Powder bed protection airflow forming device
By designing a combined structure of blower guide and suction port in additive manufacturing equipment, a uniform protective airflow is formed, which solves the problem of sintered by-product deposition in large-format additive manufacturing, and improves the quality of part forming and equipment stability.
Patent Information
- Application Number
- CN202421516676.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-29
- Publication Date
- 2025-08-15
- Estimated Expiration
- 2034-06-29
AI Technical Summary
In traditional additive manufacturing equipment, as the forming web size increases, the parabolic deposition of sintered by-products along the flow direction leads to an increase in the thickness of the powder bed, interfering with the distribution of powder laying particle size and slag falls to affect the uniformity of the powder laying layer. The effect of simply increasing the wind speed in the mainstream area is limited, and excessive wind speed leads to blowing powder loss and unstable melt pool.
The design of a blower guide, a first suction port and a second suction port is adopted to protect the airflow from the top of the forming chamber along the center to both sides. The air guide partition and an airflow diversion structure are provided inside the guide member. Combined with the fan and the filter system, a uniform wind field structure is formed to reduce splashing by-products along the process.
It effectively reduces the amount of slag in the additive manufacturing process, improves the quality of parts forming, reduces the instability of the melt pool and the unevenness of the particle size distribution of the powder, and improves the stability and forming effect of the equipment.
Smart Images
Figure CN223222471U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the field of additive manufacturing and relates to a device for forming a protective airflow, in particular to a device for forming a powder bed protective airflow. Background Art
[0002] With the continuous advancement of additive manufacturing technology, the mainstream development direction of selective laser melting (SLM) equipment is characterized by large-format, multi-beam, and strong robustness, aiming to achieve larger-sized parts, higher printing efficiency, and longer equipment stability. The protective atmosphere circulation and filtration system is an indispensable component of traditional SLM equipment. Since the high-power laser melting process on the metal powder bed is accompanied by the generation of byproducts such as metal vapor and metal droplet splashes, these byproducts must be promptly removed to prevent them from drifting and secondary deposition, which can affect the equipment's operation. With the continuous upgrading and development of additive manufacturing equipment, the build format size continues to increase. Traditional build chamber wind field structures face problems such as parabolic deposition of sintering byproducts along the flow direction, increasing the powder bed thickness, interfering with the powder spread particle size distribution, and causing slag to affect the uniformity of the underlying powder layer. Simply increasing the wind speed in the mainstream area of the build format has limited effectiveness in solving the slag problem. Excessive mainstream wind speeds can lead to economic losses due to powder blowing, and sudden changes in turbulence at the blowhole can exacerbate the unstable flow state of the melt in the melt pool, causing sintering defects. Utility Model Content
[0003] In order to solve the above-mentioned technical problems existing in the background technology, the utility model provides a powder bed protection airflow forming device which can effectively reduce the amount of slag falling in the large-format additive manufacturing process and significantly improve the forming quality of parts.
[0004] In order to achieve the above purpose, the utility model adopts the following technical solutions:
[0005] A powder bed protective airflow forming device, characterized in that: the powder bed protective airflow forming device includes a blowing guide, a first air suction port and a second air suction port; the protective airflow is transported to the interior of the forming chamber through the blowing guide arranged in the middle area of the top of the forming chamber; the protective airflow flows from the top of the forming chamber to the forming width and flows along the center of the forming width to both sides of the forming width; along the flow direction of the protective airflow on the forming width, the first air suction port and the second air suction port are relatively arranged and are located on both sides of the forming width.
[0006] The above-mentioned blowing guide member includes an inlet section, a turning section and an outlet section which are connected in sequence; the outlet section extends into the forming chamber from the top of the forming chamber and is connected with the interior of the forming chamber.
[0007] The ratio of the diameter of the inlet section to the diameter of the outlet section is 1:0.95-1.25; the cross section of the inlet section is circular, rectangular or elliptical; the cross section of the outlet section is elliptical, waist-shaped or a combination of long rectangle and semi-elliptical.
