Process method for forming aluminum alloy shell through selective laser melting

Abstract

The invention discloses a technological method for forming an aluminum alloy shell through selective laser melting. The technological method comprises the steps that S1, model treatment is conducted; s2, supporting design; s3, carrying out analog simulation; s4, selective laser melting forming; s5, post-processing is carried out; s6, quality detection; according to the method, process simulation analysis is carried out on the additive manufacturing process risk, thermal-structure coupling field simulation calculation is carried out on a component, and deformation, temperature and stress distribution of all stages such as printing, substrate cutting and support removal are analyzed; time and economic cost can be saved, and the method can also be used for exploring process parameters and formulating an optimal process scheme; by means of the reversible deformation compensation technology, the printing problem is effectively reduced, the printing precision is improved, and when the part size precision requirement is high, the technology can assist printing and accurate forming; the method disclosed by the invention can be popularized and applied to other parts formed by selective laser melting, and has wide social benefits and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy shell processing, and in particular relates to a process method for forming an aluminum alloy shell by laser selective melting. Background Art

[0002] Laser selective melting forming technology can directly obtain parts of almost any shape, with the characteristics of high precision, high efficiency and repeatability, density can reach more than 99.9%, dimensional accuracy can reach ±0.05mm, and can realize the integrated rapid forming of complex metal components. However, there are large temperature changes in the laser selective melting forming process, and there are large temperature gradients in the components, so there are very complex internal stress distributions in the components, and the components are prone to deformation and even cracking under the action of stress.

[0003] AlSi10Mg for laser selective melting is an alloy material based on aluminum with silicon, iron, copper, manganese, magnesium, chromium, zinc, titanium and other metals added. It has the characteristics of low density, high thermal conductivity, high specific strength and high wear resistance, and is used for printing thin walls and complex geometric designs. This alloy contains silicon / magnesium, which significantly enhances strength and hardness, and also has good dynamic characteristics. It is widely used in aerospace, automobile and shipbuilding.

[0004] Simufact Additive software can quickly establish additive manufacturing part models, evaluate the feasibility of additive manufacturing of parts, assist users in structural optimization design, material library establishment, process parameter selection and support scheme iteration of additive manufacturing parts, and obtain the best laser selective melting forming scheme through multiple process parameter and support scheme combination and optimization. It can also simulate processes such as heat treatment, hot isostatic pressing, and wire cutting of additively manufactured parts. The additive manufacturing process is accompanied by physical and chemical changes, and a large number of process scheme experiments are often required to verify the rationality of support structures, placement methods, etc. However, in actual production, it is impossible to explore process parameters and formulate the best process scheme through expensive physical tests and trial and error processes. Therefore, the application of virtual simulation technology for additive manufacturing has gradually increased. The simulation analysis of the entire manufacturing process is carried out before actual production. By comparing and analyzing different forming schemes, the results such as deformation, temperature and stress distribution are predicted. For this reason, the present invention proposes a process method for laser selective melting forming of aluminum alloy shells. Summary of the invention

[0005] The object of the present invention is to provide a process for forming an aluminum alloy shell by laser selective melting to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a process method for forming an aluminum alloy shell by laser selective melting, comprising the following steps: S1: model processing: adding a suitable margin to the aluminum alloy shell model, and importing it into Magics software to select a suitable placement angle;

[0007] S2: Support design: Add support to the model described in S1, by combining solid support and non-solid support;

[0008] S3: Simulation: Export the model and support described in S2 separately in .stl format, then import them into Simufact Additive for calculation and simulation, and output the aluminum alloy shell printing model;

[0009] S4: Laser selective melting forming: the model described in S3 is sliced ​​into slices with a thickness of 0.03mm-0.06mm, and the process parameters of the aluminum alloy shell part entity and support are set respectively. The main filling parameters include: powder layer thickness, scanning mode, laser power, scanning rate, scanning spacing, spot compensation, input into the laser selective melting forming equipment, and print layer by layer according to the set process parameters;

[0010] S5: Post-processing: performing annealing heat treatment on the aluminum alloy shell parts described in S4 together with the substrate, removing the support on the parts after wire cutting, and then performing surface treatment;

[0011] S6: Quality inspection: Perform nondestructive inspection and dimensional inspection on the aluminum alloy shell parts described in S5.

