A machine tool linear shaft precision maintenance test bench under multi-source heterogeneous information

Abstract

The application discloses a kind of test benches for testing precision retention of linear axis of machine tool under multi-source heterogeneous information, and relates to the field of machine tool precision retention.It includes: load loading system, simulates linear axis load force;Servo control system, controls feed axis feed speed and acceleration;Stress acquisition system, collects feed axis guide rail slider assembly stress and foundation large residual stress;Temperature measurement system, collects feed axis key heat source temperature data;Slider abnormal assembly simulation system, simulates the precision degradation state of feed axis under abnormal stress condition when four sliders are not coplanarly assembled;Geometric error measurement system, collects the running straightness error and space geometric pose error of workbench;Motion error measurement system, collects the positioning error and repeat positioning error of feed axis;Data acquisition and analysis system, integrates and processes the collected data for analysis.The application provides a practical basis for the improvement and optimization of machine tool precision retention.

Description

Technical Field

[0001] This invention relates to a test bench for testing the accuracy retention of machine tool linear axes under multi-source heterogeneous information, belonging to the field of machine tool accuracy retention. Background Technology

[0002] The linear feed system of a machine tool is a core execution component of a high-end CNC machine tool, mainly including servo motors, ball screws, and linear guides. Its accuracy retention directly determines the machining quality throughout the machine tool's entire life cycle. In actual working conditions, machine tools are subject to the coupled effects of multiple heterogeneous factors, such as the release of residual stress in the basic large components, relaxation of assembly preload, uneven thermal deformation, and medium-to-heavy-load cutting forces, which cause their geometric and motion accuracy to degrade over service time.

[0003] Currently, in the field of precision retention test bench construction, existing technologies mainly focus on the influence mechanism of external load on precision retention. These methods can describe the precision degradation mechanism of linear guide pairs under a certain load, but they fail to study the precision degradation law of linear guide pairs and the degradation law of lead screw nut positioning accuracy under the influence of multiple factors such as residual stress release, assembly stress relaxation, and temperature, as well as the abnormal wear and table posture change law caused by the non-coplanar assembly of four sliders on the guide rail. Furthermore, there is a lack of a comprehensive test device capable of real-time, dynamic, and integrated acquisition of multi-source heterogeneous data such as stress, temperature, and assembly errors under medium-to-heavy load conditions, while simultaneously recording the precision degradation process of the linear axis. This results in a lack of reliable experimental data support for theoretical research on machine tool precision retention, making it difficult to quantitatively and accurately trace the source of precision retention degradation, and also making it difficult to establish accurate precision degradation prediction models. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a test bench for testing the accuracy retention of machine tool linear axes under multi-source heterogeneous information. It mainly includes functions such as assembly bolt stress monitoring, temperature monitoring, monitoring of table motion accuracy degradation caused by wear, and monitoring of table pose changes. This test bench aims to realistically simulate the accuracy degradation process of machine tools under load, achieving simultaneous acquisition and analysis of data on the causes of accuracy degradation, the linear axis's own motion accuracy, and geometric accuracy data.

[0005] The test bench system of this invention mainly consists of the following core modules: a basic support and feed module, a load loading system, a linear motion servo control system, a stress acquisition system, a temperature measurement system, a slider abnormal assembly simulation system, a geometric error measurement system, a motion error measurement system, and a data acquisition and analysis system.

[0006] The basic support and feed module consists of the bed 3, column 12, connecting beam 11, guide rail 4, lead screw 25, lead screw nut 27, loading guide rail 5, slider 24, worktable 8, and other connecting parts.

[0007] The load loading system consists of a bed 3, a column 12, a connecting beam 11, a guide rail 4, a servo pressurizing electric cylinder 7, a pressure sensor 10, and a worktable 8. Load loading is achieved through the column 12 fixed to the bed, the connecting beam 11, and the vertical loading device 7 at the top of the connecting beam. A normal static or dynamic simulated load force is applied to the worktable 8, which moves along the linear loading guide rail 5 below. The pressure sensor 10 records the actual loading force in real time and transmits the pressure data to the CNC system in real time.

[0008] Linear motion servo control system: It consists of lead screw 25, lead screw nut 27, lead screw nut seat 26, servo motor 1, end cover 14, coupling 15, servo motor flange 16, bearing 18, tightening nut 19, etc., and simulates the periodic feed speed, acceleration and reciprocating motion trajectory of the machine tool feed system under different processing conditions.

