Method and device for enhancing initial precision retentivity of vertical machining center

Abstract

The invention discloses a method and device for enhancing the initial precision retentivity of a vertical machining center. The method for enhancing the initial precision retentivity of the vertical machining center comprises the steps that S1, the original precision and feature information of a machine tool are tested; s2, the machine tool is pre-operated, and a three-way dynamic force follow-up load is applied; potential precision problems of the machine tool are excited; s3, testing the precision and feature information of the machine tool again; s4, calculating a machine tool precision retention capability index, and judging whether the preset index is met or not; and S5, if yes, the test is ended, and if not, the machine tool is assembled and adjusted according to the index. In the running-in stage before the machine tool leaves the factory, dynamic force is actively applied in the operation process of the machine tool to excite the initial precision degradation cause of the machine tool, so that the machine tool passes through the initial precision sharp decline stage before leaving the factory; and the precision of the machine tool can be kept for a long time in the on-site service process of a user.

Description

Technical Field

[0001] This invention belongs to the field of CNC machine tool performance testing technology, specifically relating to a method and device for enhancing the initial accuracy retention of a vertical machining center. Background Technology

[0002] Due to factors such as wear and tear on dynamic mating surfaces like lead screws, nuts, and guide rails, and degradation of preload on fixed mating surfaces, domestically produced machine tools often exhibit significant accuracy degradation in the early stages of service, severely restricting their market competitiveness.

[0003] In 2014, Cai Ligang et al. from Beijing University of Technology disclosed a geometric accuracy design method for multi-axis CNC machine tools aimed at improving machining accuracy reliability in patent CN201410369530.3. This method establishes a machining accuracy reliability model and a machining accuracy sensitivity model for multi-axis CNC machine tools under multiple failure modes, optimizing geometric error terms with high machining accuracy reliability sensitivity to improve the machining accuracy reliability of the machine tool. In 2024, Ding Qicheng et al. from Chengdu Aircraft Industry (Group) Co., Ltd. disclosed a servo parameter tuning method for improving the dynamic accuracy of five-axis machine tools in patent CN202410708830.3. This method uses a convolutional neural network mapping model and a genetic algorithm to find the optimal servo parameter settings that minimize dynamic error, thereby improving the dynamic accuracy of the five-axis machine tool. In 2024, Fan Jinwei et al. from Beijing University of Technology disclosed a machine tool accuracy improvement method based on guide rail morphology design in patent CN202411917920.X. By establishing a spatial error prediction model of guide rail morphology, the guide rail morphology is actively designed, thereby improving the assembly accuracy of machine tool guide rails.

[0004] However, although scholars have proposed some methods to improve machine tool accuracy, there is still no solution to the problem of significant accuracy degradation in the early stages of machine tool service. Therefore, a method and device for enhancing the initial accuracy retention of vertical machining centers are proposed. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0006] To address this issue, the present invention proposes a method and apparatus for enhancing the initial accuracy retention of vertical machining centers. This method and apparatus addresses the rapid decline in accuracy during the initial service life of machine tools. During the running-in phase before the machine tool leaves the factory, dynamic forces are actively applied during the machine tool's operation to stimulate the causes of initial accuracy degradation, such as the decline in preload on the fixed mating surfaces and wear on the rolling mating surfaces. This allows the machine tool to overcome the rapid decline in initial accuracy before leaving the factory, ensuring that the machine tool maintains its accuracy for a long time during its service life at the user's site.

[0007] The method for enhancing the initial accuracy retention of a vertical machining center according to an embodiment of the present invention includes the following steps: Step S1. Test the original accuracy and feature information of the machine tool; Step S2. Run the machine tool and simultaneously apply a three-dimensional dynamic force follow-up load; stimulate potential problems that lead to a decrease in machine tool accuracy; Step S3. Test the machine tool accuracy and feature information again; Step S4. Calculate the accuracy retention capability index of the computer tool and determine whether it meets the preset index; Step S5. If the condition is met, the test ends; if not, the machine tool is adjusted according to the specified index; then the cycle of steps S1-S4 is repeated.

[0008] According to an embodiment of the present invention, in step S1, a laser interferometer is used to test the positioning accuracy, straightness and angle of the machine tool; a ball bar is used to test the linkage accuracy and perpendicularity of the machine tool; and the accuracy values ​​of positioning accuracy, straightness, angle, linkage accuracy and perpendicularity, as well as the curve trajectory of the coordinate position-error of the feed axis are recorded for each test.

