Optimization method for molding defect control process before assembly of electronic information equipment module

Abstract

The present invention relates to the technical field of electronic information equipment module assembly, and provides a method for optimizing the process of controlling molding defects before assembling electronic information equipment modules, including: selecting powder suitable for SLM laser selective melting; establishing an influence relationship model between process parameters and defect rate, optimizing the main process parameters of SLM laser selective melting; and positioning control of SLM printing by parameterized control of printing limit dimensions. The present invention combines technologies such as raw material composition analysis, microscopic morphology analysis, process parameter optimization, and precise printing positioning of limit dimensions for the first time, and proposes a method for optimizing the process of controlling molding defects before assembling electronic information equipment modules. The present invention is technologically advanced, mainly in that it not only meets the exploration of organizational formation rules, but also can obtain the optimal process parameter combination for printing, and can also control the formation of defects by precise positioning of the printing limit dimensions, and the technical advantages are very prominent.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic information equipment module assembly, and in particular to a method for optimizing a molding defect control process before assembling an electronic information equipment module. Background Art

[0002] Metal 3D printing, also known as additive manufacturing technology, uses high-density energy beams such as laser beams, electron beams, and plasma beams as input sources. It is a new manufacturing technology that transforms digital models into physical parts by melting and solidifying metal powder layer by layer. Selective Laser Melting (SLM), which uses AlSi10Mg aluminum alloy as a typical processing material, is an important branch of metal 3D printing. It performs well in terms of strength, precision, and density. Its strength is close to the quality of forgings, its dimensional accuracy reaches 20~50μm, its surface roughness reaches 20~30μm, and its density is close to 100%. The laser selective melting SLM technology, which uses powder bed as its main technical feature, has the characteristics of high dimensional accuracy, good surface quality, and excellent performance of molded parts. It is one of the most promising technologies in the field of rapid prototyping and manufacturing, and is an important preparation method in the field of metal 3D printing. Due to its important scientific and social significance, the research on SLM has become a hot topic at home and abroad, and has made great progress in recent years. SLM laser selective melting uses computer-aided design and manufacturing, based on the principle of "discrete->layering->superposition", and uses high-energy laser beams to directly shape metal powder into dense three-dimensional solid parts. The molding process does not require any tooling or molds, and is not limited by the complexity of the part shape. SLM laser selective melting is widely used in aerospace, automotive, energy and power and other fields. It is an important process method for the manufacturing of complete electronic information equipment and modules.

[0003] The laser selective melting technology SLM is to evenly spread a layer of powder with a thickness of 20~100μm on the substrate. The powder is evenly distributed through a liquid storage tank or hopper next to the work area. A laser beam with a power ranging from 20W to 1kW and a scanning speed of up to 15m / s is usually used. Based on the defined scanning strategy, the powder is selectively melted, the substrate is lowered, another powder layer is applied on top of the existing layer, and the melting process is repeated; the laser directed energy deposition technology is based on a digital model, with a high-energy laser beam as the heat source, and the laser beam is irradiated on the metal substrate to form a molten pool. At the same time, the metal powder is input into the molten pool and melted. The powder is melted in the molten pool. As the molten pool moves, the molten metal solidifies rapidly, and thus repeatedly, point by point and layer by layer, metal parts are formed. In the forming process of the above two technologies, an inert gas (such as argon or nitrogen) is fed into the process chamber to prevent the molten metal from reacting with other gases, especially oxygen. At present, titanium alloy, aluminum alloy, cobalt chromium and stainless steel powders are commonly used in laser forming processes. Compared with laser directed energy deposition technology, laser selective melting has lower forming efficiency, but the surface finish, dimensional tolerance and feature resolution of the formed parts are better than those of the parts made by laser directed energy deposition process. Compared with existing metal forming technologies, the metal laser forming process contains a variety of defects, such as metallurgical defects such as poor fusion and pores, as well as cracks caused by residual stress accumulated during the rapid solidification process unique to this technology. Since fatigue cracks usually start from stress concentrations such as pores and inclusions, the above defects will have a significant impact on the fatigue life of metal parts. In addition, these defects will further promote local corrosion, thereby stimulating fatigue cracking. Fatigue performance is one of the most important properties of alloy metal parts. Metal additive manufacturing parts in aerospace and biomedical applications usually need to operate under complex dynamic load conditions, and inherent laser forming process defects will significantly affect the fatigue performance of these components. Based on this, this paper reviews the typical metal laser forming process and the sources of defect formation, hoping to lay a theoretical foundation for research in this direction. Selective laser melting (SLM) 3D printing can obtain better test pieces by optimizing process parameters. This technology is becoming more and more attractive because it can produce dense and complex metal parts, especially suitable for processing complex curved conformal structures. The process principle is to evenly spread a layer of powder with a thickness of 20~100μm on the substrate, usually using a laser beam with a power of 20W to 1kW and a scanning rate of up to 15m / s. Based on the defined scanning strategy, the powder is selectively melted, the substrate is lowered, another powder layer is applied on top of the existing layer, and the melting is repeated to finally complete the parts processing.

