CN117245555A - Device and method for measuring axial deviation of thermally induced spindle and turntable of precision vertical grinding machine - Google Patents
Device and method for measuring axial deviation of thermally induced spindle and turntable of precision vertical grinding machine Download PDFInfo
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- CN117245555A CN117245555A CN202310976744.6A CN202310976744A CN117245555A CN 117245555 A CN117245555 A CN 117245555A CN 202310976744 A CN202310976744 A CN 202310976744A CN 117245555 A CN117245555 A CN 117245555A
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- 238000005259 measurement Methods 0.000 claims abstract description 73
- 238000006073 displacement reaction Methods 0.000 claims abstract description 28
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
- B24B49/12—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation involving optical means
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Abstract
The invention provides a device and a method for measuring the axis deviation of a main shaft and a rotary table of a precision vertical grinding machine, which are characterized in that: measuring the position offset of a high-precision square column arranged on the surface of a turntable in two directions by using a measuring device based on a laser displacement sensor, rotating the square column by 180 degrees, and repeating the measurement after rotating a sensor mounting plate by 90 degrees so as to eliminate the influence of the perpendicularity error of the square column on a measuring result; setting a heat engine program according to the actual working condition of the grinding machine to heat, and setting a temperature sensor around the key heat generating part to monitor the temperature field of the grinding machine until the machine reaches a heat balance state; repeating the measurement process for a plurality of times on the positions of different radiuses of the turntable before and after the heat engine, and obtaining the axis deviation of the thermally induced main shaft and the turntable at the positions of different radiuses of the turntable after processing the data; the method can obtain the axis deviation of the thermally induced main shaft and the turntable of the precise vertical grinding machine, predicts the cylindricity error of the rotary part caused by the heat generation of the machine tool, and has important significance for improving the machining precision of the precise vertical grinding machine.
Description
Technical Field
The invention relates to a device and a method for measuring thermal errors of a machine tool, in particular to a method for measuring spindle-turntable axis deviation of a precise vertical grinding machine.
Technical Field
Because of the self structural characteristics of the precise vertical grinding machine, the relative gesture of the main shaft and the axis of the rotary table has a great influence on the machining precision of rotary parts in the machining process; in the grinding process of the machine tool, the spindle and the axis of the turntable are inclined due to heat generation of the machine tool, so that the machining precision is reduced; therefore, how to accurately detect the axis error of the precise vertical thermally induced spindle and the turntable is significant in improving the processing precision of the precise vertical grinding machine.
At present, the device for measuring the thermal error of the precise vertical grinding machine is widely applied to devices such as a marble Dan Jiaoche device, a laser interferometer and the like. However, the above devices are all used for measuring errors of a feeding shaft of a machine tool or between shafts, and the relative posture between the axis of the main shaft and the axis of the rotary table is less concerned. In conclusion, a novel thermally-induced spindle-turntable axis deviation measuring method is developed aiming at the defects of the existing spindle-turntable axis deviation detecting method of the machine tool.
Disclosure of Invention
The invention aims to provide a novel device and a method for measuring the axial deviation of a thermally induced main shaft and a rotary table of a vertical grinding machine, wherein the method utilizes a measuring device which is arranged on the main shaft and is based on a laser displacement sensor to measure a high-precision square column arranged on the surface of the rotary table so as to reflect the axial deviation of the main shaft and the rotary table before and after the heat engine; installing a plurality of square columns at different radius positions of a turntable, respectively measuring before and after a heat engine to obtain the axis deviation of a thermally induced main shaft and the turntable at different radius positions of the turntable, establishing the connection between the axis deviation of the thermally induced main shaft and the turntable of the vertical grinder and the radius of the turntable, and predicting the workpiece cylindricity error caused by the axis deviation of the thermally induced main shaft and the turntable based on the connection;
the laser sensor measuring device comprises a laser displacement sensor, an upper computer, a sensor mounting plate, a custom knife handle and a balancing weight;
the laser displacement sensor is fixed on the sensor mounting plate by bolts, the sensor positioning block is used for ensuring that the directions of the two sensors are mutually perpendicular, and the sensors are connected with the upper computer and transmit data to the upper computer for data processing;
the sensor mounting plate is positioned through a cylindrical pin and is fixed on the customized cutter handle through a bolt, the bottom end of the customized cutter handle is a cylinder with the diameter of 40mm, and a threaded hole and a pin hole along the central line are formed in the bottom surface of the cylinder and are used for connecting and positioning the sensor mounting plate; the mounting plate is provided with a balancing weight to balance the gravity center, and the gravity center is kept at the center of the main shaft;
the high-precision square column is a cuboid made of an indium steel material, four side faces of the square column are grooved, and one side of the square column is provided with a through hole for installing the square column; the other three side surfaces are selected as measurement surfaces, and the verticality of the adjacent side surfaces and the verticality of the side surfaces and the bottom surface are ensured through high-precision machining; the expansion coefficient of the indium steel material is low, so that the whole square column is made of the indium steel material, and the dimension of the square column is ensured to be approximately constant when the temperature is changed;
the square column is arranged on the base plate through the bolts and the pressing plate so as to be convenient for quick assembly and disassembly and provide a positioning reference for the square column; two flanges are arranged on the substrate, and the verticality of the two flanges is positioned and ensured by using a cylindrical pin; when the square column is installed, the square column is abutted against the flange and fixed by bolts, and the other two sides are pressed by pressing plates; the substrate is utilized to install, so that the high-precision square column can be quickly assembled and disassembled, a positioning reference is provided for the high-precision square column, and errors caused by repeated installation are reduced.
