A method for optimizing machining allowances of thin-walled parts

Abstract

This invention relates to a method for optimizing machining allowances in thin-walled parts, belonging to the field of metal processing technology. It solves one of the technical problems of existing thin-walled shell-type parts: high cost and long cycle time in double-sided CNC machining, and low efficiency and high quality risk in single-sided CNC machining combined with manual grinding of the inner cavity. The invention includes the following steps: developing an initial blank model and initial machining plan; obtaining and judging the machining deformation law; correcting the initial blank model; developing a machining optimization plan; and conducting machining deformation simulation and physical verification. Based on the machining deformation law, this invention corrects the initial blank model and optimizes the machining plan accordingly, so that the allowance on the inner cavity surface is optimally distributed according to the deformation. After the pneumatic outer surface is finished, the inner cavity surface can meet the requirements of outer surface dimensions, accuracy, and weight without grinding or machining, reducing the number of machining steps on the inner cavity surface, lowering costs, improving efficiency, and reducing quality risks.

Description

Technical Field

[0001] This invention relates to the field of metal processing technology, and in particular to a method for optimizing the machining allowance of thin-walled parts. Background Technology

[0002] Shell-type parts are typical thin-walled components, often employing a grid structure of ribs and skin. Their outer surfaces, serving as aerodynamic profiles, have strict requirements for surface accuracy, while the internal cavities only limit overall wall thickness or weight, with no specific dimensional requirements. The core challenge in machining these parts is controlling machining deformation and maintaining wall thickness uniformity. Machining deformation is influenced by multiple factors, including clamping, cutting tools, process parameters, and the part's material and structure. Because machining stress accumulates continuously, deformation can only be controlled and reduced, not eliminated. Therefore, the industry typically allows for machining allowances to compensate for deformation.

[0003] Currently, deformation control technology in the field of machining is mature, but existing approaches mostly involve reducing the degree of deformation through various means and setting machining allowances based on the maximum value of deformation in order to avoid problems such as product wall thickness exceeding tolerances, external dimensions, and precision not meeting standards.

[0004] There are two main solutions for processing the skin of thin-walled shell parts, both of which have obvious drawbacks: Solution A involves leaving machining allowances on both sides of the skin thickness (i.e., the outer surface and the inner cavity surface), and forming it by CNC machining on both sides. Although the processing quality is stable, the cost and cycle time are extremely high, and the inner cavity processing requires high-value equipment for long-term operation; Solution B involves CNC machining of the pneumatic outer surface on one side, followed by manual grinding of the inner cavity to reduce weight. Although this eliminates the need for CNC machining of the inner cavity and reduces some costs, the grinding process restricts efficiency, increases labor costs, and the uncontrollable grinding amount can easily lead to wall thickness exceeding tolerances and scrapping. Furthermore, grinding can cause secondary deformation and quality risks such as exceeding tolerances in the pneumatic outer surface. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for optimizing the machining allowance of thin-walled parts, in order to solve one of the technical problems of high cost and long cycle of double-sided CNC machining of thin-walled shell parts, and low efficiency and high quality risk of single-sided CNC machining + manual grinding of the inner cavity. Under the premise of effectively controlling the weight of the parts and the machining quality, the method reduces the machining cost of batch production parts and shortens the manufacturing cycle.

[0006] This invention provides a method for optimizing the machining allowance of thin-walled parts, comprising the following steps:

[0007] S1: Develop the initial blank model and initial machining plan;

[0008] S2: Obtain and determine the deformation pattern during machining, specifically including:

[0009] S21: Simulation analysis is performed based on the initial blank model and initial machining plan;

[0010] S22: Produce test pieces based on the initial blank model and initial processing plan, and perform actual measurements on the test pieces;

[0011] S23: Combining simulation results and actual measurement results, obtain the deformation direction and deformation amount of the part from blank to finished machining: S231: Determine the deformation direction, specifically divided into overall inward deformation, overall outward deformation, and partial inward and partial outward deformation; S232: If it is overall inward deformation, directly run step S3; if it is overall outward deformation or partial inward and partial outward deformation, determine the distribution of deformation amount of the outward deformation part;

[0012] S3: Correct the initial blank model based on the machining deformation law obtained in step S2; if it is an overall inward deformation, set the inner cavity surface allowance to 0-0.5mm and distribute it evenly throughout; otherwise, set the inner cavity surface allowance of the outward deformation part according to the distribution of the deformation amount of the outward deformation part, and set the inner cavity surface allowance of the inward deformation part to 0-0.5mm.