[0008] The above-mentioned outlet section is provided with a plurality of air guide baffles; the axial direction of the air guide baffles is parallel to the flow direction of the powder bed protection airflow; the plurality of air guide baffles are symmetrically arranged along the center line of the outlet section.
[0009] The ends of the above-mentioned multiple air guide baffles are not in contact with the bottom of the outlet section.
[0010] Along the direction from the end of the long axis of the outlet section to the center line of the outlet section, the angle between the extension line of the end of the air guide baffle and the bottom of the outlet section gradually increases; the vertical distance between the end of the air guide baffle and the bottom of the outlet section gradually increases; the height of the outlet section is 80-150mm.
[0011] The above-mentioned powder bed protection airflow forming device includes an air suction duct, a filtering system and a fan; the first air suction port and the second air suction port are respectively connected to the filtering system through the air suction duct; the filtering system is connected to the blowing guide and the airflow diversion structure through the fan.
[0012] The above-mentioned powder bed protection airflow forming device also includes a diverter device, a flow ratio control device and a rectifying device; the fan is connected with the flow ratio control device and the airflow diverter structure respectively through the diverter device; the fan is connected with the flow ratio control device through the diverter device; the flow ratio control device is connected with the blowing guide through the rectifying device; the diverter device is a pipeline diverter with adjustable flow; the flow ratio control device is a butterfly valve, a conical valve or a porous plate; the rectifying device is a high-porosity honeycomb plate or a multi-layer high-opening ratio metal damping mesh.
[0013] The above-mentioned powder bed protection airflow forming device also includes an airflow diversion structure and a top blowing cavity that is connected to the airflow diversion structure; the airflow diversion structure is connected to the diversion device; the top blowing cavity is placed on the top plate of the forming chamber except for the blowing guide and the forming chamber protection mirror; the downward pressure airflow evenly distributed on the forming width is blown into the interior of the forming chamber through the airflow diversion structure and the top blowing cavity, and the downward pressure airflow rushes toward the forming width from the top of the forming chamber.
[0014] The thickness of the above-mentioned top blowing cavity is ζ, and the ζ is not less than 30mm.
[0015] The advantages of the utility model are:
[0016] The present invention provides a powder bed protective airflow forming device, comprising a blowing guide, a first air suction port, and a second air suction port; the protective airflow is delivered to the interior of the forming chamber by means of the blowing guide disposed in the middle area of the top of the forming chamber; the protective airflow flows from the top of the forming chamber to the forming width and flows along the center of the forming width to both sides of the forming width; along the flow direction of the protective airflow on the forming width, the first air suction port and the second air suction port are relatively arranged and are located on both sides of the forming width. The powder bed protective airflow forming device provided by the present invention effectively reduces the distance of the sintering by-products flowing to the air suction port, greatly reduces the amount of slag falling from the width compared to the wind field structure of the traditional additive manufacturing equipment, and improves the forming quality of the parts. The present invention effectively reduces the distance that the splashing by-products reach the air suction port during the sintering process of the molten pool of the additive manufacturing equipment, which is only 1 / 2 of the distance that the splashing by-products follow the flow of the traditional additive manufacturing wind field structure; the smaller splashing flow distance significantly improves the uniformity of the powder bed thickness and the consistency of the powder particle size distribution. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a schematic structural diagram of the powder bed protection airflow forming device provided by the present invention;
[0018] Figure 2 It is a structural schematic diagram of three different forms of blowing guide members adopted by the utility model;
[0019] Figure 3 This is a schematic structural diagram of the longitudinal center cross-section of the air blowing guide vent adopted in the present invention;
[0020] Figure 4 This is a comparison chart of the diversion effects using different air blowing guide ports;
[0021] Figure 5 This is a schematic diagram of the wind field structure of the air blowing and guide vents adopted in the present invention;
[0022] Figure 6 This is a schematic structural diagram of the main blowing area formed by using the existing blowing guide port;
[0023] Figure 7 This is a schematic structural diagram of the main blowing area of the blowing guide port provided by the utility model;
[0024] in:
[0025] 1-forming chamber; 2-optical system; 3-powder bed; 4-first air suction port; 5-second air suction port; 6-air suction duct; 7-filtration system; 8-fan; 9-diversion tee; 10-flow ratio control device; 11-rectifier; 12-blowing guide; 121-inlet section; 122-turning section; 123-outlet section; 13-air flow diversion structure; 14-top blowing cavity. DETAILED DESCRIPTION
[0026] See also Figure 1 The utility model provides a powder bed protective airflow forming device, including a blowing guide 12, a first air suction port 4 and a second air suction port 5; the protective airflow is delivered to the inside of the forming chamber 1 through the blowing guide 12 arranged in the middle area of the top of the forming chamber 1; the protective airflow flows from the top of the forming chamber 1 to the forming width and flows along the center of the forming width to both sides of the forming width; along the flow direction of the protective airflow on the forming width, the first air suction port 4 and the second air suction port 5 are arranged opposite to each other and are located on both sides of the forming width.
