Machine tool thermal-induced spatial error measurement device and measurement method

Abstract

The application discloses a machine tool thermal space error measuring device and a measuring method. The measuring device comprises a high-precision standard ball array device, a contact trigger measuring device, a first temperature sensor and a second temperature sensor. The standard ball array device comprises a "m" type mounting base, a plurality of mounting holes are arranged on the surface of the mounting base, and a single ball rod is arranged in each mounting hole according to the maximum uniform distribution principle. The second temperature sensor is arranged on the mounting base of the standard ball array device and used for detecting the temperature field of the mounting base. The contact trigger measuring device comprises a workpiece trigger probe and a host computer, and the workpiece trigger probe is arranged on a machine tool spindle. The contact trigger measuring device is used for measuring the position change of the centers of a plurality of standard balls. The first temperature sensor is arranged around a key heat generating component of a machine tool machining center and used for detecting the temperature field of the machine tool. The application can directly apply the measuring result to the bottom error compensation of a numerical control system.

Claims

1. A machine tool thermally induced spatial error measuring device, characterized in that, The measurement device includes a high-precision standard ball array device, a contact-trigger measurement device, a first temperature sensor, and a second temperature sensor; The high-precision standard ball array device is arranged on the machine tool workbench. The high-precision standard ball array device includes a "meter"-shaped mounting base. A number of mounting holes are installed on the surface of the mounting base. The mounting holes follow the principle of maximum uniform distribution and cover the machine tool workbench surface. Single ball rods are installed in the mounting holes; The second temperature sensor is arranged on the mounting base of the standard ball array device to detect the temperature field of the mounting base; The contact-trigger measurement device includes a workpiece trigger probe and its host computer. The workpiece trigger probe is installed and connected to the tool holder through a reserved connection end and is installed on the machine tool spindle through the tool holder; the contact-trigger measurement device is used to measure the position changes of the centers of multiple standard spheres to reflect the thermal-induced spatial error of the machine tool; The first temperature sensor is arranged around the key heat-generating components of the machine tool machining center to detect the machine tool temperature field.

2. The machine tool thermally induced spatial error measuring device according to claim 1, characterized in that, The mounting holes are divided into the following four levels: one central reference hole, located at the center of rotation of the base, serving as the absolute positioning reference for the entire base; eight inner ring array holes, distributed in a circular ring and equally divided at 45° circumferentially. The circular trajectory is convenient for measuring the rotation axis error and perpendicularity error of the machining center; eight middle ring array holes, distributed in a circular ring and equally divided at 45° circumferentially, with the same purpose as the inner ring array holes, facilitating the measurement of corresponding errors; four outer ring array holes, equally divided at 90° circumferentially, convenient for measuring the positioning and straightness errors of the machining center.

3. The machine tool thermally induced spatial error measuring device according to claim 1, characterized in that, The mounting base is made of stainless steel by integral part processing and manufacturing. At the same time, a ribbed structure design is adopted, and the static characteristics of the mounting base are analyzed using finite element software to verify that it meets the static stiffness requirements.

4. The machine tool thermally induced spatial error measuring device according to claim 1, characterized in that, The flatness error of the back surface of the mounting base and the flatness of the single ball rod mounting plane and the cylindricity of the mounting holes are all controlled at the micron level. Each single ball rod corresponds to the mounting hole on the mounting base, and it is ensured that each installation can position the single ball rod to the same position, avoiding errors caused by repeated installation.

5. The machine tool thermally induced spatial error measuring device according to claim 1, characterized in that, The mounting base structure adopts a lightweight design. The back surface is recessed inward, reducing the overall volume of the device and reducing the weight of the device. And there are steps and through holes at the end of the mounting base, which can ensure that the mounting base is firmly installed without deviation.

6. A method for measuring the thermally induced spatial error of a machine tool using the measuring device according to any one of claims 1-5, characterized in that, It includes the following steps: Fix the high-precision standard ball array device with single ball rods installed to the machine tool workbench, connect the workpiece trigger probe to the machine tool spindle, and ensure that the workpiece trigger probe is communicatively connected to the host computer; Start the machine tool, manually adjust the positions of the machine tool spindle and the workbench, calibrate the positions of the centers of each single ball rod and record the coordinates, ensure that the workpiece trigger probe can maintain in the normal measurement range when measuring the single ball rod, and plan the measurement path so that the machine tool X, Y, Z three translational axes and A, C rotational axes can联动 without interference between the standard ball array device and the workpiece trigger probe; Use the temperature sensors to detect the temperatures around the mounting base and the key heat-generating components of the machine tool machining center, monitor the machine tool temperature field until the machine tool reaches the thermal equilibrium state; According to the measurement data, calculate and obtain the error data belonging to the thermal deformation of the machine tool itself; After measuring the error data of the machining center under cold and hot conditions, the positional deviation between the machine tool tip and the workpiece is calculated to obtain the thermally induced error in the machine tool space. ； in, , These represent the rotation angles of axes B and C, respectively. , , These are respectively represented as the position vectors of the tool tip in the workpiece coordinate system; , , These are respectively represented as the attitude vectors of the tool tip in the workpiece coordinate system; This represents the five-axis coordinate system set internally by the machine tool when it is cold. Add the theoretical angles of rotation axes B and C ), the homogeneous transformation matrix of the tool coordinate system relative to the workpiece coordinate system under ideal conditions; This represents the homogeneous transformation matrix of the tool coordinate system relative to the workpiece coordinate system under actual conditions, calculated by combining the actual measured error after the machine tool has warmed up.

7. The method for measuring thermally induced spatial errors of machine tools according to claim 6, characterized in that, Before starting the machine tool, use the workpiece trigger probe to measure the position of all the single ball bars on the mounting base in sequence, and record the center coordinates of all the single ball bars as the initial ideal pose for all subsequent comparisons.

8. The method for measuring thermally induced spatial errors of machine tools according to claim 6, characterized in that, After starting the machine tool, when measuring the center coordinates of each single ball bar using the workpiece trigger probe, five measuring points are arranged on the ball of each single ball bar, including one in the Z direction to reflect the thermally induced position error in the Z direction at a certain point in space, and two each in the X and Y directions. After obtaining the coordinates of the five measuring points, the current true coordinates of the center of the single ball bar after thermal deformation are obtained through calculation. The true coordinates are subtracted from the initial ideal pose coordinates to obtain the thermally induced position errors in the X, Y, and Z directions at that point.

9. The method for measuring thermally induced spatial errors of machine tools according to claim 6, characterized in that, When calculating and obtaining error data attributable to the thermal deformation of the machine tool itself based on the measurement data, it is necessary to remove the displacement caused by the heating of the mounting base itself from the total error obtained by the workpiece trigger probe measurement, so as to obtain error data attributable to the thermal deformation of the machine tool itself.

10. The method for measuring thermally induced spatial errors of machine tools according to claim 9, characterized in that, The method for obtaining the displacement caused by the heating of the mounting base itself is as follows: The thermal deformation of the mounting base was analyzed by using finite element software when the initial temperature was increased to different temperatures. The three-dimensional thermal deformation data of all holes were extracted. The data was then processed by mathematical software to obtain several fitting curves of the thermal offset values ​​of each hole in the X, Y, and Z directions on the frame as a function of the temperature of the structure itself. Based on the obtained fitting curve, the predicted values ​​of hole deformation at different temperatures can be obtained.

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