A method and system for LPBF metal additive manufacturing path planning based on a thermal stress interlayer active release mechanism

Abstract

The application relates to the technical field of metal 3D printing, and discloses an LPBF metal additive manufacturing path planning method and system based on a thermal stress interlayer active release mechanism, which sets a stress release area as a target slice layer in the slice layer contour range of a 3D model; a plurality of partitions achieving the stress release function in the target slice contour layer range are acquired, the scanning path of each partition is planned respectively; laser is controlled to scan each partition according to the corresponding scanning path, and random jumping is performed among the plurality of adjacent partitions until the scanning of all the partitions is completed; the next slice layer is converted as a new target slice layer, a stress release area similar to the original target slice layer is set in the new target slice layer, and the new stress release area and the original stress release area are designed to be interlayerly dislocated; the next slice layer is repeatedly scanned and jumped until the scanning of all the slice layers in the entire 3D model is completed. The application realizes the phased reduction of thermal stress by designing a controllable stress release structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal 3D printing, in particular to a LPBF metal additive manufacturing path planning method and system based on a thermal stress interlayer active release mechanism. BACKGROUND

[0002] In the field of additive manufacturing technology, the laser powder bed fusion (LPBF) process is widely used in high-end manufacturing due to its high precision and complex structure forming advantages. However, the generation and accumulation of thermal stress in this process can cause part deformation, residual stress retention and other problems. The scientific nature of the scanning path directly determines the thermal stress distribution, printing efficiency and part forming quality. Therefore, related optimization techniques have become the core of industry research.

[0003] Although there are currently several related technical solutions, there are still obvious limitations in practical application. For example: ① By dividing the work platform and part slice data into grid regions, randomly selecting regions and scanning along a specific angle to optimize the stress timing; it uses simple rectangular grid division, which cannot provide more uniform heat distribution, and lacks a special stress release mechanism design, relying only on random scanning order to optimize stress travel timing, which cannot achieve stress release; the jump scanning strategy between regions can lead to uneven heat accumulation. ② Relying on a database and a Gaussian process proxy model, combining finite element analysis and model training to optimize 3D printing paths and reduce part deformation. It relies on complex finite element analysis and model training, which has high computational cost; it lacks a physical level stress release design and relies entirely on algorithm optimization; the grid division is fixed and does not consider the rotation changes between multiple layers; the path planning lacks a jump mechanism. ③ For high-melting-point thin-walled parts, the scanning line is segmented and scanned in a preset interval order to adapt to the material forming characteristics. Although it uses segmented scanning, it does not have a clear stress release structure design; the division and order of scanning segments mainly consider temperature gradients rather than systematic stress management.

[0004] In summary, in current LPBF metal additive manufacturing, passive uniformization of thermal stress distribution is achieved only by scanning order optimization, which cannot achieve active reduction of thermal stress, leading to stress concentration in the edge area causing warping deformation, multiple layers of fixed partition boundaries forming a penetrating stress concentration line, and Z-direction stress accumulation leading to structural failure risk. These problems directly restrict the further promotion and application of the LPBF process in high-precision and high-reliability part manufacturing. SUMMARY

[0005] The present application provides a LPBF metal additive manufacturing path planning method and system based on a thermal stress interlayer active release mechanism, which achieves phased reduction of thermal stress by designing a controllable stress release structure.

[0006] The application provides a LPBF metal additive manufacturing path planning method based on a thermal stress interlayer active release mechanism, comprising:

[0007] S1, one or more stress release areas are set in the profile range of a slice layer of a 3D model, and the stress release areas are target slice layers; wherein the stress release areas are weak scanning areas or non-scanning areas;

[0008] S2, a plurality of partitions divided by the stress release areas on the profile range of the target slice layer are obtained, and a scanning path is planned for each partition respectively;

[0009] S3, laser is controlled to scan each partition according to the corresponding scanning path, and after the scanning of a target partition is completed, an adjacent partition of the target partition is taken as a new target partition for scanning, until the scanning of all partitions of the target slice layer is completed;

[0010] S4, a next slice layer of the 3D model is converted and taken as a new target slice layer, and stress release areas similar to the original target slice layer are set in the new target slice layer, and the new stress release areas are designed to be staggered with the original stress release areas;

[0011] S5, steps S2-S4 are repeated until the scanning of all slice layers in the entire 3D model is completed.