[0009] According to an embodiment of the present invention, in step S1, vibration sensors are arranged on the machine tool guide rail slider pair, the lead screw nut pair, and the bearing seats at both ends to collect the vibration amount at the corresponding position of each vibration sensor when each feed axis of the machine tool is running at 50% of the fastest feed speed. At the same time, the position coordinates of each feed axis of the machine tool are collected from the CNC system through the data acquisition gateway, so that the position coordinates of the feed axis and the vibration amount correspond to each other in space.

[0010] According to an embodiment of the present invention, in step S1, a device for enhancing the initial accuracy retention of a vertical machining center is installed on the machine tool, and strain gauges are arranged on one side of the bed where the guide rail is installed, so that the feed axis reciprocates once, and static forces in three directions are applied to the machine tool at the same time, and strain values ​​at each coordinate position under force loading are collected synchronously through the strain gauges.

[0011] According to one embodiment of the present invention, in step S2, the feed axis is made to run at the fastest feed speed, and at the same time, the vertical machining center initial accuracy retention enhancement device is used to apply dynamic forces in the X, Y and Z directions to the machine tool, with a cumulative loading time of 72 hours.

[0012] According to one embodiment of the present invention, in step S4, the accuracy retention capability index includes: Indicator 1: Rate of change of precision value R a ; Indicator 2: Accuracy Trajectory Overlap D a ; Indicator 3: Rate of change of vibration amplitudeR v ; Indicator 4: Rate of change of strain R ε .

[0013] According to one embodiment of the present invention, the range of the accuracy retention capability index includes: Indicator 1: Rate of change of precision value R a ≤10%; Indicator 2: Accuracy Trajectory Overlap D a ≥90%; Indicator 3: Rate of change of vibration amplitude R v ≤10%; Indicator 4: Rate of change of strain R ε ≤10%.

[0014] According to one embodiment of the present invention, in step S4, the vibration amplitude change rate is used... R v and strain rate of change R ε Two items Indicators are used to determine the weak points of a machine tool; significant changes in vibration indicate severe wear at that location, while significant changes in strain indicate a degradation in bolt preload at that location.

[0015] A device for enhancing the initial accuracy retention of a vertical machining center, used to implement the method for enhancing the initial accuracy retention of a vertical machining center as described above, includes a follow-up module and a three-dimensional dynamic force loading module; the follow-up module is mounted on the machine tool worktable, the three-dimensional dynamic force loading module is disposed on the follow-up module, the three-dimensional dynamic force loading module is provided with a simulated tool holder assembly, the follow-up module is used to drive the simulated tool holder assembly to move synchronously with the machine tool, and the three-dimensional dynamic force loading module is used to output a loading force to the machine tool under test.

[0016] According to one embodiment of the present invention, the triaxial dynamic force loading module includes: Connect the base plate; The X-direction force application component includes an X-direction hydraulic cylinder support structure, an X-direction hydraulic cylinder, an X-direction force sensor, and an X-direction cross-shaped guide rail slider pair. The Y-direction force application component includes a Y-direction hydraulic cylinder support structure, a Y-direction hydraulic cylinder, a Y-direction force sensor, and a Y-direction cross-shaped guide rail slider pair. Z-direction force application component, the Z-direction force application component includes Z-direction hydraulic cylinder, Z-direction force sensor, and Z-direction cross-shaped guide rail slider pair; The connecting base plate is mounted on the follow-up module, and the X-direction force application component, Y-direction force application component and Z-direction force application component are all mounted on the connecting base plate.

[0017] The beneficial effects of this invention are as follows: During the running-in stage before the machine tool leaves the factory, this invention actively applies dynamic force during the machine tool's operation to stimulate the causes of initial accuracy degradation, such as the decline of preload on the fixed mating surfaces and the wear and tear of the rolling mating surfaces. Combined with the accuracy retention capability index, this invention identifies and traces the machine tool's shortcomings, and then enhances the machine tool's initial accuracy retention by readjusting the location of these shortcomings. This ensures that the machine tool passes through the initial rapid accuracy degradation stage before leaving the factory, guaranteeing long-term accuracy maintenance during its service at the user's site. Furthermore, this invention establishes a machine tool accuracy retention capability index, which can determine the machine tool's accuracy retention level and, based on the index, trace the source of machine tool shortcomings. The three-dimensional dynamic force loading module of the follow-up module is adopted to realize the application of dynamic forces in the X, Y and Z directions to the machine tool simultaneously while the machine tool feed axis moves.

