Thermally induced spatial posture error testing device and testing method based on inverse five-point method

Abstract

The invention provides a thermally induced spatial posture error testing device and a testing method based on an inverse five-point method. The device comprises a measuring fixture and a test rod array device. The test rod array device comprises test rods and a mounting frame. The test rods are fixed on the mounting frame and arranged in a matrix. Five displacement sensors are fixed on the measuring fixture, which are respectively used to detect the displacement changes of five measuring points on the test rod. The five measuring points include a Z-direction measuring point, two X-direction measuring points and two Y-direction measuring points. The measuring fixture is used to be fixed on a machine tool spindle. The measuring fixture can move with the machine tool spindle and measure the postures of different test rods according to a preset measurement path, thereby obtaining the thermally induced posture errors of multiple test rods, and then obtaining the position and posture changes caused by heat at different positions in the machine tool working space, that is, the thermally induced spatial posture errors of the machine tool. The device has a high confidence level, good environmental adaptability and high precision retention.

Description

Technical Field

[0001] The invention relates to a machine tool thermal error testing device and a testing method, and in particular to a thermally induced spatial posture error testing method suitable for a precision machining center. Background Art

[0002] Precision machining centers are often used to process larger holes with higher precision requirements. Figure 1 As shown in the figure, however, during the machining process, the machine tool is affected by the temporal and spatial fluctuations of the ambient temperature and the time-varying characteristics of the endogenous heat source. The thermally induced posture errors at different positions in the workspace will vary greatly, causing the actual machining point and the ideal machining point to deviate in position and posture, greatly affecting the accuracy of the machined hole. How to accurately measure the spatial thermal error and derive the deformation law of the machine tool is of great significance to realize thermal error compensation and improve the accuracy of the machine tool.

[0003] At present, the most widely used devices for measuring thermal errors in precision machining centers are ballbars and laser interferometers. However, the above devices all measure the errors of the machine tool feed axis itself or between the axes, and pay less attention to the end error of the machine tool. Although the laser tracking interferometer can measure the position error of the end of the machine tool, it lacks consideration of the end posture error.

[0004] In summary, the prior art lacks a testing device and method for thermally induced spatial posture errors of machine tools. Summary of the invention

[0005] The purpose of the present invention is to provide a device and method for testing thermally induced spatial posture errors based on the inverse five-point method, so as to solve the technical problem that the prior art lacks a device and method for testing thermally induced spatial posture errors of machine tools. The preferred technical solutions among the many technical solutions provided by the present invention can produce many technical effects as described below.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The thermally induced spatial posture error testing device based on the inverse five-point method provided by the present invention comprises a measuring fixture and a test rod array device, wherein:

[0008] The inspection rod array device comprises inspection rods and a mounting frame, the inspection rods are fixed on the mounting frame, arranged in a matrix on the front and in a plane on the back, and the inspection rod array device is used to be fixed on a machine tool workbench;

[0009] Five displacement sensors are fixed on the measuring fixture, which are respectively used to detect the displacement changes of five measuring points on the inspection rod, and the five measuring points include one Z-direction measuring point, two X-direction measuring points and two Y-direction measuring points;

[0010] The measuring fixture is used to be fixed on the machine tool spindle. The measuring fixture can move with the machine tool spindle and measure the postures of different inspection rods according to a preset measurement path, so as to obtain the thermally induced posture errors of multiple inspection rods, and then obtain the position and posture changes caused by heat at different positions in the machine tool working space.

[0011] Preferably, the measuring fixture comprises a tool handle connector, a top plate connector, a mounting top plate, a mounting vertical plate and a mounting side plate, wherein:

[0012] The top plate connecting piece is fixedly connected to the mounting top plate, and the tool handle connecting piece is fixed on the top plate connecting piece and used to be connected to the main shaft;

[0013] The mounting vertical plate and the mounting side plate are fixedly connected to the mounting top plate, and any two of the three plates are perpendicular to each other. Two displacement sensors are fixed on the mounting side plates, the two are parallel to each other and have a certain distance between them. Two displacement sensors are fixed on the mounting top plate, the two are parallel to each other and the distance between them is the same as that of the side plates. One displacement sensor is fixed on the mounting vertical plate.

[0014] The installation frame is fixed on a machine tool workbench, and the inspection rods are arranged on the installation frame. The inspection rods are distributed in a stepped manner on the front side of the installation frame and in a flat manner on the back side.

[0015] Preferably, the testing device further comprises:

[0016] Temperature sensors arranged around the key heat-generating components of the machine tool are used to monitor the temperature field of the machine tool;

[0017] The temperature sensor arranged on the test rod mounting frame is used to monitor the temperature field of the mounting frame.

[0018] Preferably, the installation frame is a thermally symmetrical structure and is made of cast iron; the inspection rod and the measuring fixture are made of materials with a low thermal expansion coefficient;

[0019] The installation frame is provided with a plurality of inspection rod installation holes on the front and back sides. The inspection rod installation holes on the front side are distributed in a stepped manner on the frame, and the inspection rod installation holes on the back side and the inspection rod installation holes on the front side are arranged alternately and distributed in a plane.

[0020] The inspection rod installation hole and the inspection rod are both numbered and engraved, and correspond one to one and the engraved lines are aligned during installation.

