Sheet part precision grinding surface warping representation and inhibition method

Abstract

The present application relates to a kind of sheet parts precision grinding surface warping characterization and inhibiting method, comprising: by designing three-factor four-level orthogonal experiment, obtain the grinding deformation of sheet parts under different grinding process parameters, propose the method for utilizing standard parabolic curve to characterize deformation curve after coordinate transformation, and use parabolic quadratic coefficient as grinding deformation evaluation index;By dry grinding and control coolant flow, obtain the grinding deformation evaluation index of sheet parts under different process parameters, based on response surface method, establish sheet parts grinding deformation prediction model and grinding zone surface highest temperature prediction model;On the basis of prediction model establishment, with the material removal rate of grinding machining as target, with grinding deformation and grinding zone surface highest temperature etc. As constraint condition, the grinding process parameters of sheet parts are optimized based on genetic algorithm.Compared with prior art, the present application has the advantages of high accuracy of grinding surface warping characterization, good inhibiting effect and the like.

Description

A method for characterizing and suppressing warpage on the precision-ground surface of thin-plate parts Technical Field

[0001] This invention relates to the field of grinding technology for thin plate parts, and in particular to a method for characterizing and suppressing surface warping in precision grinding of thin plate parts. Background Technology

[0002] Aerospace equipment often uses thin-plate parts with high precision requirements. Compared to grinding thicker parts, thin-plate parts have poor heat dissipation during grinding. Grinding heat penetrates the workpiece, leading to rapid and high temperature rise in the grinding zone. The temperature field in the grinding zone has a large gradient, resulting in uneven thermal expansion and deformation along the thickness of the thin plate, leading to uneven actual grinding depth. Increased temperature improves the material's plasticity in the grinding zone, causing greater plastic deformation under grinding force, resulting in greater residual stress on the ground surface. The grinding force, grinding heat, and residual surface stress generated during thin-plate grinding collectively create grinding deformation, which directly affects the surface shape accuracy and performance of the part. Therefore, it is necessary to identify and suppress grinding deformation during the grinding process.

[0003] The invention disclosed in CN114161240A is a grinding surface shape prediction method, grinding system and terminal equipment. The method includes: setting different attitude adjustment parameters to grind a wafer; measuring the thickness of the wafer after grinding and extracting the surface shape features of the wafer; and using a machine learning algorithm to establish a mapping relationship between the attitude adjustment parameters and the surface shape features to obtain a surface shape prediction model.

[0004] This scheme predicts wafer surface features based on the grinding posture adjustment parameters. However, it cannot identify grinding deformation based on the actual grinding surface. It relies on the accuracy of the prediction model, and the accuracy of the identified wafer surface features cannot be guaranteed. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for characterizing and suppressing warping of precision-ground surfaces of thin-plate parts, which enables accurate quantitative expression of grinding deformation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for characterizing and suppressing warpage on the precision-ground surface of thin-plate parts includes the following steps:

[0008] Obtain grinding deformation samples of thin plate parts;

[0009] The coordinates of multiple surface points of the grinding deformation sample are obtained along the length direction of the grinding deformation sample to obtain multiple discrete points of the surface profile of the grinding deformation sample. A parabolic curve fitting function is used to fit the discrete points of the surface profile of the grinding deformation sample to obtain a standard parabola of the surface profile of the grinding deformation sample. The quadratic coefficient of the standard parabola is used as an evaluation index of the deformation degree of the thin plate part.

[0010] Obtain the quadratic coefficients of thin plate parts under different grinding process parameters, construct a grinding deformation prediction model for thin plate parts, and solve the grinding process parameters of thin plate parts to achieve surface warping suppression based on the grinding deformation prediction model.

[0011] Furthermore, the process of solving the grinding process parameters for the thin plate part that achieves surface warping suppression specifically includes:

[0012] The highest surface temperature of thin plate parts under different grinding process parameters is obtained by thermal imager, and a prediction model of the highest surface temperature of thin plate parts is constructed.

[0013] The material removal rate in the grinding of thin plate parts is used as the optimization objective function. The preset conditions are that the deformation of the thin plate parts predicted by the grinding deformation prediction model is less than the maximum deformation and the maximum surface temperature of the thin plate parts predicted by the maximum surface temperature prediction model is less than the maximum temperature. The optimization range of each grinding process parameter is set, and the grinding process parameters are optimized by a genetic algorithm to obtain the grinding process parameters of thin plate parts that achieve surface warping suppression.