[0027] See also Figure 3 The blowing guide 12 used in the present invention includes an inlet section 121, a turning section 122 and an outlet section 123 that are sequentially connected; wherein the inlet section 121 is used to connect the rectifier 11, and the turning section 122 is a transition section where the cross-sectional area of the flow channel begins to change; the outlet section 123 extends from the top of the forming chamber 1 into the forming chamber 1; the inlet section 121 is connected to the interior of the forming chamber 1 through the turning section 122 and the outlet section 123; the ratio of the diameter of the inlet section 121 to the diameter of the outlet section 123 is 1:0.95~1.25; the cross section of the inlet section 121 is circular, rectangular or elliptical; the cross section of the outlet section 123 is elliptical, waist-shaped or a combination of long rectangle and semi-elliptical. Figure 2 As can be seen from (a) and (b) in the figure, the flow control components of the top blowing wind field structure of the additive manufacturing equipment have no constraints on the shape of the inlet and outlet. Figure 2 (a) shows a circular inlet and an elliptical outlet. Figure 2 (b) shows a rectangular inlet-long rectangle combined with a semi-elliptical guide outlet. When the downward projection position of the guide outlet in the top blowing main area is located at the center of the forming width, the center points of the guide outlet inlet and outlet cross sections coincide. Figure 2 (c) is the ratio of the cross-sectional area of the inlet and outlet of the blowing guide of the utility model, which is defined as S inlet :S outlet In the range of 1:0.95 to 1:1.25, when the outlet / inlet cross-sectional area ratio is too large, the expansion guide outlet cannot effectively form a fan-shaped mainstream area. Similarly, when the outlet / inlet cross-sectional area ratio is too small, the air flow acceleration of the contraction guide outlet will affect the powder bed quality.
[0028] Continue to see Figure 3 Since the blowing guide 12 is usually placed at the center of the forming range of the equipment, its internal guide structure adopts a central symmetric method. The number of guide plates on one side of the blowing guide 12 is designed to be ≥2. Figure 3The guide plates with 3 on one side are used for illustration. That is, a plurality of air guide baffles are provided on the outlet section 123; the axial direction of the air guide baffles is parallel to the flow direction of the powder bed protective airflow. The plurality of air guide baffles are symmetrically arranged along the center line of the outlet section. The ends of the plurality of air guide baffles are not in contact with the bottom of the outlet section. For example, along the direction from the end of the long axis of the outlet section to the center line of the outlet section, the angle between the extension line of the end of the air guide baffle and the bottom of the outlet section gradually increases; the vertical distance between the end of the air guide baffle and the bottom of the outlet section gradually increases. For example, the air guide baffles used in the present invention include the first air guide baffle, the second air guide baffle, the third air guide baffle and the fourth air guide baffle in sequence along the long axis direction of the outlet section 123; the first air guide baffle and the fourth air guide baffle are symmetrically arranged and have the same structure; the second air guide baffle and the third air guide baffle are symmetrically arranged and have the same structure; the first air guide baffle and the second air guide baffle are not in contact with the bottom of the outlet section 123. The structure of the air guide baffle is an arc shape or a flat folded plate shape. Here we take the flat folded plate as an example to explain the working method of the air guide baffle in detail:
[0029] First, the height h from the turning section 122 to the outlet section 123 of the blowing guide is between 80-150mm. A height that is too small will aggravate the degree of flow separation, and a height that is too large will result in a limited free diffusion stroke of the mainstream area in the working chamber and cannot effectively reduce the flow velocity; the angle α between the side wall of the top blowing port and the plane of the outlet section 123 is related to the overall height size of the working chamber of the equipment and the range of the powder bed and sintering forming width, and can be Figure 5 It can be seen from the figure that the reasonable distribution area of the top blowing mainstream area is that the mainstream area needs to be fully diffused after contacting the powder bed plane in the side view at the center cross-section position, and the diffusion angle of the mainstream area needs to completely cover the forming and sintering area within the angle α between the side wall of the blowing guide and the powder bed plane. This angle corresponds to the angle α between the side wall of the air outlet in the blowing guide and the plane of the outlet section 123; the angle between the extension line of the first air guide baffle and the bottom of the outlet section 123 is β, and the vertical distance between the extension line of the first air guide baffle and the bottom of the outlet section 123 is b1; the angle between the extension line of the second air guide baffle and the bottom of the outlet section 123 is γ, and the vertical distance between the extension line of the second air guide baffle and the bottom of the outlet section 123 is b2; the angle between the side wall of the outlet section 123 and the bottom of the outlet section 123 is α; α≤β≤α+5°, 0≤b1≤20; β≤γ≤β+15°, b1≤b2≤40. In addition, the air guide baffle also includes a fifth air guide baffle and a sixth air guide baffle that is symmetrically arranged with the fifth air guide baffle and has exactly the same structure; the first air guide baffle, the second air guide baffle, the fifth air guide baffle, the sixth air guide baffle, the third air guide baffle and the fourth air guide baffle are arranged in sequence along the long axis direction of the outlet section 123; the distance between the fifth air guide baffle and the center line of the outlet section 123 is c, A / 12≤c≤A / 3; A is the length of the outlet section 123 in the long axis direction.
[0030] The flow control effect of the top blowing mainstream area is limited by simply defining the inlet and outlet cross-sectional shapes, such as Figure 4 As shown in (a), flow separation is very likely to occur near the long axis where the curvature of the inner wall changes greatly, resulting in the outlet velocity distribution being unable to meet the wind farm design requirements. Figure 4 As shown in (b), by arranging air guide baffles inside the blowing guide member, the influence of the inner wall boundary layer flow separation on the fan-shaped mainstream area is weakened.
[0031] See also Figure 6 as well as Figure 7 , showing the comparison of the velocity distribution in the mainstream area of the blowing guide with and without the guide plate in the central cross-section of the working chamber of the additive manufacturing equipment, Figure 6 Flow separation occurs along the inner wall of the long axis of the guide tuyere, resulting in insufficient diffusion in the fan-shaped mainstream area under the influence of the adverse pressure gradient. The overall flow field structure is narrow, the flow is concentrated, and the flow velocity is high, which can easily cause powder blowing. When the laser sintering position is at the edge of the forming area, the metal splash particle byproducts generated by the molten pool outside the fan-shaped mainstream area cannot be effectively absorbed by the suction ports on both sides. Over time, this accumulation can easily lead to contamination of the optical system's protective lenses. Figure 7 With the assistance of the internal guide plates of the blowing guide, the fan-shaped mainstream area effectively covers the entire forming area. The flow field structure fully diffuses the flow velocity to improve the stability of the powder spreading effect, and constructs a uniform flow field above the forming surface from the jet flow to the central area to the air intakes on both sides.
[0032] The powder bed protective airflow generating device also includes an airflow diversion structure 13 and a top blowing cavity 14 intersecting the airflow diversion structure 13. Two sets of top blowing cavities 14 are located within the forming chamber 1 and arranged on either side of the blowing guide 12. The airflow diversion structure 13 and the top blowing cavities 14 blow downward pressure airflow uniformly distributed across the forming surface into the forming chamber 1, with the downward pressure airflow rushing toward the forming surface from the top of the forming chamber. The thickness of the top blowing cavities 14 is ζ, which is no less than 30 mm.