The method for measuring the axial deviation of the thermally induced spindle and the turntable is characterized in that the laser displacement sensor measuring device is used for measuring the position offset of the high-precision square column in two directions, the square column is reversed by 180 degrees, and the sensor mounting plate is rotated by 90 degrees and then the measurement is repeated, so that the influence of the perpendicularity error of the square column on the measuring result is eliminated; setting a heat engine program according to the actual working condition of the grinding machine to heat, and setting a temperature sensor around the key heat generating part to monitor the temperature field of the grinding machine; the method comprises the steps of carrying out multiple measurements on different radiuses of a turntable before and after a heat engine by using the measuring method, and obtaining the axis deviation of a thermally induced main shaft and the turntable at the different radiuses of the turntable;
the laser displacement sensor is used for measuring the position offset of the high-precision square column in two directions, and the measuring process can be refined into the following steps:
step 1, installing a laser displacement sensor on a sensor mounting plate according to the steps, and installing the sensor mounting plate on a custom knife handle through bolts and cylindrical pins;
step 2, placing the substrate on a turntable of a vertical grinder, and roughly setting the orientation; vertically placing the square column on the base plate, abutting the measuring surface of the square column against the flange, and tightening a bolt on the flange by using a torque wrench; adjusting the position of the substrate, measuring the side surface of the square column by using a Y-direction laser displacement sensor, and adjusting the position and the posture of the substrate after the indication is shown so as to ensure that a measuring plane is parallel to the X-axis direction of the machine tool, wherein the indication is in the measuring range of the sensor; after the pose of the square column is adjusted, fixing the base plate on the surface of the turntable; setting a machine tool program, and moving the spindle into the measuring range of the X-direction laser sensor;
step 3, setting a machine tool program to enable the main shaft to move at a constant speed along the Z axis, and performing one-time reciprocating motion on the Z axis in the measuring process; fitting the measurement data to a linear polynomial L about the Z-axis coordinate based on the laser sensor measurements x1 And L y1 ：
Wherein L is x1 、L y1 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, the superscript X1 represents the fitting result of the straight line in the X axis direction under the forward measurement, and the superscript Y1 represents the fitting result of the straight line in the Y axis direction under the forward measurement;
step 4, rotating the high-precision square column by 180 degrees and reinstalling the high-precision square column on the substrate; rotating the sensor mounting plate by 90 degrees, enabling the pin holes on the cutter handle to correspond to the pin holes on the sensor mounting plate, mounting cylindrical pins, and then screwing down bolts; the coordinate of the main shaft in the X direction is adjusted, so that the indication number of the sensor reaches a proper range;
step 5, performing reverse measurement once, setting a machine tool program, enabling the spindle to move along the Z axis, and performing reciprocating motion once on the Z axis in the measurement process; after the measurement process is finished, fitting the measurement data to a linear polynomial L about the Z-axis coordinate according to the measurement result of the laser sensor x2 And L y2 ：
Wherein L is x2 、L y2 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, the superscript X2 represents the fitting result of the Z axis along the X axis direction under the reverse measurement of the straight line, and the superscript Y2 represents the fitting result of the Z axis along the Y axis direction under the reverse measurement of the straight line;
the fitting polynomial first order coefficients of the two measurements are averaged:
wherein a is x 、a y Respectively representing fitting results in X and Y directions, a t (t=x1, x2, y1, y 2) represents the first order coefficients of the corresponding fitting polynomial;
the relative position of the measured surface of the square column and the axis of the main shaft can be changed by rotating the square column by 180 degrees, so that the perpendicularity error of the side surface and the bottom surface of the square column is counteracted by taking the average value of the two measurement results; after the measurement process is finished, respectively installing a substrate and a high-precision square column at three different radius positions of a workbench, repeating the measurement steps, reading and fitting the measurement results after each measurement, obtaining two-direction fitting results of the high-precision square column at different measurement positions according to gradients, and marking asWherein r=1, 2,3;
the sensor mounting plate is detached together with the laser displacement sensor and the high-precision square column; setting a machine tool program to enable a machine tool X, Z shaft to be linked, and setting the running speed to be 3m/min; the main shaft and the rotary table continuously rotate, wherein the rotating speed of the main shaft is set to 2500rpm, and the rotating speed of the rotary table is set to 30rpm so as to simulate the actual machining state of the machine tool; a temperature sensor is arranged at the parts of main heat generating parts of the machine tool, such as a motor, a main shaft and the like, and the temperature field of the machine tool is monitored until the machine tool reaches a heat balance state;
after the heat engine is finished, the sensor mounting plate is mounted on a special knife handle together with the laser displacement sensor, and the high-precision square column is mounted on the substrate; measuring a plurality of square columns, fitting the results to obtain two-direction fitting results of a plurality of positions, and marking asWhere r=1, 2,3.
