Forming grinding machining method for improving surface quality of inner raceway of nut of precision lead screw pair based on orthogonal test

Abstract

The invention discloses a forming grinding machining method for improving the surface quality of an inner raceway of a nut of a precision lead screw pair based on an orthogonal test, which comprises the following steps of: designing a test scheme by adopting a three-factor three-level orthogonal test, and taking three process parameters, namely a grinding wheel rotating speed, a nut rotating speed and a grinding depth, as variables; based on the test scheme, the nut is subjected to forming grinding machining, and the grinding quality of an inner raceway of the nut is evaluated; determining the matching of the optimal grinding wheel rotating speed, the optimal nut rotating speed and the optimal grinding depth technological parameters based on the molding grinding machining technological parameter data and the grinding quality of the inner raceway of the nut; and based on the optimal grinding wheel rotating speed, the nut rotating speed and the grinding depth process parameters, forming grinding machining is conducted on the nut. Test results prove that the lead limit deviations are all smaller than the design allowance 0.4 mu m, it is indicated that the surface quality of the inner raceway can be effectively improved by optimizing technological parameters, it is verified that the method can meet the machining precision requirement of the ball nut inner raceway, and the method is suitable for forming and grinding machining of the precise lead screw pair nut inner raceway.

Description

Technical Field

[0001] This invention belongs to the field of precision rolling functional component manufacturing technology, and in particular, it is a forming grinding method based on orthogonal experiment to improve the surface quality of the inner raceway of the nut of a precision lead screw pair. Background Technology

[0002] As a core functional component of CNC machine tools, the machining quality of the inner raceway of the precision lead screw directly determines the transmission accuracy, service life, and operational reliability. Currently, the inner raceway is mostly machined using profile grinding. However, due to the coupling effect of multiple factors during the grinding process, problems such as large surface roughness and large lead deviation often occur, seriously affecting product performance.

[0003] While many studies in the prior art have focused on the influence of grinding parameters on surface quality, they are mostly concentrated on grinding accuracy or single-factor analysis. There is a lack of systematic research on multi-factor matching optimization of the inner raceway of nuts, making it difficult to stably obtain high surface quality inner raceways of nuts in actual production. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments. This method effectively improves the surface quality of the inner raceway, meets the machining accuracy requirements of the inner raceway of the ball nut, and provides important theoretical support for the field of forming grinding of the inner raceway of a precision lead screw pair nut.

[0005] The technical solution to achieve the objective of this invention is: a forming grinding method for improving the surface quality of the inner raceway of a precision lead screw nut based on orthogonal experiments, the method comprising the following steps:

[0006] Step 1: A three-factor, three-level orthogonal experimental design was adopted, with the grinding wheel speed, nut speed and grinding depth as three process parameters;

[0007] Step 2: Based on the test plan in Step 1, perform form grinding on the nut and evaluate the grinding quality of the inner raceway of the nut.

[0008] Step 3: Based on the forming grinding process parameter data in Step 2 and the grinding quality of the inner raceway of the nut, determine the optimal matching of grinding wheel speed, nut speed and grinding depth process parameters;

[0009] Step 4: Based on the optimal grinding wheel speed, nut speed and grinding depth process parameters obtained in Step 3, perform shape grinding on the nut.

[0010] Furthermore, in step 1, the orthogonal experiment uses the L9.3.3 orthogonal array to arrange the experimental scheme.

[0011] Furthermore, in step 2, the grinding quality of the inner raceway of the nut is determined by the profile arithmetic mean deviation R. a As an evaluation indicator.

[0012] Furthermore, the arithmetic mean deviation R of the profile a The acquisition process is as follows:

[0013] The surface roughness of the three different inner raceways (front, middle, and rear) of the ball screw pair nut were tested multiple times.

[0014] Remove outliers from the test results;

[0015] Calculate the average of the remaining detection results as the final profile arithmetic mean deviation R. a R a The smaller the value, the better the grinding quality of the raceway inside the nut.

[0016] Furthermore, in step 2, during the grinding process, a wet grinding method is adopted, and a coolant is used for cooling.

