A forward design method of ball screw pair for high-precision thread grinder

Abstract

The application discloses a high-precision thread grinder ball screw pair forward design method, which is applied to the ball screw pair external thread grinder technical field and comprises the following steps: aiming at the reliability requirement of high-precision and heavy-load ball screw pair, taking the average failure-free working time as an optimization target; performing main failure mode, influence and harmfulness analysis on the ball screw pair, clearly defining the material requirement of the ball screw pair, and performing performance test based on the material requirement to select the optimal material; performing sensitivity analysis on the key design parameters of the ball screw pair, clearly defining the relative influence weight of different design parameters on the optimization target, constructing a reliability target optimization model of the ball screw pair, and solving the optimized key design parameter combination. The application realizes the whole-process connection from performance requirement to engineering realization to continuous improvement, and provides a systematic method framework and theoretical support for the design and improvement of the reliability of the ball screw pair.

Description

Technical Field

[0001] This invention relates to the field of ball screw pair external thread grinding machine technology, and more specifically to a forward design method for ball screw pairs for high-precision thread grinding machines. Background Technology

[0002] As a key component of precision transmission systems, the performance of ball screw pairs directly affects the accuracy and stability of mechanical equipment. Therefore, conducting technical research on the design analysis, testing evaluation, improvement, and application verification of the reliability of high-end key functional components, tackling key scientific problems, breaking through key technologies, and systematically improving the reliability indicators of functional components are of great significance for supporting the high-end development of CNC machine tools.

[0003] Existing research paradigms have significant limitations. The vast majority of work focuses on the "post-hoc" characterization and prediction of reliability status, while generally neglecting the core issue of "proactively improving" the inherent reliability of products from the design stage. This "emphasis on assessment and neglect of improvement" has resulted in a critical gap in proactively enhancing product performance through positive design.

[0004] Therefore, how to provide a forward design method for high-precision thread grinding machine ball screw pairs that can proactively improve performance from the design source, systematically optimize in a closed loop, and enhance the reliability of functional components is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a forward design method for ball screw pairs for high-precision thread grinding machines.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A forward design method for ball screw pairs used in high-precision thread grinding machines includes: Step 1: To address the reliability requirements of high-precision, heavy-duty ball screw pairs, the optimization goal is to improve the mean time between failures (MTBF). Step 2: Conduct a major failure mode, effects and hazards analysis on the ball screw assembly, clarify the material requirements of the ball screw assembly, and conduct performance tests based on the material requirements to select the optimal material; Step 3: Perform sensitivity analysis on the key design parameters of the ball screw assembly to clarify the relative influence weight of different design parameters on the optimization objective, so as to construct a reliability target optimization model for the ball screw assembly and solve for the optimized combination of key design parameters.

[0007] Optionally, in step 1, the mean time between failures (MTBF) can be expressed as a function as follows: No. Mean time between failures (MTBF) for each failure mode :

[0008] in, The number of samples; For the first The total number of revolutions at the end of each sample test; Before the specified test deadline, the cumulative total of all samples is [number]. Total number of failures for each failure mode; For the first At the end of the first sample trial The number of failures in each failure mode; For degrees of freedom of Distribution The theoretical values ​​of quantiles can be found in a table. For the first The total number of revolutions for each sample at the end of the first stress level test; For the first The total number of revolutions for each sample at the end of the second stress level test; For the first The sample, during the first stress level test time, Number of failure modes; For the first The sample during the second stress level test time, Number of failure modes; Average fault interval revolutions across all samples :

[0009] Mean Time Between Failures Mean time between failures (MTBF):

[0010] in, This is the equivalent conversion factor.

[0011] Optionally, in step 2, performance tests are conducted based on material requirements to screen for the optimal material, specifically as follows: For lead screws, contact fatigue tests were conducted using the number of revolutions and the spalling damage on the sample surface as material performance indicators to screen for the optimal material.

[0012] Optionally, in step 3, the key design parameters of the ball screw pair include: nominal diameter, lead, number of balls, and preload.