[0013] S4: Develop a processing optimization plan based on the corrected blank model obtained in step S3;

[0014] S5: Based on the processing optimization scheme obtained in step S4, perform processing deformation simulation and physical verification.

[0015] Furthermore, the thin-walled part includes a skin having an aerodynamic outer surface and an inner cavity surface; the thin-walled part is made of aluminum alloy casting.

[0016] Furthermore, in step S1, the specific steps of formulating the initial blank model include setting the allowance for both the outer surface and the inner surface of the thin-walled part to 5mm.

[0017] Furthermore, in step S232, the distribution of deformation of the outwardly deformed part is one of the following four types: overall equal deformation, overall linear deformation, overall nonlinear deformation, or partitioned multi-dimensional deformation.

[0018] Further, in step S3, the inner cavity surface allowance of the outwardly deformed portion is set according to the distribution of the deformation amount as follows: if the distribution is uniform deformation, the inner cavity surface allowance of the portion is set to be uniformly distributed, specifically the deformation amount + 1mm; if the distribution is linear deformation, the inner cavity surface allowance of the portion is set to be linearly gradually distributed, and the inner cavity surface allowance at any position is the deformation amount at that position + 1mm; if the distribution is nonlinear deformation, the inner cavity surface allowance of the portion is set to be uniformly distributed, and the inner cavity surface allowance is the maximum deformation amount of the portion + 1mm; if the distribution is multi-regional deformation, the corresponding inner cavity surface allowance is set according to the distribution of each region.

[0019] Furthermore, step S4 includes S41: process optimization: adding a semi-finishing process based on the initial processing scheme.

[0020] Furthermore, step S4 also includes S42: clamping scheme optimization: based on the initial processing scheme, add anti-vibration fixtures or support fixtures to improve clamping rigidity.

[0021] Furthermore, step S4 also includes S43: Tool selection: Based on the initial machining scheme, the machining tool is replaced, and the diameter of the replaced tool is larger than that of the tool used in the initial machining scheme.

[0022] Furthermore, step S4 also includes: S44: Process parameter optimization: Based on the initial machining scheme, reduce the feed rate and depth of cut, and reduce the cutting speed.

[0023] Further, step S5 includes: S51: Based on the processing optimization scheme, determine new simulation parameters, perform processing deformation simulation through software, and obtain simulation results; at the same time, produce new test pieces, process them according to the processing optimization scheme, and measure the wall thickness and weight of the test pieces.

[0024] Furthermore, step S5 also includes: S52: making a comprehensive judgment based on the simulation results and the physical verification: if the wall thickness and weight of the test piece meet the expected values, then the processing optimization scheme is solidified to form a solidified processing scheme; if the indicators do not meet the expected values, then the distribution of the allowance on the inner cavity surface is locally corrected, and then steps S4 to S5 are repeated until all indicators meet the requirements to form the final solidification scheme.

[0025] Furthermore, the local correction of the inner cavity surface allowance distribution specifically involves: if the wall thickness of a region is less than the expected wall thickness, then the inner cavity surface allowance of that region is increased by 0.1 mm; if the weight is greater than the expected weight, then the overall inner cavity surface allowance is decreased by 0.1 mm.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] (1) Significantly shorten the manufacturing cycle: This invention breaks away from the conventional approach of reducing the machining allowance by minimizing the deformation amount in the prior art, thereby reducing the weight of the parts. Instead, it utilizes the machining deformation law of the parts to optimize the arrangement of the allowance on the inner cavity surface of the blank model. This eliminates the need for CNC machining or manual grinding of the inner cavity to reduce weight, directly saving the entire manufacturing cycle of the inner cavity features and significantly improving production efficiency.

[0028] (2) Lower manufacturing cost and better economic efficiency: On the one hand, the allowance of the inner cavity surface of the blank model is optimized and distributed according to the deformation law, with no excess machining allowance, which reduces the manufacturing cost of the blank; on the other hand, the internal cavity CNC machining and manual grinding process is eliminated, reducing equipment usage cost and labor cost, and the overall manufacturing cost is significantly reduced, making it suitable for mass production.

[0029] (3) Stable processing quality and high consistency: The present invention uses the method of "simulation software analysis + test piece verification" to obtain the deformation law of the parts, and solidifies the processing scheme by combining simulation and physical verification. The scheme has high reliability and effectively ensures the consistency of product quality. At the same time, it completely avoids the quality risks such as wall thickness deviation and aerodynamic surface secondary deformation deviation caused by the existing manual grinding process, and improves the product qualification rate.

[0030] (4) Wide range of applications and strong practicality: This invention is applicable to various thin-walled shell parts with skin, especially thin-walled aluminum alloy casting parts; it is applicable to parts with no internal cavity processing requirements, and can also be adapted to parts with internal cavity surface quality or installation feature processing requirements, and has strong practicality and promotion value.