The method for predicting the thermal machining error of the vertical grinding machine is characterized in that the measured temperature field is used for predicting the axial line gesture of the spindle-turntable; based on the measured axis deviation of the thermally induced spindle and the turntable at a plurality of different positions, establishing a relation between the axis deviation and the radius of the turntable, and establishing an expression of the axis deviation under any radius; finally predicting workpiece cylindricity error caused by thermally induced spindle-turntable axis deviation, the method comprises the following steps:
step 1, adding a thermal load according to actual working conditions by utilizing Ansys simulation software, and correcting boundary conditions according to a measured temperature field; extracting a main shaft deformation curve and a turntable plane deformation curve according to Ansys simulation results, further calculating the rotation angle error of the main shaft and the turntable axis and predicting the deviation of the main shaft and the turntable axis;
wherein, according to the actual working condition, the feeding speed of the machine tool is 3m/min, the working environment temperature is 20 ℃, the main shaft rotating speed is 2500rpm, the rotating speed of the rotary table is set to 30rpm, the heat dissipation source of the whole machine tool is the natural convection heat exchange of the structural part of the machine tool and the air, and the natural convection heat exchange coefficient takes 9.7W/(m) according to the empirical value 2 C, a temperature; calculating to obtain the heating power added to each machine tool component;
the Ansys simulation software is utilized to obtain a complete machine temperature field and a complete machine deformation field, and the thermal load is adjusted according to the actually measured temperature field, so that the simulation result is closer to the actual one; respectively extracting deformation curves of a workbench plane and a main shaft mounting surface, and fitting the deformation curves into a space circle by using a least square method; calculating a fitting space circular vector corner error based on a direction cosine formula, and obtaining corner errors of the axis of the workbench and the axis of the main shaft in two directions, so as to predict the axis deviation of the main shaft and the rotary table;
wherein θ X 、θ Y Representing the components of the predicted thermally induced spindle-turntable axis angle along the X-direction and the Y-direction respectively, indicating the angular error of the spindle axis in both directions,/-respectively>Respectively representing the rotation angle errors of the axis of the turntable in two directions;
step 2, based on the data obtained by measurement, the following can be obtained:
the components of the included angles of the axis of the thermally induced main shaft and the rotary table at different positions along the X direction and the Y direction are respectively as follows:
wherein r=1, 2,3;
a table top of the turntable is taken as an XY plane, and the positive directions of an X axis and a Z axis of the machine tool are taken as the positive directions of the X axis and the Z axis, so that a coordinate system is established; according to the included angle between the main shaft and the turntable along the X, Y direction, the actual posture of the main shaft axis in the working space is obtained;
projecting a main shaft axis into a table top of the turntable, wherein the clamping angle between the main shaft axis and the X-axis is as follows:
wherein r=1, 2,3;
projecting the spindle axis to a plane where the turntable axis is located, wherein the included angle between the spindle axis and the turntable axis is as follows:
wherein r=1, 2,3;
the spindle-turntable axis deviations at the different radii obtained are fitted to an m-th order polynomial on the radius value:
wherein θ h (r)、θ v (r) represents the included angle between the axis of the main shaft and the axes of the X-axis and the turntable when the radius value is r, b n Coefficients representing the nth order polynomial, r representing the radius value;
based on the polynomial, the axis deviation of the thermally induced spindle and the turntable at any radius position can be obtained, and then data support is provided for predicting the cylindricity error of the workpiece;
step 3, in the actual machining process of the vertical grinding machine, the axial deviation of the main shaft can directly influence the posture of a grinding wheel arranged on the main shaft, and the axial inclination of the turntable can also lead to the axial inclination of a workpiece;
when the inner circle and the outer circle are ground, the axis deviation of the main shaft and the rotary table can cause the misalignment of the grinding wheel and the rotation axis of the workpiece, and further cause the cylindricity error of the workpiece. Assuming that the spindle coincides with the turntable center when the machine tool coordinates x=0, and that the thermally induced spindle-turntable axis deviations are respectively angular offsets around the mounting position;
considering the axis deviation of a thermally induced spindle-turntable of a machine tool, for a workpiece with a height h and a radius r, the workpiece cylindricity error according to the minimum area cylindricity method is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the components of the thermally induced spindle-turntable axis angle at radius r along the X-direction and Y-direction are shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the Y direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece;the component of the thermally induced spindle-turntable axis angle along the Y direction at radius r is shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the X direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the component of the thermally induced spindle-turntable axis angle along the X direction at radius r is shown.
Drawings
Fig. 1 is a schematic diagram of a forward measurement process, in which: 1-turntable, 2-main shaft, 3-laser sensor assembly, 4-high accuracy square column assembly.
Fig. 2 is a schematic diagram of a reverse measurement process, in which: 1-turntable, 2-main shaft, 3-laser sensor assembly, 4-high accuracy square column assembly.
Fig. 3 is a schematic diagram of a laser sensor measurement module, in which: the device comprises a 5-knife handle, a 6-balancing weight, a 7-sensor mounting plate, an 8-laser displacement sensor and a 9-sensor positioning block.