[0013] Optionally, in step 3, a reliability target optimization model for the ball screw pair is constructed, specifically as follows: Using mean time between failures (MTBF) as the model optimization objective, load spectrum as the load boundary condition required for calculation, key design parameters of the ball screw pair as optimization variables, and the relative influence weights of different parameters as weighting coefficients, a reliability target optimization model is constructed.

[0014] Optionally, step 3, in constructing the reliability target optimization model for the ball screw pair, may also include: Probabilistic problem analysis for reliability design includes uncertainty analysis of design parameters and loads, and the introduction of a stress-strength interference model. The loads borne by the components and their limits are both regarded as random variables that follow a certain probability distribution. The reliability is quantitatively solved by calculating the area of ​​the interference zone between the two on the probability distribution.

[0015] Optionally, step 3, after obtaining the optimized combination of key design parameters, also includes: Load life tests were conducted on the ball screw pairs obtained by forward design, and the differences between the evolution law of the key performance parameters of the ball screw pairs during the test and the theoretical prediction of the model were compared. At the same time, based on the evolution law, the shortcomings of the existing model were identified, and the reliability forward design model based on the ball screw pairs was modified and supplemented in a targeted manner for the key influencing factors exposed in the test. The modified model was then fed back into the forward design system.

[0016] As can be seen from the above technical solution, compared with the prior art, this invention discloses a forward design method for ball screw pairs used in high-precision thread grinding machines. Focusing on the core performance objective of improving the reliability of ball screw pairs, a forward design model of "requirement-model-design-optimization-verification-improvement" is constructed and perfected. The model and key design parameters of the ball screw pair and their impact on reliability are analyzed, emphasizing the necessity of proactive optimization in the design stage. A target optimization method is adopted to improve the fatigue life of the ball screw pair. Furthermore, the effectiveness of the design model is verified through experiments, and the design scheme is continuously corrected and optimized using a feedback mechanism. This forward design model realizes the entire process from performance requirements to engineering implementation and continuous improvement, providing a systematic methodological framework and theoretical support for the design and improvement of ball screw pair reliability. In addition, the forward design model framework of this invention is also applicable to the optimization of other performance indicators, such as the accuracy retention of ball screw pairs. By starting from the requirements of performance indicators, a corresponding requirement expression model is established, and parameter design and optimization are carried out accordingly, ultimately verified and iteratively improved through specialized performance tests. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the method flow provided by the present invention.

[0019] Figure 2 This is a schematic diagram of fault classification provided by the present invention.

[0020] Figure 3 A schematic diagram of the stress-intensity interference model provided by this invention. Detailed Implementation

[0021] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: Embodiment 1 of this invention discloses a forward design method for a ball screw pair for a high-precision thread grinding machine, such as... Figure 1 As shown, it includes: Step 1: To meet the reliability requirements of high-precision, heavy-duty ball screw pairs, the optimization goal is to improve the mean time between failures (MTBF) (in this embodiment of the invention, the optimization goal is to increase the MTBF from the current 10,000h to 20,000h).

[0023] The mean time between failures (MTBF) is expressed as a function as follows: No. Mean time between failures (MTBF) for each failure mode :

[0024] in, The number of samples; For the first The total number of revolutions at the end of each sample test; Before the specified test deadline, the cumulative total of all samples is [number]. Total number of failures for each failure mode; For the first At the end of the first sample trial The number of failures in each failure mode; For degrees of freedom of Distribution The theoretical values ​​of quantiles can be found in a table. For the first The total number of revolutions for each sample at the end of the first stress level test; For the first The total number of revolutions for each sample at the end of the second stress level test; For the first The sample, during the first stress level test time, Number of failure modes; For the first The sample during the second stress level test time, Number of failure modes; Average fault interval revolutions across all samples :

[0025] Mean Time Between Failures Mean time between failures (MTBF):

[0026] in, This is the equivalent conversion factor.

[0027] Step 2: Conduct a major failure mode, effects and hazards analysis on the ball screw assembly, clarify the material requirements of the ball screw assembly, and carry out performance tests based on the material requirements to select the optimal material.