[0031] (5) The present invention first determines the deformation direction, divides the deformation direction into overall inward deformation, overall outward deformation and partial inward and partial outward deformation, and then adopts different correction methods according to different deformation directions, which simplifies the process of optimizing the inner cavity surface allowance, while not affecting the product's processing technology and quality.

[0032] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0033] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0034] Figure 1 This is a schematic flowchart of the machining allowance optimization method for thin-walled parts according to the present invention;

[0035] Figure 2 This is a schematic diagram of the basic structure of a conventional thin-walled shell part in Embodiment 1 of the present invention;

[0036] Figure 3 This is a cross-sectional view of the allowance distribution of the initial blank model of the part in Example 1;

[0037] Figure 4 This is a cross-sectional view of the allowance distribution after the initial blank model of the part in Example 1 has been deformed according to the initial machining plan;

[0038] Figure 5 This is a cross-sectional view of the allowance distribution of the modified blank model of the part in Example 1.

[0039] Figure 6 for Figure 5 A cross-sectional view of the allowance distribution after the modified blank model is deformed according to the machining optimization scheme.

[0040] Figure 7 This is a schematic diagram of the structure of a typical thin-walled cabin component in Embodiment 2 of the present invention, wherein (a) is a front view, (b) is a side view, (c) is a top view, and (d) is a perspective view;

[0041] Figure 8 for Figure 7 A schematic diagram of the clamping scheme for typical thin-walled cabin parts;

[0042] Figure 9 for Figure 7 A top view of a typical thin-walled cabin part after deformation according to the initial machining plan;

[0043] Figure 10 for Figure 7 A schematic diagram of the allowance distribution of the modified blank model of a typical thin-walled cabin part, including the first region of the window;

[0044] Figure 11 for Figure 7 A cross-sectional view of the allowance distribution in the first region, including the window, after machining deformation of a typical thin-walled cabin part according to a machining optimization scheme.

[0045] Figure 12 for Figure 7 A cross-sectional view of the allowance distribution of the second region of a typical thin-walled cabin part in China.

[0046] Figure 13 for Figure 7 A cross-sectional view of the allowance distribution in the second region of a typical thin-walled cabin part after machining deformation according to the machining optimization scheme.

[0047] Figure label:

[0048] 1-Small end frame; 2-Pneumatic profile; 3-Skin; 31-Pneumatic profile allowance before machining; 32-Inner cavity surface allowance before machining; 33-Pneumatic profile allowance after machining; 34-Inner cavity surface allowance after machining; 35-First area; 36-Second area; 4-Large end frame; 5-Pressure plate; 6-Part body; 7-Locking mechanism; 8-Chassis; 9-Window. Detailed Implementation

[0049] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0050] Example 1

[0051] To address the technical problems of high cost and long cycle time in double-sided CNC machining of thin-walled shell parts, and low efficiency and high quality risk in single-sided CNC machining plus manual grinding of the inner cavity, this embodiment discloses a method for optimizing the machining allowance of thin-walled parts, which is applicable to aluminum alloy casting thin-walled shell parts with no machining requirements for the inner cavity.

[0052] The basic structure of conventional thin-walled shell parts applicable to this embodiment 1 is as follows: Figure 2 As shown, it includes a small end frame 1, a skin 3, and a large end frame 4, wherein the skin 3 includes an aerodynamic outer surface 2 and an inner cavity surface. It should be noted that this part is only for better illustrating the method of this embodiment and does not constitute a limitation on the technical solution of this invention; other parts with similar structures can also be applied to the method of this embodiment.

[0053] The steps of the machining allowance optimization method for thin-walled parts in this embodiment are as follows: Figure 1 As shown, it specifically includes:

[0054] S1: Develop the initial blank model and initial machining plan.

[0055] Specifically, this includes: S11: Analyzing the material characteristics of the parts: Aluminum alloys have lower strength, better toughness and ductility than titanium alloys, and are more prone to processing deformation.

[0056] S12: Based on the above analysis, formulate the initial blank model and initial machining plan, including:

[0057] (1) Blank condition: An initial machining allowance of 5mm is left on both sides of the skin thickness direction of the part (that is, the allowance 31 of the pneumatic outer surface and the allowance 32 of the inner cavity surface before machining are both set to 5mm), and the distribution is uniformly distributed throughout, such as Figure 3 As shown. This allowance can cover the maximum deformation of the part, ensuring dimensional accuracy and surface quality.