[0012] Preferably, the allowance in S1 is divided into machining allowance and grinding allowance. According to the drawing size and roughness requirements of the aluminum alloy shell and the printing results of the characteristic samples of key parts, the surfaces that need to add allowance are identified, and a 2mm allowance is added to the machined surface and a 0.2mm grinding allowance is added to the non-machined surface. The placement angle is determined to be inclined at 40° to 45° through the printing of characteristic samples and the direction of the inner flow channel, and the support is added in an open space as much as possible to facilitate manual removal of the support.

[0013] Preferably, in the support design of S2, when the overhang is less than 0.5mm, no support needs to be added, when the circular hole structure is less than 8mm, no support needs to be added, and when the bridging structure is less than 2mm, no support needs to be added. At the same time, the removal of the support and the flowability of the powder should be considered during the support design; when adding support, the support surface angle is identified as 55°, and when the surface angle is lower than 55°, support needs to be added. A combination of block grid support and solid support is adopted, and the block grid support parameters used are sheet support with no thickness of 4mm, 4mm, and a separation width of 1mm. The solid support parameters used are sheet support with a contour offset of 5mm, a segmentation width of 1.5mm, an interval of 3.5mm, and a thickness of 1mm. The block grid support and the solid support are distributed in the same area and intersect with each other, and the block grid support surrounds the solid support.

[0014] Preferably, the S3 is exported with solid supports, non-solid supports, and part entities respectively, and the triangular faces need to be simplified and stitched when exported in Magics software; then the solid supports, non-solid supports, and part entities are imported into Simufact Additive software, and the geometry is checked; a 3D printing platform is set, basic properties, chemical composition, mechanical properties, rheological curves, and inherent strains of AlSi10Mg are given, a process is created, process parameters are set, voxel grids are divided, and deformation, temperature, and stress distribution in each stage of printing, substrate cutting, support removal, and heat treatment are predicted and analyzed.

[0015] Preferably, in S3, the output geometric model is a pre-compensation of the initial deformed geometric model, and the dimensional accuracy of the aluminum alloy shell is simulated by S3, and the initial geometric shape design is adjusted by inverse deformation compensation to improve the printing accuracy; the inverse deformation compensation is a deformation geometric model obtained according to the input process parameters and the theoretical model, and the calculated deformation amount or deformation deviation value is used to correct the theoretical model, and the original geometric model is reversely compensated by the deformation result or data.

[0016] Preferably, in S4, the optimal process parameters are selected according to the stress distribution cloud map obtained by the calculation and simulation of S3, and the support scheme is optimized and iterated, and a large number of solid supports are added to the outer area for reinforcement and heat transfer optimization. The solid supports are designed as discontinuous sheets along the contour for easy removal.

[0017] Preferably, the powder layer thickness of the aluminum alloy shell in S4 is 30μm-60μm, the scanning mode is strip-shaped, the laser power is 370W-450W, the scanning rate is 1300mm / s-1650mm / s, the scanning interval is 0.09mm-0.12mm, and the spot compensation is 0.1mm; in S5, the annealing system is: (260℃-300℃)±10℃ insulation for 1h±10min, air cooling.

[0018] Preferably, in S5, the substrate must be fixed on the tooling and leveled, the molybdenum wire is adjusted to be in a charged state, and the aluminum alloy shell and the furnace test rod must be closely attached to the substrate during wire cutting to separate the substrate.