[0009] Stress monitoring and acquisition system: Strain gauges are pre-embedded in the mounting bolts of the loading guide rail 5 and the mounting bolts of the slider 24. The system monitors the relaxation data of the assembly stress of the linear shaft guide rail slider bolts in real time. Combined with an ultrasonic stress meter, it periodically detects and collects the residual stress of the basic large components such as the bed 3, column 12, and connecting beam 11, as well as the residual stress of the bed guide rail mounting surface.

[0010] Temperature measurement system: Temperature sensors are arranged at core heat sources such as the servo motor flange 16, coupling 15, lead screw nut seat 26, bearing seat end face 9, loading guide rail 5, slider 24 friction pair, etc., as well as on the bed 3, which is far from the heat sources and reflects the ambient temperature, to monitor the feed axis temperature rise data in real time. At the same time, a handheld non-contact thermometer is used periodically to detect and record the temperature of the lead screw itself as supplementary data.

[0011] The geometric error measurement system consists of a guide rail 4, four sliders 24, a worktable 8, a marble ruler 6, an eddy current displacement sensor bracket 13, and an eddy current displacement sensor. It measures the straightness error and spatial pose error of the worktable 8 in real time during operation. In conjunction with a dual-frequency laser interferometer, it periodically collects the straightness error of the worktable to verify and correct the data collected by the displacement sensor, ensuring the accuracy of the data.

[0012] Motion error measurement system: Composed of parts such as lead screw 25, lead screw nut 27, lead screw nut seat 26, grating ruler 20, grating ruler reading head 21, and reading head bracket 23, it measures the core motion accuracy data such as positioning accuracy, repeatability, and backlash of the linear axis in real time, and periodically uses a dual-frequency laser interferometer to detect motion accuracy as comparison data to ensure the accuracy of the data.

[0013] Slider abnormal assembly simulation system: It consists of parts such as slider 24, adjusting shim 22, and worktable 8. It can quantitatively adjust the height difference of the four sliders according to the needs to simulate the non-coplanar state of the sliders caused by assembly.

[0014] Data Acquisition and Analysis System: Integrates high-speed data acquisition card and signal conditioning module, develops data layer software, and monitors and collects data such as load force, servo parameters, temperature, stress, straightness, positioning accuracy, repeatability, and displacement sensor data that can calculate the worktable pose in real time, providing data support for subsequent quantitative analysis and decoupling of factors affecting accuracy retention. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall test bench for testing the accuracy retention of machine tool linear axes.

[0016] Figure 2 This is a diagram of the kinematic pair of the machine tool feed axis lead screw nut and guide rail slider.

[0017] Figure 3 Diagram showing the installation location of the pre-embedded strain gauge bolts.

[0018] Figure 4 A diagram showing the placement of displacement sensors.

[0019] Figure 5 Diagram showing the placement of temperature sensors. Detailed Implementation

[0020] Overall structural layout: From Figure 1As can be seen, the main body of the test bench is a heavy-duty foundation bed. The bed adopts a hollow box design with large openings in the side walls. The bottom of the bed uses rectangular grid-like stiffening plates, which improves the bending and torsional stiffness of the bed and effectively controls the self-weight of the bed. The hollow opening design also helps to reduce the internal temperature gradient of the bed. The small round holes on the upper side of the bed are process holes for leading out the bolt leads of the pre-embedded strain gauges, which facilitates the collection of stress data. Two linear loading guide rails 5 and a lead screw 25 located in the center are installed parallel to each other on the top of the bed. This structure is a key kinematic pair of the test bench and is also the key location for generating the main heat source and causing wear and other factors that lead to the degradation of the accuracy of the linear axis. The drive servo motor 1 is installed at the front end of the bed 3 and directly drives the lead screw 25 to rotate. The worktable 8 is mounted on the loading guide rails 5 through four sliders 24 at the bottom and is connected to the lead screw nut 27. Above the worktable is a connecting beam 11, which is connected to the column 12. The movement of the column 12 and the connecting beam 11 on the bed is realized through the guide rail 4.

[0021] Loading device: A vertical load loading mechanism servo electric cylinder 7 is installed at the top center of the connecting beam 11. The load force is applied by the servo pressurizing electric cylinder 7. The electric cylinder pressurizing mechanism can extend to apply a set pressure to the worktable 8 below to simulate the reaction force generated by the spindle head on the worktable during actual cutting of the CNC machine tool. A pressure sensor 10 is installed on the loading head of the electric cylinder to collect, record and feedback the actual load force in real time. When the worktable reciprocates in the horizontal direction below the connecting beam, the connecting beam and the worktable move simultaneously.