[0058] (2) Process flow: rough machining of pneumatic outer surface + fine machining.

[0059] (3) Clamping method: Cage clamping is adopted to ensure the stability of the parts clamping.

[0060] (4) Tool selection: Select conventional tools for machining aluminum alloys.

[0061] (5) Process parameters: Set the step distance, feed rate, depth of cut, etc. according to industry experience.

[0062] The above (2)-(5) are set by those skilled in the art according to industry practice, and will not be elaborated here.

[0063] S2: Obtain and determine the deformation pattern during machining.

[0064] Specifically, this includes: S21: Based on the initial blank model and initial machining scheme, perform simulation analysis to determine the initial simulation parameters, including machining stress values, stress distribution areas, constraint types and application positions at various parts of the part, boundary conditions, etc.; input the simulation parameters into Deform-3D (cutting process simulation software) and Ansys (machining deformation simulation software) to perform simulation analysis on the initial machining scheme and obtain the deformation trend and deformation amount simulation results of the part.

[0065] S22: Produce test pieces based on the initial blank model determined in step S12, and process them according to the initial processing plan determined in step S12. Measure the deformation of the test pieces to verify the accuracy of the simulation results.

[0066] S23: Combining simulation results and actual measurement results, obtain the deformation direction and deformation amount of the part from blank to finished machining, that is, the deformation area of ​​the part and the distribution map of the deformation value of the corresponding part on the part body, and summarize the machining deformation law.

[0067] For the part in Example 1, the deformation after processing according to the initial processing plan is as follows: Figure 4 As shown, the pneumatic profile allowance 33 is partially removed after processing. Due to the deformation, the remaining allowance layer is larger at the top and smaller at the bottom. That is, the deformation direction of the part is outward, and the distribution trend of the deformation amount is smaller at the top and larger at the bottom.

[0068] In this embodiment, the step of obtaining the machining deformation law is further divided into: S231: Determine the deformation direction, specifically divided into overall inward deformation, overall outward deformation, and partial inward and partial outward deformation; S232: If it is overall inward deformation, then directly run step S3; if it is overall outward deformation or partial inward and partial outward deformation, then determine the distribution of deformation amount of the outward deformation part.

[0069] In this embodiment, the distribution of deformation of the outward deformed part is divided into four types: (1) Overall equal deformation: the deformation of all outward deformed parts of the part is consistent; (2) Overall linear deformation: the deformation of all outward deformed parts of the part is linearly and gradually distributed in one direction (i.e. from one end to the other end, or from one side to the other side); (3) Overall nonlinear deformation: the deformation of each part is nonlinearly distributed, satisfies a certain curve equation, or has no specific pattern; (4) Partitioned multi-variable deformation: the part is divided into two or more regions, each region is one of equal deformation, linear deformation or nonlinear deformation, and the whole is a combination of multiple patterns.

[0070] It should be noted that the deformation law of machining is the result of the combined effect of multiple factors such as the material, structure, and processing plan of the part. Any change in any single factor will lead to a change in the deformation law of machining.

[0071] S3: Correcting the initial blank model based on deformation laws, specifically including:

[0072] S31: A 5mm machining allowance is reserved for the pneumatic profile surface 2 (i.e., the pneumatic profile surface allowance 31 is set to 5mm before machining). Figure 5 As shown, to ensure machining accuracy;

[0073] S32: If the deformation is inward as a whole, the allowance of the inner cavity surface is set to 0-0.5mm and evenly distributed throughout; otherwise, the allowance of the inner cavity surface of the outward deformation part is set according to the distribution of the deformation amount of the outward deformation part, and the allowance of the inner cavity surface of the inward deformation part is set to 0-0.5mm.

[0074] Specifically, the inner cavity surface allowance for the outwardly deformed portion is set according to the distribution of deformation as follows: If the distribution is uniform deformation, the inner cavity surface allowance is set to be uniformly distributed, specifically the deformation amount + 1mm; if the distribution is linear deformation, the inner cavity surface allowance is set to be linearly gradually distributed, and the inner cavity surface allowance at any position is the deformation amount at that position + 1mm; if the distribution is nonlinear deformation, the inner cavity surface allowance is set to be uniformly distributed, and the inner cavity surface allowance is the maximum deformation amount of the portion + 1mm; if the distribution is multi-zone deformation, the corresponding inner cavity surface allowance is set according to the distribution of each region.

[0075] In general, the allowance on the inner cavity surface (i.e., the allowance on the inner cavity surface 32 before machining) is optimized and distributed according to the deformation, following the principle of "small allowance in small deformation areas and large allowance in large deformation areas". The allowance value at each location is 1.0mm larger than the maximum deformation value of the corresponding area, ensuring that the inner cavity does not have a shortage after the part is machined and deformed, and avoiding the wall thickness dimension from exceeding the tolerance.