[0004] At present, the research and application focus in the field of metal 3D printing at home and abroad has been on titanium alloy, stainless steel, high temperature alloy and other material systems. In the study of the organization and performance of AlSi10Mg aluminum alloy 3D printing, it was found that the AlSi10Mg alloy formed by laser melting technology has a dense organization, fine grains, and better mechanical properties than parts formed by traditional casting. Aluminum alloys are restricted by material properties such as high thermal conductivity, high reflection, and high surface tension. The interaction between aluminum alloy powder and laser in the 3D printing additive molding process of aluminum alloy materials is complex, the energy fluctuation of laser or electron beam, the inconsistency of powder particle size, and the structural mutation of the parts themselves. The printing process generally requires filling with inert gas or vacuuming the molding chamber, but the concentration of inert gas and the vacuum degree of the vacuum chamber will not be 100%, and it is inevitable that some materials will be oxidized. There are tiny macroscopic defects in the printed samples (comprehensive volume defects such as spheroidization, oxidation, cracks, porosity, lack of elements, etc.), and the molding and processing processes lack the support of basic data. Since 3D printing technology is not affected by the complexity of parts, it has incomparable advantages over traditional casting methods, and does not require mold opening, which is particularly suitable for rapid product verification.

[0005] The main source of spherical or elliptical pores is the residual air in the atmosphere protection chamber during the printing of metal powder and parts. In addition, the energy supplied to the molten pool should also be optimized. Any deviation from the optimal energy may lead to poor fusion or highly unstable molten pool and vaporization. Excessive energy will cause violent convection and significant steam recoil, resulting in jet splashing and instability. The above phenomena will lead to the formation of pores in the molten pool. Since the surface tension of the liquid metal is dominant, the shape of the pores is usually spherical or elliptical. In addition, spherical powder particles show higher density due to enhanced powder fluidity relative to shaped powder particles with the same process parameters. And spherical powder also reduces splashing, so it will reduce the number of defects to a certain extent. In the case of too high energy density, circular / spherical defects are generated on the surface of the part due to the shear force exerted on the liquid surface by surface tension. Long and narrow defects formed by insufficient energy density around unmelted particles perpendicular to the deposition direction.

[0006] Oxide particles are believed to be one of the causes of porosity formation in some alloys, such as AlSi10Mg, during laser forming. These oxide particles may be formed due to oxidation of the evaporated alloy by residual oxygen in the argon atmosphere. More oxide particles were observed on the laser melted surface of the part during the process. The molten aluminum alloy cannot wet the oxides and oxide particles, which inhibits the consolidation of the molten metal. Oxidation of the laser processed metal leads to the formation of metal-ceramic interfaces in the sintering pool, which reduces liquid-solid wettability. The lack of wettability of the solid particles and the underlying matrix can cause balling in various metals. Since the laser forming process is performed in a point-by-point and layer-by-layer manner, the balling effect can lead to the formation of discontinuous tracks, poor line-to-line bonding, porosity, and even delamination. Extremely high scanning speeds can also cause liquid balls to splash, resulting in lack of fusion and defect formation. Balling can also cause the molten material to solidify as a row of droplets instead of a continuous layer.