[0019] Preferably, in S5, a hammer and a chisel are used to chisel off most of the supports on the part, during which the angle of the part needs to be adjusted. For parts that are difficult to reach with the chisel, a screwdriver or side cutting pliers are used to clamp off the supports; an angle grinder is used to cut and remove the supports on the large plane; in S5, an electric grinding pen is used to grind the support surface of the part, and a grinding gun is used to polish the removed support part to a bright finish, and sandblasting is performed after grinding is completed.

[0020] Preferably, in S6, the aluminum alloy housing part is subjected to nondestructive testing and blue light scanning, and compared with a theoretical model of the part to obtain a qualified part.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a process method for laser selective melting forming an aluminum alloy shell, performs process simulation analysis on the risks of the additive manufacturing process, performs simulation calculation of the thermal-structural coupling field of the component, and analyzes the deformation, temperature and stress distribution in various stages such as printing, substrate cutting, and support removal; it can not only save time and economic costs, but also be used to explore process parameters and formulate the best process plan; through the technology of anti-deformation compensation, it can effectively reduce printing problems and improve printing accuracy. When the part size accuracy requirements are high, this technology can assist in accurate printing; the method described in the present invention can be extended to other parts formed by laser selective melting, and has broad social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the process of the present invention; DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1 , a technical solution is provided: a process method for forming an aluminum alloy shell by laser selective melting, comprising the following steps: S1: model processing: adding a suitable margin to the aluminum alloy shell model, and importing it into Magics software to select a suitable placement angle;

[0025] S2: Support design: Add support to the model described in S1, by combining solid support and non-solid support;

[0026] S3: Simulation: Export the model and support described in S2 separately in .stl format, then import them into Simufact Additive for calculation and simulation, and output the aluminum alloy shell printing model;

[0027] S4: Laser selective melting forming: the model described in S3 is sliced ​​into slices with a thickness of 0.03mm-0.06mm, and the process parameters of the aluminum alloy shell part entity and support are set respectively. The main filling parameters include: powder layer thickness, scanning mode, laser power, scanning rate, scanning spacing, spot compensation, input into the laser selective melting forming equipment, and print layer by layer according to the set process parameters;

[0028] S5: Post-processing: performing annealing heat treatment on the aluminum alloy shell parts described in S4 together with the substrate, removing the support on the parts after wire cutting, and then performing surface treatment;

[0029] S6: Quality inspection: Perform nondestructive inspection and dimensional inspection on the aluminum alloy shell parts described in S5.

[0030] In the present embodiment, preferably, the allowance in S1 is divided into machining allowance and grinding allowance. According to the drawing size and roughness requirements of the aluminum alloy shell and the printing results of the characteristic samples of key parts, the surfaces that need to add allowance are identified, and a 2mm allowance is added to the machined surface and a 0.2mm grinding allowance is added to the non-machined surface. The placement angle is determined to be inclined at 40° to 45° through the printing of characteristic samples and the direction of the inner flow channel, and the support is added in an open space as much as possible to facilitate manual removal of the support.

[0031] In this embodiment, preferably, in the support design of S2, when the overhang is less than 0.5mm, no support is required, when the circular hole structure is less than 8mm, no support is required, and when the bridging structure is less than 2mm, no support is required. At the same time, the removal of the support and the flowability of the powder should be considered during the support design; when adding support, the support surface angle is identified as 55°, and when the surface angle is lower than 55°, support needs to be added. A combination of block grid support and solid support is adopted, and the block grid support parameters used are sheet support with no thickness of 4mm, 4mm, and separation width of 1mm. The solid support parameters used are sheet support with a contour offset of 5mm, a segmentation width of 1.5mm, an interval of 3.5mm, and a thickness of 1mm. The block grid support and the solid support are distributed in the same area and intersect with each other, and the block grid support surrounds the solid support.

[0032] In this embodiment, preferably, the S3 is exported with solid supports, non-solid supports, and part entities respectively, and the triangular faces need to be simplified and stitched when exported in the Magics software; then the solid supports, non-solid supports, and part entities are imported into the Simufact Additive software, and the geometry is checked; a 3D printing platform is set, and AlSi10Mg is given basic properties, chemical composition, mechanical properties, rheological curves, and inherent strains, a process is created, and process parameters are set, the voxel grid is divided, and the deformation, temperature, and stress distribution in each stage of printing, substrate cutting, support removal, and heat treatment are predicted and analyzed.