Fig. 4 is a schematic diagram of a high-precision square column assembly, in which: 10-high-precision square columns, 11-pressing plates, 12-flanges and 13-substrates.
Fig. 5 is a schematic diagram of a temperature sensor layout.
Fig. 6 is a thermal load addition schematic.
Fig. 7 is a schematic diagram of spindle-turntable axis deviation calculation.
FIG. 8 is a schematic diagram of a calculation of the thermal cylindricity error of a workpiece.
Fig. 9 is a flow chart of thermally induced spindle-turntable axis deviation measurement.
Detailed Description
The invention will be further described with reference to the drawings and the specific examples.
FIG. 3 is a schematic view of a laser sensor measurement module, wherein the sensor mounting plate 7 is positioned by a cylindrical pin and is fixed on the custom knife handle by bolts; the bottom end of the customized knife handle is a cylinder with the diameter of 40mm, and a threaded hole and a pin hole along the central line are processed on the bottom surface of the cylinder and are used for connecting and positioning with the sensor mounting plate; the sensor positioning block 9 is positioned by utilizing a pin hole and is mounted on the sensor mounting plate by using a bolt, and the side surfaces of the two positioning blocks ensure verticality tolerance; the sensor mounting plate 7 is provided with corresponding threaded holes according to the sensor mounting requirement, and the sensor surface is tightly positioned during mounting so as to ensure that the directions of the two sensors are mutually perpendicular, and the bolts are screwed for fixation. The mounting plate is provided with a balancing weight 6 to balance the gravity center, the gravity center is kept near the center of the main shaft, and the balancing weight 6 is fixed on the mounting plate by bolts;
fig. 4 is a schematic diagram of an assembly of a high-precision square column, wherein the high-precision square column 10 is a cuboid made of an indium steel material, four sides of the square column are grooved, and one side of the square column is provided with a through hole for installing the square column; the other three side surfaces are selected as measurement surfaces, and the verticality of the adjacent side surfaces and the verticality of the side surfaces and the bottom surface are ensured through high-precision machining; the expansion coefficient of the indium steel material is low, so that the whole square column is made of the indium steel material, and the dimension of the square column is ensured to be approximately constant when the temperature is changed;
the base plate 13 is arranged on the surface of the workbench through T-shaped nuts and bolts; the square column is arranged on the base plate through the bolts and the pressing plate so as to quickly assemble and disassemble the square column and provide a positioning reference for the square column; two flanges 12 are arranged on the base plate, are positioned by using cylindrical pins and ensure the verticality of the two flanges, and are provided with through holes for fixing square columns; the square column 10 is tightly abutted against the flange and fixed by bolts when being installed, and the other two sides are tightly pressed by the pressing plate 11; the substrate is utilized to install, so that the high-precision square column can be quickly assembled and disassembled, a positioning reference is provided for the high-precision square column, and errors caused by repeated installation are reduced.
The invention provides a method for testing the axial deviation of a thermally-induced main shaft and a turntable of a vertical grinding machine, which is characterized in that the laser displacement sensor measuring device is used for measuring the position offset of a high-precision square column in two directions, the square column is reversed by 180 degrees, and the measurement is repeated after a sensor mounting plate is rotated by 90 degrees, so that the influence of the perpendicularity error of the square column on a measuring result is eliminated; setting a heat engine program according to the actual working condition of the grinding machine to heat, and setting a temperature sensor around the key heat generating part to monitor the temperature field of the grinding machine; repeating the measurement process for a plurality of times on the positions of different radiuses of the turntable before and after the heat engine, and obtaining the axis deviation of the thermally induced main shaft and the turntable at the positions of different radiuses of the turntable after processing the data; the complete measurement process can be referred to the flowchart shown in fig. 9;
the method for measuring the position offset of the high-precision square column in two directions by using the laser displacement sensor measuring device comprises the following steps of:
step 1, installing a laser displacement sensor on a sensor mounting plate according to the steps, and installing the sensor mounting plate on a custom knife handle through bolts and cylindrical pins;
step 2, carrying out forward measurement as shown in figure 1, and placing the substrate on a turntable of a vertical grinder to approximately align; vertically placing the square column on the base plate, abutting the measuring surface of the square column against the flange, and tightening a bolt on the flange by using a torque wrench; adjusting the position of the substrate, measuring the side surface of the square column by using a Y-direction laser displacement sensor, and adjusting the position and the posture of the substrate after the indication is shown so as to ensure that a measuring plane is parallel to the X-axis direction of the machine tool, wherein the indication is in the measuring range of the sensor; after the pose of the square column is adjusted, fixing the base plate on the surface of the turntable; setting a machine tool program, and moving the spindle into the measuring range of the X-direction laser sensor;
step 3, setting a machine tool program to enable the main shaft to move at a constant speed along the Z axis, and performing one-time reciprocating motion on the Z axis in the measuring process; fitting the measurement data to a linear polynomial L about the Z-axis coordinate based on the laser sensor measurements x1 And L y1 ：
Wherein L is x1 、L y1 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, the superscript X1 represents the fitting result of the straight line in the X axis direction under the forward measurement, and the superscript Y1 represents the fitting result of the straight line in the Y axis direction under the forward measurement;
step 4, rotating the high-precision square column by 180 degrees and reinstalling the high-precision square column on the substrate; as shown in fig. 2, the sensor mounting plate is rotated by 90 degrees, pin holes on the cutter handle correspond to the pin holes on the sensor mounting plate and cylindrical pins are arranged, and then bolts are screwed; the coordinate of the main shaft in the X direction is adjusted, so that the indication number of the sensor reaches a proper range;