[0033] See also Figure 1The powder bed protection airflow forming device also includes an air suction duct 6, a filter system 7, and a fan 8. The first air suction port 4 and the second air suction port 5 are respectively connected to the filter system 7 through the air suction duct 6. The filter system 7 is connected to the blowing guide 12 and the airflow diversion structure 13 through the fan 8. The powder bed protection airflow forming device also includes a diversion device, a flow ratio control device 10, and a rectification device 11. The fan 8 is respectively connected to the flow ratio control device 10 and the airflow diversion structure 13 through the diversion device. The flow ratio control device 10 is connected to the blowing guide 12 through the rectification device 11. The flow ratio control system composed of the diversion device, the flow ratio control device 10, etc. can achieve precise control of the ratio of the circulation volume flow of the blowing guide 12 to the total circulation volume flow, increase the flow velocity of the downward pressure flow field in the top blowing cavity to improve the lens protection effect, and enhance the negative pressure suction of the first and second air suction ports. It can also stabilize the wind speed at the outlet of the blowing guide to avoid problems such as powder blowing and dust from the powder bed.
[0034] When the powder bed protective airflow forming device provided by the present invention is in use, the optical system 2 of the galvanometer-field mirror-protective mirror structure is fixed on the top of the main working cavity forming chamber 1 of the SLM equipment, and the high-energy-density laser is irradiated on the powder bed 3 located at the bottom of the forming chamber through the optical system 2. During the sintering process, the molten pool produces metal droplets, splashing particles and other by-products that are carried away by the first air suction port 4 and the second air suction port 5 on both sides of the bottom along with the flow of the wind field in the working cavity, and are collected in the air suction duct 6 to the filtration system 7 for centralized filtration treatment. The fan 8 provides a pressure increase for the circulating fluid and maintains the volume flow rate of the overall circulating atmosphere to be stable under the working state. The fan outlet is connected to the inlet of the diversion tee 9 through a pipeline.
[0035] Among them, the diversion tee 9 divides the overall circulation flow into two branches, among which the branch of the upper top blowing mainstream area passes through the flow ratio control device 10 and the rectifier device 11, and then enters the working chamber through the blowing guide 12 to form a fan-shaped jet, which flows to the center of the powder bed 3 at the bottom of the forming chamber. The speed stagnates to form a high-pressure area, thereby forming a wind field structure from the central high-pressure area to the left and right suction ports above the forming width, and removes the by-products such as metal vapor, plasma plume, and metal particles splashed from the molten pool generated during the high-energy density laser sintering process; the other branch, that is, the lens protection gas branch on the right side, enters the top blowing cavity 14 at the top of the working cavity through the airflow diversion structure 13, and forms a uniform downward pressure flow field under the action of the pressure difference resistance of the outlet orifice plate on the lower side of the cavity, isolating the metal smoke and dust floating with the turbulent flow in the working cavity, thereby achieving effective protection of the optical lens.
[0036] In particular, the diversion tee 9 in the flow control system is a specially designed, irregular tee pipe structure. Rough flow control is achieved by adjusting the ratio of the flow cross-sectional area of the branch flow in the upper top blowing main stream area to the flow cross-sectional area of the lens protection branch flow on the right side of the air diversion section. Combined with the resistance adjustment of the flow ratio control device 10, such as a butterfly valve, conical valve, or porous orifice plate, precise control of the ratio of the branch flow rate in the top blowing main stream area to the total circulation flow rate is achieved. The rectifier 11 typically uses a high-porosity honeycomb orifice plate or a multi-layer high-opening ratio metal damping mesh to improve the uniformity of the inlet velocity distribution of the blowing guide 12. The airflow diversion structure 13 in the lens protection air branch evenly inputs the flow into the top blowing cavity 14. Only when the cavity thickness ζ is ≥30 mm can the pressure difference resistance effectively distribute the airflow at the orifice plate outlet, thereby achieving a uniform downward pressure lens protection flow field.