[0021] The present invention also provides a testing method, using the above-mentioned thermally induced spatial posture error testing device based on the inverse five-point method, the testing method comprises:

[0022] The finite element analysis method is used to perform thermal characteristic analysis on the installation frame of the inspection rod array device to predict the position offset of the inspection rod installation holes under different ambient temperatures, thereby obtaining a position offset correction model for all the inspection rod installation holes.

[0023] Preferably, the method for predicting the position offset of the inspection rod installation hole by finite element analysis comprises the following steps:

[0024] The thermal expansion coefficient, specific heat capacity and thermal conductivity of the cast iron material used are tested, and the results are substituted into the finite element model to analyze the thermal deformation of the installation frame of the inspection rod array device when the initial temperature is raised to different temperatures, and the three-dimensional thermal deformation data of all the inspection rod installation holes are extracted. The data is processed to obtain several fitting curves of the thermal offset values ​​of each inspection rod installation hole on the installation frame in the three directions of X, Y, and Z as the temperature of the structure changes;

[0025] With the help of the obtained fitting curve, the thermal offset value of the inspection rod mounting hole generated after the structural temperature of the inspection rod array device changes is predicted, thereby obtaining the deformation prediction results of the inspection rod mounting hole at different times when the target temperature of the inspection rod array device is increased or decreased. The predicted results are eliminated from the measurement results of the displacement sensor, thereby realizing the correction of the thermal offset of the hole.

[0026] Preferably, the testing method further comprises:

[0027] When measuring the spatial thermally induced posture error of a horizontal machining center, the five-step stepped surface of the inspection rod array device, i.e., the front face of the device, faces the main shaft of the machine tool, and the bottom face contacts the workbench for installation and positioning. The measuring fixture is installed on the main shaft of the horizontal machining center for measurement. In this measurement mode, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on two body diagonals in the working space of the horizontal machining center, the thermally induced posture errors of several points on five face diagonals, and the thermally induced posture errors in the direction of one coordinate axis can be obtained.

[0028] When measuring the plane thermal posture error of the horizontal machining center, the back of the inspection rod array device is facing the machine tool spindle, and the bottom surface is in contact with the worktable for installation and positioning. The measuring device is installed on the spindle of the horizontal machining center for measurement. In this measurement mode, the machine tool performs two-axis linkage, and the thermal posture errors of several points on a plane in the workspace of the horizontal machining center can be obtained. At the same time, the thermal posture errors on the two diagonals and the thermal posture errors in the directions of the two coordinate axes are also measured;

[0029] When measuring the spatial thermally induced posture error of the vertical machining center, the front side of the inspection rod array device is facing the machine tool spindle, and the back side is in contact with the workbench for installation and positioning. The measuring fixture is installed on the spindle of the vertical machining center for measurement. In this measurement mode, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on two body diagonals in the working space of the vertical machining center and the thermally induced posture errors of several points on five face diagonals can be obtained. The inspection rod array device is rotated 180 degrees along the Z axis of the machine tool, and the spatial thermally induced posture error measurement is performed again. The thermally induced posture errors of several points on the other two body diagonals in the working space of the vertical machining center can be obtained, thereby realizing the thermally induced posture error test of a total of four body diagonals in the working space of the vertical machining center.

[0030] Preferably, the test method comprises the following steps:

[0031] Step 1, installing the displacement sensor on the measuring fixture and fixing it to the spindle of the machine tool, and connecting the other end of the displacement sensor to the host computer to collect displacement information;

[0032] Step 2, install all the inspection sticks on the installation frame according to the serial numbers, align the engraved lines of the inspection sticks with the engraved lines of the inspection stick installation holes on the frame, and form the inspection stick array device;

[0033] Step 3: According to the testing requirements of the machine tool, place the assembled inspection rod array device on the machine tool workbench, use a level to ensure that the device is placed horizontally, use a micrometer to align the device, ensure that the measured surface of the device is perpendicular to the main axis of the machine tool, and use a pressing plate to press the inspection rod array device;

[0034] Step 4: Start the machine tool, manually adjust the position of the machine tool spindle and the worktable, calibrate the position of each inspection rod and record the coordinates, ensure that each displacement sensor can maintain a normal measurement range when measuring the inspection rod, plan the measurement path, and write the measurement program;

[0035] Step 5: Write a machine tool heat-up program according to the actual working conditions, requiring that the X, Y, and Z axes of the machine tool be linked without interference between the measuring fixture and the inspection rod array device;

[0036] Step 6: Setting temperature sensors on the installation frame and key heat-generating components of the machine tool to monitor the temperature field of the machine tool;

[0037] Step 7: Before the machine is heated up, all the inspection rods are measured, and the displacement sensor is reset when measuring the first inspection rod, and the measurement results are regarded as the initial posture states of different points of the machine tool in the cold state;

[0038] Step 8: Warm up the machine tool and measure the inspection rod array device once at a set interval until the machine tool reaches a thermal equilibrium state, thereby obtaining the thermally induced posture error of the machine tool at different points at any working time.