step 5, performing reverse measurement once, setting a machine tool program, enabling the spindle to move along the Z axis, and performing reciprocating motion once on the Z axis in the measurement process; upper partAfter the measurement process is finished, fitting the measurement data to a linear polynomial L about the Z-axis coordinate according to the measurement result of the laser sensor x2 And L y2 ：
Wherein L is x2 、L y2 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, the superscript X2 represents the fitting result of the Z axis along the X axis direction under the reverse measurement of the straight line, and the superscript Y2 represents the fitting result of the Z axis along the Y axis direction under the reverse measurement of the straight line;
the fitting polynomial first order coefficients of the two measurements are averaged:
wherein a is x 、a y Respectively representing fitting results in X and Y directions, a t (t=x1, x2, y1, y 2) represents the first order coefficients of the corresponding fitting polynomial;
the relative position of the measured surface of the square column and the axis of the main shaft can be changed by rotating the square column by 180 degrees, so that the perpendicularity error of the side surface and the bottom surface of the square column is counteracted by taking the average value of the two measurement results; respectively installing a substrate and a high-precision square column at three different radial positions of a workbench, respectively carrying out the measurement processes, reading and fitting the measurement results after each measurement, obtaining two-direction fitting results of the high-precision square column at different measurement positions according to gradients, and marking asWherein r=1, 2,3;
the sensor mounting plate is detached together with the laser displacement sensor and the high-precision square column; setting a machine tool program to enable a machine tool X, Z shaft to be linked, and setting the running speed to be 3m/min; the main shaft and the rotary table continuously rotate, wherein the rotating speed of the main shaft is set to 2500rpm, and the rotating speed of the rotary table is set to 30rpm so as to simulate the actual machining state of the machine tool; a temperature sensor is arranged at the parts of main heat generating parts of the machine tool, such as a motor, a main shaft and the like, and the temperature field of the machine tool is monitored until the machine tool reaches a heat balance state; the number and the position of the temperature sensor can be arranged as shown in table 1, and the specific arrangement position can be arranged as shown in fig. 5;
table 1 temperature sensor layout
After the heat engine is finished, the sensor mounting plate is mounted on a special knife handle together with the laser displacement sensor, and the high-precision square column is mounted on the substrate; measuring a plurality of square columns, fitting the results to obtain two-direction fitting results of a plurality of positions, and marking asWhere r=1, 2,3.
The method for predicting the thermal machining error of the vertical grinding machine is characterized by predicting the axial line gesture of a main shaft-rotary table by using the measured temperature field; based on the measured axis deviation of the thermally induced spindle and the turntable at a plurality of different positions, establishing a relation between the axis deviation and the radius of the turntable, and establishing an expression of the axis deviation under any radius; finally predicting workpiece cylindricity errors caused by the axis deviation of the thermally induced spindle and the turntable; the method can be refined as the following steps:
step 1, adding a thermal load according to actual working conditions by utilizing Ansys simulation software, and correcting boundary conditions according to a measured temperature field; extracting a main shaft deformation curve and a turntable plane deformation curve according to Ansys simulation results, further calculating the rotation angle error of the main shaft and the turntable axis and predicting the deviation of the main shaft and the turntable axis;
wherein, according to the actual working condition, the feeding speed of the machine tool is 3m/min, the working environment temperature is 20 ℃, the main shaft rotating speed is 2500rpm, the rotating speed of the rotary table is set to 30rpm, the heat dissipation source of the whole machine tool is the natural convection heat exchange of the structural part of the machine tool and the air, and the natural convection heat exchange coefficient is empirically determinedThe value is 97W/(m) 2 C, a temperature; calculating to obtain the heat generation power added to each machine tool part, and loading the heat generation power to the corresponding heat generation part as shown in fig. 6;
the Ansys simulation software is utilized to obtain a complete machine temperature field and a complete machine deformation field, and the thermal load is adjusted according to the actually measured temperature field, so that the simulation result is closer to the actual one; respectively extracting deformation curves of a workbench plane and a main shaft mounting surface, and fitting the deformation curves into a space circle by using a least square method; based on a direction cosine formula, calculating a fitting space circle normal vector corner error, and obtaining corner errors of the workbench axis and the spindle axis in two directions, thereby obtaining predicted spindle-turntable axis deviation:
the heat generating power added to each machine tool part is obtained through calculation according to the actual working conditions; the Ansys simulation software is utilized to obtain a complete machine temperature field and a complete machine deformation field, and the thermal load is adjusted according to the actually measured temperature field, so that the simulation result is closer to the actual one; respectively extracting deformation curves of a workbench plane and a main shaft mounting surface, and fitting the deformation curves into a space circle by using a least square method; calculating a fitting space circular vector corner error based on a direction cosine formula, and obtaining corner errors of the axis of the workbench and the axis of the main shaft in two directions, so as to predict the axis deviation of the main shaft and the rotary table;
wherein θ X 、θ Y Representing the components of the predicted thermally induced spindle-turntable axis angle along the X-direction and the Y-direction respectively, indicating the angular error of the spindle axis in both directions,/-respectively>Respectively showing the axes of the rotary tables atAngle error in both directions;
step 2, based on the data obtained by measurement, the following can be obtained:
the components of the included angles of the axis of the thermally induced main shaft and the rotary table at different positions along the X direction and the Y direction are respectively as follows:
wherein r=1, 2,3;
a table top of the turntable is taken as an XY plane, and the positive directions of an X axis and a Z axis of the machine tool are taken as the positive directions of the X axis and the Z axis, so that a coordinate system is established; according to the included angle between the main shaft and the turntable along the X, Y direction, the actual posture of the main shaft axis in the working space is obtained;
