Machine tool assembly consistency evaluation method and apparatus

Abstract

A machine tool assembly consistency evaluation method, relating to the field of machine tool assembly. By means of steps such as component dynamic stiffness testing, complete machine tool dynamic stiffness testing, frequency response function analysis, determination of the range of a characteristic frequency, dynamic stiffness data statistics collection, acquisition of theoretical values for dynamic stiffness evaluation, and dynamic stiffness evaluation, quality control is performed on critical components from sub-assembly to final assembly, and assembly consistency testing is performed at each stage of assembly. If an assembly quality problem or inconsistency is detected, the problems can be solved at an early stage, thereby shortening troubleshooting time and improving assembly efficiency, improving the assembly precision and efficiency of a machine tool, and ensuring the quality and performance of a product. Also provided is a machine tool assembly consistency evaluation apparatus.

Description

A method and apparatus for evaluating the consistency of machine tool assembly Technical Field

[0001] This invention relates to the field of machine tool assembly, and in particular to a method for evaluating the consistency of machine tool assembly and an apparatus for implementing the above method. Background Technology

[0002] The performance reliability of complex mechanical systems is ensured through the joint efforts of design, manufacturing, and assembly. Assembly is the final step in manufacturing complex systems and also the most crucial step in ensuring product quality. The quality and consistency of assembly directly determine the final performance of the mechanical structure. For complex mechanical systems like machine tools, the assembly process is even more complex, with significant and difficult-to-quantify human factors influencing the quality and consistency of assembly.

[0003] Assembly consistency of CNC machine tools has become a key factor restricting the development of high-end CNC machine tools in my country. Multiple CNC machine tools manufactured in the same batch have significant differences in processing performance, poor consistency, and poor accuracy retention. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a machine tool assembly consistency evaluation method that can improve the assembly accuracy and efficiency of machine tools and ensure the quality and performance of machine tools.

[0005] In order to overcome the shortcomings of the prior art, the second objective of this invention is to provide a machine tool assembly consistency control device that can improve the assembly accuracy and efficiency of machine tools and ensure the quality and performance of machine tools.

[0006] One of the objectives of this invention is achieved through the following technical solution:

[0007] A method for evaluating the consistency of machine tool assembly includes the following steps:

[0008] Dynamic stiffness test of components: The base component, the base-beam component and the spindle box-saddle component are hammered respectively. The hammering point is used as the test point. There are two test points. The two test points are located in different positions. Vibration signals in the corresponding direction near the test point are collected.

[0009] Overall mechanical stiffness test: The spindle box-saddle assembly is installed on the crossbeam, and the turntable assembly is installed on the base. The assembly is hammered, and the hammering point is used as the test point. There are three test points, and the three test points are located in different positions. Vibration signals in the corresponding directions near the test points are collected.

[0010] Frequency response function analysis: Using the hammer impact signal as the excitation signal and the vibration signal as the response signal, calculate the frequency response function between the excitation signal and the response signal. The horizontal axis represents the excitation frequency and the vertical axis represents the response amplitude. Record the frequency values ​​of the significant peaks in the frequency response function curves of each component and assembly.

[0011] Determine the characteristic frequency range: Change the assembly conditions of the whole machine to obtain the frequency response function curves under different assembly conditions and the frequency values ​​at multiple corresponding prominent peaks. Extract the frequencies where the frequency values ​​or response amplitudes change significantly as characteristic frequencies and determine the range of characteristic frequencies.

[0012] Dynamic stiffness data statistics: Statistically analyze the dynamic stiffness curves of multiple machine tools within the characteristic frequency range;

[0013] Theoretical value acquisition for dynamic stiffness evaluation: The minimum dynamic stiffness of the machine tool within the characteristic frequency range is taken as the dynamic stiffness value, and the dynamic stiffness value and the characteristic frequency range are taken as the theoretical values ​​for consistency evaluation.