[0018] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the steps of the present invention; Figure 2 This is a schematic diagram of the initial precision retention enhancement structure device of the present invention installed on a vertical machining center; Figure 3 This is a schematic diagram of the triaxial dynamic force loading module of the present invention installed on the dynamic module; Figure 4 This is a schematic diagram of the three-dimensional dynamic force loading module of the present invention; Figure label: 1. Follow-up module; 2. Three-way dynamic force loading module; 21. Connecting base plate; 22. X-direction hydraulic cylinder support structure; 23. X-direction hydraulic cylinder; 24. X-direction force sensor; 25. X-direction cross-rail slider pair; 26. Y-direction hydraulic cylinder support structure; 27. Y-direction hydraulic cylinder; 28. Y-direction force sensor; 29. ​​Y-direction cross-rail slider pair; 210. Z-direction hydraulic cylinder; 211. Z-direction force sensor; 212. Z-direction cross-rail slider pair; 213. Three-way connecting block; 214. Simulated tool holder assembly. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0022] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] The following describes in detail, with reference to the accompanying drawings, a method and apparatus for enhancing the initial accuracy retention of a vertical machining center according to an embodiment of the present invention.

[0024] like Figure 1-4 As shown, the method for enhancing the initial accuracy retention of a vertical machining center according to an embodiment of the present invention includes the following steps: Step S1. Test the original accuracy and feature information of the machine tool; Step S2. Run the machine tool and simultaneously apply a three-dimensional dynamic force follow-up load; stimulate potential problems that lead to a decrease in machine tool accuracy; Step S3. Test the machine tool accuracy and feature information again; Step S4. Calculate the accuracy retention capability index of the computer tool and determine whether it meets the preset index; Step S5. If the condition is met, the test ends; if not, the machine tool is adjusted according to the specified index; then the cycle of steps S1-S4 is repeated.

[0025] In this embodiment, during the running-in stage before the machine tool leaves the factory, dynamic forces are actively applied during the operation of the machine tool to induce the initial precision degradation causes such as the decline of preload on the fixed mating surface and the wear of the rolling mating surface. This allows the machine tool to pass through the initial stage of rapid precision degradation before leaving the factory, ensuring that the precision of the machine tool can be maintained for a long time during its service at the user's site.

[0026] In step S1, a laser interferometer is used to test the positioning accuracy, straightness, and angle of the machine tool; a ball bar is used to test the linkage accuracy and perpendicularity of the machine tool; and the accuracy values ​​of positioning accuracy, straightness, angle, linkage accuracy, and perpendicularity, as well as the curve trajectory of the coordinate position-error of the feed axis, are recorded for each test.

[0027] In step S1, vibration sensors are arranged on the machine tool guide rail slider pair, lead screw nut pair, and bearing seats at both ends to collect the vibration amount at the corresponding position of each vibration sensor when each feed axis of the machine tool is running at 50% of the fastest feed speed. At the same time, the position coordinates of each feed axis of the machine tool are collected from the CNC system through the data acquisition gateway, so that the position coordinates of the feed axis and the vibration amount correspond to each other in space.

[0028] In step S1, a device to enhance the initial accuracy retention of a vertical machining center is installed on the machine tool. Strain gauges are arranged on one side of the bed where the guide rails are mounted, so that the feed axis reciprocates once, and static forces in three directions are applied to the machine tool at the same time. The strain values ​​at each coordinate position under the force loading are collected synchronously through the strain gauges.

[0029] In step S2, the feed axis is made to run at the fastest feed speed, and the initial accuracy retention enhancement device of the vertical machining center is used to apply dynamic forces in the X, Y and Z directions to the machine tool for a total loading time of 72 hours.

[0030] In step S4, the accuracy retention capability indicators include: Indicator 1: Rate of change of precision value R a ; Indicator 2: Accuracy Trajectory Overlap Da ; Indicator 3: Rate of change of vibration amplitude R v ; Indicator 4: Rate of change of strain R ε .

[0031] The range of the accuracy retention capability index includes: Indicator 1: Rate of change of precision value R a ≤10%; Indicator 2: Accuracy Trajectory Overlap D a ≥90%; Indicator 3: Rate of change of vibration amplitude R v ≤10%; Indicator 4: Rate of change of strain R ε ≤10%.

