Error measurement method for machine tool and machine tool

An error measurement method for a machine tool for measuring an error in a machine tool, wherein

• the machine tool includes two or more translational axes, one or more rotation axes or a translational axis different from the translational axes, a table configured to hold a workpiece, and a spindle head configured to hold a tool, the two or more translational axes enable a relative motion of two degrees or more of translational freedom of the tool held onto the spindle head with respect to the workpiece,
• the error measurement method comprising:
• installing a target on the table, positioning the two or more translational axes and the rotation axis or the different translational axis under a plurality of conditions, and detecting a position of the target using a sensor mounted to the spindle head to acquire a measured value regarding the position of the target for each of the positioning conditions and to acquire an error value regarding the position of the target based on each of the acquired measured values;
• calculating at least one disturbance index value indicative of a degree of disturbance in the measurement for each of the positioning conditions;
• and
• determining whether the disturbance index value exceeds a preliminarily set threshold.

A machine tool comprising:

• two or more translational axes;
• a table configured to hold a workpiece;
• a spindle head configured to hold a tool, the translational axes enabling a relative motion of two degrees or more of translational freedom of the tool held onto the spindle head with respect to the workpiece;
• an error value acquisition unit configured to detect a position of each target using a sensor mounted to the spindle head in a state where a masterwork having a plurality of the targets is installed on the table to acquire a measured value regarding the position of each of the targets and to acquire an error value regarding the position of each of the targets using each of the acquired measured values and a preliminarily acquired calibration value regarding the position of each of the targets;
• a disturbance index value calculation unit configured to calculate at least one disturbance index value indicative of a degree of disturbance in the measurement for each of the targets;
• and
• a threshold determination unit configured to determine whether the disturbance index value exceeds a preliminarily set threshold.

A machine tool comprising:

• two or more translational axes;
• one or more rotation axes or a translational axis different from the translational axes;
• a table configured to hold a workpiece;
• a spindle head configured to hold a tool, the two or more translational axes enabling a relative motion of two degrees or more of translational freedom of the tool held onto the spindle head with respect to the workpiece;
• an error value acquisition unit configured to position the two or more translational axes and the rotation axis or the different translational axis under a plurality of conditions in a state where a target is installed on the table and detect a position of the target using a sensor mounted to the spindle head to acquire a measured value regarding the position of the target for each of the positioning conditions and to acquire an error value regarding the position of the target based on each of the acquired measured values;
• a disturbance index value calculation unit configured to calculate at least one disturbance index value indicative of a degree of disturbance in the measurement for each of the positioning conditions;
• and
• a threshold determination unit configured to determine whether the disturbance index value exceeds a preliminarily set threshold.