[0017] Furthermore, step 3, based on the forming grinding process parameter data from step 2 and the grinding quality of the inner raceway of the nut, determines the optimal matching of the grinding wheel speed, nut speed, and grinding depth process parameters. The specific process includes:

[0018] Step 3-1: For each process parameter, accumulate the surface roughness measurement results at a certain level to obtain the result. And calculate the average value. This represents the cumulative value of surface roughness measurements for the i-th level of the process parameters;

[0019] Step 3-2: For each process parameter, select the smallest value. The corresponding level value is taken as the optimal value of this process parameter;

[0020] This yields the optimal combination of grinding wheel speed, nut speed, and grinding depth process parameters.

[0021] Furthermore, the method also includes execution after step 3 and before step 4:

[0022] Step 31: Through range analysis, obtain the significance value of the influence of each process parameter on the grinding quality.

[0023] Step 32: Prioritize the process parameters according to their significance level, as a reference for considering the priority of process parameters in subsequent forming grinding processes.

[0024] Furthermore, the specific process of step 31 is as follows:

[0025] For each process parameter, obtain all corresponding parameters. The difference between the maximum and minimum values ​​in the range is denoted as the R-value, which serves as the significance value.

[0026] Step 32 is as follows:

[0027] The three process parameters are arranged in descending order based on the R value. The larger the R value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

[0028] Furthermore, replace step 31 with:

[0029] By using multifactor ANOVA to analyze grinding quality, the significance value of the influence of each process parameter on grinding quality was obtained.

[0030] Furthermore, the process of obtaining the significance value of the influence of each process parameter on the grinding quality through multi-factor variance analysis is as follows:

[0031] Step 31-1: Calculate the average surface roughness of all process parameters under all different combinations of level values;

[0032] Step 31-2, based on the average values ​​of all process parameters Calculate the sum of squares corresponding to the process parameter using the average value obtained in step 5-1;

[0033] Step 31-3: Calculate the degrees of freedom and mean square values ​​for different process parameters;

[0034] Step 31-4: Calculate the ratio of the mean square value from step 31-3 to the preset mean square error value, and use it as the F statistic.

[0035] Steps 31-5: Based on the F statistic, look up the F distribution table to obtain the corresponding probability value P, which is used as the significance value of the process parameter;

[0036] The specific process of step 32 is as follows:

[0037] The process parameters are prioritized according to their significance values ​​P from smallest to largest. The smaller the P value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

[0038] Compared with the prior art, the significant advantages of this invention are:

[0039] (1) Through a three-factor, three-level orthogonal experimental design (L9.3.3), the comprehensive influence of grinding wheel speed, nut speed and grinding depth on surface roughness was systematically analyzed, overcoming the limitations of traditional single-factor experiments and realizing multi-factor synergistic optimization.

[0040] (2) The key influencing factors (grinding wheel speed and grinding depth) and their optimal ranges in the process parameters have been identified. These key parameters can be monitored and stabilized during the production process, thereby greatly reducing the quality fluctuations of products within and between batches.

[0041] (3) This method is applicable to various types of nuts (such as GZ4010-5 and SN2250), has good applicability and engineering application value, and can be widely used in the manufacture of high-precision lead screw pairs.

[0042] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the process parameters optimization for grinding the inner raceway of the nut according to one embodiment of the present invention.

[0044] Figure 2 This is a schematic diagram of the L9.3.3 standard orthogonal array in one embodiment.

[0045] Figure 3 This is a range analysis plot from one embodiment.

[0046] Figure 4 This is a comparison chart of surface roughness measurement results under different parameter combinations in one embodiment.

[0047] Figure 5 A multifactor ANOVA plot in one embodiment. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0049] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0050] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0051] In one embodiment, combined Figure 1 A forming grinding method for improving the surface quality of the inner raceway of a precision lead screw nut based on orthogonal experiments is provided. The method includes the following steps:

[0052] Step 1: A three-factor, three-level orthogonal experimental design is adopted, with the grinding wheel speed, nut speed, and grinding depth as three process parameters. Preferably, the grinding wheel is a ceramic-bonded grinding wheel, and the abrasive is corundum or silicon carbide.

[0053] Step 2: Based on the test plan in Step 1, perform form grinding on the nut and evaluate the grinding quality of the inner raceway of the nut.