[0039] Preferably, according to the measurement result of the displacement sensor, the influence of the ambient temperature on the position of the installation hole of the inspection rod is eliminated, and the measurement data is calculated and processed to obtain the thermally induced spatial posture error of the machine tool:

[0040]

[0041] in, , , Represents the three thermally induced spatial position errors of machine tools, , Denotes two thermally induced spatial attitude errors of machine tools, , , , , It represents the deformation values ​​measured at the five points X1, X2, Y1, Y2 and Z of the displacement sensor after eliminating the influence of ambient temperature. It represents the distance between the two displacement sensors in the same measuring direction of the high-precision inspection rod. Indicates the distance between the center of the front bearing of the spindle and the measuring center of the end of the inspection rod;

[0042] After obtaining the thermally induced posture errors of all points in space, the thermal deformation law of the machine tool can be analyzed: by analyzing the changes in the thermally induced errors of all the inspection rods in the X direction at different times, the left and right offset law of the column of the machine tool after heating can be determined; by analyzing the changes in the thermally induced errors of all the inspection rods in the Y direction at different times, the elongation law of the column of the machine tool after heating can be determined; by analyzing the changes in the thermally induced errors of all the inspection rods in the Z direction at different times, the pitch change law of the column of the machine tool after heating can be determined; by analyzing the changes in the posture errors of all the inspection rods around the X-axis at different times, the pitch deformation law of the spindle axis relative to the workpiece axis after heating can be determined; by analyzing the changes in the posture errors of all the inspection rods around the Y-axis at different times, the yaw deformation law of the spindle axis relative to the workpiece axis after heating can be determined.

[0043] The thermally induced spatial posture error testing device and testing method based on the inverse five-point method provided by the present invention have the following beneficial effects compared with the prior art: the device has high processing accuracy and rigidity, and has environmental adaptability, and can adapt to the measurement of thermally induced spatial posture errors of machine tools under different ambient temperatures. The device has high processing accuracy, rigidity and environmental adaptability, and the static and dynamic characteristics of the device are good, which can ensure that the position of the test rod mounting hole does not change substantially. A three-coordinate measuring machine is used to measure the spacing of the test rod mounting holes of the device and the posture of the test rod, and the measurement results are used as the geometric reference of the entire device, and on this basis, a position offset correction model of all test rod mounting holes is established after the temperature of the device changes, so as to adapt to the measurement of thermally induced posture errors under different ambient temperatures. Since the test rod array has multiple test rods, the thermally induced posture errors of multiple points can be obtained, thereby obtaining the thermally induced posture errors of the machine tool working space, which is convenient for exploring the deformation law of the machine tool after heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 This is a schematic diagram of the thermal deformation of the machine tool.

[0046] Figure 2 This is the assembly drawing of the measuring fixture using the reverse five-point method.

[0047] Figure 3 This is the assembly drawing of the inverse five-point method inspection rod array device.

[0048] Figure 4 It is a schematic diagram of the actual working conditions for the confidence assessment and assurance of the measuring device;

[0049] Figure 5 It is a schematic diagram of geometric accuracy measurement for confidence assessment and assurance of the measuring device;

[0050] Figure 6 It is a model of the variation of the hole spacing with temperature for the confidence evaluation and assurance of the measuring device;

[0051] Figure 7 It is a schematic diagram of hole spacing correction for confidence assessment and assurance of the measuring device;

[0052] Figure 8 It is a schematic diagram of horizontal machining center measurement;

[0053] Fig. 9It is a schematic diagram of the measurement of the vertical machining center;

[0054] Fig.10 It is a schematic diagram of the layout of the temperature sensor from the first perspective.

[0055] Fig.11 This is a schematic diagram of the layout of the temperature sensor from the second perspective.

[0056] Fig.12 It is the flow chart of thermal-induced spatial posture error measurement.

[0057] Fig.13 This is a schematic diagram of the inverse five-point method calculation.

[0058] In the figure, 1, tool handle connector; 2, top plate connector; 3, top plate installation; 4, vertical plate installation; 5, side plate installation; 6, displacement sensor; 7, inspection rod; 8, frame installation. DETAILED DESCRIPTION

[0059] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0060] In the description of the present invention, it should be understood that the terms "center", "length", "width", "height", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "side" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0061] Combine the following Figure 2-Figure 13 The technical solution provided by the present invention is described in more detail.

[0062] Embodiment 1:

[0063] See also Figure 2 , Figure 3 and Fig.13As shown, the present embodiment provides a thermally induced spatial posture error testing device based on the inverse five-point method, including a measuring fixture and a test rod array device, wherein: the test rod array device includes a test rod 7 and a mounting frame 8, the test rod 7 is fixed on the mounting frame 8, and is arranged in a matrix; five displacement sensors 6 are fixed on the measuring fixture, which are respectively used to detect the displacement changes of five measuring points on the test rod 7, and the five measuring points include a Z-direction measuring point, two X-direction measuring points and two Y-direction measuring points; the measuring fixture is used to be fixed on the main shaft of the machine tool, and the measuring fixture can move with the main shaft of the machine tool, and measure the postures of different test rods 7 according to a preset measurement path, so as to obtain the thermally induced posture errors of multiple test rods 7, and then obtain the position and posture changes caused by heat at different positions in the working space of the machine tool.

