-mounting seat, 361-guide slope, 362-bolt, 363-guide shovel. DETAILED DESCRIPTION

[0025] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Embodiment 1, as Figure 1 and Figure 3As shown, the embodiment of the present invention provides a powder taking device for laser powder bed melting, including a powder bed 1, a powder storage tank 2, a powder taking mechanism 3, a powder spreading mechanism 4, an overflow powder tank 6, and a protective cover 7 (for easy observation of the internal structure, Figure 1 The front plate and the right plate are hidden in it), a pendulum 8, a visual sensing module and a control module, wherein the visual sensing module includes a high-definition camera 5 and a visual control chip module.

[0028] like Figure 1-2 As shown, the powder bed 1 is arranged horizontally, and a protective cover 7 is arranged on the top, and the powder bed 1 and the protective cover 7 form a box structure; the powder taking mechanism 3 includes a powder storage hopper 31, a motor 33, a connecting seat 34, a fixed plate 35, a lower powder plate 32 and a guide plate 36. The fixed plate 35 and the guide plate 36 are respectively arranged on the upper and lower sides of the lower powder plate 32 and fit with its upper surface and lower surface respectively; the fixed plate 35 is provided with a positioning groove 351 that runs through the thickness direction, and the discharge port at the lower end of the powder storage hopper 31 is inserted into the positioning groove 351, and the fixed plate 35 is provided with a mounting seat 352, and the mounting seat 352 is fixedly connected to the side plate of the box; the upper end of the powder storage hopper 31 is provided with a mounting plate 311, and the mounting plate 311 is fixedly connected to the top plate of the box; the guide plate 36 is fixedly connected to the fixed plate 35 by bolts 362, and the front edge of the guide plate 36 is provided with a guide slope 361, and the rear end is provided with a guide for collecting the gap between the lower powder plate 32 and the guide plate 36. The connecting seat 34 is provided with a connecting end 341 and a ball screw nut pair transmission structure connected thereto. The motor 33 drives the connecting end 341 to move horizontally through the ball screw nut pair transmission structure. The connecting end 341 is connected to the middle part of the rear end of the lower powder plate 32. The lower powder plate 32 is provided with a lower powder groove 321 which runs through the thickness direction. The discharge port at the lower end of the powder storage hopper 31 is connected to the lower powder groove 321 to form a lower powder channel. The lower powder plate 32 can move horizontally along the powder spreading direction under the drive of the motor 33 to adjust the size of the lower powder channel.

[0029] like Figure 1-3As shown, the motor 33 and the connecting seat 34 on the powder taking mechanism 3 are arranged on the outside of the side plate of the box body, and the powder storage hopper 31, the fixing plate 35, the lower powder plate 32 and the guide plate 36 are all arranged inside the box body near the inner side of the side plate; the powder spreading mechanism 4 is arranged below the guide plate 36, and is used to receive the powder falling from the guide slope 361, which can move horizontally across the surface of the powder bed 1 and spread the powder on the surface of the powder bed 1; the high-definition camera 5 is arranged on the outside of the top plate of the box body; the powder storage tank 2 is arranged on the outside of the top plate of the protective cover 7, and the lower end opening of the powder storage tank 2 is connected with the feed port at the upper end of the powder storage hopper 31 through the opening on the top plate; a base plate 11 which can move up and down is provided in the middle of the powder bed 1, and a first strip-shaped overflow powder port and a second overflow powder port are provided on both sides of the base plate 11, and the first overflow powder port and the second overflow powder port are respectively connected through The connecting pipe is connected to the powder overflow tank 6 below the powder bed 1; the first powder overflow port is located below the guide shovel 363, and the second powder overflow port is provided with a long strip pendulum 8 with a "+"-shaped cross-section. The two ends of the pendulum 8 are hinged to the powder bed 1, and the second powder overflow port can be covered when the pendulum 8 is in a naturally drooping state; the control module can control the motor 33 to drive the powder lower plate 32 to move to adjust the size of the powder lower channel, the high-definition camera 5, the visual control chip module, the control module and the motor 33 are electrically connected in sequence, the high-definition camera 5 is used to take full-frame photos of the powder bed 1, and the visual control chip module can calculate the amount of powder shortage or excess on the powder bed 1 through the analysis of the photo results, and calculate the moving coordinate data of the motor 33 according to the amount of powder increased or decreased as needed, and input it to the control module.

[0030] When the motor 33 receives the moving command from the control module, the motor 33 drives the lower powder plate 32 to move backward until the lower powder trough 321 is connected to the discharge port of the powder storage hopper 31 to form a lowering channel, and the powder in the powder storage hopper 31 falls into the storage space formed by the lower powder trough 321 and the guide plate 36 through the lower powder channel. During the backward movement of the lower powder plate 32, the lower powder channel gradually becomes larger, and the amount of powder in the storage space continuously increases. When the powder amount reaches the set value, the motor 33 drives the lower powder plate 32 to move forward until the lower powder trough 321 moves to the front end edge of the guide plate 36, and the powder leaks out and falls into the powder spreading mechanism 4 below along the guide slope 361, and the powder spreading mechanism 4 spreads the powder on the powder bed 1.

[0031] During printing, the powder amount control method is as follows:

[0032] 1) Initial printing: Under different material, process, layer thickness and printing model conditions, the initial powder amount and powder spreading are determined according to the theoretically calculated layer thickness and bulk density.

