Numerical control device and numerical control meihod for machine tool

A numerical control device for a machine tool, the numerical control device controlling a machine tool having a main spindle for attaching a tool, a table holding a workpiece and a jig, three translational axes, and one or more rotation axes, the numerical control device comprising:

• an axis-dependent deformation error estimation unit that calculates an estimated value of an axis-dependent deformation error caused by a deformation of the machine tool due to operation of at least one of the translational axes and the rotation axes, based on at least an axis-dependent deformation error parameter and command values of the at least one of the translational axes and the rotation axes;
• an input unit that receives a mass and a barycentric position of at least one of the workpiece and the jig;
• a gravitational deformation estimation unit that calculates an estimated value of a gravitational deformation error caused by the mass of the at least one of the workpiece and the jig based on a gravitational deformation error parameter, the mass and the barycentric position received at the input unit, and the command values;
• a correction value calculation unit that calculates correction values of the at least one of the translational axes and the rotation axes with respect to an error of a position and a posture of the tool with respect to the workpiece, based on at least one of the estimated value of the axis-dependent deformation error, the estimated value of the gravitational deformation error, and the command values;
• an addition unit that adds the correction values to the command values;
• and
• an error identification unit that measures a position of a target mounted on any one of the main spindle and the table using a measurement unit mounted on another of the main spindle and the table and identifies the axis-dependent deformation error parameter based on three-dimensional coordinate values of a plurality of the measured positions of the target,
• wherein the axis-dependent deformation error estimation unit calculates the estimated value of the axis-dependent deformation error based on the axis-dependent deformation error parameter identified in the error identification unit and the command value.

A numerical control method for controlling a machine tool having a main spindle for attaching a tool, a table holding a workpiece and a jig, three translational axes, and one or more rotation axes, the numerical control method comprising:

• calculating an estimated value of an axis-dependent deformation error caused by a deformation of the machine tool due to operation of at least one of the translational axes and the rotation axes, based on at least an axis-dependent deformation error parameter and command values of the at least one of the translational axes and the rotation axes;
• obtaining a mass and a barycentric position of at least one of the workpiece and the jig;
• calculating an estimated value of a gravitational deformation error caused by the mass of the at least one of the workpiece and the jig, based on at least a gravitational deformation error parameter, the mass and the barycentric position obtained by the obtaining, and the command values;
• calculating correction values of the at least one of the translational axes and the rotation axes with respect to an error of at least one of a position and a posture of the tool with respect to the workpiece, based on the estimated value of the axis-dependent deformation error, the estimated value of the gravitational deformation error, and the command values;
• and
• adding the correction values to the command values,
• wherein the axis-dependent deformation error estimation unit calculates the estimated value of the axis-dependent deformation error using a function of a geometric error of six degrees of freedom of the rotation axes taking the command value of the rotation axes as a variable.