Selective laser melting additive manufacturing device

Abstract

The invention provides a selective laser melting additive manufacturing device, which belongs to the technical field of additive manufacturing and comprises a working platform, a laser head and a powder supply nozzle are arranged above the working platform, a forming platform is arranged in the middle of the working platform, is positioned in a forming cavity and is in close contact with the forming cavity, and the bottom of the forming platform is connected with a lifting mechanism. A powder spreading box is arranged on the working platform and connected with a driving mechanism, the driving mechanism drives the powder spreading box to slide on the working platform in a reciprocating mode, and the powder spreading device is characterized in that sliding pressing mechanisms are arranged on the two sides of the working platform, and the powder spreading box is connected with the sliding pressing mechanisms in a sliding mode and is pressed on the working platform under the action of the sliding pressing mechanisms. Downward pressure is applied to the powder spreading box in the whole sliding powder spreading process of the powder spreading box, powder leakage is reduced, in addition, the sliding pressing mechanism provides elasticity in the vertical direction for the powder spreading box, and direct collision and serious friction are avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and particularly relates to a selective laser melting additive manufacturing device. Background Art

[0002] Additive manufacturing, also known as 3D printing, is a technology that constructs objects layer by layer. It is based on digital model files and uses powdery metal or plastic and other bondable materials. After selective heating and curing, the materials are used to form objects. Currently, various additive manufacturing devices mainly achieve powder supply through the linear sliding of the powder spreading mechanism, control the thickness of each layer of powder by lifting the workbench, and then achieve selective heating by controlling the running trajectory of the laser head, ultimately achieving the effect of layer-by-layer printing. However, when using such additive manufacturing devices, the following problems exist: Taking the prior art "CN218799128U Additive Manufacturing Scraper-Free Powder Spreading Device" as an example, during the use of this device, powder spreading is achieved through the lateral reciprocating movement of the powder supply chamber. Since it comes into contact with the forming bottom plate during the movement, there will inevitably be a gap between the two. Therefore, when supplying powder, metal powder will leak into the gap. When too much powder leaks and fills the gap, as the powder supply chamber moves, this powder will "lift" the powder supply chamber upward by a certain distance. At this time, when controlling the thickness of each layer of powder by lowering the forming platform, an error will occur. Due to the existence of the "lifting" phenomenon, the actual thickness of each layer of powder is greater than the ideal thickness, that is, the actual thickness = ideal thickness + "lifting" distance. Therefore, the processing accuracy will be affected. At the same time, since the metal powder particles are relatively hard, when they are filled between the powder supply chamber and the forming bottom plate, the friction will increase. Especially when there are large powder particle clusters in the powder, due to the lack of elasticity of the scraper in the prior art, when encountering large particle clusters, there will be a direct mechanical collision and it is impossible to avoid or cross the particle clusters. Therefore, it will cause relatively serious wear and damage, affecting the service life of the equipment. In addition, when the leaked powder accumulates too much, it will cover the surface of the forming bottom plate and diffuse into the air with the airflow, which is not conducive to cleanliness and the air quality of the factory. In the prior art "CN115301955A Scraper Powder Cleaning Device and Method for Powder Spreading Additive Manufacturing Equipment" or "CN214494940U A Powder Spreading Device for Additive Manufacturing", although the problem of excessive accumulation of leaked powder on the working platform is solved to a certain extent through the setting of the powder recovery bin, this method can only treat the symptoms, not the root cause, and the effect is extremely limited.

[0003] In addition, after the parts are processed by the above additive manufacturing devices, since the part body and the uncured powder are still mixed together, if they are directly clamped and taken out by a conventional manipulator, it is inevitable that a small amount of powder will be clamped and taken away together, which will also cause the powder to diffuse into the air and is not conducive to powder recycling and reuse. Summary of the Invention

[0004] The present invention provides a selective laser melting additive manufacturing device to solve the problems raised in the above-mentioned background art.