[0064] The measuring fixture includes a tool handle connecting member 1, a top plate connecting member 2, a mounting top plate 3, a mounting vertical plate 4 and a mounting side plate 5, wherein: the top plate connecting member 2 is fixedly connected to the mounting top plate 3, the tool handle connecting member 1 is fixed on the top plate connecting member 2, and is used to be connected to the main shaft; the mounting vertical plate 4 and the mounting side plate 5 are both fixedly connected to the mounting top plate 3, and any two of the three plates are perpendicular to each other, two displacement sensors 6 are fixed on the mounting side plate 5, two displacement sensors 6 are fixed on the mounting top plate 3, and one displacement sensor 6 is fixed on the mounting vertical plate 4.

[0065] See also Figure 3 As an optional implementation, the mounting frame 8 is supported on the machine tool table, and the inspection rod 7 is arranged on the mounting frame. The inspection rod 7 is distributed in a stepped manner on the front side of the mounting frame 8 and in a flat manner on the back side.

[0066] The present invention provides that due to the influence of the spatiotemporal fluctuations of ambient temperature and the time-varying characteristics of endogenous heat sources, the thermally induced posture errors at different positions in the working space of the machining center will have large differences; for this purpose, a device and method for measuring the thermally induced spatial posture errors of machine tools are proposed. The idea of ​​this method draws on the five-point method. The five-point method uses a displacement sensor installed on the workbench to measure the inspection rod on the spindle to measure the posture error of the spindle.

[0067] Drawing on the five-point method, a thermally induced spatial posture error measurement method and device based on the inverse five-point method are proposed, which are characterized in that the displacement sensor 6 is installed on the main shaft through a fixture to measure the inspection rod array device on the workbench.

[0068] like Fig.13As shown, in the inverse five-point measurement method, each inspection rod 7 is arranged with five measuring points, including a measuring point in the Z direction, which is used to reflect the thermally induced position error in the Z direction at a certain point in space; two measuring points in the X and Y directions, respectively, and the inverse five-point calculation is performed on the data of the two measuring points in the X and Y directions to solve the thermally induced posture error of the point around the Y axis and the X axis, and the thermally induced position error in the X and Y directions at the point is further obtained based on the two posture errors obtained, thereby obtaining the position change of the tool relative to the workpiece and the degree of deviation of the tool axis relative to the workpiece axis.

[0069] A mounting frame 8 is placed on the workbench, and multiple inspection rods 7 are arranged and installed at different positions of the mounting frame 8 to form an inspection rod array device. The measurement fixture is used to measure each inspection rod 7 at different times when the machine tool is cold and hot, and the thermally induced posture errors of multiple inspection rods 7 can be obtained, thereby obtaining the position and posture changes caused by heat at different positions in the machine tool workspace, providing experimental support for the traceability analysis of thermal deformation of the machine tool and the prediction of workpiece processing accuracy.

[0070] An inverse five-point measurement fixture with a displacement sensor 6 installed on the spindle (such as Figure 2 ), and a high-precision test rod array device mounted on a workbench (such as Figure 3 ), used to measure the thermally induced spatial posture error of the machine tool; displacement sensor 6, used to measure the displacement change of five key measuring points of the inspection rod 7 to reflect the thermally induced spatial posture error of the machine tool; temperature sensors arranged around the key heat-generating components of the machining center, used to monitor the temperature field of the machine tool; temperature sensors arranged on the mounting frame 8, used to monitor the temperature field of the mounting frame 8; the measured data are processed to obtain the thermally induced spatial posture error of the machining center. The device has a high confidence level and can adapt to the measurement of the thermally induced spatial posture error of the machine tool under different ambient temperatures.

[0071] Among them, the inverse five-point method measurement device includes an inverse five-point method measurement fixture with a displacement sensor 6 and a test rod array device; the test rod array device is placed on the workbench of the machine tool, and the measurement fixture is installed on the spindle of the machine tool, so as to realize the measurement of the thermally induced spatial posture error of the machine tool.

[0072] The measuring fixture includes a displacement sensor 6 and its host computer, as well as a mounting top plate 3, a mounting side plate 5, a mounting vertical plate 4, a top plate connecting member 2 and a tool handle connecting member 1 made of invar; the displacement sensor 6 is fixed to three mutually perpendicular and orthogonal mounting plates by bolts, and is connected to the host computer for data acquisition and transmission; the sensor mounting plates are positioned by cylindrical pins and connected by bolts, and the whole is fixed to the top plate connecting member 2 by bolts, and the top plate connecting member 2 is fixed to the tool handle connecting member 1 by bolts.

[0073] like Figure 2, which is the assembly drawing of the measurement fixture of the inverse five-point method. The displacement sensor 6 is fixed on the mounting top plate 3, the mounting side plate 5 and the mounting vertical plate 4 by bolts. The distance between the sensor detection end face and each plate is 10mm to avoid the influence of the mounting plate on the measurement result. The sensor is clamped by bolts to ensure that its position does not change. The mounting top plate 3 and the top plate connecting piece 2 are connected by bolts. There is a 50mm spacing between the mounting vertical plate 4 and the top plate connecting piece 2 to avoid interference between the sensor tail wiring and the fixture. The top plate connecting piece 2 is connected to the tool handle connecting piece 1 by bolts. The tool handle connecting piece 1 has an outer diameter of 25mm and can be directly clamped to the tool handle and connected to the spindle.