[0076] In this embodiment, the machining deformation law of the part obtained in step S23 is an overall linear deformation, such as... Figure 4 As shown, the deformation of the part gradually changes linearly from the large end frame 4 to the small end frame 1, with the uppermost part deforming radially outward by 0.5mm and the lowermost part deforming radially outward by 2.5mm, exhibiting a gradual change between 0.5mm and 2.5mm. Therefore, the allowance on the inner cavity surface is corrected to a linear gradual distribution from 1.0mm to 3.5mm from the small end frame 1 to the large end frame 4, as shown. Figure 5 As shown, the allowance at each point on the inner cavity surface is greater than the maximum deformation of the corresponding area.

[0077] In this step, the key is to ensure that the allowance value at each location is slightly greater than the maximum deformation at that location. Since the deformation pattern of each part is different, the distribution of allowance when correcting the blank is also different.

[0078] S33: Calculate the weight of the blank model using the measurement module of commonly used design software (such as UG) to ensure that the part weight index is met.

[0079] S4: Develop a processing optimization plan based on the corrected blank model obtained in step S3.

[0080] Since the allowance on the inner cavity surface of the blank model is significantly reduced compared to the initial design, the overall rigidity of the part is weakened, making it more prone to machining deformation and chatter. Therefore, it is necessary to develop a machining optimization plan based on the modified blank model to solve the problems of machining deformation and chatter caused by the weakened overall rigidity of the part.

[0081] In this embodiment, targeted optimization can be performed from four aspects: process flow, clamping scheme, tool selection, and process parameters, thereby redefining the content of each step. All four aspects can be selected, or only one or a few aspects can be selected.

[0082] Specifically, this includes: S41: Process optimization: Based on the initial processing plan, a semi-finishing process is added, which is processed in multiple layers, first roughing, then semi-finishing, and finally finishing, to gradually release processing stress and reduce deformation.

[0083] For example, if the maximum deformation of the initial blank model after processing using the initial machining scheme is 3.5mm, and the initial blank model is corrected according to step S3, the maximum deformation will increase to 3.6mm if the initial machining scheme is still used, which is detrimental to the forming quality of the part. Through step S41, the deformation of the part can be controlled to reduce the maximum deformation of the part to within 3.5mm, that is, the maximum deformation of the part will not increase due to the weakening of the part's rigidity caused by the reduction of the allowance.

[0084] S42: Clamping scheme optimization: Add anti-vibration fixtures or support fixtures to improve clamping rigidity and reduce part vibration. The specific fixture type shall be set by those skilled in the art according to industry practice.

[0085] S43: Tool Selection: Based on the initial machining plan, replace the machining tool with one of larger diameters than the tool used in the initial plan. This improves tool rigidity and cutting stability. The specific tool type should be selected by those skilled in the art based on industry conventions.

[0086] S44: Process parameter optimization: Reduce feed rate and depth of cut, and lower cutting speed to prevent machining chatter.

[0087] The above steps S41-S44 can be selected simultaneously, or only one or a few of them can be selected.

[0088] S5: Based on the processing optimization scheme obtained in step S4, perform processing deformation simulation and physical verification.

[0089] S51: Based on the proposed processing optimization scheme, determine the new simulation parameters, and use Deform-3D and Ansys software again to perform processing deformation simulation and obtain simulation results; at the same time, produce new test pieces, process them according to the processing optimization scheme, and measure the wall thickness and weight of the test pieces to complete the physical verification.

[0090] S52: Make a comprehensive judgment based on the simulation results and the physical verification: If the wall thickness and weight of the test piece meet the expected values, then solidify the process flow, clamping method, tool selection, process parameters, etc., to form a solidified processing plan; if the indicators do not meet the expected values, then make local corrections to the processing allowance distribution, and then repeat S4 to S5 until all indicators meet the requirements to form the final solidified plan.

[0091] Specifically, the local correction of the machining allowance distribution involves the following steps: if the wall thickness of a region is less than the expected wall thickness, the allowance on the inner cavity surface of that region is increased by 0.1 mm; if the weight is greater than the expected weight, the overall allowance on the inner cavity surface is decreased by 0.1 mm. Ultimately, it is necessary to ensure that the allowance on the inner cavity surface at each location is within the range of (deformation + 0.5 mm) - (deformation + 1.5 mm) for that location.

[0092] This correction method can further optimize the distribution of the allowance on the inner surface of the part, thereby improving the surface quality and consistency of the product.