[0005] The technical solution of the present invention is as follows: A selective laser melting additive manufacturing device includes a working platform. Above the working platform, there is a laser head and a powder supply nozzle. In the middle of the working platform, there is a forming platform. The forming platform is located inside the forming cavity and is in close contact with the forming cavity. The bottom of the forming platform is connected to a lifting mechanism. A powder spreading box is arranged on the working platform, and the powder spreading box is connected to a driving mechanism. The driving mechanism drives the powder spreading box to slide back and forth on the working platform. Its characteristic lies in that sliding pressing mechanisms are arranged on both sides of the working platform. The powder spreading box is slidably connected to the sliding pressing mechanisms and is pressed against the working platform under the action of the sliding pressing mechanisms.

[0006] Preferably, the sliding pressing mechanism includes a pressing plate. Both ends of the pressing plate are connected to the bases on both sides of the working platform through first and second adjusting members. The first and second adjusting members can drive the two ends of the pressing plate to move up and down, so as to adjust the height of the pressing plate.

[0007] Preferably, both ends of the powder spreading box have ear seats. Elastic members are fixed on the ear seats. Wheels are fixed on the tops of the elastic members through wheel frames. The tops of the wheels are in contact with the pressing plate and are pressed down.

[0008] Preferably, the elastic member is a spring telescopic rod, and the wheel is a universal wheel or a ball.

[0009] Preferably, the first adjusting member is a long threaded rod. After passing through the pressing plate, it is screwed onto the bases on both sides of the working platform. The second adjusting member is a nut.

[0010] Preferably, the driving mechanism is connected to a floating fixing seat. The floating fixing seat includes a fixing seat. A floating seat is elastically connected to the fixing seat. The driving mechanism is fixedly connected to the floating seat.

[0011] Preferably, through holes are opened on the floating seat. After a bolt passes through the through holes, it is tightened on the fixing seat. A second elastic member is arranged between the lower surface of the floating seat and the fixing seat.

[0012] Preferably, through holes are opened on the floating seat. After a bolt passes through the through holes, it is tightened on the fixing seat. A second elastic member is arranged between the lower surface of the floating seat and the fixing seat. A second elastic member is arranged between the nut of the bolt and the upper surface of the floating seat.

[0013] Preferably, the pressing plate is in an arc shape with a lower middle part and higher sides.

[0014] Preferably, both ends of the working platform in the sliding direction of the powder spreading box are open structures. A waste powder recovery box is arranged at the bottom of the opening. The top surface of the waste powder recovery box is a filter plate, and a vibration mechanism is arranged on the filter plate. The width of the waste powder recovery box is greater than that of the working platform, and the height is lower than that of the working platform. The edge position extends under the working platform.

[0015] Through the above technical solutions, the present invention sets a sliding pressing mechanism, which applies a downward pressure to the powder spreading box throughout the process of sliding and spreading powder, presses the powder spreading box tightly on the workbench, reduces the gap between the two, and thus greatly reduces powder leakage. It not only avoids the occurrence of the "padding" phenomenon, improves the processing accuracy, but also avoids dust pollution. By arranging the driving mechanism on the sliding pressing mechanism, the pressing effect of the powder spreading box is further improved, ensuring that the sliding pressing mechanism can fully play its role. In addition, the sliding pressing mechanism provides "elasticity" in the vertical direction for the powder spreading box. When encountering particle clusters or hard bumps in the powder, the spring can be compressed upward to cross the particle cluster, avoiding direct collision and severe friction. Description of the Drawings

[0016] Figure 1 is a schematic diagram of the overall structure of the device; Figure 2 is a schematic diagram of the bottom structure of the device; Figure 3 is Figure 1 a partial enlarged view of A in Figure 4 is an enlarged view of the powder spreading box of the device; Figure 5 is Figure 1 a partial enlarged view of B in In the figure, 1 - sliding pressing mechanism, 11 - pressing plate, 12 - boss, 13 - first adjusting member, 14 - second adjusting member, 15 - elastic member, 16 - wheel frame, 17 - wheel; 2 - powder spreading box, 21 - powder spreading box body, 22 - powder spreading box cover, 23 - ear seat, 24 - powder supply hole; 3 - driving mechanism, 4 - working platform, 41 - rear area, 42 - front area, 5 - forming platform, 6 - waste powder recovery box, 61 - filter plate, 7 - floating fixing seat, 71 - fixing seat, 72 - floating seat, 73 - bolt, 74 - second elastic member; 8 - lifting mechanism, 81 - lifting driving device, 82 - lifting mechanism base, 9 - leg, 10 - forming cavity. Detailed Embodiments