[0022] In the stress monitoring and acquisition system, strain gauges are pre-embedded in the mounting bolts of the loading guide rail 5 and the slider 24. The installation positions of the pre-embedded strain gauge bolts are as follows: Figure 3 As shown, there are a total of 54 stress data acquisition lines. These lines are led out through small circular holes pre-drilled on the upper side of the machine bed. After signal amplification, the data is transmitted to the CNC system via a data acquisition device. This system monitors and records bolt assembly stress data in real time, and through calculation and analysis, derives the assembly preload relaxation data over time. Combined with an ultrasonic stress meter, residual stress in the foundation components is periodically detected, and residual stress values ​​are collected from the machine bed and the mounting surfaces of the machine bed guideways.

[0023] Temperature Measurement System: Temperature sensors are located at key heat sources such as the servo motor flange 16, coupling 15, lead screw nut seat 26, bearing seat end face 9, loading guide rail 5, and slider 24 friction pair, as well as on the bed 3, which is far from the heat sources and reflects the ambient temperature. The placement of the temperature sensors is as follows: Figure 5As shown, the specific locations are as follows: T1 motor flange end face, T2 coupling end face, T3 motor end bearing housing front face, T4 motor end bearing housing rear face, T5 slider 1, T6 lead screw nut housing end face, T7 slider 2, T8 tail end bearing housing rear face, T9 tail end bearing housing front face, T10 machine bed 1, T11 slider 3, T12 slider 4, T13 machine bed 2. Guide rails 1 (T14-T19) are divided into 6 equal parts, and guide rails 2 (T20-T25) are divided into 6 equal parts. A temperature sensor is attached to each location to monitor the feed axis temperature rise data in real time. Simultaneously, a handheld non-contact thermometer is used periodically to detect and record the temperature of the lead screw itself as supplementary data.

[0024] The geometric error measurement system consists of guide rails 4, sliders 24, a worktable 8, a marble ruler 6, displacement sensor brackets 13, and eddy current displacement sensors. The eddy current displacement sensors are positioned on the worktable near the four sliders via the displacement sensor brackets. Each bracket holds four displacement sensors. Taking one bracket as an example, probes D2 and D4 are positioned downwards, using the top surface of the marble ruler as a reference, to measure the straightness error of the worktable in the vertical plane. Probes D1 and D3 are positioned horizontally, using the side surface of the marble ruler as a reference, to measure the straightness error of the worktable in the horizontal plane. Two displacement sensors are arranged in each direction; one is the primary measuring sensor, and the other is a control sensor to verify the correctness and effectiveness of the data acquisition. Displacement sensors D5-D16 are arranged in the same way as D1-D4, collecting error values ​​at the four corners of the worktable. Through the D1-D16 displacement sensors, not only can the change in straightness during worktable movement be monitored, but the positional change data of the worktable can also be calculated mathematically. This allows for real-time measurement of the straightness and spatial orientation errors of the worktable during operation. In conjunction with a dual-frequency laser interferometer, straightness errors are periodically collected to further verify the accuracy of the data measured by the displacement sensor. Deviations can be corrected using data measured by the laser interferometer. The D17 displacement sensor is positioned at the end of the leadscrew to measure its thermal elongation. The placement of the eddy current displacement sensor is as follows... Figure 4 As shown.

[0025] Motion error measurement system: Composed of parts such as lead screw 25, lead screw nut 27, lead screw nut seat 26, grating ruler 20, grating ruler reading head 21, and reading head bracket 23, it measures the core motion accuracy data such as positioning accuracy, repeatability, and backlash of the linear axis in real time, and periodically uses a dual-frequency laser interferometer to detect motion accuracy as comparison data to ensure the accuracy of the data.

[0026] The abnormal assembly simulation system for sliders consists of slider 24, adjusting shims 22, and a worktable 8. It allows for quantitative adjustment of the height difference between the four sliders to simulate the non-coplanar state of the sliders caused by assembly issues. Under this non-ideal state, the linear motion servo control system and load loading system are activated to accelerate the wear and degradation of the guide rail and ball screw, acquiring wear pattern data of the guide rail slider under strained conditions. This allows for the acquisition of degradation data for the entire lifecycle of the guide rail slider within a relatively short test cycle.