[0093] S6: Mass production.

[0094] The blanks are manufactured according to the final curing scheme, and the parts are mass-produced. After the parts are finished from blank to final surface finishing, the allowance in all parts of the internal cavity tends to be evenly distributed and is slightly higher than the theoretical value of the parts. Figure 6 As shown, the weight requirements of the parts can be met without manually polishing the inner cavity surface to reduce weight.

[0095] Furthermore, this method is also applicable to thin-walled parts with machining requirements for their internal cavities, such as parts with quality requirements for the internal cavity surface or parts with mounting features that require machining. The specific implementation steps are the same as described above. By adopting the method of this embodiment, the amount of internal cavity machining can be effectively reduced, thus lowering machining costs.

[0096] Compared with existing technologies, the machining allowance optimization method for thin-walled parts provided in this embodiment eliminates the need for CNC machining or manual grinding to reduce weight on the inner cavity surface, directly saving the inner cavity manufacturing process and significantly shortening the production cycle. Simultaneously, because the inner cavity surface allowance is precisely matched with the deformation pattern, there is no excess machining allowance, reducing the cost of the blank and eliminating the inner cavity machining process, resulting in lower overall manufacturing costs. Through physical simulation and physical verification of the solidified process, the solution is reliable, and the product consistency is good, while avoiding part deformation and out-of-tolerance surface issues caused by manual grinding for weight reduction. This method has been successfully applied in multiple products with good results, and its advantages are particularly prominent in aluminum alloy casting parts.

[0097] Example 2

[0098] Another specific embodiment of the present invention, such as Figures 7-13 As shown, a machining allowance optimization method based on the machining allowance optimization method in Example 1 is disclosed for a typical thin-walled cabin part.

[0099] The product involved in this embodiment 2 is a typical thin-walled cabin part. This part is an aluminum alloy cast thin-walled shell part 6, with end frames at both ends and mating mounting holes. Between the two ends is a skin 3, and the skin 3 has two symmetrically distributed through windows 9, such as... Figure 7 As shown.

[0100] The core technical specifications of this part are as follows: the material is ZL114A cast aluminum alloy; the profile of the aerodynamic outer surface 2 is ±0.3mm; there are no dimensional requirements for the inner cavity; the wall thickness tolerance of the skin 3 is 2±0.5mm; the weight of the part is ≤40kg (the theoretical model weight is 33.7kg). The specific steps are as follows:

[0101] S1: Develop the initial blank model and initial machining plan.

[0102] S11: Analysis of the material characteristics of the part: The material is ZL114A cast aluminum alloy;

[0103] The part only has dimensional requirements for the aerodynamic outer surface 2, while there are no dimensional requirements for the inner cavity. Moreover, the weight index is much greater than the theoretical model weight. Therefore, the aerodynamic outer surface is machined according to the theoretical model, and the inner cavity can be higher than the theoretical model while meeting the weight requirements.

[0104] S12: The initial processing plan is as follows:

[0105] (1) Blank condition: The machining allowance on both sides of the thickness of the skin 3 of the casting blank (i.e., the pneumatic outer surface 2 and the inner cavity surface) is set to 5mm, and the machining allowance of the end frames at both ends is set to 3mm.

[0106] (2) Clamping method: such as Figure 8 As shown, the chassis 8 is fixed on the machine tool worktable. The chassis 8 clamps the outer circle of the large end of the part, the pressure plate 5 presses it from the small end of the part, and the locking mechanism 7 connects the pressure plate 5 and the chassis 8, so that the part body 6 is fixed in a "cage".

[0107] (3) Process flow: First, leave a 2mm allowance for rough machining of the pneumatic outer surface (remove 3mm allowance), and then finish machine the pneumatic outer surface to the required position;

[0108] (4) Tool selection: Select conventional tools for machining aluminum alloys;

[0109] (5) Process parameters: step distance 0.7, feed speed 2500mm / min, cutting depth 3mm.

[0110] The above parameters are all set by those skilled in the art based on their experience or common sense, and can be adjusted according to the actual situation.

[0111] S2: Obtain the deformation characteristics of machining.

[0112] S21: Based on the initial processing plan, determine the initial simulation parameters and perform simulation analysis using Deform-3D and Ansys software.

[0113] S22: Produce test pieces for processing verification.

[0114] S23: Combining simulation results and actual measurement results, the machining deformation law of the part is obtained.