projecting a main shaft axis into a table top of the turntable, wherein the clamping angle between the main shaft axis and the X-axis is as follows:
wherein r=1, 2,3;
projecting the spindle axis to a plane where the turntable axis is located, wherein the included angle between the spindle axis and the turntable axis is as follows:
wherein r=1, 2,3;
the spindle-turntable axis deviations at the different radii obtained are fitted to an m-th order polynomial on the radius value:
wherein θ h (r)、θ v (r) represents the included angle between the axis of the main shaft and the axes of the X-axis and the turntable when the radius value is r, b n Coefficients representing the nth order polynomial, r representing the radius value;
based on the polynomial, the axis deviation of the thermally induced spindle and the turntable at any radius position can be obtained, and then data support is provided for predicting the cylindricity error of the workpiece;
step 3, in the actual machining process of the vertical grinding machine, the axial deviation of the main shaft can directly influence the posture of a grinding wheel arranged on the main shaft, and the axial inclination of the turntable can also lead to the axial inclination of a workpiece;
as shown in figure 8, when the inner and outer circles are ground, the contact point of the grinding wheel and the workpiece is deviated due to the fact that deflection angles in the radial direction and the tangential direction exist between the axes of the main shaft and the rotary table, and cylindricity errors are generated in the rotary workpiece; assuming that the spindle coincides with the turntable center when the machine tool coordinates x=0, and that the thermally induced spindle-turntable axis deviations are respectively angular offsets around the mounting position;
considering the axis deviation of a thermally induced spindle-turntable of a machine tool, for a workpiece with a height h and a radius r, the workpiece cylindricity error according to the minimum area cylindricity method is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the components of the thermally induced spindle-turntable axis angle at radius r along the X-direction and Y-direction are shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the Y direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece;the component of the thermally induced spindle-turntable axis angle along the Y direction at radius r is shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the X direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the component of the thermally induced spindle-turntable axis angle along the X direction at radius r is shown.
The invention finally obtains the thermally-induced perpendicularity error between two linear axes of the machine tool. The drawings are only for the purpose of illustrating the invention and are not to be construed as limiting the invention, but are intended to cover all modifications, equivalent arrangements, improvements, etc. that are within the spirit and scope of the invention.
Claims (3)
1. The device and the method for measuring the axial deviation of the thermally induced main shaft and the rotary table of the precise vertical grinding machine are characterized in that: the method comprises the steps that a measuring device based on a laser displacement sensor and arranged on a main shaft and a high-precision square column arranged on the surface of a turntable are used for representing the axes of the main shaft and the turntable respectively, and the deviation of the axis of the main shaft and the turntable is reflected by measuring the relative positions of the laser displacement sensor and the high-precision square column in two directions; setting temperature sensors around key heat generating components of the precise vertical grinding machine to monitor the temperature field of the grinding machine, setting a heat engine program according to actual working conditions, installing a plurality of square columns at different radius positions of the rotary table, and respectively measuring before and after the heat engine to obtain the axis deviation of the thermally induced main shaft and the rotary table at the different radius positions of the rotary table; processing the measured data, establishing a relation between the axis deviation of the thermally induced spindle and the turntable of the precision vertical grinding machine and the radius of the turntable, and predicting the workpiece cylindricity error caused by the axis deviation of the thermally induced spindle and the turntable based on the relation;
the laser sensor measuring device comprises a laser displacement sensor, an upper computer of the laser displacement sensor, a sensor mounting plate, a sensor positioning block, a customized cutter handle and a balancing weight; the laser displacement sensor is fixed on the sensor mounting plate by bolts, the sensor positioning block is used for ensuring that the directions of the two sensors are mutually perpendicular, and the sensor is connected with the upper computer and transmits data to the upper computer for data processing; the sensor mounting plate is positioned through a cylindrical pin and is fixed on the customized cutter handle through a bolt, the bottom end of the customized cutter handle is a cylinder with the diameter of 40mm, and a threaded hole and a pin hole along the central line are formed in the bottom surface of the cylinder and are used for connecting and positioning the sensor mounting plate; the mounting plate is provided with a balancing weight to balance the gravity center, and the gravity center is kept at the center of the main shaft;
the high-precision square column is a cuboid made of an indium steel material, four side faces of the square column are grooved, and one side of the square column is provided with a through hole for installing the square column; the other three side surfaces are selected as measurement surfaces, and the verticality of the adjacent side surfaces and the verticality of the side surfaces and the bottom surface are ensured through high-precision machining; the expansion coefficient of the indium steel material is low, so that the whole square column is made of the indium steel material, and the dimension of the square column is ensured to be approximately constant when the temperature is changed; the square column is arranged on the base plate through the bolts and the pressing plate so as to quickly assemble and disassemble the square column and provide a positioning reference for the square column; two flanges are arranged on the substrate, and the verticality of the two flanges is positioned and ensured by using a cylindrical pin; when the square column is installed, the square column is abutted against the flange and fixed by bolts, and the other two sides are pressed by pressing plates; the substrate is utilized to install, so that the high-precision square column can be quickly assembled and disassembled, a positioning reference is provided for the high-precision square column, and errors caused by repeated installation are reduced.