[0033] In this embodiment, preferably, in S3, the output geometric model is a pre-compensation of the initial deformed geometric model, and the dimensional accuracy of the aluminum alloy shell is simulated by S3, and the initial geometric shape design is adjusted by reverse deformation compensation to improve the printing accuracy; the reverse deformation compensation is a deformation geometric model obtained according to the input process parameters and the theoretical model, and the calculated deformation amount or deformation deviation value is used to correct the theoretical model, and the original geometric model is reversely compensated by the deformation result or data.

[0034] In this embodiment, preferably, in S4, the optimal process parameters are selected according to the stress distribution cloud map obtained by the calculation and simulation of S3, and the support scheme is optimized and iterated, and a large number of solid supports are added to the outer area for reinforcement and heat transfer optimization. The solid supports are designed to be discontinuous sheets along the contour for easy removal.

[0035] In this embodiment, preferably, the powder layer thickness of the aluminum alloy shell in S4 is 30μm-60μm, the scanning mode is strip-shaped, the laser power is 370W-450W, the scanning rate is 1300mm / s-1650mm / s, the scanning interval is 0.09mm-0.12mm, and the spot compensation is 0.1mm; in S5, the annealing system is: (260℃-300℃)±10℃ insulation for 1h±10min, air cooling.

[0036] In this embodiment, preferably, in S5, the substrate must be fixed on the tooling and leveled, the molybdenum wire is adjusted to be in a charged state, and the aluminum alloy shell and the furnace test rod must be separated from the substrate in close contact with the substrate during wire cutting.

[0037] In this embodiment, preferably, in S5, a hammer and a chisel are used to chisel off most of the supports on the parts, during which the angle of the parts needs to be adjusted. For parts that are difficult to reach with the chisel, a screwdriver or side cutting pliers are used to clamp off the supports; an angle grinder is used to cut and remove the supports on the large plane; in S5, an electric grinding pen is used to grind the support surface of the parts, and a grinding gun is used to polish the removed support parts to a bright finish, and sandblasting is performed after grinding is completed.

[0038] In this embodiment, preferably, in S6, the aluminum alloy shell part is subjected to nondestructive testing and blue light scanning, and compared with the theoretical model of the part to obtain a qualified part.

[0039] Although embodiments of the present invention have been shown and described (see the above detailed description for details), it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for forming an aluminum alloy shell by laser selective melting, characterized in that: The following steps are involved: S1: Model processing: add appropriate margin to the aluminum alloy shell model, and import it into Magics software to select the appropriate placement angle; S2: Support design: Add support to the model described in S1, by combining solid support and non-solid support; S3: Simulation: Export the model and support described in S2 separately in .stl format, then import them into SimufactAdditive for calculation and simulation, and output the aluminum alloy shell printing model; S4: Laser selective melting forming: the model described in S3 is sliced ​​into slices with a thickness of 0.03mm-0.06mm, and the process parameters of the aluminum alloy shell part entity and support are set respectively. The main filling parameters include: powder layer thickness, scanning mode, laser power, scanning rate, scanning spacing, spot compensation, input into the laser selective melting forming equipment, and print layer by layer according to the set process parameters; S5: Post-processing: performing annealing heat treatment on the aluminum alloy shell parts described in S4 together with the substrate, removing the support on the parts after wire cutting, and then performing surface treatment; S6: Quality inspection: Perform nondestructive inspection and dimensional inspection on the aluminum alloy shell parts described in S5.