[0054] Step 3: Based on the forming grinding process parameter data in Step 2 and the grinding quality of the inner raceway of the nut, determine the optimal matching of grinding wheel speed, nut speed and grinding depth process parameters;

[0055] Step 4: Based on the optimal grinding wheel speed, nut speed and grinding depth process parameters obtained in Step 3, perform shape grinding on the nut.

[0056] Furthermore, in one embodiment, the orthogonal experiment in step 1 uses an L9.3.3 orthogonal array to arrange the experimental scheme.

[0057] Furthermore, in one embodiment, the grinding quality of the inner raceway of the nut in step 2 is expressed using the profile arithmetic mean deviation R. a As an evaluation indicator.

[0058] Preferably, in some embodiments, the contour arithmetic mean deviation R a The acquisition process is as follows:

[0059] The surface roughness of the three different inner raceways (front, middle, and rear) of the ball screw pair nut were tested multiple times.

[0060] Remove outliers from the test results;

[0061] Calculate the average of the remaining detection results as the final profile arithmetic mean deviation R. a R a The smaller the value, the better the grinding quality of the inner raceway of the nut.

[0062] Furthermore, in one embodiment, during the grinding process in step 2, a wet grinding method is used, and a coolant is used for cooling.

[0063] Furthermore, in one embodiment, step 3, based on the forming grinding process parameter data from step 2 and the grinding quality of the inner raceway of the nut, determines the optimal matching of the grinding wheel speed, nut speed, and grinding depth process parameters. The specific process includes:

[0064] Step 3-1: For each process parameter, accumulate the surface roughness measurement results at a certain level to obtain the result. And calculate the average value. This represents the cumulative value of surface roughness measurement results for the i-th level of the process parameters;

[0065] Step 3-2: For each process parameter, select the smallest value. The corresponding level value is taken as the optimal value of this process parameter;

[0066] This yields the optimal combination of grinding wheel speed, nut speed, and grinding depth process parameters.

[0067] Furthermore, in one embodiment, the method further includes execution after step 3 and before step 4:

[0068] Step 31: Through range analysis, obtain the significance value of the influence of each process parameter on the grinding quality.

[0069] Step 32: Prioritize the process parameters according to their significance level, as a reference for considering the priority of process parameters in subsequent forming grinding processes.

[0070] Preferably, in some embodiments, step 31 specifically involves the following process:

[0071] For each process parameter, obtain all corresponding parameters. The difference between the maximum and minimum values ​​in the range is denoted as the R-value, which serves as the significance value.

[0072] Step 32 is as follows:

[0073] The three process parameters are arranged in descending order based on the R value. The larger the R value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

[0074] Furthermore, in one embodiment, step 31 can be replaced with:

[0075] By using multifactor ANOVA to analyze grinding quality, the significance value of the influence of each process parameter on grinding quality was obtained.

[0076] Preferably, in some embodiments, the process of obtaining the significance value of the influence of each process parameter on the grinding quality through multi-factor variance analysis is as follows:

[0077] Step 31-1: Calculate the average surface roughness of all process parameters under all different combinations of level values;

[0078] Step 31-2, based on the average values ​​of all process parameters Calculate the sum of squares corresponding to the process parameter using the average value obtained in step 5-1;

[0079] Here, the specific calculation is as follows: calculate the average value for each... Square the difference between the average obtained in step 5-1 and the average value obtained in step 5-1, and then sum them up.

[0080] Step 31-3: Calculate the degrees of freedom and mean square values ​​for different process parameters;

[0081] Here, the degree of freedom = number of horizontal values ​​- 1; for example, if a certain process parameter has three different horizontal values, then the degree of freedom is 2.

[0082] Here, mean square value = sum of squares / degrees of freedom;

[0083] Step 31-4: Calculate the ratio of the mean square value from step 31-3 to the preset mean square error value, and use it as the F statistic.

[0084] Steps 31-5: Based on the F statistic, look up the F distribution table to obtain the corresponding probability value P, which is used as the significance value of the process parameter;

[0085] The specific process of step 32 is as follows:

[0086] The process parameters are prioritized according to their significance values ​​P from smallest to largest. The smaller the P value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

[0087] Here, the process parameters can be classified into different levels by setting a significance level. For example, if the first significance level is set to 0.05 and the second significance level is set to 0.01, the parameter is considered insignificant if the significance level is higher than the first significance level, highly significant if the significance level is lower than the second significance level, and otherwise generally significant.