2. The method for testing the axial deviation of the thermally induced spindle and the turntable of the precision vertical grinding machine according to claim 1, wherein the laser displacement sensor measuring device is used for measuring the position offset of the high-precision square column in two directions, then the square column is rotated by 180 degrees, and the sensor mounting plate is rotated by 90 degrees and then the measurement is repeated, so that the influence of the perpendicularity error of the square column on the measurement result is eliminated; setting a heat engine program according to the actual working condition of the grinding machine to heat, and setting a temperature sensor around the key heat generating part to monitor the temperature field of the grinding machine until the machine reaches a heat balance state; the method comprises the steps of carrying out multiple measurements on different radiuses of a turntable before and after a heat engine by using the measuring method, and obtaining the axis deviation of a thermally induced main shaft and the turntable at the different radiuses of the turntable;
the laser displacement sensor is used for measuring the position offset of the high-precision square column in two directions, and the measuring process can be refined into the following steps:
step 1, installing a laser displacement sensor on a sensor mounting plate according to the steps, and installing the sensor mounting plate on a custom knife handle through bolts and cylindrical pins;
step 2, placing the substrate on a turntable of a precise vertical grinding machine, and roughly aligning the substrate; vertically placing the square column on the base plate, abutting the measuring surface of the square column against the flange, and tightening a bolt on the flange by using a torque wrench; adjusting the position of the substrate, measuring the side surface of the square column by using a Y-direction laser displacement sensor, and adjusting the position and the posture of the substrate after the indication is shown so as to ensure that a measuring plane is parallel to the X-axis direction of the machine tool, wherein the indication is in the measuring range of the sensor; after the pose of the square column is adjusted, fixing the base plate on the surface of the turntable; setting a machine tool program, and moving the spindle into the measuring range of the X-direction laser sensor;
step 3, setting a machine tool program to enable the main shaft to move at a constant speed along the Z axis, and performing one-time reciprocating motion on the Z axis in the measuring process; fitting the measurement data to a linear polynomial L about the Z-axis coordinate based on the laser sensor measurements x1 And L y1 ：
Wherein L is x1 、L y1 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, and the superscript X1 represents the fitting of the Z axis along the X axis direction under the positive measurement of the straight lineAs a result, the superscript Y1 indicates that the straight line is a fitting result of the positive measurement in the direction of the Y axis along the Z axis;
step 4, rotating the high-precision square column by 180 degrees and reinstalling the high-precision square column on the substrate; rotating the sensor mounting plate by 90 degrees, enabling the pin holes on the cutter handle to correspond to the pin holes on the sensor mounting plate, mounting cylindrical pins, and then screwing down bolts; the coordinate of the main shaft in the X direction is adjusted, so that the indication number of the sensor reaches a proper range;
step 5, performing reverse measurement once, setting a machine tool program, enabling the spindle to move along the Z axis, and performing reciprocating motion once on the Z axis in the measurement process; after the measurement process is finished, fitting the measurement data to a linear polynomial L about the Z-axis coordinate according to the measurement result of the laser sensor x2 And L y2 ：
Wherein L is x2 、L y2 Representing the relative distance value of the sensor and the square column, a n The coefficient of the fitting polynomial is represented, Z represents the coordinate value of the Z axis, the superscript X2 represents the fitting result of the Z axis along the X axis direction under the reverse measurement of the straight line, and the superscript Y2 represents the fitting result of the Z axis along the Y axis direction under the reverse measurement of the straight line;
the fitting polynomial first order coefficients of the two measurements are averaged:
wherein a is x 、a y Respectively representing fitting results in X and Y directions, a t (t=x1, x2, y1, y 2) represents the first order coefficients of the corresponding fitting polynomial;
respectively installing a substrate and a high-precision square column at three different radial positions of a workbench, respectively carrying out the measurement processes, reading and fitting the measurement results after each measurement, obtaining two-direction fitting results of the high-precision square column at different measurement positions according to gradients, and marking asWherein r=1, 2,3;
the sensor mounting plate is detached together with the laser displacement sensor and the high-precision square column; setting a machine tool program to enable a machine tool X, Z shaft to be linked, and setting the running speed to be 3m/min; the main shaft and the rotary table continuously rotate, wherein the rotating speed of the main shaft is set to 2500rpm, and the rotating speed of the rotary table is set to 30rpm so as to simulate the actual machining state of the machine tool; a temperature sensor is arranged at the parts of main heat generating parts of the machine tool, such as a motor, a main shaft and the like, and the temperature field of the machine tool is monitored until the machine tool reaches a heat balance state;
after the heat engine is finished, the sensor mounting plate is mounted on a special knife handle together with the laser displacement sensor, and the high-precision square column is mounted on the substrate; measuring a plurality of square columns, fitting the results to obtain two-direction fitting results of a plurality of positions, and marking asWhere r=1, 2,3.