[0014] Dynamic stiffness evaluation: Hammer impact test is performed on the part or whole machine to be evaluated. Based on the test results, the actual frequency value of the significant peak in the frequency response function curve is extracted. The actual frequency value is compared with the theoretical characteristic frequency range. The actual dynamic stiffness value is compared with the theoretical dynamic stiffness value. The assembly consistency is evaluated based on the two comparison results.

[0015] Furthermore, in the component dynamic stiffness test step, the base component is supported by base mounting feet, and the test is conducted after the base is leveled, with the test point located at the bottom of the base.

[0016] Furthermore, in the component dynamic stiffness test step, the base-beam component is a component in which the beam is mounted on the base component, and the test point is located at the bottom of the beam.

[0017] Furthermore, in the component dynamic stiffness test step, the spindle box and slide saddle component are suspended by nylon ropes during the test, and the test point is located on the spindle flange surface.

[0018] Furthermore, in the overall mechanical stiffness test step, two of the three test points are located on the spindle flange face, and the other test point is located on the turntable.

[0019] Furthermore, in the component dynamic stiffness test step and the whole machine dynamic stiffness test step, the frequency of the vibration signal is more than 2.5 times the natural frequency of the component structure or the whole machine structure.

[0020] Furthermore, in the component dynamic stiffness test step and the whole body dynamic stiffness test step, the number of hammer blows at each test point is multiple, and the vibration signal is collected when the coherence of the vibration signal reaches more than 85%.

[0021] Furthermore, in the component dynamic stiffness test step and the whole-body dynamic stiffness test step, the hammering directions of multiple test points are perpendicular.

[0022] Furthermore, in the step of determining the characteristic frequency range, changing the assembly conditions of the whole machine specifically involves changing at least one of the following: bolt preload torque, number of fasteners, insert preload force, and surface roughness.

[0023] The second objective of this invention is achieved by the following technical solution:

[0024] A machine tool assembly consistency evaluation device is provided for implementing any of the above-mentioned machine tool assembly consistency evaluation methods. The machine tool assembly consistency evaluation device includes an impact hammer, an acceleration sensor, and a processor. The impact hammer applies hammering to components and the whole machine. The acceleration sensor collects vibration signals generated by the hammering. The processor is communicatively connected to the acceleration sensor and is located within the vibration signal.

[0025] Compared to existing technologies, the machine tool assembly consistency evaluation method of this invention controls the quality of key components from sub-assembly to final assembly through steps such as component dynamic stiffness testing, overall dynamic stiffness testing, frequency response function analysis, determination of characteristic frequency range, dynamic stiffness data statistics, acquisition of theoretical values ​​for dynamic stiffness evaluation, and dynamic stiffness evaluation. Assembly consistency testing is conducted at each stage of assembly, allowing for early intervention to address assembly quality issues or consistency problems, shortening troubleshooting time and improving assembly efficiency. This enhances the assembly accuracy and efficiency of machine tools, ensuring product quality and performance. Attached Figure Description

[0026] Figure 1 is a flowchart of the machine tool assembly consistency evaluation method of the present invention;

[0027] Figure 2 shows the test items of the machine tool assembly consistency evaluation method of the present invention;

[0028] Figure 3 is a schematic diagram of the measuring points of the base component in the machine tool assembly consistency evaluation method of the present invention;

[0029] Figure 4 is a schematic diagram of the measuring points of the base-beam component in the machine tool assembly consistency evaluation method of the present invention.

[0030] Figure 5 is a schematic diagram of the measuring points of the spindle box-saddle component in the machine tool assembly consistency evaluation method of the present invention;

[0031] Figure 6 is a schematic diagram of the measurement points of the whole machine components in the machine tool assembly consistency evaluation method of the present invention;

[0032] Figure 7 shows the frequency response function curves between the excitation signal and the response signal;

[0033] Figure 8 shows a comparison of frequency response functions under different assembly conditions;

[0034] Figure 9 is a statistical chart of machine tool dynamic stiffness data. Detailed Implementation

[0035] 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.