[0007] In addition, due to improper process parameters such as laser power, scanning speed and scanning spacing, metal laser forming processes have been shown to be feasible, although the resulting tensile strength is usually lower than that of at least one material and unfusion is often visible at the interface. In general, due to insufficient energy, lack of bonding between layers results in LOF defects. LOF defects are areas of unprocessed powder, mainly appearing between layers or laser tracks, with sharp edges. Typically, large LOF defects contain unmelted or partially melted particles. Cracks may also occur during the process. In the case of excessive energy density, circular / spherical defects will be generated on the surface due to shear forces exerted on the liquid surface by surface tension. Elongated narrow defects formed by insufficient energy density around unmelted particles perpendicular to the deposition direction. Since the process of laser selective melting is carried out in a point-by-point and layer-by-layer manner, the spheroidization effect may lead to the formation of discontinuous tracks, poor line-to-line bonding, porosity and even delamination. During the printing process, due to the residual air in the atmosphere protection chamber, or the energy provided to the molten pool deviating from the optimal value, or improper setting of process parameters such as laser power, scanning speed and scanning spacing, pores may be formed in the molten pool, which in turn causes the occurrence of porosity defects. Another disadvantage of this technology is the high surface roughness and difficulty in controlling dimensional accuracy.

[0008] Therefore, the present invention proposes a process optimization method for controlling molding defects before assembly of electronic information equipment modules. The process optimization method is a combined optimization method, namely: "powder selection and optimization suitable for SLM printing + manufacturing process parameter optimization + parametric control of printing limit size positioning". First, select powder suitable for SLM laser selective melting. Selecting appropriate powder for different application scenarios can reduce the formation of pores; secondly, use the Box-Behnken Design design module in the Design-Expert special optimization design tool to establish an influence relationship model between process parameters and defect rate, and optimize the main process parameters of SLM laser selective melting: laser power, powder layer thickness, scanning spacing, and scanning rate; finally, by parametrically controlling the printing limit size (limit wall thickness, limit aperture, etc.), the SLM printing is positioned to improve printing accuracy and reduce surface roughness, thereby controlling defect formation.

[0009] To this end, the present invention provides a method for optimizing the process of molding defect control before assembly of electronic information equipment modules. The main innovation is to propose a complete set of methods for optimizing the process of molding defect control. This method systematically solves the problem of molding defects before assembly of electronic information equipment modules from the selection of 3D printing powder to the optimization of process parameters and the control of extreme dimensional accuracy under parameter control. Summary of the invention

[0010] In view of the technical characteristics of SLM laser selective melting, the present invention provides a process optimization method for controlling molding defects before assembly of electronic information equipment modules. The process optimization method is a combined optimization method, namely: "powder selection and optimization suitable for SLM printing + manufacturing process parameter optimization + parametric control of printing limit size positioning", which can solve the technical problem of molding defects before assembly of electronic information equipment modules.

[0011] The present invention provides a method for optimizing the process of controlling molding defects before assembly of an electronic information equipment module, comprising the following steps:

[0012] Choose powder suitable for SLM laser selective melting;

[0013] The influence relationship model between process parameters and defect rate was established, and the main process parameters of SLM laser selective melting were optimized;

[0014] The SLM printing is positioned by parameterizing the printing limit size.

[0015] Furthermore, it is necessary to select powder suitable for SLM laser selective melting according to different application scenarios.

[0016] Furthermore, the selected powders need to be analyzed as follows:

[0017] Characterize and analyze the microstructure of the powder;

[0018] The phase composition of the powder is calibrated by X-ray diffraction analysis method;

[0019] The microscopic morphology of the powders was analyzed by scanning electron microscopy and electron backscatter diffraction.