[0074] like Figure 3 The test rod array device includes a high-precision test rod 7 made of Invar material and a mounting frame 8 cast from ductile iron. Several test rod mounting holes are provided on the front and back sides of the mounting frame 8. The test rod mounting holes on the front are distributed in a specific spatial range in a stepped manner, and the test rod mounting holes on the back are distributed in a specific plane. The frame structure adopts a lightweight design, and the back holes and the front holes are arranged alternately, which reduces the overall volume of the device, reduces the weight of the device, and facilitates transportation and use; considering the limit of the machine tool translation axis, the lowest test rod mounting hole is at a certain distance from the workbench, ensuring that all test rods 7 can be detected during actual use. The holes of the test rod 7 and the test rod mounting frame 8 are numbered and engraved, and they correspond one to one and the engraved lines are aligned during installation. The test rod 7 is positioned on the mounting frame 8 through the short shaft end face, and is tightened with a nut on the back side.

[0075] The measurement results of this device have a high degree of confidence, such as Figure 4-Figure 7 As shown in the diagram of confidence assessment and assurance of the measuring device, the device has high machining accuracy and rigidity, and has environmental adaptability, and can adapt to the measurement of thermally induced spatial posture errors of machine tools under different ambient temperatures. The device has high machining accuracy, rigidity and environmental adaptability:

[0076] On the one hand, the static and dynamic characteristics of the device are good, which can ensure that the position of the test rod installation hole does not change basically; the installation frame 8 is cast with high-strength ductile iron, and the structural design of the reinforcing ribs is adopted. The static characteristics of the test rod array device using reinforcing ribs are analyzed using finite element software to verify that it has high static stiffness; the installation frame 8 adopts an integrated frame structure, which can minimize the measurement deviation caused by the processing error of the frame, and increase the contact area at the part where the device needs to be pressed, effectively reducing the stress concentration problem and preventing the device from being deformed greatly after clamping. In addition, the dynamic characteristics of the device are analyzed to obtain the natural frequencies of each order, which are compared with the vibration frequency of the machine tool during the actual measurement process to determine whether there is resonance between the device and the machine tool.

[0077] At the same time, very high requirements are placed on the cylindricity error and roundness error of the inspection rod 7; the flatness error of the bottom and back surfaces of the mounting frame 8 and the cylindricity of the mounting holes are all controlled at the micron level, and the dimensional tolerance between holes is also very high precision. Each inspection rod 7 corresponds to the mounting hole on the mounting frame 8 one by one, and the alignment of the engraved lines of the two ensures that the inspection rod 7 can be positioned at the same position each time it is installed, avoiding errors caused by repeated installation.

[0078] On the other hand, a three-coordinate measuring machine is used to measure the spacing between the test rod mounting holes on the mounting frame 8 and the posture of each test rod 7, and the measurement results are used as the geometric reference of the entire device, and on this basis, the environmental adaptability of the device is verified. The test rod 7 and the measuring fixture are both made of Invar material. According to the thermal expansion coefficient of Invar material and the length of the test rod 7, the maximum thermal deformation generated within a certain temperature range is solved, and this error is eliminated in the measurement results; therefore, the use of Invar material can adapt to the measurement of machine tool spatial posture errors under different ambient temperatures.

[0079] The mounting frame 8 is a thermally symmetrical structure, and is cast from ductile iron. Compared with Invar, ductile iron has a larger thermal expansion coefficient, and will produce larger thermal deformation when heated, causing the position of the hole to shift.

[0080] Embodiment 2:

[0081] The present embodiment provides a testing method, using the thermally induced spatial posture error testing device based on the inverse five-point method of the above-mentioned embodiment, the testing method comprises: adopting a finite element analysis method to perform a thermal characteristic analysis on the mounting frame 8 of the inspection rod array device, to predict the position offset of the inspection rod mounting holes under different ambient temperatures, thereby obtaining a position offset correction model for all the inspection rod mounting holes.

[0082] The finite element analysis method is used to perform thermosetting analysis on the mounting frame 8 to predict the position offset of the inspection rod mounting hole under different ambient temperatures. The method of predicting the position offset of the inspection rod mounting hole by finite element analysis includes the following steps:

[0083] Step 1: Test the thermal expansion coefficient, specific heat capacity and thermal conductivity of the cast iron material used, and substitute the results into the finite element model, analyze the thermal deformation of the mounting frame 8 when the initial temperature is raised to different temperatures, extract the three-dimensional thermal deformation data of all the inspection rod mounting holes, process the data, and obtain several fitting curves of the thermal offset values ​​in the three directions of X, Y, and Z of each inspection rod mounting hole on the mounting frame as the temperature of the structure changes. The results show that the three-dimensional deformation of all the inspection rod mounting holes of the device is linear.

[0084] Step 2: With the help of the obtained fitting curve, predict the thermal deformation of all the inspection rod mounting holes of the mounting frame 8 after the structural temperature changes. Predict the deformation results of the mounting frame 8 at different times when the temperature rises and drops to a certain temperature, and compare the predicted results with the simulation.

[0085] By comparison, the accuracy of the prediction method is verified. Therefore, it is only necessary to use a temperature sensor to perform real-time detection of the temperature change of the mounting frame 8 during the measurement process of the inverse five-point method measurement device. By obtaining the temperature change value of the mounting frame 8, the positions of all inspection rod mounting holes can be corrected, thereby achieving better environmental adaptability of the inverse five-point method thermally induced spatial posture error measurement device. Based on the above analysis results, it is believed that the results obtained by the device measurement have a high degree of confidence.

