A process for improving the forming quality of overhanging circular hole structures in powder bed fusion forming
By adjusting the laser powder bed process parameters and argon protection, the problems of powder agglomeration and adhesion in suspended circular holes were solved, achieving high-quality suspended circular hole forming under unsupported structures and avoiding additional production cycles and costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGZHOU UNIV
- Filing Date
- 2023-10-19
- Publication Date
- 2026-07-31
AI Technical Summary
During the laser powder bed melting process, powder agglomeration and adhesion in the suspended circular hole structure leads to a decrease in forming quality. Furthermore, the lack of a support structure in post-processing increases the production cycle and cost, while also posing a risk of stress concentration.
By adjusting the process parameters of laser scanning rate, laser power, and scanning line angle, combined with pure argon gas protection, the forming of suspended circular holes under unsupported structures can be achieved. Specific adjustment methods include: for parts with a suspension angle of less than 45°, reducing laser power, increasing scanning rate, and reducing scanning line angle; for parts with a suspension angle of greater than 45°, appropriately reducing laser power, increasing scanning rate, and increasing scanning line angle.
Without increasing the production cycle, it effectively reduces powder adhesion on the top surface of the overhanging round hole, reduces roundness, and improves the forming quality of the overhanging round hole, without requiring additional post-processing.
Smart Images
Figure CN117399641B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of additive manufacturing technology, and in particular to a process method for improving the surface quality of alloy powder melt-formed parts. Background Technology
[0002] Laser powder bed fusion (LPBF) is a method that directly melts metal powder materials without the addition of binders. In this process, the forming cylinder descends, the powder cylinder rises, an automatic powder spreading device spreads the powder, and the laser selectively melts the powder based on a two-dimensional slice model of the part. By repeating these steps, a complete part can be obtained.
[0003] However, machining overhanging circular holes often leads to powder agglomeration and adhesion, affecting the forming quality of the top of the overhanging structure. Furthermore, the closed internal channel structure is difficult to improve the forming quality of the top surface through post-processing methods such as grinding and polishing after machining. In addition, adding support structures increases the production cycle of the part, and post-processing these support structures also increases production time and cost. Moreover, removing the support structures may lead to stress concentration and even the risk of cracking. Summary of the Invention
[0004] The technical problem to be solved by this invention is: how to reduce powder adhesion on the top surface of the suspended circular hole, reduce the roundness of the suspended circular hole, and improve the forming quality of the suspended circular hole structure without increasing the production cycle or without a supporting structure.
[0005] Therefore, the present invention provides a process method for improving the surface quality of alloy powder melt-formed parts, comprising the following steps:
[0006] Step 1: Select the alloy powder to be printed;
[0007] Step 2: Based on the suspension angle of the suspended circular hole, set the process parameters, including the laser scanning rate, laser power, and scanning line angle. The scanning rate should not exceed 2000 mm / s, and the laser power should be in the range of 200-400W.
[0008] Step 3: Introduce pure argon gas and perform the printing.
[0009] Using the above technical solution, even without a support structure, no additional post-processing is required. Different process parameters can be set according to the overhang angle. For parts with an overhang angle less than 45°, the laser power can be appropriately reduced, the scanning rate increased, and the scanning line angle decreased. For parts with an overhang angle greater than 45°, the laser power can be appropriately reduced, the scanning rate increased, and the scanning line angle increased. By adjusting the above process parameters, powder adhesion on the top surface of the overhanging circular hole can be effectively reduced, the roundness of the overhanging circular hole can be reduced, and the forming quality of the overhanging circular hole can be improved.
[0010] Furthermore, in step two, the suspension angle is the angle between the suspension surface of the circular hole part and the substrate.
[0011] Furthermore, in step two, the scanning line angle is the angle between the laser scanning direction and the edge of the overhanging surface contour.
[0012] Furthermore, in step two, the powder layer thickness and the spacing between the molten pools in the laser powder melting bed are set.
[0013] Furthermore, in step two, the thickness of the powder layer is set to 30 μm.
[0014] Furthermore, in step two, the molten pool spacing is set to 60 μm.
[0015] Furthermore, in step one, the selected aluminum alloy powder is Al-Mg alloy powder, Al-Mg-Cu alloy powder, Al-Si alloy powder, Al-Zn alloy powder, or Ti-6Al-4V alloy powder with a particle size in the range of 15-53μm.
[0016] Furthermore, in step three, argon gas with a purity of 99.99% needs to be continuously introduced during the powder bed melting and forming process, and the oxygen content in the cavity during the powder bed melting and forming process is not higher than 0.1%.