[0017] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0018] As Figures 1-5 shown, a selective laser melting additive manufacturing device provided by the present invention includes a working platform 4. Above the working platform 4, there is a powder feeding nozzle and a forming laser head (which belongs to the prior art and is not shown in the figure). A space is left in the middle position of the working platform 4 for the forming platform 5 to pass through. The forming platform 5 is placed inside the forming cavity 10, and its edge is in close contact with the inner wall of the forming cavity 10. A lifting mechanism 8 is provided at the bottom of the forming platform 5 to drive the lifting of the forming platform 5. Specifically, the lifting mechanism 8 includes a lifting driving device 81, which can be selected from mechanical devices such as electric cylinders and gear racks in the prior art that can achieve linear reciprocating motion and can accurately control the stroke. The lifting driving device 81 is installed on the ground or other positions through the lifting mechanism base 82. A powder spreading box 2 is arranged on the working platform 4. As Figure 4 shown, the powder spreading box 2 is a rectangular frame structure as a whole. One side of it is connected with a driving mechanism 3. Under the action of the driving mechanism 3, the powder spreading box 2 is driven to slide reciprocally on the working platform 4. To prevent the metal powder stored in the powder spreading box 2 from leaking from the top during the sliding process, a powder spreading box cover 22 is installed on the top of the powder spreading box 2. During use, if the metal powder in the powder spreading box 2 is about to be exhausted, the powder spreading box cover 22 can be opened, and a powder spraying mechanism in the prior art can be used to supplement the metal powder into it. To avoid frequently opening and closing the powder spreading box cover 22 and improve the powder supplement efficiency, a long strip-shaped powder feeding hole 24 can be opened at the central position of the powder spreading box cover 22. When supplementing the metal powder, the powder feeding nozzle is inserted into the powder feeding hole 24, and the powder feeding nozzle is controlled to move along the powder feeding hole 24 and spray powder at the same time, so that the powder spreading box cover 22 does not need to be opened to achieve rapid supplement.

[0019] To prevent the metal powder from leaking from the bottom of the powder spreading box 2 when the powder spreading box 2 slides on the working platform 4, a sliding pressing mechanism 1 is arranged on the working platform 4. During the sliding process of the powder spreading box 2, it is always pressed tightly on the working platform 4 under the action of the sliding pressing mechanism 1, reducing the gap between the powder spreading box 2 and the working platform 4, thereby reducing or even completely avoiding the leakage of metal powder. Specifically, as Figure 3As shown, the sliding clamping mechanism 1 includes a clamping plate 11, which is mounted on the work platform through first and second adjusting members. In this embodiment, the first adjusting member 13 is a long screw and the second adjusting member 14 is a nut. The long screw passes through the clamping plate 11 and is tightened on the work platform 4. The nut cooperates with the long screw to fix the clamping plate 11 at the top position of the long screw. When in use, the height of the clamping plate 11 can be adjusted by loosening the nut and adjusting the extension length of the long screw. It is easy for those skilled in the art to know that in order to achieve the height adjustment of the clamping plate 11, other alternatives can also be used, such as a screw nut structure, a hole and pin matching structure, etc. Correspondingly, the powder box 2 has ear seats 23 at both ends, and an elastic member 15 is fixed on the ear seat 23. The wheel 17 is fixed to the top of the elastic member 15 through the wheel frame 16. Preferably, the elastic member 15 can be a spring telescopic rod, and the wheel 17 can also be a universal wheel or a ball bearing. During operation, the top of wheel 17 contacts pressing plate 11, and the height of pressing plate 11 is adjusted by the first and second adjusting members, so that pressing plate 11 applies a certain downward pressure on wheel 17. The elastic member 15 contracts under pressure and transmits the pressure to powder box 2 through ear seat 23, thereby pressing powder box 2 against work platform 4. The position of first adjusting member 13 should be staggered with the movement trajectory of ear seat 23, wheel 17, wheel frame 16 and other components to avoid collision and interference.