[0032] Specifically, the accuracy retention capability index of the computer tool is calculated based on the accuracy values ​​of positioning accuracy, straightness, angle, linkage accuracy, and perpendicularity obtained before and after loading, as well as the curve trajectory of the feed axis coordinate position-error, obtained in steps one and three. The specific calculation method is as follows: Indicator 1:

[0033] In the formula, R a For the rate of change of the precision value, e af This is the precision value after loading. e be The accuracy values ​​are those before loading; if each accuracy value tested meets the requirements... R a If the percentage is ≤10%, then indicator one is met; Indicator 2:

[0034] In the formula, D a For accuracy trajectory overlap. The area of ​​the overlapping portion of the curve trajectory of the feed axis coordinate position - error before and after loading and the area enclosed by the coordinate axes of the curve trajectory. A be The area enclosed by the curve of the feed axis's coordinate position before loading versus the coordinate axis of that curve; if each accuracy trajectory tested satisfies D a If the percentage is ≥90%, then indicator two is met; Indicator 3:

[0035] In the formula, R v The rate of change of vibration amplitude. V af This represents the peak value of the vibration at the corresponding location of the vibration sensor after loading. V be This represents the peak value of the vibration at the corresponding location of the vibration sensor before loading; if the measured vibration at each corresponding location satisfies... R v If the percentage is ≤10%, then indicator three meets the standard; Indicator 4:

[0036] In the formula, R ε For the rate of change of strain, ε be This represents the peak value of the strain at the coordinate position after loading. ε be The peak value of the strain at the coordinate position before loading; if each test position satisfies R ε If the percentage is ≤10%, then indicator four meets the standard; If all four indicators meet the standards, the machine tool meets the factory requirements and the test ends; if any one indicator fails to meet the standards, the machine tool does not meet the factory requirements and step S5 needs to be continued.

[0037] In step S4, the rate of change of vibration amplitude is used. R v and strain rate of change R ε Two indicators are used to determine the weak points of a machine tool: a significant change in vibration indicates severe wear at that location, and a significant change in strain indicates a degradation in the bolt preload at that location.

[0038] A device for enhancing the initial accuracy retention of a vertical machining center, used to implement the aforementioned method for enhancing the initial accuracy retention of a vertical machining center, includes a follower module 1 and a three-dimensional dynamic force loading module 2. The follower module 1 is mounted on the machine tool worktable, and the three-dimensional dynamic force loading module 2 is located on the follower module 1, controlling the follower module 1 to move synchronously with the X-axis servo motor of the machine tool. The three-dimensional dynamic force loading module 2 is equipped with a simulated tool holder assembly 214, and the follower module 1 drives the simulated tool holder assembly 214 to move synchronously with the machine tool. The three-dimensional dynamic force loading module 2 is used to output a loading force to the machine tool under test.

[0039] Specifically, the three-directional dynamic force loading module 2 includes: a connecting base plate 21, an X-direction force application component, a Y-direction force application component, and a Z-direction force application component.

[0040] The X-direction force application component includes an X-direction cylinder support structure 22, an X-direction cylinder 23, an X-direction force sensor 24, and an X-direction cross-shaped guide rail slider assembly 25. The X-direction cylinder 23 is fixedly installed on the X-direction cylinder support structure 22, the X-direction force sensor 24 is installed on the output end of the X-direction cylinder 23, and the X-direction cross-shaped guide rail slider assembly 25 is installed on the X-direction force sensor 24.

[0041] The Y-direction force application component includes a Y-direction cylinder support structure 26, a Y-direction cylinder 27, a Y-direction force sensor 28, and a Y-direction cross-shaped guide rail slider assembly 29. The Y-direction cylinder 27 is fixedly installed on the Y-direction cylinder support structure 26, the Y-direction force sensor 28 is installed on the output end of the Y-direction cylinder 27, and the Y-direction cross-shaped guide rail slider assembly 29 is installed on the Y-direction cross-shaped guide rail slider assembly 29.

[0042] The Z-direction force application assembly includes a Z-direction hydraulic cylinder 210, a Z-direction force sensor 211, and a Z-direction cross-shaped guide rail slider assembly 212. The Z-direction force sensor 211 is mounted on the output end of the Z-direction hydraulic cylinder 210, and the Z-direction cross-shaped guide rail slider assembly 212 is mounted on the Z-direction force sensor 211.

[0043] The connecting base plate 21 is mounted on the follower module 1. The X-direction hydraulic cylinder support structure 22, the Y-direction hydraulic cylinder support structure 26 and the Z-direction hydraulic cylinder 210 are all fixedly installed on the connecting base plate 21. The simulated tool holder assembly 214 is connected to the X-direction cross rail slider pair 25, the Y-direction cross rail slider pair 29 and the Z-direction cross rail slider pair 212 through the three-way connecting block 213.

