| 摘要 |
PROBLEM TO BE SOLVED: To correct thermal displacement at a low cost, and achieve correct thermal displacement correction without elongating processing time by additionally using a sensor. SOLUTION: A position of a feed shaft is monitored, an average moving speed and moving frequency of the feed shaft for every position correcting unit time are determined, and correction quantity δn is determined by use of an approximate expression based on the speed and frequency to be renewed (c7, c8). Position correction quantity to a command position is determined based on the correction quantity, and the command position is corrected based on the position correction quantity. When power is recharged, initial correction quantity is determined based on power off time to be memorized (c1-c6). Since the correction quantity is determined by use of the approximate expression, a sensor is not required, but thermal displacement correction can be constantly performed. When change of the correction quantity is large (c10), thermal displacement quantity is measured by a sensor to be the correction quantity (c11, c12), so precision is improved. The number of measuring times by the sensor is reduced, thereby processing time can be shortened. |