[0012] Further, in the scanning of the stress release areas, the laser energy density adopted is 0-40% of the ordinary laser energy density, and the ordinary laser energy density is the laser energy density for scanning a plurality of partitions;

[0013] When the laser energy density is 0% of the ordinary laser energy density, the stress release area is a non-scanning area; when the laser energy density is any value in the remaining values, the stress release area is a weak scanning area.

[0014] Further, the stress release area is 5-15% of the total area of the target slice layer.

[0015] Further, the stress release area is set to be in a joint type, a cavity type or a polygon boundary type;

[0016] The joint type is to set a continuous joint strip with a certain width at the boundary of each partition, that is, the profile range of the target slice layer is divided into a plurality of partitions by a line segment with a certain width and continuity;

[0017] The cavity type is to set a circular or polygonal non-scanning area as a cavity in each partition after obtaining a plurality of partitions;

[0018] The polygon boundary mode is to divide the target slice layer contour range into any number of polygons, and the edges of the polygons are used as the stress release area.

[0019] Further, in the target slice layer, each partition forms an independent area, and each partition has the same shape, or each partition has the same area.

[0020] Further, the stress release area in the target slice layer is used as a target stress release area, and the stress release area in the slice layer adjacent to the target slice layer is used as an adjacent stress release area, and the target stress release area is rotated by a set angle based on the center point of the target slice layer to obtain the adjacent stress release area.

[0021] Further, in the 3D model, the rotation angle of the stress release area between every two slice layers is randomly changed.

[0022] Further, the stress release area in the target slice layer is used as a target stress release area, and the stress release area in the slice layer adjacent to the target slice layer is used as an adjacent stress release area, and the target stress release area is translated by a set distance to obtain the adjacent stress release area; wherein the set distance is greater than or equal to 50% of the width of the stress release area.

[0023] Further, the scanning path of each partition in the target slice layer is a random or linear scanning path.

[0024] The application also provides a LPBF metal additive manufacturing path planning system based on a thermal stress interlayer active release mechanism, comprising:

[0025] A setting module is configured to set one or more stress release areas in the contour range of the slice layer of the 3D model, and use the stress release areas as a target slice layer; wherein the stress release areas are weak scanning areas or non-scanning areas.

[0026] An acquisition module is configured to acquire a plurality of partitions divided by the stress release areas in the contour range of the target slice layer, and plan a scanning path for each partition respectively.

[0027] A control module is configured to control a laser to scan each partition according to the corresponding scanning path, and after completing the scanning of a target partition, use the adjacent partition of the target partition as a new target partition for scanning, until the scanning of all partitions of the target slice layer is completed.

[0028] A conversion module is configured to convert to the next slice layer of the 3D model, and use the next slice layer as a new target slice layer, set a similar stress release area in the new target slice layer as the original target slice layer, and use layer interposition design for the new stress release area and the original stress release area.

[0029] A circulation module is configured to repeat steps S2-S4 until scanning of all slice layers in the entire 3D model is completed.

[0030] The present application has the following advantages:

[0031] 1. The active release mechanism of thermal stress is set, i.e. a plurality of non-scanning areas or scanning areas are set in each slice layer of the 3D model, which can reduce the total amount of residual stress by 40-60%, and reduce the edge deformation by 60-80%, so that the flatness of the thin-walled part is ≤0.05mm / m.

[0032] 2. Process compatibility breakthrough is achieved, which is suitable for any scanning mode (vector / point scanning), any partition form (honeycomb / rectangle / custom polygon), and supports multi-material system, and the process window is widened by 30%.

[0033] 3. Efficiency-quality collaborative optimization is achieved, i.e. the multiple partitions formed by a plurality of stress release areas are scanned one by one, which can reduce 15% of the idle time, and the stress release structure ratio is ≤15%, and the un-fusion defect rate is <0.3%. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a flowchart of the LPBF metal additive manufacturing path planning method based on the interlayer active release mechanism of thermal stress of the present application.

[0035] Figure 2 It is a structural schematic diagram of the LPBF metal additive manufacturing path planning system based on the interlayer active release mechanism of thermal stress of the present application.