[0115] S231: This involves partial inward and partial outward deformation. Specifically, using the horizontal plane as a reference plane, the part is divided into four regions by a central cross: two first regions 35 including the window and two second regions 36 excluding the window. The two first regions 35 deform outward, while the two second regions 36 deform slightly inward, resulting in an overall "elliptical" deformation trend. Figure 9As shown, the black solid line is the outline of the initial blank model, the blue dashed line is the region division line, and the gray dotted line is the outline of the initial blank model after processing by the initial processing scheme.

[0116] S232: The distribution of deformation in the first region 35 is a linear deformation, specifically, the deformation gradually increases from the small end to the large end of the part, and the deformation range is 0.5 to 3 mm.

[0117] S3: Correct the initial blank model based on deformation law.

[0118] The initial blank model was corrected based on the principle that some parts deform inward and others outward, and the outward deformation region undergoes linear deformation as a whole.

[0119] S31: The pneumatic outer surface 2 has a pre-reserved machining allowance of 5mm (i.e., the pneumatic outer surface allowance 31 is set to 5mm before machining), and is evenly distributed.

[0120] S32: The inner cavity surface allowance of the two first regions 35 (i.e., the inner cavity surface allowance 32 before machining) is optimized and distributed according to the deformation. It is set as a gradual value of 1.5~4.0mm from the small end to the large end of the part. The allowance at each location is greater than the maximum deformation of the corresponding region (1.5mm>0.5mm, 4.0mm>3mm). Figure 10 As shown;

[0121] The inner surface allowance of the two second regions 36 (i.e., the inner surface allowance 32 before machining) is set to 0.5mm and evenly distributed, such as... Figure 12 As shown. The second region 36 of the part is deformed inward as a whole. Theoretically, no allowance needs to be left. Leaving a low allowance of 0.5mm can be used to prevent casting defects and improve product quality.

[0122] S33: The weight of the corrected blank model was calculated using the measurement module of the UG model, and the weight was found to be 37.5kg, which meets the requirement of part weight index ≤40kg.

[0123] S4: Develop a processing optimization plan.

[0124] Because the allowance on the inner cavity surface (i.e., the allowance of 32 on the inner cavity surface before machining) is reduced, the overall rigidity of the part becomes weaker, making it prone to machining deformation and chatter. Therefore, the initial machining scheme is optimized as follows:

[0125] S41: Process Flow: Add a semi-finishing step to release machining stress. Adjust the process as follows: first, leave a 3mm allowance for rough machining (remove 2mm), then leave a 1mm allowance for semi-finishing (remove 2mm), and finally finish machining (remove 1mm) to achieve the desired pneumatic profile. Layered machining decomposes a single large cutting amount into multiple layers of small cutting amounts. After each layer of cutting, the stress is rebalanced, reducing stress abrupt changes and minimizing part deformation.

[0126] S42: The clamping scheme remains unchanged;

[0127] S43: The choice of cutting tool remains unchanged;

[0128] S44: Process parameters: Optimize the main machining parameters, reduce the step distance from 0.7 to 0.5, and reduce the feed rate from 2500mm / min to 2100mm / min, in order to solve the problem that when the part allowance becomes smaller, the rigidity weakens, which leads to increased chatter and makes it impossible to complete the machining of the part.

[0129] S5: Based on the processing optimization scheme obtained in step S4, perform processing deformation simulation and physical verification.

[0130] S51: Based on the processing optimization scheme formulated in step S4, determine the new simulation parameters, and use Deform-3D and Ansys software again to perform processing deformation simulation and obtain simulation results; at the same time, produce multiple test pieces, process them according to the processing optimization scheme formulated in step S4, and conduct actual measurements to verify the deformation, wall thickness, weight and other indicators of the test pieces.

[0131] S52: Make a comprehensive judgment based on the simulation results and the physical verification results: The results are as follows Figure 11 , Figure 13 As shown, the pneumatic outer surface allowance 33 was completely removed after machining, and the inner cavity surface allowance 34 was uniform and small. The deformation and wall thickness uniformity of the part met the requirements, and the final part weight was 38kg to 39kg. The part quality consistency was high, meeting the core requirement of weight ≤40kg. Therefore, the process flow, clamping method, tool selection, and process parameters of this embodiment 2 were solidified to form a solidified processing scheme.

[0132] S6: Mass production.

[0133] The blanks are manufactured and the parts are machined according to the solidification process plan to achieve batch processing of this typical thin-walled cabin part. The material allowance distribution of the parts after processing is as follows: Figure 11 , Figure 13 As shown, the allowance on the inner cavity surface tends to be uniform and relatively small, slightly higher than the theoretical value, and all technical specifications can be met without manual grinding to reduce weight.