[0014] Furthermore, the grinding process parameters for the thin plate parts include grinding depth, grinding wheel linear speed, feed rate, and coolant flow rate ratio.

[0015] Furthermore, the independent variables of the grinding deformation prediction model for thin plate parts include grinding depth, grinding wheel linear speed, feed rate, and coolant flow rate ratio.

[0016] Furthermore, the independent variables of the prediction model for the highest surface temperature of the thin plate part include grinding depth, grinding wheel linear speed, and feed rate.

[0017] Furthermore, the formula for calculating the material removal rate is as follows:

[0018] η = a p bv w

[0019] In the formula, η is the material removal rate, and a p b is the grinding depth, v is the grinding width, and v is the grinding depth. w This refers to the feed rate.

[0020] Furthermore, based on the highest surface temperature of the thin plate parts under different grinding process parameters, a multiple linear regression model is used to obtain a prediction model for the highest surface temperature of the thin plate parts.

[0021] Furthermore, the process of obtaining the coordinates of multiple surface points of the ground deformation sample along its length is as follows:

[0022] The grinding deformation sample is positioned and clamped using a measuring fixture and placed on the worktable of a coordinate measuring machine, so that the length direction of the grinding deformation sample is parallel to the X direction of the coordinate measuring machine. Then, the coordinate measuring machine selects multiple straight lines along the length direction of the grinding deformation sample and randomly selects multiple surface point coordinates on each straight line.

[0023] Furthermore, after fitting the discrete points of the surface profile of the ground deformed sample, the process further includes:

[0024] The slopes of the two endpoints of the fitted curve are calculated, and then the fitted curve is rotated to make the slope zero. The vertex of the fitted curve is then translated to the origin to obtain the standard parabola.

[0025] Furthermore, the method is used for thin-walled samples with a thickness of less than 3 mm.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) In this invention, the discrete deformation curves reconstructed from the deformed surfaces of thin plate parts after coordinate measuring machine measurement all roughly exhibit a parabolic shape. A parabolic curve fitting function is used to fit the discrete points of the surface contour, and the fitted parabola is subjected to coordinate rotation transformation to obtain the standard parabola y = px. 2 It can achieve a quantitative expression of the grinding deformation of thin plates.

[0028] (2) This invention proposes a method for characterizing and suppressing warping of the precision grinding surface of thin plate parts. The quadratic coefficient p can be used to evaluate the degree of deformation of thin plate parts and to calculate the deformation of each point of the part in the length direction. The quadratic coefficient p is used as the evaluation index of grinding deformation of thin plate parts, so as to realize the warping deformation of different positions of the part corresponding to different grinding process parameters.

[0029] (3) This invention proposes a method for characterizing and suppressing surface warping of thin plate parts in precision grinding. By dry grinding and controlling the flow rate of coolant, the grinding deformation evaluation index of thin plate parts under different process parameters is obtained, and a prediction model for the grinding deformation evaluation index of thin plate parts is established. By monitoring the temperature value of the grinding area, the grinding deformation prediction model and the maximum temperature prediction model of the grinding area are obtained based on multiple linear regression. The grinding area temperature and the grinding deformation evaluation index are optimized to obtain ideal grinding process parameters and guide the actual grinding process of thin plate parts. Attached Figure Description

[0030] Figure 1 is a flowchart illustrating a method for characterizing and suppressing surface warping of thin plate parts during precision grinding, provided in an embodiment of the present invention.

[0031] Figure 2 is a schematic diagram of a grinding test process provided in an embodiment of the present invention;

[0032] Figure 3 is a structural design diagram of a measuring fixture provided in an embodiment of the present invention;

[0033] Figure 4 illustrates a method for measuring coordinate points on a grinding surface provided in an embodiment of the present invention.

[0034] Figure 5 shows a discrete deformation curve obtained by coordinate measuring machine according to an embodiment of the present invention;

[0035] Figure 6 shows a contour fitting curve of a thin plate part provided in an embodiment of the present invention;

[0036] Figure 7 shows a coordinate-transformed contour curve of a thin plate part provided in an embodiment of the present invention;

[0037] Figure 8 is a residual plot of a quadratic term coefficient regression equation provided in an embodiment of the present invention;

[0038] Figure 9 shows the warpage deformation indices p and v in the grinding process of a thin plate part provided in an embodiment of the present invention. s -a p Response surface plot;

[0039] Figure 10 shows the warpage deformation indices p and v in a thin plate part grinding process according to an embodiment of the present invention. s -v w Response surface plot;