[0036] The implementation of the present application, functional characteristics and advantages will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0037] It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0038] In the traditional LPBF (Laser Powder Bed Fusion) process, thermal stress is passively homogenized rather than actively released, and the edge deformation caused by residual stress causes interlayer stress superposition, fixed partition boundary forms stress concentration line, and scanning path thermal accumulation is uneven, which makes the printing efficiency low.

[0039] The present application proposes a thermal stress interlayer active release mechanism, pre-setting a controllable stress release structure (including but not limited to a joint, a cavity or a polygon boundary) in the layer, adopting a partition migration scanning strategy to block the thermal stress propagation path, avoiding stress superposition through multi-layer dynamic misregistration design, and finally realizing the phased reduction of thermal stress.

[0040] As shown in Figure 1 The present application provides a LPBF metal additive manufacturing path planning method based on a thermal stress interlayer active release mechanism, comprising:

[0041] S1, one or more stress release areas are set in the slicing layer contour range of the 3D model, and are used as target slicing layers; wherein the stress release area is a weak scanning area or a non-scanning area.

[0042] In the scanning of the stress release area, the laser energy density used is 0-40% of the ordinary laser energy density, and the ordinary laser energy density is the laser energy density of scanning multiple partitions; when the laser energy density is 0% of the ordinary laser energy density, the stress release area is a non-scanning area; when the laser energy density is any value in the remaining values, the stress release area is a weak scanning area. Finally, the stress release area is 5-15% of the total area of the target slicing layer.

[0043] In one embodiment, the stress release area is set as a joint type, a cavity type or a polygon boundary type.

[0044] (1) Joint type: a continuous joint strip of a certain width is set at each partition boundary (such as a hexagonal honeycomb side), that is, the target slicing layer contour range is divided into multiple partitions by a line segment of a certain width and continuity.

[0045] (2) Cavity type: after obtaining multiple partitions, a circular or polygonal non-scanning area is set inside each partition as a cavity, and the cavity area can be used as a further stress release area of the joint type, and the cavity area is not scanned.

[0046] (3) Polygon boundary type: the target slicing layer contour range is divided into any number of polygons (such as rectangles, triangles), and the edges of the polygons are used as the stress release area. Similarly, on the basis of the polygon boundary type, a non-scanning area of the cavity type can also be set to further release stress.

[0047] The above various setting modes of the stress release area can actively block the heat conduction path during scanning, so that the residual stress is released in the layer in stages, rather than being uniformly distributed.

[0048] S2, obtain a plurality of partitions of the target slice layer profile range divided by the stress release area, and plan a scanning path for each partition respectively.

[0049] (1) Set the target slice layer partition

[0050] In the target slice layer, each partition forms an independent area (such as a hexagon, a rectangle, or a triangle).

[0051] (2) Set the adjacent slice layer partition transformation strategy

[0052] a. Rotation: the stress release area in the target slice layer is taken as the target stress release area, and the stress release area in the adjacent slice layer of the target slice layer is taken as the adjacent stress release area. The target stress release area is rotated by a set angle with the center point of the target slice layer to obtain the adjacent stress release area. The rotation angle of the stress release area between every two slice layers changes randomly (i.e., the adjacent slice layer can be rotated clockwise or counterclockwise with the center point as the reference for the target slice layer, and the rotation angle is any angle that ensures the adjacent layer stress release area to be staggered).

[0053] b. Translation: the stress release area in the target slice layer is taken as the target stress release area, and the stress release area in the adjacent slice layer of the target slice layer is taken as the adjacent stress release area. The target stress release area is translated by a set distance to obtain the adjacent stress release area.

[0054] The interlayer staggered design is adopted to avoid stress propagation channels through the interlayer staggered design, and three-dimensional stress reduction is achieved by combining partition migration scanning, and Z-direction stress blocking is achieved.

[0055] S3, control the laser to scan each partition according to the corresponding scanning path, and after completing the scanning of a target partition, take the adjacent partition of the target partition as a new target partition for scanning, until the scanning of all partitions of the target slice layer is completed.

[0056] The scanning path of each partition in the target slice layer is a random or linear scanning path, which can be set by a preset algorithm or manually planned independently.

[0057] Random / linear scanning path is used in the partition of the target slice layer, and after completing a set number of point scanning (laser scanning can be in the form of point scanning or line scanning), it is randomly jumped to the adjacent partition for scanning.

[0058] S4, switch to the next slice layer of the 3D model, and set it as a new target slice layer, set a similar stress release area in the new target slice layer as the original target slice layer, and the new stress release area is designed to be staggered with the original stress release area.