[0044] Z-direction cross-rail slider pair 212 is connected to the lower end of the three-way connecting block 213, Y-direction cross-rail slider pair 29 and X-direction cross-rail slider pair 25 are respectively connected to the adjacent two sides of the three-way connecting block 213, and simulated tool holder assembly 214 is installed on the upper end of the three-way connecting block 213.

[0045] The X-direction cylinder 23, Y-direction cylinder 27, and Z-direction cylinder 210 are all used to actively output loading force to the three-way connecting block 213; the X-direction force sensor 24, Y-direction force sensor 28, and Z-direction force sensor 211 are used to monitor the magnitude of the loading force in real time and form a closed-loop feedback control; the X-direction cross-rail slider pair 25, Y-direction cross-rail slider pair 29, and Z-direction cross-rail slider pair 212 are used to prevent the extension rods of the cylinders connected to them from being subjected to lateral forces; the simulated tool holder assembly 214 is used to connect the three-way dynamic force loading module 2 to the machine tool spindle.

[0046] Example 1 Taking the initial accuracy retention enhancement test of a three-axis vertical machining center as an example.

[0047] Step S1. Test the original accuracy and feature information of the machine tool; During the running-in phase before the machine tool leaves the factory, a laser interferometer is used to test the positioning accuracy, straightness, and angle of the X, Y, and Z axes, and a ball bar is used to test the linkage accuracy and perpendicularity. The accuracy values ​​for positioning, straightness, angle, linkage, and perpendicularity are recorded for each step, along with the curve trajectory of the feed axis's coordinate position versus error. Vibration sensors are placed at 15 measuring points on the guide rails, sliders, lead screws, and bearing seats at both ends of the X, Y, and Z axes. A CNC program is written to run the X, Y, and Z axes at a speed of 5000 mm / min, and data is collected simultaneously using vibration sensors and a data acquisition gateway. The vibration and position coordinates of each measuring point during machine tool operation are recorded, and the position coordinates correspond spatially to the vibration. A reinforcement device is installed on the machine tool, and the simulated tool holder assembly 214 of the reinforcement device is connected to the machine tool spindle. The base plate of the follower module 1 is connected to the machine tool worktable. Strain gauges are arranged on one side of the bed-guide rail mounting surface of the X, Y, and Z axes of the machine tool, totaling 36 measuring points. A CNC program is written to make the X axis of the machine tool run at a speed of 5000 mm / min. At the same time, the reinforcement device applies static forces in the X, Y, and Z directions to the machine tool, and the strain values ​​of each measuring point under force loading are collected synchronously through strain gauges.

[0048] Step S2. Apply three-dimensional dynamic force follow-up loading to the machine tool; The machine tool's X-axis is made to run at a speed of 5000 mm / min. At the same time, a dynamic force is applied to the machine tool in the X, Y, and Z directions using a booster device. The dynamic force amplitude is 2000 N and the frequency is 10 Hz. The cumulative loading time is 72 hours.

[0049] Step S3. Re-measure the accuracy and feature information of the machine tool after loading; Stop loading and, following the requirements of step S1, test the accuracy and feature information of the machine tool again after loading.

[0050] Step S4. Calculation and judgment of accuracy retention capability index; Based on the accuracy and feature information data obtained before and after loading obtained in steps S1 and S3, the accuracy retention capability index of the computer tool is calculated according to the calculation formulas of indexes one to four. Through calculation, it was found that the accuracy value change rate of the straightness of the machine tool in the X-axis and Y-axis directions, the accuracy trajectory coincidence, and the strain change rate did not meet the standards.

[0051] Step S5. Trace the source of the machine tool's shortcomings and readjust it.

[0052] By observing the strain changes on the X-axis bed-guide rail mounting surface, it was found that the cause of the change in the straightness of the X-axis Y direction was a change in the pre-tightening state of the wedge block on the side of the guide rail. After readjusting the wedge block on the X-axis side guide rail, steps S1-S4 were repeated, and it was found that all four indicators met the standards, thus ending the test.