[0020] Furthermore, the main process parameters of the SLM laser selective melting include laser power, powder layer thickness, scanning spacing and scanning rate.

[0021] Furthermore, the response surface methodology is used to establish an influence relationship model between process parameters and defect rate in order to optimize various process parameters.

[0022] Furthermore, the limit dimensions include limit wall thickness and limit pore diameter.

[0023] Furthermore, when controlling the limit wall thickness, the method for positioning control of SLM printing is:

[0024] When controlling the limit wall thickness, the micro-channel printing test of the limit wall thickness is used to analyze the influence of the SLM printing process parameters on the dimensional accuracy and surface roughness of the limit wall thickness, determine the maximum inclination angle placement direction, and the limit printing capacity of the limit wall thickness; use macro deformation, micro surface morphology and roughness observations to obtain the optimal SLM printing process parameters, and use the optimal SLM printing process parameters to perform positioning control on SLM printing.

[0025] Furthermore, when controlling the limit aperture, the method for positioning control of SLM printing is:

[0026] When controlling the limit aperture, firstly, through the printing test research with different apertures, the comprehensive treatment measures of online annealing, strong support constraint and optimization of weak structure with stress concentration in the maximum inclination angle placement direction are determined; secondly, through the micro-channel printing test with different apertures, the influence of SLM printing process parameters on the limit aperture size accuracy and surface roughness is analyzed to determine the limit printing capacity of the limit aperture; the optimal SLM printing process parameters are obtained by using macro deformation, micro surface morphology and roughness observation; the optimal SLM printing process parameters are used to perform positioning control on SLM printing.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. The present invention combines for the first time the technologies of raw material composition analysis, micromorphology analysis, process parameter optimization and extreme size precise printing positioning, and proposes a method for optimizing the process of controlling molding defects before assembly of electronic information equipment modules. The present invention is technologically advanced, mainly in that it not only satisfies the exploration of organizational formation rules, but also can obtain the optimal process parameter combination for printing, and can also control the formation of defects by precisely positioning the extreme size of printing, and the technical advantages are very prominent.

[0029] 2. The present invention can not only realize molding defect control, but also improve printing accuracy, reduce surface roughness, and thus control the formation of defects from the source.

[0030] 3. The present invention is particularly suitable for a new generation of electronic information equipment - a multifunctional radio frequency skin antenna, which can significantly improve the functional performance of the aircraft, especially the stealth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 It is a flow chart of a method for optimizing a molding defect control process before assembly of an electronic information equipment module in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0035] Example

[0036] like Figure 1 As shown, this embodiment proposes a method for optimizing the process of controlling molding defects before assembly of an electronic information equipment module, comprising the following steps:

[0037] First, for different application scenarios, when selecting powder suitable for SLM laser selective melting, it is necessary to determine whether the selected powder has uniform particles and whether smaller pores can be generated when spreading the powder to improve the density after printing. Usually, 3D printed parts of aerospace electronic information equipment modules mainly use AlSi10Mg powder. The microstructure of AlSi10Mg dense samples was characterized and analyzed to obtain the organizational formation law of 3D printing materials; the phase composition of AlSi10Mg dense samples was calibrated by X-ray diffraction analysis method, and it was found that the phase composition of AlSi10Mg dense samples was mainly α-Al matrix and eutectic Si. The phase characteristics were consistent with those of conventional AlSi10Mg castings. Scanning Electron Microscope (SEM) and Electron Back Scatter Diffraction (EBSD) were used to analyze the microscopic morphology, and it was observed that the organization of AlSi10Mg dense samples was divided into gray-based α-Al matrix and white secondary phase eutectic Si; the inside of the molten pool was a fine-grained area, and the overlapping area of ​​adjacent molten pools was a coarse-grained area. Between the "fine-grained area" and the "coarse-grained area", the eutectic Si was in the form of dispersed particles.