[0040] Figure 11 shows the warpage deformation indices p and v in a thin plate part grinding process according to an embodiment of the present invention. s -H response surface plot;

[0041] Figure 12 shows the warpage deformation indices p and a in a thin plate part grinding process according to an embodiment of the present invention. p -v wResponse surface plot;

[0042] Figure 13 shows the warpage deformation indices p and a in a thin plate part grinding process according to an embodiment of the present invention. p -H response surface plot;

[0043] Figure 14 shows the warpage deformation indices p and v in a thin plate part grinding process according to an embodiment of the present invention. w -H response surface plot;

[0044] Figure 15 shows the highest surface temperature T of a part provided in an embodiment of the present invention. max With v s -a p Response surface plot;

[0045] Figure 16 shows the highest surface temperature T of a part provided in an embodiment of the present invention. max With v s -v w Response surface plot;

[0046] Figure 17 shows the highest surface temperature T of a part provided in an embodiment of the present invention. max With a p- v w Response surface plot;

[0047] Figure 18 is a schematic diagram of the optimization process of grinding process parameters provided in an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0050] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0051] Example 1

[0052] As shown in Figure 1, this embodiment provides a method for characterizing and suppressing warpage on the precision-ground surface of thin-plate parts, including the following steps:

[0053] S1: Obtain grinding deformation samples of thin plate parts;

[0054] S2: Obtain the coordinates of multiple surface points of the grinding deformation sample along the length direction of the grinding deformation sample to obtain multiple discrete points of the surface profile of the grinding deformation sample; use a parabolic curve fitting function to fit the discrete points of the surface profile of the grinding deformation sample to obtain a standard parabola of the surface profile of the grinding deformation sample, and use the quadratic coefficient of the standard parabola as an evaluation index of the deformation degree of the thin plate part.

[0055] The discrete deformation curves reconstructed from the deformed surface of thin plate parts after coordinate measuring machine (CMM) measurements generally exhibit a parabolic shape. Therefore, a parabolic curve fitting function can be used to fit the discrete points of the surface profile. By performing coordinate rotation transformation on the fitted parabola, the standard parabola y = px is obtained. 2 ;

[0056] The quadratic coefficient p can be used to evaluate the degree of deformation of thin plate parts and to calculate the deformation at each point along the length of the part; this quadratic coefficient p is used as an evaluation index for grinding deformation of thin plate parts.

[0057] S3: Obtain the quadratic coefficients of thin plate parts under different grinding process parameters, construct a grinding deformation prediction model for thin plate parts, and solve the grinding process parameters of thin plate parts to achieve surface warping suppression based on the grinding deformation prediction model.

[0058] By dry grinding and controlling the coolant flow rate, evaluation indices for grinding deformation of thin plate parts under different process parameters are obtained, and a prediction model for the evaluation indices of grinding deformation of thin plate parts is established.

[0059] The process of solving the grinding process parameters for thin plate parts to achieve surface warping suppression specifically includes:

[0060] The highest surface temperature of thin plate parts under different grinding process parameters is obtained by thermal imager, and a prediction model of the highest surface temperature of thin plate parts is constructed.

[0061] Specifically, by monitoring the temperature values ​​in the grinding zone, a prediction model for the highest temperature in the grinding zone of thin plate parts can be obtained through multiple linear regression.

[0062] The material removal rate in the grinding of thin plate parts is used as the optimization objective function. The preset conditions are that the deformation of the thin plate parts predicted by the grinding deformation prediction model is less than the maximum deformation and the maximum surface temperature of the thin plate parts predicted by the maximum surface temperature prediction model is less than the maximum temperature. The optimization range of each grinding process parameter is set, and the grinding process parameters are optimized by a genetic algorithm to obtain the grinding process parameters of thin plate parts that achieve surface warping suppression.

[0063] For example, the following describes a specific implementation process of the method for characterizing and suppressing warpage on the precision-ground surface of the above-mentioned thin-plate parts.

[0064] This implementation process used quenched 45# thin steel plates as the test material. The test specimens were processed by wire electrical discharge machining. Before the grinding test, both planes of the specimens were pre-ground to ensure the thickness of the specimens and the parallelism of the test surface, minimizing the impact on the grinding deformation test results. After pre-grinding, the surfaces of all test specimens were measured using a Zeiss Duramax coordinate measuring machine (Duramax, Zeiss, Germany). The vertical coordinate range was within 5 μm, and the thickness of the test material specimens was within 3 mm.