[0053] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for enhancing the initial accuracy retention of a vertical machining center, characterized in that, Includes the following steps: Step S1. Test the original accuracy and feature information of the machine tool; Step S2. Run the machine tool and simultaneously apply a three-dimensional dynamic force follow-up load; stimulate potential problems that lead to a decrease in machine tool accuracy; Step S3. Test the machine tool accuracy and feature information again; Step S4. Calculate the accuracy retention capability index of the computer tool and determine whether it meets the preset index; Step S5. If the condition is met, the test ends; if not, the machine tool is adjusted according to the specified index; then the cycle of steps S1-S4 is repeated.

2. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 1, characterized in that, In step S1, a laser interferometer is used to test the positioning accuracy, straightness, and angle of the machine tool; a ball bar is used to test the linkage accuracy and perpendicularity of the machine tool; and the accuracy values ​​of positioning accuracy, straightness, angle, linkage accuracy, and perpendicularity, as well as the curve trajectory of the coordinate position-error of the feed axis, are recorded for each test.

3. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 2, characterized in that, In step S1, vibration sensors are arranged on the machine tool guide rail slider pair, lead screw nut pair, and bearing seats at both ends to collect the vibration amount at the corresponding position of each vibration sensor when each feed axis of the machine tool is running at 50% of the fastest feed speed. At the same time, the position coordinates of each feed axis of the machine tool are collected from the CNC system through the data acquisition gateway, so that the position coordinates of the feed axis and the vibration amount correspond to each other in space.

4. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 3, characterized in that, In step S1, a device to enhance the initial accuracy retention of a vertical machining center is installed on the machine tool. Strain gauges are arranged on one side of the bed where the guide rails are mounted, so that the feed axis reciprocates once, and static forces in three directions are applied to the machine tool at the same time. The strain values ​​at each coordinate position under the force loading are collected synchronously through the strain gauges.

5. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 1, characterized in that, In step S2, the feed axis is made to run at the fastest feed speed, and the initial accuracy retention enhancement device of the vertical machining center is used to apply dynamic forces in the X, Y and Z directions to the machine tool for a total loading time of 72 hours.

6. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 1, characterized in that, In step S4, the accuracy retention capability indicators include: Indicator 1: Rate of change of precision value R a ; Indicator 2: Accuracy Trajectory Overlap D a ; Indicator 3: Rate of change of vibration amplitude R v ; Indicator 4: Rate of change of strain R ε .

7. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 6, characterized in that, The range of the accuracy retention capability index includes: Indicator 1: Rate of change of precision value R a ≤10%; Indicator 2: Accuracy Trajectory Overlap D a ≥90%; Indicator 3: Rate of change of vibration amplitude R v ≤10%; Indicator 4: Rate of change of strain R ε ≤10%.

8. The method for enhancing the initial accuracy retention of a vertical machining center according to claim 7, characterized in that, In step S4, the rate of change of vibration amplitude is used. R v and strain rate of change R ε Two items Indicators are used to determine the weak points of a machine tool; significant changes in vibration indicate severe wear at that location, while significant changes in strain indicate a degradation in bolt preload at that location.

9. A device for enhancing the initial accuracy retention of a vertical machining center, used to implement the method for enhancing the initial accuracy retention of a vertical machining center as described in any one of claims 1-8, characterized in that, It includes a follow-up module (1) and a three-dimensional dynamic force loading module (2); the follow-up module (1) is installed on the machine tool workbench, the three-dimensional dynamic force loading module (2) is located on the follow-up module (1), the three-dimensional dynamic force loading module (2) is provided with a simulated tool holder assembly (214), the follow-up module (1) is used to drive the simulated tool holder assembly (214) to move synchronously with the machine tool, and the three-dimensional dynamic force loading module (2) is used to output loading force to the machine tool under test.

10. The device for enhancing the initial accuracy retention of a vertical machining center according to claim 9, characterized in that, The triaxial dynamic force loading module (2) includes: Connecting base plate (21); The X-direction force application component includes an X-direction hydraulic cylinder support structure (22), an X-direction hydraulic cylinder (23), an X-direction force sensor (24), and an X-direction cross-shaped guide rail slider pair (25). The Y-direction force application component includes a Y-direction hydraulic cylinder support structure (26), a Y-direction hydraulic cylinder (27), a Y-direction force sensor (28), and a Y-direction cross-shaped guide rail slider pair (29). Z-direction force application component, the Z-direction force application component includes Z-direction hydraulic cylinder (210), Z-direction force sensor (211), and Z-direction cross-shaped guide rail slider pair (212). The connecting base plate (21) is mounted on the follower module (1), and the X-direction force application component, Y-direction force application component and Z-direction force application component are all mounted on the connecting base plate (21).

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