[0086] The thermally induced spatial posture error measurement method based on the inverse five-point method proposed in the present invention uses a fixture to measure the inspection rod array device fixed on the workbench, and the inspection rod 7 is arranged with five measuring points, including one in the Z direction, reflecting the thermally induced position error in the Z direction at a certain point in space, and two in the X and Y directions respectively. The inverse five-point method is used to calculate the data of the two measuring points in the X and Y directions to solve the thermally induced posture errors of the point around the Y and X axes, and the thermally induced position errors in the X and Y directions at the point are further obtained based on the two posture errors obtained by solving them.

[0087] Since the inspection rod array device has multiple inspection rods 7, the thermally induced posture errors of multiple points can be obtained, thereby obtaining the thermally induced posture errors of the machine tool working space, which is convenient for exploring the deformation law of the machine tool after heating.

[0088] As attached Figure 8 and Fig. 9 This measurement method is suitable for measuring horizontal machining centers and vertical machining centers.

[0089] When measuring the spatial thermally induced posture error of a horizontal machining center, the five-step stepped surface of the inspection rod array device, i.e., the front face of the device, faces the main shaft of the machine tool, and the bottom face contacts the workbench for installation and positioning. The measuring fixture is installed on the main shaft of the horizontal machining center for measurement. In this measurement mode, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on two body diagonals in the working space of the horizontal machining center, the thermally induced posture errors of several points on five face diagonals, and the thermally induced posture errors in the direction of one coordinate axis can be obtained.

[0090] When measuring the plane thermal posture error of the horizontal machining center, the back of the inspection rod array device is facing the machine tool spindle, and the bottom surface is in contact with the worktable for installation and positioning. The measuring device is installed on the spindle of the horizontal machining center for measurement. In this measurement mode, the machine tool performs two-axis linkage, and the thermal posture errors of several points on a plane in the workspace of the horizontal machining center can be obtained. At the same time, the thermal posture errors on the two diagonals and the thermal posture errors in the directions of the two coordinate axes are also measured;

[0091] When measuring the spatial thermally induced posture error of the vertical machining center, the front side of the inspection rod array device is facing the machine tool spindle, and the back side is in contact with the workbench for installation and positioning. The measuring fixture is installed on the spindle of the vertical machining center for measurement. In this measurement mode, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on two body diagonals in the working space of the vertical machining center and the thermally induced posture errors of several points on five face diagonals can be obtained. The inspection rod array device is rotated 180 degrees along the Z axis of the machine tool, and the spatial thermally induced posture error measurement is performed again. The thermally induced posture errors of several points on the other two body diagonals in the working space of the vertical machining center can be obtained, thereby realizing the thermally induced posture error measurement of a total of four body diagonals in the working space of the vertical machining center.

[0092] Taking the measurement of thermally induced posture error of a precision horizontal coordinate boring machine as an example, the heat-up program is set according to the actual working conditions of the precision horizontal coordinate boring machine, and temperature sensors are installed around the key heat-generating components to monitor the temperature field of the boring machine until the machine reaches thermal equilibrium. The inspection rod array device is measured every one hour before and after the heat-up to obtain the thermally induced posture error of the boring machine at different working times.

[0093] The inverse five-point method measuring fixture is used to measure the posture states of all the inspection rods 7 of the inspection rod array device. The measurement process can be broken down into the following steps:

[0094] Step 1: Figure 2 As shown in the assembly diagram of the inverse five-point method measuring fixture, the displacement sensor 6 is installed on the inverse five-point method measuring fixture according to the previous steps, and is clamped with bolts. The sensor mounting plate is connected to the top plate connector 2 and the tool handle connector 1 by bolts to complete the assembly of the inverse five-point method measuring fixture, and fixed to the spindle of the precision coordinate boring machine. The other end of the displacement sensor 6 is connected to the host computer to collect displacement information.

[0095] Step 2: Figure 3 As shown in the assembly diagram of the test rod array device, all the test rods 7 are installed on the installation frame 8 according to the numbers, so that the engraved lines of the test rods 7 are aligned with the engraved lines of the holes on the installation frame, and nuts are used to tighten them at the rear.

[0096] Step 3: Figure 8 and Fig. 9 As shown in the measurement diagrams of different machining centers, according to the testing requirements of the machine tool, the assembled inspection rod array device is placed on the machine tool workbench, a level is used to ensure that the device is placed horizontally, a micrometer is used to align the device, and a pressure plate is used to press the inspection rod array device.

[0097] Step 4: Start the machine tool, manually adjust the position of the machine tool spindle and worktable, calibrate the position of each inspection rod 7 and record the coordinates to ensure that each displacement sensor 6 can maintain a normal measurement range when measuring the inspection rod 7, as shown in the attached figure. Figure 3 As shown in the inspection rod array device, the measurement path is planned and the error measurement program is written.

[0098] Step 5: Write a machine tool heat-up program according to the actual working conditions, requiring the machine tool X, Y, and Z axes to be linked without interference between the inverse five-point measurement fixture and the inspection rod array device.

[0099] Step 6: See Fig.10 and Fig.11 , Fig.12 As shown, temperature sensors are installed on the mounting frame 8 and key heat-generating parts of the machine tool such as the motor, guide rail, bearing seat, etc. to monitor the temperature field of the machine tool in real time until the machine tool reaches a thermal equilibrium state; the number and position of the temperature sensors can be arranged as shown in Table 1, and the specific arrangement position can be adopted Fig.10 and Fig.11 Layout shown.

