Thermal displacement compensation apparatus and thermal displacement compensation method for machine tool

A thermal displacement compensation apparatus for machine tool, comprising:

• a temperature measuring unit that measures temperatures of respective units of a machine tool;
• a thermal displacement estimating unit that estimates a thermal displacement of the machine tool from the temperatures based on a preliminarily set thermal displacement estimation formula;
• a thermal displacement compensation unit that compensates an axis command value based on the estimated thermal displacement;
• a displacement measuring unit that measures a displacement of the machine tool after compensating the axis command value;
• a data recording unit that records temperature information at the displacement measurement by the displacement measuring unit and the displacement;
• a thermal displacement compensation learning unit that determines the thermal displacement estimation formula based on the temperature information and the displacement recorded in the data recording unit;
• and
• a displacement measurement timing diagnostic unit that compares the temperature information at a past displacement measurement recorded in the data recording unit with current temperature information obtained from the temperature measuring unit, and determines whether to measure the displacement by the displacement measuring unit or not at a predetermined diagnosis timing.