Control system of machine tool

Patent metadata

Field	Value
Publication number	US-10001212-B2
Application number	US-201514860779-A
Country	US
Kind code	B2
Filing date	Sep 22, 2015
Priority date	Sep 30, 2014
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A control system of a machine tool with a rotary type spindle and a feed axis which generates feed motion of the spindle, comprising a current detecting part which detects a current through a spindle motor for driving the spindle, a temperature detecting part which detects a motor temperature, a remaining time estimating part which uses a predetermined maximum allowable temperature and a detected temperature value by the temperature detecting part as the basis to estimate a remaining time until the motor temperature would reach the maximum allowable temperature on the assumption that the detected current value by the current detecting part at the time of the detected temperature value would continue to flow through the spindle motor, and a feed speed changing part which changes speed of the feed motion in accordance with the estimated value of the remaining time.

First claim

The invention claimed is:

1. A control system of a machine tool,
the machine tool including
a rotary spindle,
a feed axis configured to generate feed motion of said spindle with respect to a workpiece, and
a spindle motor configured to rotate the spindle,

the control system comprising:
a current detector configured to detect a current value of a current flowing through the spindle motor,
a temperature detector configured to detect, at a first time, a temperature value of a temperature of said spindle motor,
a load calculator configured to calculate a load of the spindle motor based on the current value detected by the current detector,
a controller configured to
based on a predetermined maximum allowable temperature of said spindle motor and the temperature value detected at said first time, estimate a remaining time from the first time when the temperature value is detected until a second time when the temperature of said spindle motor reaches the maximum allowable temperature in a case where the current value detected by said current detector at said first time continues to flow through said spindle motor from the first time to the second time,
perform override control of the spindle motor by changing a speed of said feed motion of the spindle in accordance with the estimated value of said remaining time, and
repeat the override control of the spindle motor in accordance with the estimated value of said remaining time until the load of the spindle motor calculated by the load calculator is equal to or less than a continuous rated load of the spindle motor.

2. The control system according to claim 1 , wherein
said controller is configured to decrease the speed of said feed motion with a predetermined slope and by a predetermined amount of change in response to the estimated value of said remaining time being equal to or less than a predetermined threshold value.

3. The control system according to claim 2 , wherein said controller is configured to
decrease the speed of said feed motion by said amount of change, and then
increase the speed of said feed motion by another amount of change smaller than said amount of change.

4. The control system according to claim 1 , further comprising:
a speed sensor configured to detect a speed value of the speed of said feed motion,
wherein the controller is configured to
in response to the estimated value of said remaining time being equal to or less than a predetermined threshold value, calculate a correspondence between the speed of said feed motion and said remaining time based on the estimated value of said remaining time, the detected speed value, and the detected current value,
specify a speed value of said feed motion corresponding to said threshold value of said remaining time, from said calculated correspondence, and
decrease the speed of said feed motion toward the specified speed value.

Assignees

• Fanuc Corp

Inventors

• Morita Yuuki
• Tajima Daisuke

Classifications

• B23Q17/008 Primary

  Life management for parts of the machine (tool life management B23Q17/0995) · CPC title

• G05B19/404

  characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia (G05B19/19, G05B19/41 take precedence) · CPC title

• F16H61/46 Primary

  Automatic regulation in accordance with output requirements · CPC title

• F16H61/42

  involving adjustment of a pump or motor with adjustable output or capacity · CPC title

• B23Q17/0985

  by measuring temperature · CPC title