[0036] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be fixed through another intermediate component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may be fixed through another intermediate component. When a component is said to be "set on" another component, it can be set directly on the other component or it may be set through another intermediate component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] Please refer to Figure 1. This application discloses a machine tool assembly consistency evaluation method, which includes the following steps:

[0039] Dynamic stiffness test of components: The base component, the base-beam component and the spindle box-saddle component were hammered respectively. The hammering point was used as the test point. There were two test points in total. The two test points were located in different positions. Vibration signals in the corresponding directions near the test points were collected.

[0040] Overall mechanical stiffness test: The spindle box-saddle assembly is installed on the crossbeam, and the turntable assembly is installed on the base. The assembly is hammered, and the hammering point is used as the test point. There are three test points, and the three test points are located in different positions. Vibration signals in the corresponding directions near the test points are collected.

[0041] Frequency response function analysis: Using the hammer impact signal as the excitation signal and the vibration signal as the response signal, calculate the frequency response function between the excitation signal and the response signal. The horizontal axis represents the excitation frequency and the vertical axis represents the response amplitude. Record the frequency values ​​of the significant peaks in the frequency response function curves of each component and assembly.

[0042] Determine the characteristic frequency range: Change the assembly conditions of the whole machine to obtain the frequency response function curves under different assembly conditions and the frequency values ​​at multiple corresponding prominent peaks. Extract the frequencies where the frequency values ​​or response amplitudes change significantly as characteristic frequencies and determine the range of characteristic frequencies.

[0043] Dynamic stiffness data statistics: Statistically analyze the dynamic stiffness curves of multiple machine tools within the characteristic frequency range;

[0044] Theoretical value acquisition for dynamic stiffness evaluation: The minimum dynamic stiffness of the machine tool within the characteristic frequency range is taken as the dynamic stiffness value, and the dynamic stiffness value and the characteristic frequency range are taken as the theoretical values ​​for consistency evaluation.

[0045] Dynamic stiffness evaluation: Hammer impact test is performed on the part or whole machine to be evaluated. Based on the test results, the actual frequency value of the significant peak in the frequency response function curve is extracted. The actual frequency value is compared with the theoretical characteristic frequency range. The actual dynamic stiffness value is compared with the theoretical dynamic stiffness value. The assembly consistency is evaluated based on the two comparison results.

[0046] Specifically, as shown in Figure 2, the objects to be tested include components and the complete machine. The components include the base component, the base-crossbeam component, and the spindle box-saddle component. Since the machine tool assembly consistency evaluation method requires an evaluation standard, i.e., a theoretical value, the components and the complete machine that have passed the consistency test are used in the component dynamic stiffness test and the complete machine dynamic stiffness test steps to obtain the evaluation standard for the components and the complete machine that have passed the consistency test.

[0047] The dynamic stiffness of the base component, the base-crossbeam component, and the spindle box-saddle component are tested in two mutually perpendicular directions, which are the X and Y directions in this embodiment. The dynamic stiffness of the entire machine is tested in three mutually perpendicular directions, which are the X, Y, and Z directions in this embodiment. The dynamic stiffness test in different directions is achieved by collecting vibration signals in different directions corresponding to different impact directions.

[0048] As shown in Figure 3, when testing the base component, the base is supported by mounting feet and leveled before testing. The test point is located at the bottom of the base. The arrows in the figure indicate the direction of the excitation force (hammering force), and the location of the arrows is the location of the excitation point. The sampling point is located near the excitation point. The two test points are test point 1 and test point 2, both located at the bottom of the base. Test point 1 is in the x-axis of the machine tool, and test point 2 is in the y-axis of the machine tool.

[0049] As shown in Figure 4, when testing the crossbeam-base component, the crossbeam is installed on the base component. The two test points are test point 1 and test point 2. Both test point 1 and test point 2 are located at the bottom of the crossbeam. Test point 1 is in the x-direction of the machine tool, and test point 2 is in the y-direction of the machine tool.