3. The method for predicting thermal machining errors of a precision vertical grinder according to claim 1, wherein the spindle-turntable axis posture is predicted using the measured temperature field; based on the measured axis deviation of the thermally induced spindle and the turntable at a plurality of different positions, establishing a relation between the axis deviation and the radius of the turntable, and establishing an expression of the axis deviation under any radius; finally predicting workpiece cylindricity error caused by thermally induced spindle-turntable axis deviation, the method comprises the following steps:
step 1, adding a thermal load according to actual working conditions by utilizing Ansys simulation software, and correcting boundary conditions according to a measured temperature field; extracting a main shaft deformation curve and a turntable plane deformation curve according to Ansys simulation results, further calculating the rotation angle error of the main shaft and the turntable axis and predicting the deviation of the main shaft and the turntable axis;
the heat generating power added to each machine tool part is obtained through calculation according to the actual working conditions; the Ansys simulation software is utilized to obtain a complete machine temperature field and a complete machine deformation field, and the thermal load is adjusted according to the actually measured temperature field, so that the simulation result is closer to the actual one; respectively extracting deformation curves of a workbench plane and a main shaft mounting surface, and fitting the deformation curves into a space circle by using a least square method; calculating a fitting space circular vector corner error based on a direction cosine formula, and obtaining corner errors of the axis of the workbench and the axis of the main shaft in two directions, so as to predict the axis deviation of the main shaft and the rotary table;
wherein θ X 、θ Y Representing the components of the predicted thermally induced spindle-turntable axis angle along the X-direction and the Y-direction respectively, indicating the angular error of the spindle axis in both directions,/-respectively>Respectively representing the rotation angle errors of the axis of the turntable in two directions;
step 2, based on the data obtained by measurement, the following can be obtained:
the components of the included angles of the axis of the thermally induced main shaft and the rotary table at different positions along the X direction and the Y direction are respectively as follows:
wherein r=1, 2,3;
a table top of the turntable is taken as an XY plane, and the positive directions of an X axis and a Z axis of the machine tool are taken as the positive directions of the X axis and the Z axis, so that a coordinate system is established; according to the included angle between the main shaft and the turntable along the X, Y direction, the actual posture of the main shaft axis in the working space is obtained;
projecting a main shaft axis into a table top of the turntable, wherein the clamping angle between the main shaft axis and the X-axis is as follows:
wherein r=1, 2,3;
projecting the spindle axis to a plane where the turntable axis is located, wherein the included angle between the spindle axis and the turntable axis is as follows:
wherein r=1, 2,3;
the spindle-turntable axis deviations at the different radii obtained are fitted to an m-th order polynomial on the radius value:
wherein θ h (r)、θ v (r) represents the included angle between the axis of the main shaft and the axes of the X-axis and the turntable when the radius value is r, b n Coefficients representing the nth order polynomial, r representing the radius value;
based on the polynomial, the axis deviation of the thermally induced spindle and the turntable at any radius position can be obtained, and then data support is provided for predicting the cylindricity error of the workpiece;
step 3, in the actual machining process of the precise vertical grinding machine, the axial deviation of the main shaft can directly influence the posture of a grinding wheel arranged on the main shaft, and the axial inclination of the turntable can also lead to the axial inclination of a workpiece;
when the inner circle and the outer circle are ground, the axis deviation of the main shaft and the rotary table can cause the misalignment of the grinding wheel and the rotation axis of the workpiece, and further cause the cylindricity error of the workpiece. Assuming that the spindle coincides with the turntable center when the machine tool coordinates x=0, and that the thermally induced spindle-turntable axis deviations are respectively angular offsets around the mounting position;
considering the axis deviation of a thermally induced spindle-turntable of a machine tool, for a workpiece with a height h and a radius r, the workpiece cylindricity error according to the minimum area cylindricity method is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the components of the thermally induced spindle-turntable axis angle at radius r along the X-direction and Y-direction are shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the Y direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece;the component of the thermally induced spindle-turntable axis angle along the Y direction at radius r is shown.
When (when)When the workpiece cylindricity error caused by the axis of the thermally induced spindle-turntable along the X direction is as follows:
wherein e MZC Representing a cylindricity error according to a minimum region cylindricity method; h represents the height of the workpiece; r represents the radius of the workpiece;the component of the thermally induced spindle-turntable axis angle along the X direction at radius r is shown.
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