[0134] The machining allowance optimization method for thin-walled parts in this embodiment 2 optimizes the distribution of machining allowance in the blank by understanding and utilizing the machining deformation law of the part. This achieves high allowance machining on one side of the thin-walled part and natural weight reduction without machining of the inner cavity surface, effectively solving the problems of high cost, long cycle and high quality risk of the prior art. The combination of simulation and verification ensures the reliability of the solution. After the machining solution is solidified, it can be directly applied to mass production, significantly improving production efficiency, reducing manufacturing costs and ensuring machining quality.

[0135] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for optimizing machining allowances of thin-walled parts, characterized in that, Includes the following steps: S1: Develop the initial blank model and initial machining plan; S2: Obtain and determine the deformation pattern during machining, specifically including: S21: Simulation analysis is performed based on the initial blank model and initial machining plan; S22: Produce test pieces based on the initial blank model and initial processing plan, and perform actual measurements on the test pieces; S23: Combining simulation results and actual measurement results, obtain the deformation direction and deformation amount of the part from blank to finished machining: S231: Determine the deformation direction, specifically divided into overall inward deformation, overall outward deformation, and partial inward and partial outward deformation; S232: If it is overall inward deformation, directly run step S3; if it is overall outward deformation or partial inward and partial outward deformation, determine the distribution of deformation amount of the outward deformation part; S3: Correct the initial blank model based on the machining deformation law obtained in step S2; if it is an overall inward deformation, set the inner cavity surface allowance to 0-0.5mm and distribute it evenly throughout; otherwise, set the inner cavity surface allowance of the outward deformation part according to the distribution of the deformation amount of the outward deformation part, and set the inner cavity surface allowance of the inward deformation part to 0-0.5mm. S4: Develop a processing optimization plan based on the corrected blank model obtained in step S3; S5: Based on the processing optimization scheme obtained in step S4, perform processing deformation simulation and physical verification.

2. The method for optimizing machining allowance of thin-walled parts according to claim 1, characterized in that, The thin-walled part includes a skin having an aerodynamic outer surface and an inner cavity surface; the thin-walled part is made of aluminum alloy casting.

3. The method for optimizing machining allowance of thin-walled parts according to claim 1 or 2, characterized in that, In step S1, the specific steps of formulating the initial blank model include setting the allowance of the outer surface and the allowance of the inner cavity surface of the thin-walled part to 5mm.

4. The method for optimizing machining allowances for thin-walled parts according to claim 3, characterized in that, In step S232, the distribution of deformation of the outwardly deformed part is one of the following four types: overall equal deformation, overall linear deformation, overall nonlinear deformation, or partitioned multi-dimensional deformation.

5. The method for optimizing machining allowances for thin-walled parts according to claim 4, characterized in that, In step S3, the inner cavity surface allowance of the outwardly deformed portion is set according to the distribution of deformation as follows: if the distribution is uniform deformation, the inner cavity surface allowance is set to be uniformly distributed, specifically the deformation amount + 1mm; if the distribution is linear deformation, the inner cavity surface allowance is set to be linearly gradually distributed, and the inner cavity surface allowance at any position is the deformation amount at that position + 1mm; if the distribution is nonlinear deformation, the inner cavity surface allowance is set to be uniformly distributed, and the inner cavity surface allowance is the maximum deformation amount of the portion + 1mm; if the distribution is multi-regional deformation, the corresponding inner cavity surface allowance is set according to the distribution of each region.

6. The method for optimizing machining allowance of thin-walled parts according to claim 5, characterized in that... Step S4 includes S41: Process optimization: adding a semi-finishing process based on the initial processing plan.

7. The method for optimizing machining allowances for thin-walled parts according to claim 6, characterized in that, Step S4 also includes S42: Clamping scheme optimization: Based on the initial machining scheme, add anti-vibration fixtures or support fixtures to improve clamping rigidity.

8. The method for optimizing machining allowances for thin-walled parts according to claim 1, characterized in that, Step S4 also includes S43: Tool selection: Based on the initial machining scheme, the machining tool is replaced, and the diameter of the replaced tool is larger than that of the tool used in the initial machining scheme.

9. The method for optimizing machining allowance of thin-walled parts according to claim 8, characterized in that, Step S4 also includes: S44: Process parameter optimization: Based on the initial machining scheme, reduce the feed rate and depth of cut, and reduce the cutting speed.

10. The method for optimizing machining allowance of thin-walled parts according to claim 1, characterized in that, Step S5 includes: S51: Based on the processing optimization scheme, determine new simulation parameters, perform processing deformation simulation through software, and obtain simulation results; at the same time, produce new test pieces, process them according to the processing optimization scheme, and measure the wall thickness and weight of the test pieces.

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