2. The process for forming an aluminum alloy shell by laser selective melting according to claim 1 is characterized in that: The allowance in S1 is divided into machining allowance and grinding allowance. According to the drawing size and roughness requirements of the aluminum alloy shell and the printing results of the key parts of the characteristic samples, the surfaces that need to add allowance are identified, and a 2mm allowance is added to the machined surface and a 0.2mm grinding allowance is added to the non-machined surface. The placement angle is determined to be 40° to 45° through the printing of characteristic samples and the direction of the inner flow channel, and the support is added in an open space as much as possible to facilitate manual removal of the support.

3. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In the support design of S2, when the overhang is less than 0.5 mm, no support is needed; when the circular hole structure is less than 8 mm, no support is needed; when the bridge structure is less than 2 mm, no support is needed; at the same time, the removal of the support and the flowability of the powder should be considered during the support design; When adding support, the support surface angle is identified as 55°. When the surface angle is lower than 55°, support needs to be added. A combination of block grid support and solid support is adopted. The block grid support parameters used are sheet support with no thickness, 4mm X interval, 4mm Y interval, and 1mm separation width. The solid support parameters used are sheet support with a contour offset of 5mm, a segmentation width of 1.5mm, an interval of 3.5mm, and a thickness of 1mm. The block grid support and the solid support are distributed in the same area and intersect with each other, and the block grid support surrounds the solid support.

4. The process for forming an aluminum alloy shell by laser selective melting according to claim 1 is characterized in that: In the S3, solid supports, non-solid supports, and part entities are exported respectively. When exported in Magics software, the triangular faces need to be simplified and stitched; then the solid supports, non-solid supports, and part entities are imported into Simufact Additive software, and the geometry is checked; a 3D printing platform is set up, basic properties, chemical composition, mechanical properties, rheological curves, and inherent strains of AlSi10Mg are given, a process is created, process parameters are set, voxel grids are divided, and deformation, temperature, and stress distribution in each stage of printing, substrate cutting, support removal, and heat treatment are predicted and analyzed.

5. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In said S3, the output geometric model is a geometric model for pre-compensation of the initial deformation, the dimensional accuracy of the aluminum alloy shell is simulated by said S3, and the initial geometric shape design is adjusted by anti-deformation compensation to improve the printing accuracy; The reverse deformation compensation is to obtain a deformation geometric model based on the input process parameters and the theoretical model, and to correct the theoretical model with the calculated deformation amount or deformation deviation value, so as to reversely compensate the original geometric model through the deformation result or data.

6. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In S4, according to the stress distribution cloud map obtained by the calculation and simulation of S3, the optimal process parameters are selected, and the support scheme is optimized and iterated. A large number of solid supports are added to the outer area for reinforcement and heat transfer optimization. The solid supports are designed to be discontinuous sheets along the contour for easy removal.

7. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: The powder layer thickness of the aluminum alloy shell in S4 is 30μm-60μm, the scanning mode is strip-shaped, the laser power is 370W-450W, the scanning rate is 1300mm / s-1650mm / s, the scanning interval is 0.09mm-0.12mm, and the spot compensation is 0.1mm; in S5, the annealing system is: (260℃-300℃)±10℃ insulation for 1h±10min, air cooling.

8. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In S5, the substrate must be fixed on the fixture and leveled, and the molybdenum wire must be adjusted to be in a charged state. During wire cutting, the aluminum alloy shell and the furnace test rod must be closely attached to the substrate to separate them from the substrate.

9. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In the S5, a hammer and a chisel are used to chisel off most of the supports on the parts. During this process, the angle of the parts needs to be adjusted. For parts that are difficult to reach with the chisel, a screwdriver or side cutting pliers are used to clamp off the supports; an angle grinder is used to cut and remove the supports on the large plane; in the S5, an electric grinding pen is used to grind the support surface of the parts, and a grinding gun is used to polish the removed support parts to a bright finish, and sandblasting is performed after grinding is completed.

10. The process for forming an aluminum alloy shell by laser selective melting according to claim 1, characterized in that: In S6, the aluminum alloy housing part is subjected to nondestructive testing and blue light scanning, and compared with the theoretical model of the part to obtain a qualified part.

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