[0028] Perform a Major Failure Mode, Effects, and Criticality Analysis (FMECA) on the ball screw assembly to identify the most hazardous and vulnerable components that should be prioritized for avoidance or control in the design, thereby clarifying the material requirements for the ball screw assembly. Specifically: Fault classification of ball screw pairs, such as Figure 2 As shown; The main failure modes of ball screw pairs are shown in Table 1. Table 1. Main failure modes of ball screw pairs

[0029] The fault weighting table for ball screw pairs is shown in Table 2. Table 2. Fault Weighting Table for Ball Screw Pairs

[0030] The results of the FMECA analysis are shown in Table 3. Table 3. FMECA Analysis Results

[0031] Performance tests are conducted based on material requirements to screen for the optimal material, specifically: Taking lead screws as an example, contact fatigue tests were conducted using the number of revolutions and the spalling damage on the sample surface as material performance indicators to screen for the optimal material, as follows: Based on the FMECA analysis results, the following candidate materials for the lead screw were selected in this embodiment of the invention: Material 1 (GB50CrMo) and Material 2 (GCr15) are materials that have been widely used, and Material 3 (G50CrMo) is a new material developed by a certain company. The chemical element content (%) of the three materials is shown in Table 4.

[0032] Table 4: Chemical element content (%) of the three materials

[0033] Contact fatigue tests were conducted, and the number of cycles for the three materials is shown in Table 5. Table 5. Number of cycles for the three materials

[0034] Regarding the surface spalling damage of the samples from the three materials, all three materials exhibited significant spalling when the vibration stopped at the 3g vibration threshold. The largest spalling area for GCr15 was 1.908 mm². 2 The maximum spalling area of ​​G50CrMo is 0.337 mm. 2 The maximum spalling area of ​​GB50CrMo is 1.221 mm. 2 Based on the analysis of contact fatigue cycle count and surface spalling damage, G50CrMo is the preferred material.

[0035] Step 3: Perform sensitivity analysis on the key design parameters of the ball screw assembly (based on numerical simulation or surrogate model) to clarify the relative influence weight of different design parameters on the optimization target (i.e., mean time between failures), so as to construct a reliability target optimization model for the ball screw assembly and solve for the optimized combination of key design parameters.

[0036] Key design parameters for ball screw assemblies include: nominal diameter, lead, number of balls, and preload.

[0037] Construct a reliability target optimization model for the ball screw pair, specifically as follows: With mean time between failures (MTBF ≥ 20000 h) as the model optimization objective, load spectrum as the load boundary condition required for calculation, key design parameters of the ball screw pair as optimization variables, and the relative influence weights of different parameters as weighting coefficients, a reliability target optimization model is constructed.

[0038] The final output is a set of design parameters that simultaneously meet the fatigue life reliability constraints. For example, nominal diameter d0 = 40 mm, lead Ph = 10 mm, number of balls N = 60, preload Fp = 0.1 Ca, etc.

[0039] Since any design and service condition inherently involves uncertainties, constructing a reliability target optimization model for ball screw pairs also includes: Probabilistic problem analysis for reliability design includes uncertainty analysis of design parameters (such as dimensional tolerances and material property dispersion) and loads (such as fluctuations in the load spectrum itself). A stress-strength interference model is introduced, treating both the loads (stress) borne by the components and their ultimate strength as random variables following a certain probability distribution. Reliability is quantitatively determined by calculating the area of ​​the interference region between the two on the probability distribution. Figure 3 As shown.

[0040] After obtaining the optimized combination of key design parameters, the solution also includes: Load life tests were conducted on the ball screw pairs obtained through forward design. The evolution of key performance parameters (including friction torque and stroke error, in addition to mean time between failures) during the tests was compared with the theoretical predictions of the model. This verified the accuracy of the established model and the applicability and engineering feasibility of the forward design method for high-precision, heavy-duty ball screw pair design. Based on the evolution patterns, shortcomings in the existing model regarding assumptions, parameter selection, and consideration of influencing factors were identified. Targeted corrections and supplements were made to the reliability forward design model based on the ball screw pairs to address the key influencing factors revealed in the tests. For example, the load application form, stiffness decay characteristics, and preload variation were reasonably characterized to improve the model's ability to describe and predict the service behavior of the ball screw pairs. The corrected model was then fed back into the forward design system to iteratively update the selection principles and optimization objectives of design parameters, forming a closed-loop design mechanism of "verification-feedback-improvement" to achieve continuous improvement in the reliability of the ball screw pairs.