[0100]

[0101] Table 1 Temperature sensor layout

[0102] Step 7: Before warming up the machine, Figure 3 As shown in the assembly diagram of the test rod array device, all the test rods 7 are measured, and the displacement sensor 6 is cleared when measuring the first test rod 7; the machine tool is heated up, as shown in the attached Figure 7 As shown in the flow chart of thermal-induced spatial posture error measurement, the inspection rod array device is measured once every hour until the machine tool reaches a thermal equilibrium state and the measurement is stopped.

[0103] According to the measurement results of displacement sensor 6, the influence of ambient temperature on the deformation of the frame structure is eliminated, and the following Fig.13 The measured data is calculated and processed to obtain the thermally induced spatial posture error of the machine tool:

[0104] ;

[0105] in, , , Represents the three thermally induced spatial position errors of machine tools, , Denotes two thermally induced spatial attitude errors of machine tools, , , , , It represents the deformation values ​​measured at the five points of displacement sensor 6X1, X2, Y1, Y2, and Z after eliminating the influence of ambient temperature. Indicates the distance between two sensors in the same measuring direction of the high-precision inspection rod 7, Indicates the distance between the center of the spindle front bearing and the measuring center of the end of the inspection rod 7.

[0106] In the description of this specification, specific features, structures or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0107] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0108] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A thermally induced spatial posture error test device based on the inverse five-point method, characterized in that: It includes a measuring fixture and a test rod array device, wherein: The inspection rod array device comprises inspection rods and a mounting frame, the inspection rods are fixed on the mounting frame, and the inspection rod array device is used to be fixed on a machine tool workbench; Five displacement sensors are fixed on the measuring fixture, which are respectively used to detect the displacement changes of five measuring points on the inspection rod, and the five measuring points include one Z-direction measuring point, two X-direction measuring points and two Y-direction measuring points; The measuring fixture is used to be fixed on the main shaft of the machine tool. The measuring fixture can move with the main shaft of the machine tool and measure the postures of different inspection rods according to a preset measurement path, so as to obtain the thermally induced posture errors of multiple inspection rods, and then obtain the position and posture changes caused by heat at different positions in the working space of the machine tool; The measuring fixture comprises a tool handle connecting piece, a top plate connecting piece, a mounting top plate, a mounting vertical plate and a mounting side plate, wherein: the top plate connecting piece is fixedly connected to the mounting top plate, the tool handle connecting piece is fixed on the top plate connecting piece and is used to connect with the spindle; The mounting vertical plate and the mounting side plate are fixedly connected to the mounting top plate, and any two of the three plates are perpendicular to each other, two displacement sensors are fixed to the mounting side plates, the two are parallel to each other and there is a distance between them, two displacement sensors are fixed to the mounting top plate, the two are parallel to each other and the distance between them is the same as that of the side plates, and one displacement sensor is fixed to the mounting vertical plate; The mounting frame is fixed on the machine tool workbench, and the inspection rods are arranged on the mounting frame. The inspection rods are distributed in a stepped manner on the front side of the mounting frame and in a flat manner on the back side. The installation frame is a thermally symmetrical structure and is made of cast iron; the inspection rod and the measuring fixture are made of materials with a low thermal expansion coefficient; The installation frame is provided with a plurality of inspection rod installation holes on the front and back sides, the inspection rod installation holes on the front side are distributed in a stepped manner on the frame, and the inspection rod installation holes on the back side and the inspection rod installation holes on the front side are arranged alternately and distributed in a plane; The inspection rod installation hole and the inspection rod are both numbered and engraved, and correspond to each other one by one and align the engraved lines during installation; When measuring the spatial thermally induced posture error of a horizontal machining center, the five-step stepped surface of the inspection rod array device, i.e., the front face of the device, faces the main shaft of the machine tool, and the bottom face contacts the workbench for installation and positioning. The measuring fixture is installed on the main shaft of the horizontal machining center for measurement. At this time, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on two body diagonals in the working space of the horizontal machining center, the thermally induced posture errors of several points on five face diagonals, and the thermally induced posture errors in the direction of one coordinate axis can be obtained. When measuring the plane thermal posture error of the horizontal machining center, the back of the inspection rod array device is facing the machine tool spindle, and the bottom surface is in contact with the worktable for installation and positioning. The measuring device is installed on the spindle of the horizontal machining center for measurement. At this time, the machine tool performs two-axis linkage, and the thermal posture errors of several points on a plane in the workspace of the horizontal machining center can be obtained. At the same time, the thermal posture errors on the two diagonals and the thermal posture errors in the directions of the two coordinate axes are also measured; When measuring the spatial thermally induced posture error of the vertical machining center, the front side of the inspection rod array device is facing the machine tool spindle, and the back side is in contact with the workbench for installation and positioning. The measuring fixture is installed on the spindle of the vertical machining center for measurement. At this time, the machine tool performs three-axis linkage, and the thermally induced posture errors of several points on the two body diagonals in the working space of the vertical machining center and the thermally induced posture errors of several points on the five face diagonals can be obtained. The inspection rod array device is rotated 180 degrees along the Z axis of the machine tool, and the spatial thermally induced posture error is measured again. The thermally induced posture errors of several points on the other two body diagonals in the working space of the vertical machining center can be obtained, thereby realizing the thermally induced posture error test of a total of four body diagonals in the working space of the vertical machining center.