[0050] As shown in Figure 5, when testing the spindle box-saddle section, the spindle box and saddle components are lifted using nylon ropes, and the test points are located on the spindle flange surface. The two test points are test point 1 and test point 2, both located on the spindle flange surface. Test point 1 is in the x-axis of the machine tool, and test point 2 is in the y-axis of the machine tool.

[0051] As shown in Figure 6, during the testing of the entire machine, the spindle box-saddle assembly is mounted on the crossbeam, and the turntable assembly is mounted on the base. The three test points are test point 1, test point 2, and test point 3. Test points 1 and 2 are both located on the spindle flange surface. Test point 1 is in the x-axis of the machine tool, and test point 2 is in the y-axis of the machine tool. Test point 3 is on the turntable, in the radial direction of the worktable.

[0052] During testing, a hammer is used to strike designated points and directions on the structure, and an accelerometer is used to collect vibration signals in the corresponding direction near the strike location. The sampling frequency is at least 2.5 times the natural frequency of the structural features; preferably, in this embodiment, the sampling frequency is at least 2.56 times the natural frequency of the structural features. During the test, each measuring point is struck three times. When the coherence is good, reaching 85% or more, the data meets the requirements, and the data is collected. Preferably, in this embodiment, the coherence reaches 95% or more.

[0053] In the frequency response function analysis step, the frequency response function curve is shown in Figure 7.

[0054] In determining the characteristic frequency range, the specific steps of changing the assembly conditions of the entire machine are: changing at least one of the following: bolt preload torque, number of fasteners, insert preload force, and surface roughness. A comparison of the frequency response functions under different assembly conditions is shown in Figure 8.

[0055] In the dynamic stiffness data statistics step, the machine tools included in the statistics are components and complete machines, specifically those components and complete machines that meet consistency standards. The dynamic stiffness curves of multiple machine tools within the characteristic frequency range are shown in Figure 9. The minimum dynamic stiffness of the machine tool within the characteristic frequency range is taken as the dynamic stiffness value. The dynamic stiffness value and the characteristic frequency range are used as theoretical values ​​for consistency evaluation.

[0056] In this embodiment, the theoretical values ​​for the consistency evaluation of a certain series of machine tools are shown in Table 1:

[0057] Table 1

[0058] In the dynamic stiffness evaluation step, the part to be evaluated can be a component or a complete machine. Depending on the specific type and category of the part to be evaluated, such as a base component, a base-beam component, a spindle box-saddle component, or a complete machine, the corresponding methods in the component dynamic stiffness test and the complete machine dynamic stiffness test steps are used to conduct a hammer test. Based on the test results, the actual frequency value at the significant peak in the frequency response function curve is extracted. The actual frequency value is compared with the theoretical characteristic frequency range, and the actual dynamic stiffness value is compared with the theoretical dynamic stiffness value. The assembly consistency is evaluated based on the two comparison results.

[0059] This application also relates to a machine tool assembly consistency evaluation device for implementing the above-mentioned machine tool assembly consistency evaluation method. The machine tool assembly consistency evaluation device includes an impact hammer, an acceleration sensor, and a processor. The impact hammer applies hammering to the components and the whole machine. The acceleration sensor collects the vibration signal generated by the hammering. The processor is communicatively connected to the acceleration sensor and is in the vibration signal.

[0060] The impact hammer is used to apply excitation. The 086C03 model impact hammer has a sensitivity of 2.314mV / N, a range of ±2200N, and a resonant frequency of ≥22KHz.

[0061] The accelerometer is a unidirectional accelerometer.

[0062] Compared to existing technologies, the machine tool assembly consistency evaluation method of this invention controls the quality of key components from sub-assembly to final assembly through steps such as component dynamic stiffness testing, overall dynamic stiffness testing, frequency response function analysis, determination of characteristic frequency range, dynamic stiffness data statistics, acquisition of theoretical values ​​for dynamic stiffness evaluation, and dynamic stiffness evaluation. Assembly consistency testing is conducted at each stage of assembly, allowing for early intervention to address assembly quality issues or consistency problems, shortening troubleshooting time and improving assembly efficiency. This enhances the assembly accuracy and efficiency of machine tools, ensuring product quality and performance.