[0041] Therefore, a forward design model for ball screw pair reliability with self-correction capability is constructed. Compared with the traditional design method that mainly relies on experience and reverse correction, the forward design model proposed in this invention introduces experimental verification and feedback mechanisms, enabling the ball screw pair design process to have continuous evolution and performance improvement capabilities.

[0042] Furthermore, the forward design model framework of this invention is also applicable to the optimization of other performance indicators, such as the accuracy retention of ball screw pairs. Starting from the requirements of performance indicators (e.g., the target requirement of improving accuracy retention from the original 4000h to 5000h), a corresponding requirement expression model (accuracy degradation model) is established, and parameter design and optimization are carried out accordingly. Finally, it is verified and iteratively improved through specialized performance tests.

[0043] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0044] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A forward design method for a ball screw pair for a high-precision thread grinding machine, characterized in that, include: Step 1: To address the reliability requirements of high-precision, heavy-duty ball screw pairs, the optimization goal is to improve the mean time between failures (MTBF). Step 2: Conduct a major failure mode, effects and hazards analysis on the ball screw assembly, clarify the material requirements of the ball screw assembly, and carry out performance tests based on the material requirements to select the optimal material; Step 3: Perform sensitivity analysis on the key design parameters of the ball screw assembly to clarify the relative influence weight of different design parameters on the optimization objective, so as to construct the reliability target optimization model of the ball screw assembly and solve the optimized combination of key design parameters.

2. The positive design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, In step 1, the function expression of the mean time between failures (MTBF) is as follows: No. Mean time between failures (MTBF) for each failure mode : in, The number of samples; For the first The total number of revolutions at the end of each sample test; Before the specified test deadline, the cumulative total of all samples is [number]. Total number of failures for each failure mode; For the first At the end of the first sample trial The number of failures in each failure mode; For degrees of freedom of Distribution The theoretical values ​​of quantiles can be found in a table. For the first The total number of revolutions for each sample at the end of the first stress level test; For the first The total number of revolutions for each sample at the end of the second stress level test; For the first The sample, during the first stress level test time, Number of failure modes; For the first The sample during the second stress level test time, Number of failure modes; Average fault interval revolutions across all samples : Mean Time Between Failures Mean time between failures (MTBF): in, This is the equivalent conversion factor.

3. The positive design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, In step 2, performance tests are conducted based on the material requirements to screen for the optimal material, specifically as follows: For lead screws, contact fatigue tests were conducted using the number of revolutions and the spalling damage on the sample surface as material performance indicators to screen for the optimal material.

4. The forward design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, In step 3, the key design parameters of the ball screw assembly include: nominal diameter, lead, number of balls, and preload.

5. The forward design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, In step 3, a reliability target optimization model for the ball screw pair is constructed, specifically as follows: The reliability target optimization model is constructed by taking the mean time between failures (MTBF) as the model optimization objective, the load spectrum as the load boundary condition required for calculation, the key design parameters of the ball screw pair as optimization variables, and the relative influence weights of different parameters as weighting coefficients.

6. The forward design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, Step 3, constructing the reliability target optimization model for the ball screw pair, further includes: Probabilistic problem analysis for reliability design includes uncertainty analysis of design parameters and loads, and the introduction of a stress-strength interference model. The loads borne by the components and their limits are both regarded as random variables that follow a certain probability distribution. The reliability is quantitatively solved by calculating the area of ​​the interference zone between the two on the probability distribution.

7. The forward design method for a ball screw pair for a high-precision thread grinding machine according to claim 1, characterized in that, Step 3, after obtaining the optimized combination of key design parameters, also includes: Load life tests were conducted on the ball screw pairs obtained by forward design, and the differences between the evolution law of the key performance parameters of the ball screw pairs during the test and the theoretical prediction of the model were compared. At the same time, based on the evolution law, the shortcomings of the existing model were identified. For the key influencing factors exposed in the test, the reliability forward design model based on the ball screw pairs was modified and supplemented in a targeted manner, and the modified model was fed back into the forward design system.

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