2. The thermally induced spatial posture error testing device based on the inverse five-point method according to claim 1 is characterized in that: The testing device also includes: Temperature sensors arranged around the key heat-generating components of the machine tool are used to monitor the temperature field of the machine tool; The temperature sensor arranged on the test rod mounting frame is used to monitor the temperature field of the mounting frame.

3. A testing method, characterized in that: Using the thermally induced spatial posture error testing device based on the inverse five-point method according to claim 1 or 2, the testing method comprises: The finite element analysis method is used to perform thermal characteristic analysis on the installation frame of the inspection rod array device to predict the position offset of the inspection rod installation holes under different ambient temperatures, thereby obtaining a position offset correction model for all the inspection rod installation holes.

4. The testing method according to claim 3, characterized in that: The method for predicting the position offset of the inspection rod installation hole through finite element analysis comprises the following steps: The thermal expansion coefficient, specific heat capacity and thermal conductivity of the cast iron material used are tested, and the results are substituted into the finite element model to analyze the thermal deformation of the installation frame of the inspection rod array device when the initial temperature is raised to different temperatures, and the three-dimensional thermal deformation data of all the inspection rod installation holes are extracted. The data is processed to obtain several fitting curves of the thermal offset values ​​of each inspection rod installation hole on the installation frame in the three directions of X, Y, and Z as the temperature of the structure changes; With the help of the obtained fitting curve, the thermal offset value of the inspection rod mounting hole generated after the structural temperature of the inspection rod array device changes is predicted, thereby obtaining the deformation prediction results of the inspection rod mounting hole at different times when the target temperature of the inspection rod array device is increased or decreased. The predicted results are eliminated from the measurement results of the displacement sensor, thereby realizing the correction of the thermal offset of the hole.

5. The testing method according to claim 3, characterized in that: The test method includes the following steps: Step 1, installing the displacement sensor on the measuring fixture and fixing it to the spindle of the machine tool, and connecting the other end of the displacement sensor to the host computer to collect displacement information; Step 2, install all the inspection sticks on the installation frame according to the serial numbers, align the engraved lines of the inspection sticks with the engraved lines of the inspection stick installation holes on the frame, and form the inspection stick array device; Step 3: According to the testing requirements of the machine tool, place the assembled inspection rod array device on the machine tool workbench, use a level to ensure that the device is placed horizontally, use a micrometer to align the device, ensure that the measured surface of the device is perpendicular to the main axis of the machine tool, and use a pressing plate to press the inspection rod array device; Step 4: Start the machine tool, manually adjust the position of the machine tool spindle and the worktable, calibrate the position of each inspection rod and record the coordinates, ensure that each displacement sensor can maintain a normal measurement range when measuring the inspection rod, plan the measurement path, and write the measurement program; Step 5: Write a machine tool heat-up program according to the actual working conditions, requiring that the X, Y, and Z axes of the machine tool be linked without interference between the measuring fixture and the inspection rod array device; Step 6: Setting temperature sensors on the installation frame and key heat-generating components of the machine tool to monitor the temperature field of the machine tool; Step 7: Before the machine is heated up, all the inspection rods are measured, and the displacement sensor is reset when measuring the first inspection rod, and the measurement results are regarded as the initial posture states of different points of the machine tool in the cold state; Step 8: Warm up the machine tool and measure the inspection rod array device once at a set interval until the machine tool reaches a thermal equilibrium state, thereby obtaining the thermally induced posture error of the machine tool at different points at any working time.

6. The testing method according to claim 5, characterized in that: According to the measurement results of the displacement sensor, the influence of the ambient temperature on the position of the installation hole of the inspection rod is eliminated, and the measurement data is calculated and processed to obtain the thermally induced spatial posture error of the machine tool: in, , , Represents the three thermally induced spatial position errors of machine tools, , Denotes two thermally induced spatial attitude errors of machine tools, , , , , It represents the deformation values ​​measured at the five points X1, X2, Y1, Y2 and Z of the displacement sensor after eliminating the influence of ambient temperature. It represents the distance between the two displacement sensors in the same measuring direction of the high-precision inspection rod. Indicates the distance between the center of the front bearing of the spindle and the measuring center of the end of the inspection rod; After obtaining the thermally induced posture errors of all points in space, the thermal deformation law of the machine tool can be analyzed: by analyzing the changes in the thermally induced errors of all the inspection rods in the X direction at different times, the left and right offset law of the column of the machine tool after heating can be determined; by analyzing the changes in the thermally induced errors of all the inspection rods in the Y direction at different times, the elongation law of the column of the machine tool after heating can be determined; by analyzing the changes in the thermally induced errors of all the inspection rods in the Z direction at different times, the pitch change law of the column of the machine tool after heating can be determined; by analyzing the changes in the posture errors of all the inspection rods around the X-axis at different times, the pitch deformation law of the spindle axis relative to the workpiece axis after heating can be determined; by analyzing the changes in the posture errors of all the inspection rods around the Y-axis at different times, the yaw deformation law of the spindle axis relative to the workpiece axis after heating can be determined.

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