[0088] In one embodiment, a forming grinding system for improving the surface quality of the inner raceway of a precision lead screw nut based on orthogonal experiments is provided, the system comprising:

[0089] The first module is used to implement the experimental design using a three-factor, three-level orthogonal experimental design, with the grinding wheel speed, nut speed, and grinding depth as three process parameters;

[0090] The second module is used to: perform shaping grinding on the nut based on the experimental plan, and evaluate the grinding quality of the inner raceway of the nut;

[0091] The third module is used to: determine the optimal matching of grinding wheel speed, nut speed and grinding depth process parameters based on the forming grinding process parameter data and the grinding quality of the inner raceway of the nut;

[0092] The fourth module is used to perform shape grinding on the new nut based on the optimal grinding wheel speed, nut speed, and grinding depth process parameters.

[0093] As a specific example, the invention will be further described and verified in detail in one embodiment.

[0094] The profile arithmetic mean deviation R is measured using a nut internal thread surface roughness testing device. a To evaluate the surface finish of the internal thread of the ball screw nut, the morphology of the nut's internal thread is transmitted to the industrial control computer system via probe movement. The morphology of the internal thread is then analyzed to obtain the arithmetic mean deviation R of the nut's internal thread profile. a .

[0095] Combination Figure 2 A three-factor, three-level analysis diagram of the grinding process parameters for the internal thread of a nut, selecting the grinding wheel speed v. s Nut rotation speed v w and grinding depth a g Three main parameters affecting the quality of the internal thread of a nut ground by a grinding wheel. Based on the model and technical requirements of the ball screw pair nut, the grinding wheel speed generally ranges from 30 m / s to 40 m / s in grinding the inner raceway of the ball screw pair nut. In this example, 30 m / s, 33 m / s, and 36 m / s are selected as three levels of grinding wheel speed (not limited to three levels). The nut speed generally ranges from 15 to 30 mm / s in grinding the inner raceway of the nut. In this example, 17 mm / s, 21 mm / s, and 25 mm / s are selected as three levels of nut speed. Based on daily grinding experience, the grinding depth is selected as 0.012 mm, 0.015 mm, and 0.018 mm as three levels to avoid excessive grinding temperature and burning of the inner raceway surface of the nut.

[0096] Combination Figure 3The range analysis chart shows that among the three factors—grind wheel speed, nut speed, and grinding depth—R1 = 0.8, R2 = 0.2, and R3 = 0.71, i.e., R1 > R3 > R2. Therefore, it can be considered that the grinding wheel speed has the greatest impact on the surface roughness during nut internal thread grinding, followed by the grinding depth, while the nut speed has the least impact on surface roughness. The size can be used to determine the speed v of the grinding wheel. s =36m / s, nut rotation speed v w =25m / s, grinding depth a g When the surface roughness is 0.012 mm, the surface roughness obtained when grinding the internal thread of the nut is the smallest.

[0097] Combination Figure 4 The graph compares the surface roughness measurement results under different parameter combinations, showing the average roughness at different levels of the three factors: grinding wheel speed, workpiece speed, and grinding depth. The graph illustrates the influence of these three factors on surface roughness: the higher the grinding wheel speed, the lower the average roughness; however, the workpiece speed and grinding depth have no significant effect on the average roughness, showing no linear relationship.

[0098] Combination Figure 5 A multivariate ANOVA plot, with p-values ​​similar to F-values, can be used to determine the significance of a factor's effect on the dependent variable. Typically, the p-value is compared to a set significance level, commonly 0.05 and 0.01. When the p-value is less than the set significance level, the factor is considered to have a significant effect on the dependent variable. The grinding wheel speed p = 0.004, which is less than the significance level of 0.01; the nut speed p = 0.071, which is greater than the significance level of 0.05; and the grinding depth p = 0.006, which is less than the significance level of 0.01. Therefore, we can conclude that the grinding depth and grinding wheel speed have the most significant impact on the surface roughness of the internal thread of the nut ground by grinding wheel, while the nut speed has no significant effect on surface roughness. Therefore, when optimizing grinding process parameters, we need to focus on the influence of grinding wheel speed and grinding depth on the surface quality of the nut's internal thread.