[0020] In addition, since the working platform 4 is divided into the rear area 41, the middle forming area and the front area 42, when the powder box 2 moves to the middle forming area, it participates in the powder forming process and controls the thickness of each layer of powder through the lifting drive device 81. Therefore, the "raising" phenomenon of the powder box 2 should be avoided as much as possible in this area, that is, a large downward pressure should be applied to the powder box 2. When the powder box 2 moves to other areas, the downward pressure can be appropriately reduced to relax the elastic member 15 to a certain extent, thereby extending its service life. To achieve the above effect, the pressing plate 11 is moved along the Figure 1 The sliding direction is designed to be an arc shape with a low center (low in the middle molding area) and high at both ends. When the powder box 2 moves from other areas to the middle molding area, the height of the pressing plate 11 decreases, thereby further compressing the elastic member 15, thereby applying greater pressure to the powder box 2 in this area.

[0021] It should be noted that in the above embodiments, the powder spreading box 2 is fixedly connected to the driving mechanism 3, and the driving mechanism 3 is usually fixed to the ground or other platforms through a common base. At this time, the connection between the powder spreading box 2 and the driving mechanism 3 is a rigid connection, and the connection between the driving mechanism 3 and its base is also a rigid connection. The height of the powder spreading box 2 is rigidly limited, so the gap size between it and the working platform 4 is also rigidly limited. When the sliding pressing mechanism 1 presses down on the powder spreading box 2, the powder spreading box 2 cannot freely descend relative to it. The maximum distance it can descend only depends on the micro-deformation of the driving mechanism 3 and its base. Once the maximum size of this micro-deformation is reached, even if there is still a gap between the powder spreading box 2 and the working platform 4, the powder spreading box 2 cannot continue to descend to eliminate this gap. Therefore, the rigid connection between the powder spreading box 2, the driving mechanism 3 and its base affects the pressing-down effect of the sliding pressing mechanism 1 on the powder spreading box 2 and is not conducive to completely eliminating the gap between the powder spreading box 2 and the working platform 4. Especially as the use time increases and the gap between the powder spreading box 2 and the working platform 4 becomes larger and larger due to continuous friction, the sliding pressing mechanism 1 may completely lose its function. Therefore, to solve this problem and achieve a non-rigid connection between the powder spreading box 2 and the driving mechanism 3 to provide more space for the descent of the powder spreading box 2, the present invention also provides a floating fixed seat 7. Specifically, as Figure 5 shown, the floating fixed seat 7 includes a fixed seat 71, and a floating seat 72 is arranged on the fixed seat 71. The driving mechanism 3 is fixed to the floating seat 72. The floating seat 72 can select a suitable type according to the specific external shape structure of the driving mechanism 3. For example, if the driving mechanism 3 is an electric telescopic rod, according to its columnar external shape, the floating seat 72 can select a structure similar to a clamp. To achieve the floating effect, the floating seat 72 is elastically connected to the fixed seat 71. As Figure 5 shown, through holes are opened on the floating seat 72, and bolts 73 pass through the through holes and are tightened on the fixed seat 71. Second elastic members 74 are arranged between the nuts of the bolts 73 and the upper surface of the floating seat 72, and between the lower surface of the floating seat 72 and the fixed seat 71. The second elastic members 74 can be selected from springs or elastic rubber rings, etc. Through the above structure, the floating seat 72 can not only keep the driving mechanism 3 relatively stable, but also provide a descending space by compressing the second elastic members 74 when the powder spreading box 2 needs to descend. To save costs, the second elastic members 74 can be only arranged between the upper surface of the floating seat 72 and the fixed seat 71. The nuts are in direct contact with the upper surface of the floating seat 72 as long as it does not affect the descent of the floating seat 72. Since the driving mechanism 3 is relatively long and the powder spreading box 2 is located at one end of it, when the powder spreading box 2 descends, one end of the driving mechanism 3 will tilt downward. Therefore, to ensure its stability, in a preferred embodiment, as Figure 1 shown, at certain intervals on each driving mechanism 3, two (or more) floating fixed seats 7 are arranged.