Claims
1. A powder bed protection airflow forming device, characterized by: The powder bed protective airflow forming device comprises a blowing guide (12), a first air suction port (4) and a second air suction port (5); the outlet of the blowing guide (12) is away from the forming surface; the protective airflow is transported into the forming chamber (1) through the blowing guide (12) arranged in the middle area of the top of the forming chamber (1); the protective airflow flows from the top of the forming chamber (1) to the forming surface and flows along the center of the forming surface to both sides of the forming surface; along the flow direction of the protective airflow on the forming surface, the first air suction port (4) and the second air suction port (5) are arranged opposite to each other and are located on both sides of the forming surface; The blowing guide member (12) comprises an inlet section (121), a turning section (122) and an outlet section (123) which are connected in sequence; the outlet section (123) extends from the top of the forming chamber (1) into the forming chamber (1) and is connected to the interior of the forming chamber (1); a plurality of air guide baffles are provided on the outlet section (123); the axial direction of the air guide baffles is parallel to the flow direction of the powder bed protective airflow; and the plurality of air guide baffles are symmetrically arranged along the center line of the outlet section (123).
2. The powder bed protective airflow forming device according to claim 1, characterized in that: The ratio of the diameter of the inlet section (121) to the diameter of the outlet section (123) is 1:0.95-1.25; the cross section of the inlet section (121) is circular, rectangular or elliptical; the cross section of the outlet section (123) is elliptical, waist-shaped or a combination of a long rectangle and a semi-elliptical.
3. The powder bed protective airflow forming device according to claim 2, characterized in that: The ends of the plurality of air guide baffles are not in contact with the bottom of the outlet section (123).
4. The powder bed protective airflow forming device according to claim 3, characterized in that: Along the direction from the end of the long axis of the outlet section (123) to the center line of the outlet section (123), the angle between the extension line of the end of the air guide baffle and the bottom of the outlet section (123) gradually increases; the vertical distance between the end of the air guide baffle and the bottom of the outlet section (123) gradually increases; the height of the outlet section (123) is 80-150 mm.
5. The powder bed protection airflow forming device according to any one of claims 1 to 4, characterized in that: The powder bed protection airflow forming device comprises an air suction duct (6), a filter system (7) and a fan (8); the first air suction port (4) and the second air suction port (5) are respectively connected to the filter system (7) through the air suction duct (6); the filter system (7) is connected to the blowing guide (12) and the airflow diversion structure (13) through the fan (8).
6. The powder bed protective airflow forming device according to claim 5, characterized in that: The powder bed protection airflow forming device further comprises a diverter, a flow ratio control device (10) and a rectifying device (11); the fan (8) is connected to the flow ratio control device (10) through the diverter; the flow ratio control device (10) is connected to the blowing guide (12) through the rectifying device (11); the diverter is a pipeline diverter capable of regulating flow; the flow ratio control device (10) is a butterfly valve, a conical valve or a porous plate; the rectifying device (11) is a high-porosity honeycomb plate or a multi-layer high-opening ratio metal damping mesh.
7. The powder bed protective airflow forming device according to claim 6, characterized in that: The powder bed protective airflow forming device further comprises an airflow diversion structure (13) and a top blowing cavity (14) communicating with the airflow diversion structure (13); the airflow diversion structure (13) is communicated with the diversion device; the top blowing cavity (14) is placed on the top plate of the forming chamber (1) in an area other than the blowing guide (12) and the protective mirror of the forming chamber (1); a downward pressure airflow uniformly distributed on the forming surface is blown into the interior of the forming chamber (1) through the airflow diversion structure (13) and the top blowing cavity (14), and the downward pressure airflow rushes toward the forming surface from the top of the forming chamber.
8. The powder bed protective airflow forming device according to claim 7, characterized in that: The thickness of the top blowing cavity (14) is ζ, which is not less than 30 mm.