[0059] S5, repeat steps S2-S4 until the scanning of all slice layers in the entire 3D model is completed.

[0060] In the present application, the area ratio of the stress release area is used to control the thermal stress reduction efficiency, the partition migration jump setting is used for thermal accumulation control, and the interlayer staggered setting is used for Z-direction stress blocking effect control; the parameters can be dynamically adjusted according to the material thermal expansion coefficient (such as increasing the joint width of titanium alloy and increasing the jump frequency of high-temperature alloy). For example, high-strength alloy (such as 718) adopts a cavity type stress release structure, thin-walled parts (such as Al alloy) adopt a joint type stress release structure, and large-size components adopt a polygon boundary type stress release structure.

[0061] The present application actively blocks the heat conduction path by pre-setting a non-scanning or weak scanning stress release structure (joint / cavity / boundary), and the stress release structure accounts for 5-15% of the area of the target slice layer, and the position / form can be programmed. After completing the set partition scanning, jump to a randomly selected adjacent partition, and the jump threshold is dynamically matched with the material thermal properties. Multi-layer dynamic staggered control is adopted, the interlayer stress release structure is staggered by ≥50% of the width of the stress release area, and the rotation angle of the adjacent slice layer partition changes randomly. The following technical effects are finally achieved:

[0062] 1. Active release of thermal stress, i.e. setting multiple non-scanning areas or weak scanning areas in each slice layer of the 3D model, which can reduce the total amount of residual stress by 40-60%, while reducing the edge deformation by 60-80%, so that the flatness of thin-walled parts is ≤0.05mm / m.

[0063] 2. Process compatibility breakthrough, suitable for any scanning method (vector / point scanning), any partition form (honeycomb / rectangle / custom polygon), and supporting multi-material systems, with a process window widened by 30%.

[0064] 3. Efficiency-quality collaborative optimization, i.e. scanning multiple partitions formed by multiple stress release areas one by one, which can reduce 15% of the idle time, while the stress release structure accounts for ≤15%, and the un-melted defect rate is <0.3%.

[0065] The present application also provides an LPBF metal additive manufacturing path planning system based on the interlayer active release mechanism of thermal stress, comprising:

[0066] The setting module is configured to set one or more stress release regions in the profile range of a slice layer of the 3D model as a target slice layer, wherein the stress release region is a weak scanning region or a non-scanning region.

[0067] The acquisition module is configured to acquire a plurality of partitions of the target slice layer profile range divided by the stress release region, and plan a scanning path for each partition respectively.

[0068] The control module is configured to control the laser to scan each partition according to the corresponding scanning path, and after completing the scanning of a target partition, the adjacent partition of the target partition is taken as a new target partition for scanning until the scanning of all partitions of the target slice layer is completed.

[0069] The conversion module is configured to convert to a next slice layer of the 3D model and take it as a new target slice layer, set a stress release region similar to the original target slice layer in the new target slice layer, and the new stress release region and the original stress release region are designed with interlayer misregistration.

[0070] The cycle module is configured to repeat steps S2-S4 until the scanning of all slice layers in the entire 3D model is completed.

[0071] Each of the above modules is used to correspondingly execute each step in the LPBF metal additive manufacturing path planning method based on the thermal stress interlayer active release mechanism described above, and the specific implementation mode is described above with reference to the method embodiment, which will not be described here.

[0072] The application can be applied in the turbine blade edge anti-deformation / satellite support lightweight manufacturing in the field of aerospace, can make the residual stress drop by 60%, and avoid Z-direction fracture. In the field of medical devices, the application can be applied in the low-stress printing of porous implants / degradable magnesium alloy supports, which can improve the structural integrity and reduce the post-processing cost by 40%. In the field of energy equipment, the application can be applied in the fuel cell bipolar plate flow channel / zirconium alloy components of nuclear reactors, which can improve corrosion resistance and thermal fatigue life. In the field of precision electronics, the application can be applied in the MEMS copper alloy heat sink / microcavity of radio frequency devices, which can control the size precision within ±0.02mm and realize thermal deformation control. In the field of mold manufacturing, the application can be applied in the profile cooling mold special-shaped flow channel / micro-injection nozzle, which can improve the cooling efficiency by 30% and realize support-free printing. In the emerging field of space manufacturing (microgravity stress control) / metamaterial lattice (acoustic performance customization), the application can adapt to the parameter system and realize cross-scale application.