[0022] In addition, due to the cooperation between the sliding pressing mechanism and the floating seat, the powder spreading box has a certain "elasticity" in the vertical direction. When the powder spreading box moves and collides with hard particles or hard powder lumps in the powder, it will compress the spring upward, resulting in a certain degree of sliding, avoiding the hard particles or hard powder lumps, and preventing violent collisions, which helps to improve the service life of the workpiece.

[0023] To facilitate the cleaning of the powder between the powder spreading box 2 and the working platform 4, as Figure 1 , 3 shown, bosses 12 are respectively arranged at both ends of the working platform 4. The top of the boss 12 is a smooth arc shape, and its overall height is greater than the distance from the bottom of the ear seat 23 to the working platform 4. During use, if you want to clean the powder between the powder spreading box 2 and the working platform 4, you can first control the driving mechanism 3 to drive the powder spreading box 2 to move to one end of the working platform 4. When it reaches the position of the boss 12, since its height is higher than that of the ear seat 23, it will push the ear seat 23 upward by a certain distance. The ear seat 23 drives the powder spreading box 2 to move upward, so that a gap appears at the bottom of the powder spreading box 2. At this time, a blowing device or a dust suction device can be used to clean the powder at this place.

[0024] As Figure 1As shown in the figure, the working platform 4 is open at both ends in the sliding direction of the powder spreading box 2. Taking the forming platform 5 as the boundary, the working platform 4 is divided into a front area 42 and a rear area 41. The widths of the front area 42 and the rear area 41 are both greater than the width of the powder spreading box 2, so that the powder spreading box 2 can stay here. Waste powder recovery boxes 6 are arranged at the bottom ends of the front area 42 and the rear area 41 (i.e., the bottom of the open structure) to collect the metal powder leaked during the processing (the waste powder recovery box 6 at the position of the rear area 41 is not shown in the figure). During the working process of the powder spreading box 2, the leaked powder will accumulate on the surface of the working platform 4. The driving mechanism 3 can drive the powder spreading box 2 to move to the edge positions of the front area 42 and the rear area 41, so that the edge of the powder spreading box 2 is roughly flush with the edge of the working platform 4, thereby pushing the leaked powder out of the working platform 4 and falling into the waste powder recovery box 6. In order to improve the powder recovery effect, the width of the waste powder recovery box 6 is greater than that of the working platform 4, the height is lower than that of the working platform 4, and the edge position extends a certain distance below the working platform 4. This can ensure that the powder falling from the working platform 4 can be completely received by the waste powder recovery box 6 and will not scatter to the ground. To prevent the powder in the waste powder recovery box 6 from being directly exposed and blown into the air to pollute the environment, a filter plate 61 structure can be set on the top surface of the waste powder recovery box 6. After the powder falls on the surface of the filter plate 61, it falls into the box body through the sieve holes and will not be directly exposed to the air. To ensure that all the powder on the surface of the filter plate 61 can pass through the sieve holes and fall into the waste powder recovery box 6, a vibration mechanism can be added to the filter plate 61 to form a vibrating screen system. In addition, when a boss 12 is arranged on one side of the waste powder recovery box 6, the functions of the two will interfere. Therefore, a waste powder recovery box 6 can be arranged at one end of the working platform 4 to recover the powder, and a boss 12 can be arranged at the other end for cleaning the bottom of the powder spreading box 2.