[0038] Secondly, the Box-Behnken Design module in the Design-Expert special optimization design tool is used to optimize the main process parameters of SLM laser selective melting, such as "laser power, powder layer thickness, scanning spacing and scanning rate". The main factors affecting the formation of defects include: laser power, powder layer thickness, scanning spacing and scanning rate, etc. Multiple process parameters will have an interactive effect on the formation of defects. Therefore, it is difficult to obtain process parameters with good molding performance through single-factor experiments. It is necessary to use the response surface method (Response Surface Methodology, RSM) to establish an influence relationship model between process parameters and defect rate in order to optimize multiple process parameters. That is, a global approximation with defect rate as the output variable is constructed to replace the real response surface. Generally, a second-order polynomial is used to represent the functional relationship between the input factor and the response surface. The quadratic polynomial equation is:

[0039]

[0040] Where: y is the response value; β (including , , ) is the coefficient calculated by least squares fitting; x (including , ) is the input process parameter, i and j are the indexes of the input process parameters, i≠j, and n is the total number of input process parameters. The above formula can be used to obtain the process parameters with the best molding performance. Through experimental design, the optimal response value is obtained, and the optimal combination of process parameters is obtained. For each layer of cladding in the process of printing the test block, the laser power, scanning speed, and scanning spacing are applied to each layer of the cladding layer repeatedly for melting. After laser in-situ remelting, the morphology and roughness of different surfaces of the dense thin-walled test block, the amount of powder adsorbed on the side of the test block is significantly reduced, and the surface roughness is reduced to 15.2μm, a decrease of about 40%.

[0041] Finally, high-precision printing positioning of extreme dimensions. By parameterizing the printing extreme dimensions (extreme wall thickness, extreme aperture, etc.), positioning of SLM printing is controlled, thereby improving printing accuracy, reducing surface roughness, and controlling defect formation. Among them:

[0042] When controlling the limit wall thickness, the micro-channel printing test of the limit wall thickness is carried out to analyze the influence of SLM printing process parameters (including laser power, scanning speed, scanning spacing, printing inclination angle, powder layer thickness, scanning mode, heating temperature, etc.) on the dimensional accuracy and surface roughness of the limit wall thickness, and determine the placement direction of the cold plate with a maximum inclination angle of 38° and the limit printing capacity of the limit wall thickness of 1.6mm; the optimal SLM printing process parameters are obtained by using analysis methods such as macro deformation, micro surface morphology and roughness observation, namely: laser power P=300W; scanning speed V=1600mm / s; scanning spacing S=0.14mm; powder layer thickness Lt=0.04mm; linear grating cross scanning; 120℃ active heating; and the optimal SLM printing process parameters are used to control the positioning of SLM printing.

[0043] When controlling the limit aperture, firstly, through different aperture printing test studies, comprehensive treatment measures such as online annealing, strong support constraint and optimization of weak structures with stress concentration in the placement direction of the cold plate with a maximum inclination angle of 38° are determined; secondly, through micro-channel printing tests with different apertures, the influence of SLM printing process parameters (including laser power, scanning speed, scanning spacing, printing inclination angle, powder layer thickness, scanning mode, heating temperature, etc.) on the limit aperture size accuracy and surface roughness is analyzed, and the limit printing capacity of the limit aperture of 0.6mm is determined; the optimal SLM printing process parameters are obtained by using analytical methods such as macro deformation, micro surface morphology and roughness observation, namely: laser power P=300W; scanning speed V=1600mm / s; scanning spacing S=0.14mm; powder layer thickness Lt=0.04mm; linear grating cross scanning; 120℃ active heating; and the optimal SLM printing process parameters are used to position and control SLM printing.