[0017] Furthermore, the scanning path of the laser scanning line is a single-channel scan.
[0018] Furthermore, it also includes step four: after printing, cleaning the powder off the surface of the part, removing the part from the substrate by wire cutting, and cleaning the part.
[0019] Furthermore, in step four, the surface of the part is ultrasonically cleaned under alcohol conditions.
[0020] The beneficial effects of this invention are:
[0021] 1. The method of the present invention provides a process for improving the forming quality of a powder bed melt-formed suspended circular hole structure without additional post-processing, under the condition of no support structure.
[0022] 2. For parts with an overhang angle of 45° or less, appropriately reduce the laser power, increase the scanning rate, and decrease the scanning line angle; for parts with an overhang angle greater than 45°, appropriately reduce the laser power, increase the scanning rate, and increase the scanning line angle. By adjusting these process parameters, the roundness of the overhanging hole can be reduced without increasing the production cycle, effectively improving the forming quality of the overhanging hole. Attached Figure Description
[0023] Figure 1 These are microscopic morphology images of the top surface of the formed part under different working conditions with a suspension angle of 60° in Embodiment 1 of the present invention.
[0024] Figure 2 These are test images of the roundness of the formed parts under different working conditions under a 60° suspension angle in Embodiment 1 of the present invention.
[0025] Figure 3 These are microscopic morphology images of the top surface of the formed part under different working conditions with a suspension angle of 30° in Embodiment 2 of the present invention.
[0026] Figure 4 These are test images of the roundness of the formed parts under different working conditions with a suspension angle of 30° in Embodiment 2 of the present invention. Detailed Implementation
[0027] Now, in conjunction with the appendix Figure 1-4 The present invention will be described in further detail below. These accompanying drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.
[0028] Example 1
[0029] A process for improving the surface quality of alloy powder melt-formed parts includes the following steps:
[0030] Step 1: Select the alloy powder for printing. The aluminum alloy powder is Al-Mg alloy powder, Al-Mg-Cu alloy powder, Al-Si alloy powder, Al-Zn alloy powder, or Ti-6Al-4V powder with a particle size in the range of 15-53μm. In this embodiment, the overhang angle of the suspended circular hole is 60°, and the selected aluminum alloy powder is AlSi with a particle size range of 15-53μm. 10 Mg spherical powder, supplied by Concept Laser;
[0031] Step 2: Use Magics software to slice the STL model into layers and set the process parameters for printing. The process parameters include laser power P, laser scanning rate V, and scanning line angle. The unit of laser power is W, the unit of scanning rate is mm / s, and the unit of scanning line angle is °. Import the data into the powder bed fusion molding equipment. The scanning rate does not exceed 2000 mm / s, and the laser power ranges from 240 to 400 W. The equipment used in this embodiment is Concept Laser M2 (Germany), which has a preset powder layer thickness t (in μm) of 30 μm, a melt pool spacing h (in μm) of 60 μm, and a single-pass scanning strategy.
[0032] Step 3: Load the powder into the Concept Laser M2, introduce high-purity argon gas with a purity of 99.99%, and start printing when the oxygen content is below 0.1%.
[0033] Step 4: After the experiment, clean up the powder, remove the part from the substrate by wire cutting, and clean the surface of the part by ultrasonic vibration under alcohol conditions.
[0034] Step 5: Characterize the top surface morphology of the suspended circular hole to determine the surface quality of the formed part. In this embodiment, the roundness of the formed specimen is measured using a Hexagon EAGLE-MD 3020 image measuring instrument (China), and the microstructure of the top surface is observed using a field emission scanning electron microscope (FEIQuanta 250FEG, USA).
[0035] Print parts under different laser power and scanning rate conditions according to the above steps. Set 6 sets of process parameters under different laser power and scanning line angle conditions, namely 240W, 1200mm / s, scanning line angle 0°, 240W, 1200mm / s, scanning line angle 45°, 240W, 1200mm / s, scanning line angle 90°, 360W, 1200mm / s, scanning line angle 0°, 360W, 1200mm / s, scanning line angle 45°, and 360W, 1200mm / s, scanning line angle 90°. Complete the part processing and cleaning according to steps two to five. The quality of the suspended circular hole under different working conditions was observed, and its roundness was measured. The results are as follows: (a) 240W-1200mm / s - scan line angle 0°; (b) 240W-1200mm / s - scan line angle 45°; (c) 240W-1200mm / s - scan line angle 90°; (d) 360W-1200mm / s - scan line angle 0°; (e) 360W-1200mm / s - scan line angle 45°; (f) 360W-1200mm / s - scan line angle 90°. Figure 1 , Figure 2As shown in Table 1, the average roundness values are as follows.