[0025] The design of the waste powder recovery box 6 can also facilitate the removal of the formed part. The specific use process is as follows: B1: After the last layer of the part is formed, the driving mechanism 3 drives the powder spreading box 2 to stay in the front area 42 or the rear area 41; B2: Control the forming platform 5 to drive the part and the metal powder that has not participated in the forming to rise until the top surface of the forming platform 5 is flush with the working platform 4; B3: The driving mechanism 3 drives the powder spreading box 2 to move across the forming platform 5 and push the part and the metal powder that has not participated in the forming to the opposite edge of the working platform 4; B4: Under the action of gravity, the part and the metal powder that has not participated in the forming fall onto the filter plate 61. The metal powder falls into the waste powder recovery box 6 through the sieve holes, and the part stays on the filter plate 61 to realize the separation of the part and the powder; B5: Use manual or automatic transportation devices to take away the part; B6: Carry out the forming process of the next part.

[0026] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A selective laser melting additive manufacturing device, comprising a working platform, a laser head and a powder supply nozzle are arranged above the working platform, a forming platform is arranged in the middle of the working platform, the forming platform is located in a forming cavity and is in close contact with the forming cavity, the bottom of the forming platform is connected to a lifting mechanism, a powder spreading box is arranged on the working platform, the powder spreading box is connected to a driving mechanism, and the driving mechanism drives the powder spreading box to reciprocate on the working platform, characterized in that, Sliding pressing mechanisms are provided on both sides of the working platform. The powder spreading box is slidably connected to the sliding pressing mechanisms and is pressed against the working platform under the action of the sliding pressing mechanisms.

2. The selective laser melting additive manufacturing device according to claim 1, wherein, The sliding pressing mechanisms include pressing plates. Both ends of the pressing plates are connected to the bases on both sides of the working platform through the first and second adjusting members. The first and second adjusting members can drive the two ends of the pressing plates to move up and down, thereby adjusting the height of the pressing plates.

3. The selective laser melting additive manufacturing device according to claim 2, wherein, Both ends of the powder spreading box have ear seats. Elastic members are fixed on the ear seats. Wheels are fixed on the tops of the elastic members through wheel frames. The tops of the wheels are in contact with the pressing plates and are pressed down.

4. The selective laser melting additive manufacturing device according to claim 3, characterized in that, The elastic members are spring telescopic rods, and the wheels are universal wheels or balls.

5. The selective laser melting additive manufacturing device according to claim 3, wherein The first adjusting member is a long threaded rod which passes through the pressing plate and is screwed onto the bases on both sides of the working platform. The second adjusting member is a nut.

6. The selective laser melting additive manufacturing device according to claim 1, characterized in that The driving mechanism is connected with a floating fixing seat. The floating fixing seat includes a fixing seat. A floating seat is elastically connected to the fixing seat. The driving mechanism is fixedly connected to the floating seat.

7. The selective laser melting additive manufacturing device according to claim 6, wherein Through holes are formed in the floating seat. Bolts pass through the through holes and are tightened on the fixing seat. A second elastic member is arranged between the lower surface of the floating seat and the fixing seat. A second elastic member is arranged between the nuts of the bolts and the upper surface of the floating seat.

8. The selective laser melting additive manufacturing device according to claim 7, characterized in that, A convex platform is arranged at the end of the working platform. The top of the convex platform is in a smooth arc shape, and its overall height is greater than the distance from the bottom of the ear seat to the working platform.

9. The selective laser melting additive manufacturing device according to claim 2, wherein, The pressing plates are in an arc shape with a lower middle part and higher sides.

10. The selective laser melting additive manufacturing device according to claim 1, characterized in that, The end of the working platform in the sliding direction of the powder spreading box is of an open structure. A waste powder recovery box is arranged at the bottom of the opening. The top surface of the waste powder recovery box is a filter plate. A vibration mechanism is arranged on the filter plate. The width of the waste powder recovery box is greater than that of the working platform, and the height is lower than that of the working platform. The edge position of the waste powder recovery box extends under the working platform.

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