[0065] Figure 2 illustrates the grinding test process. The thin plate part was fixed to the electromagnetic worktable of a CNC surface grinder, with the long side of the sample parallel to the X-axis of the grinder, i.e., the long side of the electromagnetic worktable. An infrared thermal imager lens was positioned to target the chip removal area of ​​the grinding wheel. This infrared thermal imager was directly connected to a PC via USB, and its parameters and temperature field were measured using dedicated software installed on the PC.

[0066] When measuring the deformation of thin sheet metal parts using a Zeiss coordinate measuring machine (CMM), the positioning of the sample needs to be addressed. A measuring fixture, as shown in Figure 3, was designed to address this issue, taking into account the sample and the deformation phenomenon. The measuring fixture consists of a base, a fixed end, a positioning element, and a clamping element. After the ground and deformed sample is positioned and clamped in the measuring fixture, it is placed on the CMM's worktable, with the sample's length direction parallel to the CMM's X-axis. Hot melt adhesive is used to fix the bottom of the fixture. Three straight lines are selected along the length of the thin sheet metal part, and 20 points are randomly selected on each line. The (x, y, z) coordinate values ​​of each point are read, as shown in Figure 4.

[0067] Figure 5 shows the discrete deformation curves reconstructed from the deformed surface of the thin plate part after coordinate measuring machine measurement. The deformation curves of all test samples are roughly parabolic. The discrete points of the surface profile are fitted using a parabolic curve fitting function, and the fitted curves are shown in Figure 6.

[0068] Due to the dimensional errors of the part itself and the installation errors of the measuring fixture, the surface deformation of the part will exhibit a certain degree of asymmetry, and the fitted curve will be a parabola of the form y = px(xc). However, the grinding conditions are basically the same at every point on the surface of the thin plate part, so the concave trend should be basically symmetrical. A coordinate transformation is performed on the fitted parabola, and the slope k of the line connecting the two endpoints of the curve is obtained. The coordinate system is then rotated according to this slope k, i.e., a coordinate rotation is performed on the fitted curve, placing both ends of the fitted curve at the same height. The coordinate transformation formula is as follows:

[0069] x2=x1×cosγ-y1×sinγ

[0070] y2=x1×sinγ+y1×cosγ

[0071] In the formula, γ = atan(k) represents the radians of counterclockwise rotation of the coordinate system. By shifting the vertex of the parabola to the origin, the fitted curve transforms into the standard parabola y = px (as shown in Figure 7). 2 .

[0072] The quadratic coefficient p can be used to evaluate the degree of deformation of thin plate parts and to calculate the deformation at each point along the length of the part. Using this quadratic coefficient p as an evaluation index for grinding deformation of thin plate parts, and considering that the evaluation index p is influenced by grinding process parameters and their interactions, resulting in numerous variables, a prediction model for the evaluation index p of grinding deformation of thin plate parts is established as follows:

[0073]

[0074] The residual results of the prediction model for the grinding deformation evaluation index p of thin plate parts are shown in Figure 8, and are uniformly distributed on both sides of the zero point. The functional relationship between the grinding deformation evaluation index and the grinding process parameters are shown in Figures 9 to 17. From the functional relationship graphs, it can be seen that the grinding deformation of thin plate parts increases with the grinding depth a. p With v w The value increases with the increase of the grinding wheel linear velocity v. s It decreases as it increases.

[0075] After applying coolant, the coolant flow rate ratio is changed. The grinding deformation evaluation index p of thin plate parts is obtained, with the coolant flow rate ratio ranging from 0-100%. Based on the obtained grinding deformation evaluation index p, the prediction model is corrected, and the prediction model for the grinding deformation evaluation index p of thin plate parts is obtained as follows:

[0076]

[0077] The highest surface temperature T of the thin sheet metal part measured by the thermal imager max The predictive regression equation is:

[0078]

[0079] To achieve high-quality grinding of thin sheet metal parts, the deformation after machining must meet the design requirements for dimensional accuracy. Simultaneously, grinding burns are not allowed on the workpiece surface during machining. Therefore, the optimization process of grinding parameters focuses on the warpage deformation index p and the maximum surface temperature T of the thin sheet metal parts. max These are constraints.

[0080] The method for calculating the material removal rate η in grinding is as follows:

[0081]

[0082] In the formula a p b is the grinding depth (mm), b is the grinding width (mm), L is the length of the thin plate part (mm), and v is the grinding depth. w The feed rate is (mm / s).