[0033] 2) Real-time monitoring of the printing process. In the subsequent printing process, each time the powder is spread, the high-definition camera 5 takes a full-frame photo of the powder bed 1. The visual control chip module analyzes whether there is a shortage of powder on the powder bed 1, or whether there is excess powder on the pendulum 8, based on the photo results, and quantitatively calculates the size and position of the powder-shortage area, or the area of ​​excess powder. If the powder bed 1 is short of powder and the powder-shortage area is in the center of the printing format, the control module controls the powder taking mechanism 3 to increase the powder taking amount, re-spread the powder, and make up for the powder-shortage area; if the powder-shortage area is at the end of the printing format, not in the part slicing printing area, and the area of ​​the powder-shortage area is smaller than the set value (for example, 100mm 2 ) then there is no need to increase the powder intake; if the powder shortage area is at the end of the printing format and not in the part slice printing area, but the area of ​​the powder shortage area is larger than the set value (for example, 100mm 2 ) the control module needs to control the powder taking mechanism 3 to increase the powder taking amount, re-spread the powder, and make up for the powder shortage area; if there is excess powder on the pendulum 8 and the amount exceeds the set value (for example, 100mm 2 ) then gradually reduce the amount of powder taken in the next layer until the excess powder area is smaller than the set value; if there is excess powder on the pendulum 8 and the amount is smaller than the set value (for example 100mm 2 ) The amount of powder taken in the next layer will be consistent with that in this layer.

[0034] The present invention adopts the above-mentioned technical solution, and a high-definition camera is set to take full-frame photos of each layer of powder laid. The visual control chip module is used to analyze the photo results to calculate the amount of powder shortage or excess powder on the powder bed, and the increase or decrease of the powder taking amount of the powder taking mechanism is adjusted accordingly. Compared with the prior art, the present invention has the following beneficial effects: 1) Based on the closed-loop control of visual recognition, the powder taking amount can be automatically adjusted to achieve the optimization of the powder taking amount, while reducing the influence of frequent manual replacement of the overflow powder tank on the printing continuity, thereby improving product quality; 2) Powder can be taken in real time during the printing process to adapt to the printing process, material and layer thickness, without the need to determine the powder amount of each layer through offline trial and error, thereby improving printing efficiency; 3) Excess powder is reduced, and the production cost caused by powder waste and frequent manual replacement of the overflow powder tank is reduced.

[0035] Embodiment 2, a 3D printer, the 3D printer comprises the above-mentioned powder collection device for laser powder bed melting.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A powder collecting device for laser powder bed melting, comprising a powder bed (1) and a powder collecting mechanism (3), characterized in that: The powder collecting device (3) further comprises a visual sensing module and a control module, wherein the visual sensing module, the control module and the powder collecting mechanism (3) are electrically connected in sequence, the visual sensing module is used to take pictures and analyze the amount of powder shortage or excess powder on the powder bed (1) and determine the appropriate amount of powder to be collected accordingly, the control module is used to control the powder collecting mechanism (3) to collect powder according to the appropriate amount of powder to be collected, the powder collecting mechanism (3) comprises a powder storage hopper (31), a lower powder plate (32) and a motor (33), the lower powder plate (32) is provided with a lower powder groove (321), the discharge port at the lower end of the powder storage hopper (31) is connected to the lower powder groove (321) to form a lower powder channel, the control module can control the motor (33) to drive the lower powder plate (32) to move to adjust the size of the lower powder channel, and the powder bed (1) A base plate (11) which can move up and down is provided in the middle part, and strip-shaped powder overflow ports (12) are provided on both sides of the base plate (11) on the powder bed (1), and also include a powder overflow tank (6) arranged below the powder bed (1), and the powder overflow port (12) is connected with the powder overflow tank (6) through a connecting pipe, and the powder overflow port (12) includes a first powder overflow port, and the first powder overflow port is located below the powder storage hopper (31), and the powder overflow port (12) also includes a second powder overflow port, and the second powder overflow port and the first powder overflow port are respectively arranged on both sides of the base plate (11), and a long strip pendulum (8) with a +-shaped cross-section is provided in the second powder overflow port, and the two ends of the pendulum (8) are hinged to the powder bed (1), and the second powder overflow port can be covered when the pendulum (8) is in a naturally drooping state.

2. The powder collecting device for laser powder bed melting according to claim 1 is characterized in that: The visual sensing module comprises a high-definition camera (5) and a visual control chip module. The high-definition camera (5) is used to take full-frame photos of the powder bed (1). The visual control chip module can analyze the amount of powder shortage or excess on the powder bed (1) based on the photo results.

3. The powder collecting device for laser powder bed melting according to claim 2 is characterized in that: The powder bed (1) and the protective cover (7) form a box structure. The powder storage hopper (31) and the lower powder plate (32) are arranged inside the box. The motor (33) is arranged on the outer side of the box side plate and connected to the lower powder plate (32) through the opening on the side plate. The high-definition camera (5) is arranged on the outer side of the box top plate. A powder spreading mechanism (4) that can move along the surface of the powder bed (1) is provided below the lower powder plate (32). The powder spreading mechanism (4) is used to spread the powder dropped from the lower powder channel on the surface of the powder bed (1).

4. The powder collecting device for laser powder bed melting according to claim 3 is characterized in that: It also includes a powder storage tank (2), which is arranged on the outside of the top plate of the protective cover (7), and the lower end opening of the powder storage tank (2) is connected to the feed port at the upper end of the powder storage hopper (31) through an opening on the top plate.

5. A 3D printer, characterized in that: A powder collecting device for laser powder bed melting comprising any one of claims 1-4.

Images