[0073] It is to be understood that the terminology "including", "comprising", or any other variation thereof, is intended to cover a non-exclusive inclusion such that process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises a... " does not, without more constraints, exclude the presence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0074] The above description is merely the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made according to the content of the present application specification and drawings, or directly or indirectly applied to other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A path planning method for LPBF metal additive manufacturing based on an active interlayer thermal stress release mechanism, characterized in that, include: S1. Set one or more stress relief regions within the outline of the slice layer of the 3D model, and use them as the target slice layer; wherein, the stress relief region is a weak scanning region or a non-scanning region; in scanning the stress relief region, the laser energy density used is 0~40% of the ordinary laser energy density, and the ordinary laser energy density is the laser energy density used to scan multiple partitions; when the laser energy density is 0% of the ordinary laser energy density, the stress relief region is a non-scanning region; when the laser energy density is any of the remaining values, the stress relief region is a weak scanning region; S2. Obtain multiple partitions of the target slice layer contour range divided by the stress relief region, and plan the scanning path for each partition; wherein, the stress relief region is set as a seam type or a polygonal boundary type; The seam type involves setting a continuous seam strip of a set width at each partition boundary, that is, dividing the target slice layer outline into multiple partitions by a continuous line segment of a set width; the polygon boundary type involves dividing the target slice layer outline into an arbitrary number of polygons, with the edges of the polygons serving as the stress relief area. After dividing the target slice layer outline range into multiple partitions using the seam-like or polygonal boundary method, a circular or polygonal non-scanning area is also set inside each partition. S3. Control the laser to scan each partition according to its set scanning path, and after completing the scanning of a target partition, take the adjacent partitions of the target partition as new target partitions for scanning, until the scanning of all partitions of the target slice layer is completed. S4. Switch to the next slice layer of the 3D model and use it as the new target slice layer. Set a stress release area in the new target slice layer that is similar to the original target slice layer, and the new stress release area and the original stress release area adopt an interlayer misalignment design. S5. Repeat steps S2 to S4 until all slice layers in the entire 3D model have been scanned.

2. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 1, characterized in that, The stress relief zone is 5-15% of the total area of ​​the target slice layer.

3. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 1, characterized in that, In the target slice layer, each partition forms an independent region.

4. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 1, characterized in that, The stress relief region in the target slice layer is taken as the target stress relief region, and the stress relief region in the slice layer adjacent to the target slice layer is taken as the adjacent stress relief region. The target stress relief region is rotated by a set angle with the center point of the target slice layer as a reference to obtain the adjacent stress relief region.

5. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 4, characterized in that, In the 3D model, the rotation angle of the stress relief area varies randomly between every two slice layers.

6. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 1, characterized in that, The stress relief region in the target slice layer is taken as the target stress relief region, and the stress relief region in the slice layer adjacent to the target slice layer is taken as the adjacent stress relief region. The target stress relief region is translated by a set distance to obtain the adjacent stress relief region.

7. The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to claim 1, characterized in that, The scan path for each partition in the target slice layer is either random or linear.

8. An LPBF metal additive manufacturing path planning system based on an active interlayer thermal stress release mechanism, characterized in that, The LPBF metal additive manufacturing path planning method based on the active interlayer thermal stress release mechanism according to any one of claims 1 to 7, the system comprising: The setting module is used to set one or more stress relief regions within the outline of a slice layer of a 3D model, and to serve as the target slice layer; wherein, the stress relief region is a weakly scanned region or a non-scanned region; The acquisition module is used to acquire multiple partitions of the stress relief region in relation to the contour range of the target slice layer, and to plan the scanning path for each partition. The control module is used to control the laser to scan each partition according to its corresponding scanning path, and after completing the scanning of a target partition, to scan the adjacent partitions of the target partition as new target partitions, until the scanning of all partitions of the target slice layer is completed. The conversion module is used to convert to the next slice layer of the 3D model and use it as the new target slice layer. The new target slice layer sets a stress relief area similar to the original target slice layer, and the new stress relief area and the original stress relief area adopt an interlayer misalignment design. The loop module is used to repeat steps S2 to S4 until all slice layers in the entire 3D model have been scanned.

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