[0083] Let the length of the thin plate part be L. The maximum deformation after grinding must be less than y0. The corresponding evaluation index for warpage deformation during grinding is p0. Then p0*(0.5L) 2 =y0, because the material of the part will suffer low-temperature tempering burns at 450℃, therefore the highest temperature T max The temperature was controlled to be below 400℃, and the relevant parameters for the optimization process are shown in Table 1.

[0084] Table 1 Objective function and constraints for grinding process parameter optimization

[0085]

[0086] The genetic algorithm was used to optimize the grinding process parameters for warpage deformation index during grinding. The parameter settings of the genetic algorithm are shown in Table 2.

[0087] Table 2. Relevant parameters of the genetic algorithm

[0088]

[0089] After ten iterations, the objective function converged, and the optimization process is shown in Figure 18. The optimized result, after conversion, is: v s =29.845m / s, a p =5.35μm, v w =1.05m / min, At this point, the predicted warpage deformation index of the thin plate part during grinding is p = 2E-6. Under the conditions of meeting the dimensional accuracy requirements of the thin plate part grinding process and preventing part burning, the most efficient grinding process is achieved.

[0090] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for characterizing and suppressing surface warping of precision-ground thin-plate parts, characterized in that, Includes the following steps: Obtain grinding deformation samples of thin plate parts; The coordinates of multiple surface points of the grinding deformation sample are obtained along the length direction of the grinding deformation sample to obtain multiple discrete points of the surface profile of the grinding deformation sample. A parabolic curve fitting function is used to fit the discrete points of the surface profile of the grinding deformation sample to obtain a standard parabola of the surface profile of the grinding deformation sample. The quadratic coefficient of the standard parabola is used as an evaluation index of the deformation degree of the thin plate part. The quadratic coefficients of thin plate parts under different grinding process parameters are obtained, and a grinding deformation prediction model for thin plate parts is constructed. Based on the grinding deformation prediction model for thin plate parts, the grinding process parameters for thin plate parts that achieve surface warping suppression are calculated. The process of solving the grinding process parameters for thin plate parts that achieve surface warping suppression specifically includes: obtaining the highest surface temperature of thin plate parts under different grinding process parameters using a thermal imager, and constructing a prediction model for the highest surface temperature of thin plate parts. The material removal rate in the grinding of thin plate parts is used as the optimization objective function. The preset conditions are that the deformation of the thin plate parts predicted by the grinding deformation prediction model is less than the maximum deformation and the maximum surface temperature of the thin plate parts predicted by the maximum surface temperature prediction model is less than the maximum temperature. The optimization range of each grinding process parameter is set, and a genetic algorithm is used to optimize the grinding process parameters to obtain the grinding process parameters for achieving surface warping suppression. The grinding process parameters for thin plate parts include grinding depth, grinding wheel linear speed, feed rate, and coolant flow rate ratio.

2. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, The independent variables of the grinding deformation prediction model for thin plate parts include grinding depth, grinding wheel linear speed, feed rate, and coolant flow rate ratio.

3. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, The independent variables of the prediction model for the highest surface temperature of the thin plate part include grinding depth, grinding wheel linear speed, and feed rate.

4. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, The formula for calculating the material removal rate is: In the formula, For material removal rate, For grinding depth, For grinding width, This refers to the feed rate.

5. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, Based on the highest surface temperature of thin plate parts under different grinding process parameters, a prediction model for the highest surface temperature of thin plate parts is obtained by performing multiple linear regression.

6. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, The process of obtaining the coordinates of multiple surface points of the grinding deformation sample along its length is as follows: the grinding deformation sample is positioned and clamped by a measuring fixture and placed on the worktable of a coordinate measuring machine, so that the length direction of the grinding deformation sample is parallel to the X direction of the coordinate measuring machine. Then, multiple straight lines are selected along the length direction of the grinding deformation sample by the coordinate measuring machine, and multiple surface point coordinates are randomly selected on each straight line.

7. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, After fitting the discrete points of the surface contour of the ground deformation sample, the process further includes: solving the slope of the two ends of the obtained fitting curve, then performing coordinate rotation on the fitting curve to make the slope zero; and translating the vertex of the fitting curve to the origin of the coordinate system to obtain the standard parabola.

8. The method for characterizing and suppressing surface warping of precision-ground thin-plate parts according to claim 1, characterized in that, The method is used for thin-walled samples with a thickness of less than 3 mm.

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