[0044] It should be noted that there will inevitably be some errors in the Z-axis zeroing of lasers and most printers. If the Z-axis zero point is set too low, the first layer will be thinner than the set layer height; conversely, if the Z-axis zero point is set too high, the first layer will be thicker than the set layer height. In addition, since the exposure time of the bottom layer is usually much longer than that of the ordinary layer, skirt problems will occur in bottom printing. Although the tolerance compensation in the 3D printing preprocessing software can be used to offset this, if the accuracy requirements are very high, it will take some time to adjust the compensation value. In addition, it will be more difficult to disassemble the model when printing with the bottom, and there is a risk of damaging the model. The advantage of bottom printing is that the bottom does not need to be supported, the printed surface is smooth, and no post-processing is required. The above-mentioned problems of bottom printing do not exist in tilted printing. Therefore, it is necessary to optimize and determine the maximum tilt angle placement direction when controlling the printing limit size.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing the process of controlling molding defects before assembly of electronic information equipment modules, characterized in that: The steps include: Select a powder suitable for SLM laser selective melting, the powder is AlSi10Mg powder; the selected powder needs to be analyzed as follows: characterize the microstructure of the powder; calibrate the phase composition of the powder using an X-ray diffraction analysis method; perform electron microscope scanning and electron backscatter diffraction analysis on the microscopic morphology of the powder to determine whether the selected powder has uniform particles and whether pores can be generated when the powder is spread; The influence relationship model between process parameters and defect rate is established, and the main process parameters of SLM laser selective melting are optimized; the main process parameters of SLM laser selective melting include laser power, powder layer thickness, scanning spacing and scanning rate; the influence relationship model between process parameters and defect rate is established by response surface method to optimize multiple process parameters; that is, a global approximation with defect rate as output variable is constructed to replace the real response surface, and the functional relationship between input factors and response surface is expressed by second-order polynomial, and the quadratic polynomial equation is: Where: y is the response value; , , are the coefficients calculated by least squares fitting; , is the input process parameter, i and j are the indexes of the input process parameters, i≠j, and n is the total number of input process parameters; The above formula is used to obtain the process parameters with the best molding performance, and the optimal response value is obtained through experimental design, and the optimal combination of process parameters is obtained; Positioning control of SLM printing is performed by parameterizing the printing limit dimensions; the limit dimensions include the limit wall thickness and the limit aperture; When controlling the limit wall thickness, the method for positioning control of SLM printing is as follows: when controlling the limit wall thickness, through the micro-channel printing test of the limit wall thickness, the influence of SLM printing process parameters on the limit wall thickness dimensional accuracy and surface roughness is analyzed, and the maximum inclination angle of the cold plate at 38° and the limit printing capacity of the limit wall thickness of 1.6mm are determined; the optimal SLM printing process parameters are obtained by using macro deformation, micro surface morphology and roughness observation, namely: laser power P=300W; scanning speed V=1600mm / s; scanning spacing S=0.14mm; powder layer thickness Lt=0.04mm; linear grating cross scanning; 120℃ active heating; using the optimal SLM printing process parameters to position control SLM printing; When controlling the limit aperture, the method for positioning control of SLM printing is as follows: when controlling the limit aperture, firstly, through different aperture printing test studies, determine the comprehensive treatment measures of online annealing, strong support constraint and optimization of weak structure with stress concentration in the maximum inclination angle placement direction; secondly, through micro-channel printing tests with different apertures, analyze the influence of SLM printing process parameters on the limit aperture size accuracy and surface roughness, and determine the limit printing capacity of the limit aperture of 0.6mm; use macro deformation, micro surface morphology and roughness observation to obtain the optimal SLM printing process parameters, namely: laser power P=300W; scanning speed V=1600mm / s; scanning spacing S=0.14mm; powder layer thickness Lt=0.04mm; linear grating cross scanning; 120℃ active heating; use the optimal SLM printing process parameters to position control SLM printing.

2. The method for optimizing the process of controlling molding defects before assembly of electronic information equipment modules according to claim 1, characterized in that: It is necessary to select powder suitable for SLM laser selective melting according to different application scenarios.

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