[0027] Data Acquisition and Analysis System: This system integrates a high-speed data acquisition card and a signal conditioning module, develops data layer software, and sets input data such as motor speed, acceleration, simulated load force magnitude, and frequency. It then completes the data acquisition and monitoring setup. Specifically, it monitors changes in worktable posture and linearity using a geometric error measurement system composed of horizontal and vertical eddy current displacement sensors on the worktable support; monitors temperature changes at key points using a temperature measurement system composed of PT100 temperature sensors placed at various heat sources; monitors changes in assembly preload using a stress acquisition system composed of bolts with embedded strain gauges; and monitors changes in linear axis positioning accuracy and repeatability using a motion error measurement system composed of a grating ruler and lead screw nut. The data acquisition and analysis system transmits all of this data to the CNC system interface.

Claims

1. A test bench for testing the accuracy retention of machine tool linear axes under multi-source heterogeneous information, characterized in that, include: The load loading system is used to apply simulated load forces to the linear axis of the test bench; Linear motion servo control system is used to control the feed axis to execute the set feed speed, acceleration and reciprocating motion trajectory; The stress acquisition system is used to collect the assembly stress of the linear shaft guide rail and the slider, as well as the residual stress of the basic large components. Temperature measurement system used to collect temperature data at key heat sources on a linear axis; The geometric error measurement system is used to collect the straightness error and spatial pose error of the workbench during operation. Motion error measurement system, used to collect positioning error and repeatability error of linear axis; The abnormal assembly simulation system for sliders is used to simulate the accuracy degradation under the condition of non-coplanar assembly of four sliders. In addition, a data acquisition and analysis system is used to integrate, process, and analyze the data collected by the above systems.

2. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The load loading system includes a bed (3), columns (12), connecting beams (11), guide rails (4), servo pressurizing cylinders (7), pressure sensors (10), and a worktable (8). The bed (3) is horizontally positioned, the columns (12) are fixedly installed on the bed (3) and stand vertically on both sides of the bed, and the connecting beams (11) are fixedly connected to the tops of the columns (12) on both sides, so that the columns (12) and the connecting beams (11) form a portal frame structure. The guide rails (4) are laid parallel to both sides of the bed (3), and the bottom of the columns (12) is slidably installed on the bed via sliders. The portal frame can reciprocate along the guide rail (4) on the guide rail (4); the servo pressurizing electric cylinder (7) is fixedly installed at the top middle position of the connecting beam (11), and its telescopic end extends vertically downward and is connected to the pressure sensor (10). The lower end of the pressure sensor (10) is set opposite to the upper surface of the worktable (8) and is used to apply a normal static or dynamic simulated load force to the worktable (8) moving along the loading guide rail (5); the pressure sensor (10) is set at the loading end of the servo pressurizing electric cylinder (7) and is used to record the actual loading force in real time.

3. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The linear motion servo control system includes a lead screw (25), a lead screw nut (27), a lead screw nut seat (26), a servo motor (1), an end cover (14), a coupling (15), a servo motor flange (16), a bearing (18), and a tightening nut (19). The lead screw (25) is arranged along the length of the bed (3), and its two ends are rotatably supported on the bed (3) by the bearings (18). The bearings (18) are axially positioned on the outside by the end cover (14). The tightening nut (19) is threaded to the end of the lead screw to preload the bearing. The servo motor (1) is connected to the end of the lead screw by the end cover (14). The servo motor flange (16) is fixedly installed at the front end of the bed (3). The output shaft of the servo motor (1) is coaxially fixedly connected to one end of the lead screw (25) through the coupling (15) to drive the lead screw (25) to rotate. The lead screw nut (27) is threadedly fitted onto the lead screw (25). The lead screw nut seat (26) is fixedly fitted onto the outside of the lead screw nut (27). The upper end of the lead screw nut seat (26) is fixedly connected to the bottom of the worktable (8) to convert the rotational motion of the lead screw into the linear reciprocating motion of the worktable along the loading guide rail (5).

4. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The stress acquisition system includes strain gauges embedded in the mounting bolts of the loading guide rail (5) and the mounting bolts of the slider (24) for real-time monitoring of the relaxation data of the bolt assembly stress; the loading guide rail (5) is laid parallel to the top two sides of the bed (3), the slider (24) is slidably mounted on the loading guide rail (5), and the bottom of the worktable (8) is fixedly connected to the slider (24); the strain gauge signal lines embedded in each mounting bolt are led out through the process holes opened in the side wall of the bed (3); it also includes an ultrasonic stress meter for periodically detecting the residual stress of the bed (3), column (12), connecting beam (11) and the mounting surface of the bed guide rail.

5. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The temperature measurement system includes temperature sensors arranged on the end face of the servo motor flange (16), the end face of the coupling (15), the end face of the lead screw nut seat (26) housing, the end face of the bearing seat (9), the friction pair between the loading guide rail (5) and the slider (24), and the bed (3). Each temperature sensor is fixed to the surface of the corresponding temperature measurement point by means of thermally conductive adhesive or threaded connection, and is used to monitor the feed shaft temperature rise data in real time. It also includes a handheld non-contact thermometer for periodically detecting the temperature of the lead screw body as supplementary data.

6. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The geometric error measurement system includes a guide rail (4), a slider (24), a worktable (8), a marble ruler (6), an eddy current displacement sensor bracket (13), and an eddy current displacement sensor. The guide rail (4) is laid parallel to both sides of the bed (3), and the marble ruler (6) is laid parallel to the bed (3) and located outside the loading guide rail (5). The worktable (8) is slidably mounted on the loading guide rail (5) via four sliders (24) at the bottom. The eddy current displacement sensor bracket (13) is fixedly mounted on the worktable (8) and located close to the four sliders (24). The eddy current displacement sensor is fixedly mounted on the sensor bracket (13). The straightness error and spatial pose error of the worktable in the vertical and horizontal planes are measured with the top and side surfaces of the marble ruler (6) as references. The system also uses a dual-frequency laser interferometer to periodically collect the running straightness error of the worktable to verify and correct the data collected by the displacement sensor.

7. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The motion error measurement system includes a lead screw (25), a lead screw nut (27), a lead screw nut seat (26), a grating ruler (20), a grating ruler reading head (21), and a reading head bracket (23). The grating ruler (20) is arranged parallel to the lead screw (25) and fixedly installed on the bed (3). The reading head bracket (23) is fixedly installed on the bottom of the worktable (8) or on the lead screw nut seat (26). The grating ruler reading head (21) is fixedly installed on the reading head bracket (23) and is arranged opposite to the grating ruler (20). It is used to read the position information of the worktable in real time and measure the positioning accuracy, repeatability, and backlash of the linear axis. The system is also used in conjunction with a dual-frequency laser interferometer to periodically detect motion accuracy as comparative data.

8. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The abnormal assembly simulation system for the slider includes a slider (24), an adjusting shim (22), and a worktable (8). The adjusting shim (22) is set between the mounting surfaces of the slider (24) and the worktable (8). The slider (24) is fixedly connected to the threaded hole on the slider (24) by bolts passing through the worktable (8) and the adjusting shim (22) in sequence. The installation height difference of the four sliders (24) relative to the bottom surface of the worktable (8) is quantitatively adjusted by selecting adjusting shims (22) of different thicknesses to simulate the non-coplanar state of the sliders caused by assembly.

9. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information as described in claim 1, characterized in that, The data acquisition and analysis system includes a high-speed data acquisition card and a signal conditioning module. The high-speed data acquisition card is electrically connected to the pressure sensor (10), strain gauge, temperature sensor, eddy current displacement sensor and grating ruler reading head (21) via signal lines. It is used to acquire load force, servo parameters, temperature, stress, straightness, positioning accuracy, repeatability, and displacement sensor data for calculating the workbench posture in real time, providing data support for the quantitative analysis and decoupling of factors affecting accuracy retention.

10. The test bench for maintaining the accuracy of machine tool linear axes under multi-source heterogeneous information according to claim 6, characterized in that, Four eddy current displacement sensors are installed on the sensor bracket (13) near each slider (24). Two probes are arranged vertically downwards with their sensing ends facing the top surface of the marble ruler (6) to measure the straightness of the worktable in the vertical plane. The other two probes are arranged horizontally with their sensing ends facing the side of the marble ruler (6) to measure the straightness of the worktable in the horizontal plane. A main measuring sensor and a control sensor are set in the same direction to verify the validity of the data acquisition. A displacement sensor bracket is also fixedly installed at the end of the lead screw (25). A displacement sensor (D17) for measuring the thermal elongation data of the lead screw is installed on the bracket. The sensing end of the displacement sensor (D17) is set opposite to the end face of the lead screw (25).

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