Method for calculating compensation parameter of motion error in machine tool, and machine tool

A method for calculating a compensation parameter of a motion error in a machine tool, wherein

• the machine tool includes a table configured to hold a workpiece, a main spindle configured to hold a tool, and three or more translational axes, the main spindle is configured to perform a relative motion of three degrees or more of translational freedom with respect to the table, and the machine tool is configured to compensate for a motion error of the translational axis in accordance with a predetermined compensation parameter, and
• the compensation parameter is calculated using a square calibration master that includes a predetermined measurement surface A and a measurement surface B perpendicular to the measurement surface A, and an angle between the measurement surface A and the measurement surface B of the square calibration master is known, wherein
• the method comprises:
• installing the square calibration master on the table, and measuring each of the measurement surface A and the measurement surface B of the square calibration master by a position measurement sensor attached to the main spindle;
• measuring the measurement surface A and the measurement surface B by the position measurement sensor by changing a direction of the square calibration master;
• calculating a first squareness between the measurement surface A and the measurement surface B from a measurement result of the measurement surface A and the measurement surface B obtained by the installing of the square calibration master and the measuring of the measurement surfaces;
• calculating a second squareness between the measurement surface A and the measurement surface B from a measurement result of the measurement surface A and the measurement surface B obtained by the measuring of the measurement surfaces by changing the direction of the square calibration master;
• calculating a difference between the first squareness and the second squareness;
• comparing the difference with a preliminarily set difference threshold value;
• calculating an average value of the first squareness and the second squareness when the difference is equal to or less than the difference threshold value, and calculating an angular deviation of the translational axis and calculating a corrected squareness based on the angular deviation and the first squareness or the second squareness when the difference exceeds the difference threshold value;
• and
• setting the compensation parameter based on the average value or the corrected squareness.

A machine tool that includes a table configured to hold a workpiece, a main spindle configured to hold a tool, and three or more translational axes, the main spindle being configured to perform a relative motion of three degrees or more of translational freedom with respect to the table, and the machine tool being configured to compensate for a motion error of the translational axis in accordance with a predetermined compensation parameter, the machine tool comprising:

• a first measuring unit configured to measure each of a measurement surface A, a measurement surface B, and a measurement surface C of a square calibration master by a position measurement sensor attached to the main spindle in a state where the square calibration master is installed on the table, the measurement surface A being a predetermined measurement surface, the measurement surface B and the measurement surface C being perpendicular to the measurement surface A and parallel to one another, and an angle between the measurement surface A and the measurement surface B and an angle between the measurement surface A and the measurement surface C of the square calibration master being known;
• a first squareness calculating unit that calculates a first squareness from a measurement result of the measurement surface A and the measurement surface B obtained by the first measuring unit;
• a second squareness calculating unit that calculates a second squareness from a measurement result of the measurement surface A and the measurement surface C obtained by the first measuring unit;
• a difference calculating unit that calculates a difference between the first squareness and the second squareness;
• a determining unit that compares the difference with a preliminarily set difference threshold value;
• a squareness identifying unit that calculates an average value of the first squareness and the second squareness when the difference is equal to or less than the difference threshold value, and calculates an angular deviation of the translational axis and calculates a corrected squareness based on the angular deviation and the first squareness or the second squareness when the difference exceeds the difference threshold value;
• and
• a compensation parameter setting unit that sets the compensation parameter based on the average value or the corrected squareness.

A machine tool that includes a table configured to hold a workpiece, a main spindle configured to hold a tool, and three or more translational axes, the main spindle being configured to perform a relative motion of three degrees or more of translational freedom with respect to the table, and the machine tool being configured to compensate for a motion error of the translational axis in accordance with a predetermined compensation parameter, the machine tool comprising:

• a first measuring unit that measures each of a measurement surface A and a measurement surface B of a square calibration master by a position measurement sensor attached to the main spindle in a state where the square calibration master is installed on the table, the measurement surface A being a predetermined measurement surface, the measurement surface B being perpendicular to the measurement surface A, and an angle between the measurement surface A and the measurement surface B of the square calibration master being known;
• a second measuring unit that measures the measurement surface A and the measurement surface B by the position measurement sensor by changing a direction of the square calibration master;
• a first squareness calculating unit that calculates a first squareness from a measurement result of the measurement surface A and the measurement surface B obtained by the first measuring unit;
• a second squareness calculating unit that calculates a second squareness from a measurement result of the measurement surface A and the measurement surface B obtained by the second measuring unit;
• a difference calculating unit that calculates a difference between the first squareness and the second squareness;
• a determining unit that compares the difference with a preliminarily set difference threshold value;
• a squareness identifying unit that calculates an average value of the first squareness and the second squareness when the difference is equal to or less than the difference threshold value, and calculates an angular deviation of the translational axis and calculates a corrected squareness based on the angular deviation and the first squareness or the second squareness when the difference exceeds the difference threshold value;
• and
• a compensation parameter setting unit that sets the compensation parameter based on the average value or the corrected squareness.