[0063] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These are all equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of these fall within the protection scope of the present invention.

Claims

1. A method for evaluating the consistency of machine tool assembly, characterized in that, Includes the following steps: Dynamic stiffness test of components: The base component, the base-beam component and the spindle box-saddle component are hammered respectively. The hammering point is used as the test point. There are two test points. The two test points are located in different positions. Vibration signals in the corresponding direction near the test point are collected. Overall mechanical stiffness test: The spindle box-saddle assembly is installed on the crossbeam, and the turntable assembly is installed on the base. The assembly is hammered, and the hammering point is used as the test point. There are three test points, and the three test points are located in different positions. Vibration signals in the corresponding directions near the test points are collected. Frequency response function analysis: Using the hammer impact signal as the excitation signal and the vibration signal as the response signal, calculate the frequency response function between the excitation signal and the response signal. The horizontal axis represents the excitation frequency and the vertical axis represents the response amplitude. Record the frequency values ​​of the significant peaks in the frequency response function curves of each component and assembly. Determine the characteristic frequency range: Change the assembly conditions of the whole machine to obtain the frequency response function curves under different assembly conditions and the frequency values ​​at multiple corresponding prominent peaks. Extract the frequencies where the frequency values ​​or response amplitudes change significantly as characteristic frequencies and determine the range of characteristic frequencies. Dynamic stiffness data statistics: Statistically analyze the dynamic stiffness curves of multiple machine tools within the characteristic frequency range; Theoretical value acquisition for dynamic stiffness evaluation: The minimum dynamic stiffness of the machine tool within the characteristic frequency range is taken as the dynamic stiffness value, and the dynamic stiffness value and the characteristic frequency range are taken as the theoretical values ​​for consistency evaluation. Dynamic stiffness evaluation: Hammer impact test is performed on the part or whole machine to be evaluated. Based on the test results, the actual frequency value of the significant peak in the frequency response function curve is extracted. The actual frequency value is compared with the theoretical characteristic frequency range. The actual dynamic stiffness value is compared with the theoretical dynamic stiffness value. The assembly consistency is evaluated based on the two comparison results.

2. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step, the base component is supported by base mounting feet, and the test is carried out after the base is adjusted to be level. The test point is located at the bottom of the base.

3. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step, the base-beam component is formed by mounting the beam on the base component, and the test point is located at the bottom of the beam.

4. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step, the spindle box and slide saddle component are suspended by nylon ropes during the test, and the test point is located on the spindle flange surface.

5. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the overall mechanical stiffness test procedure, two of the three test points are located on the spindle flange face, and the other test point is located on the turntable.

6. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step and the whole machine dynamic stiffness test step, the frequency of the vibration signal is more than 2.5 times the natural frequency of the component structure or the whole machine structure.

7. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step and the whole body dynamic stiffness test step, the number of hammer blows at each test point is multiple. When the vibration signal coherence reaches more than 85%, the vibration signal is collected.

8. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the component dynamic stiffness test step and the whole-body dynamic stiffness test step, the hammering directions at multiple test points are perpendicular.

9. The machine tool assembly consistency evaluation method according to claim 1, characterized in that: In the step of determining the characteristic frequency range, changing the assembly conditions of the whole machine specifically involves changing at least one of the following: bolt preload torque, number of fasteners, insert preload force, and surface roughness.

10. A machine tool assembly consistency evaluation device, used to implement the machine tool assembly consistency evaluation method as described in any one of claims 1-9, characterized in that: The machine tool assembly consistency evaluation device includes an impact hammer, an acceleration sensor, and a processor. The impact hammer applies hammering to the components and the whole machine. The acceleration sensor collects the vibration signal generated by the hammering. The processor is communicatively connected to the acceleration sensor and is in contact with the vibration signal.

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