US Patent No. 9,956,660

CONTROLLER FOR A MACHINE TOOL TO PERFORM EFFICIENT WARM-UP CONTROL


Patent No. 9,956,660
Issue Date May 01, 2018
Title Controller For A Machine Tool To Perform Efficient Warm-up Control
Inventorship Yasuaki Koyama, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,956,660

1. A controller for a machine tool, the controller being configured to drive at least one motor based on a machining program to drive a spindle and a feed screw of the machine tool, the controller comprising:a memory that stores, as target thermal displacement states of the spindle and the feed screw, thermal displacement states of the spindle and the feed screw when operated by respective warm-up operations such that thermal displacements of the spindle and the feed screw are saturated, wherein a thermal displacement state indicates at least one of thermal displacement amounts, thermal displacement distributions, and temperature distributions, and wherein a thermal displacement is determined to be saturated when displacement is stabilized; and
a processor configured to:
calculate the thermal displacement states for the spindle and the feed screw, wherein the thermal displacement state of the spindle is calculated by dividing the spindle into a plurality of sections, calculating temperatures of the plurality of sections of the spindle, and calculating heat conduction between adjacent sections of the spindle, and wherein the thermal displacement of the feed screw is calculated by dividing the feed screw into a plurality of sections, calculating temperatures of the plurality of sections of the feed screw, and calculating heat conduction between adjacent sections of the feed screw;
determine a warm-up operation pattern of the spindle and a warm-up pattern of the feed screw on the basis of the thermal displacement states calculated for the spindle and the feed screw, wherein, when the thermal displacement of the machine tool is saturated, the warm-up operation pattern of the spindle is determined from a rotating speed of the spindle obtained based on a total value of the temperatures of the plurality of sections of the spindle, and from a frequency of acceleration and deceleration of the spindle obtained based on an average value of temperature differences between adjacent sections of the spindle,
and the warm-up operation pattern of the feed screw is determined from a feed rate obtained based on a total value of thermal displacement amounts of the plurality of sections of the feed screw, and from turning points obtained based on the thermal displacement amounts of the plurality of sections of the feed screw;
drive the at least one motor according to the warm-up operation patterns determined for the spindle and the feed screw, wherein the spindle and the feed screw are driven to perform the respective warm-up operations up to a warm-up operation termination; and
determine the warm-up operation termination by calculating a current thermal displacement state of the spindle and a current thermal displacement state of the feed screw, comparing the calculated respective current thermal displacement states of the spindle and the feed screw with the stored respective target thermal displacement states of the spindle and the feed screw, and respectively stopping the at least one motor driving the spindle or the feed screw in response to a respective difference between the calculated respective current thermal displacement state and the stored respective target thermal displacement state of the spindle or the feed screw being not larger than a respective predetermined threshold value, to terminate the respective warm-up operation of the spindle or the feed screw.