[0099] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention without departing from its spirit and scope should be included within the protection scope of the present invention.

Claims

1. A forming grinding method for improving the surface quality of the inner raceway of a precision lead screw nut based on orthogonal experiments, characterized in that, The method includes the following steps: Step 1: A three-factor, three-level orthogonal experimental design was adopted, with the grinding wheel speed, nut speed and grinding depth as three process parameters; Step 2: Based on the test plan in Step 1, perform form grinding on the nut and evaluate the grinding quality of the inner raceway of the nut. Step 3: Based on the forming grinding process parameter data in Step 2 and the grinding quality of the inner raceway of the nut, determine the optimal matching of grinding wheel speed, nut speed and grinding depth process parameters; Step 4: Based on the optimal grinding wheel speed, nut speed and grinding depth process parameters obtained in Step 3, perform shape grinding on the nut.

2. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 1, characterized in that, In step 1, the orthogonal experiment uses the L9.3.3 orthogonal array to arrange the experimental scheme.

3. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 1, characterized in that, In step 2, the grinding quality of the inner raceway of the nut is determined by the arithmetic mean deviation R of the profile. a As an evaluation indicator.

4. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 3, characterized in that, The arithmetic mean deviation of the profile R a The acquisition process is as follows: The surface roughness of the three different inner raceways (front, middle, and rear) of the ball screw pair nut were tested multiple times. Remove outliers from the test results; Calculate the average of the remaining detection results as the final profile arithmetic mean deviation R. a R a The smaller the value, the better the grinding quality of the raceway inside the nut.

5. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 1, characterized in that, In step 2, during the grinding process, wet grinding is used, and coolant is used for cooling.

6. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 1, characterized in that, Step 3, based on the forming grinding process parameter data from Step 2 and the grinding quality of the inner raceway of the nut, determines the optimal matching of grinding wheel speed, nut speed, and grinding depth process parameters. The specific process includes: Step 3-1: For each process parameter, accumulate the surface roughness measurement results at a certain level to obtain the result. And calculate the average value. This represents the cumulative value of surface roughness measurement results for the i-th level of the process parameters; Step 3-2: For each process parameter, select the smallest value. The corresponding level value is taken as the optimal value of this process parameter; This yields the optimal combination of grinding wheel speed, nut speed, and grinding depth process parameters.

7. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 6, characterized in that, The method also includes execution after step 3 and before step 4: Step 31: Through range analysis, obtain the significance value of the influence of each process parameter on the grinding quality. Step 32: Prioritize the process parameters according to their significance level, as a reference for considering the priority of process parameters in subsequent forming grinding processes.

8. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 7, characterized in that, Step 31 is as follows: For each process parameter, obtain all corresponding parameters. The difference between the maximum and minimum values ​​in the range is denoted as the R-value, which serves as the significance value. Step 32 is as follows: The three process parameters are arranged in descending order based on the R value. The larger the R value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

9. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 7, characterized in that, Replace step 31 with: By using multifactor ANOVA to analyze grinding quality, the significance value of the influence of each process parameter on grinding quality was obtained.

10. The forming grinding method for improving the surface quality of the inner raceway of a precision lead screw pair nut based on orthogonal experiments according to claim 9, characterized in that, The process of obtaining the significance value of the influence of each process parameter on the grinding quality through multi-factor variance analysis is as follows: Step 31-1: Calculate the average surface roughness of all process parameters under all different combinations of level values; Step 31-2, based on the average values ​​of all process parameters Calculate the sum of squares corresponding to the process parameter by comparing it with the average value obtained in step 5-1; Step 31-3: Calculate the degrees of freedom and mean square values ​​for different process parameters; Step 31-4: Calculate the ratio of the mean square value from step 31-3 to the preset mean square error value, and use it as the F statistic. Steps 31-5: Based on the F statistic, look up the F distribution table to obtain the corresponding probability value P, which is used as the significance value of the process parameter; The specific process of step 32 is as follows: The process parameters are prioritized according to their significance values ​​P from smallest to largest. The smaller the P value, the greater the influence of the process parameter on the surface roughness during the grinding of the inner raceway of the nut.

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