[0036] The results above show that, under the condition that the laser scanning rate and scanning line angle remain unchanged, appropriately reducing the laser power can effectively reduce the powder adhesion phenomenon on the top surface of the suspended circular hole, reduce the roundness of the suspended circular hole, and improve the forming quality of the suspended circular hole; under the condition that the laser power and laser scanning rate remain unchanged, appropriately increasing the scanning line angle can effectively reduce the powder adhesion phenomenon on the top surface of the suspended circular hole, reduce the roundness of the suspended circular hole, and improve the forming quality of the suspended circular hole.
[0037] Example 2
[0038] The difference from Example 1 is that the suspension angle of the suspended circular hole in this example is 30°. Different process parameters are set under the condition of a 30° suspension angle: laser power (W), scanning rate (mm / s), and scanning line angle: (a) 240W-1200mm / s-scanning line angle 0°; (b) 240W-1200mm / s-scanning line angle 45°; (c) 240W-1200mm / s-scanning line angle 90°; (d) 300W-1200mm / s-scanning line angle 0°; (e) 300W-1200mm / s-scanning line angle 45°; (f) 300W-1200mm / s-scanning line angle 90°. The top surface morphology of the suspended circular hole is as follows: Figure 3 , Figure 4 As shown in Table 2, the average roundness data results are presented.
[0039] Table 1 Roundness values of formed parts under 60° overhanging circular hole condition
[0040]
[0041] Table 2 Roundness values of formed parts under 30° hanging hole condition.
[0042]
[0043] The comparison results above show that, under a 60° overhang angle, appropriately reducing the laser power and increasing the scanning line angle can effectively reduce the powder adhesion phenomenon on the top surface of the overhanging circular hole and reduce the roundness; under a 30° overhang angle, appropriately reducing the laser power and decreasing the scanning line angle can effectively reduce the powder adhesion phenomenon on the top surface of the overhanging circular hole and reduce the roundness.
[0044] In summary, without a support structure and without additional post-processing, for parts with an overhang angle of 45° or less, appropriately reduce the laser power, increase the scanning rate, and decrease the scanning line angle; for parts with an overhang angle greater than 45°, appropriately reduce the laser power, increase the scanning rate, and increase the scanning line angle. By adjusting these process parameters, the roundness of the overhanging hole can be reduced without increasing the production cycle, effectively improving the forming quality of the overhanging hole.
[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A process method for improving the forming quality of suspended circular hole structures formed by laser powder bed fusion molding, characterized in that, Includes the following steps: Step 1: Select the alloy powder to be printed; Step 2: Based on the suspension angle of the suspended circular hole, set the laser scanning rate, laser power, and scanning line angle, as follows: When the overhang angle is 60°, the laser power is set to 240W, the scanning line angle is 90°, and the scanning rate is 1200mm / s; When the overhang angle is 30°, the laser power is set to 240W, the scanning line angle is 0°, and the scanning speed is 1200mm / s; Step 3: Introduce argon gas with a purity of 99.99% to perform the printing process; The overhang angle is the angle between the overhang surface of the circular hole part and the substrate, and the scanning line angle is the angle between the laser scanning direction and the edge of the overhang surface contour. Step two also includes setting the powder layer thickness and molten pool spacing during the laser powder bed melting process, with the powder layer thickness being 30 μm and the molten pool spacing being 60 μm.
2. A process for enhancing the quality of a suspended circular hole structure formed by laser powder bed fusion according to claim 1, wherein In step one, the selected alloy powder is Al-Mg alloy powder, Al-Mg-Cu alloy powder, Al-Si alloy powder, Al-Zn alloy powder, or Ti-6Al-4V alloy powder with a particle size in the range of 15-53μm.
3. A process for enhancing the quality of a suspended circular hole structure formed by laser powder bed fusion according to claim 1, wherein In step three, argon gas with a purity of 99.99% needs to be continuously introduced during the laser powder bed melting process, and the oxygen content in the cavity during the laser powder bed melting process is not higher than 0.1%.
4. The process of claim 1, wherein, The scanning path of the laser scanning line is a single-track scan.
5. The process of claim 1, wherein, It also includes step four: after printing, cleaning the powder off the surface of the part, removing the part from the substrate by wire cutting, and cleaning the part.
6. A process for enhancing the quality of a suspended circular hole structure formed by laser powder bed fusion according to claim 5, wherein In step four, the surface of the part is cleaned by ultrasonic vibration under alcohol conditions.