Control device for machine tool performing oscillation cutting

Patent metadata

Field	Value
Publication number	US-10286513-B2
Application number	US-201815943441-A
Country	US
Kind code	B2
Filing date	Apr 2, 2018
Priority date	Apr 4, 2017
Publication date	May 14, 2019
Grant date	May 14, 2019

Abstract

A control part of a control device includes a learning controller and a learning determination part. The learning controller performs learning control in which a correction amount of a resultant command is obtained, based on an oscillation phase obtained from an oscillation command and the resultant command, and the correction amount is added to the resultant command. The learning determination part determines whether or not the oscillation amplitude of the oscillation command is smaller than a predetermined threshold, and when the oscillation amplitude is smaller than the predetermined threshold value, the learning determination part both sets the oscillation command generated by an oscillation command generation part to zero and turns off the learning control or only turns off the learning control.

First claim

The invention claimed is:

1. A control device for controlling a machine tool for cutting an outer peripheral surface or an inner peripheral surface of a workpiece with a tool, the machine tool having a spindle for performing a relative rotation between the workpiece and the tool around a central axis of the workpiece, and at least one feed axis for performing a relative feeding between the tool and the workpiece along a generatrix of the outer peripheral surface or the inner peripheral surface of the workpiece, the control device comprising:
a position command generation part for generating a position command for the at least one feed axis based on a relative rotation speed of the workpiece and the tool and a relative feed speed of the tool and the workpiece; and
a feed axis control part that controls the at least one feed axis according to the position command,
the feed axis control part having an oscillation command generation part that generates an oscillation command for the at least one feed axis based on the rotation speed and the position command such that the tool intermittently cuts the workpiece at an oscillation frequency which is a positive non-integral multiple of the rotation speed, and the feed axis control part being configured to control the at least one feed axis based on a resultant command obtained by adding the oscillation command to a position deviation, which is a difference between the position command and an actual position of the at least one feed axis,
the feed axis control part further comprising:
a learning controller that obtains a correction amount of the resultant command based on an oscillation phase obtained from the oscillation command and the resultant command and which adds the correction amount to the resultant command; and
a determination part which determines whether or not an oscillation amplitude of the oscillation command is smaller than a predetermined threshold value, and when the oscillation amplitude is smaller than the predetermined threshold value, the determination part turns off the learning controller and sets the oscillation command generated by the oscillation command generating part to zero or only turns off the learning controller.

2. The control device according to claim 1 , wherein the predetermined threshold value is an absolute value determined on a zero basis, or is a relative value determined on the basis of the oscillation amplitude of the oscillation command when the position command per unit time is constant.

3. The control device according to claim 2 , wherein the timing at which both the learning control is turned off and the oscillation command is set to zero by the determination part is a timing at which the oscillation command first becomes zero after the oscillation amplitude of the oscillation command becomes smaller than the predetermined threshold value.

4. The control device according to claim 1 , wherein a feed axis control part is provided for each of a plurality of feed axes, and the determination part of each feed axis control part notifies all of the determination parts of the feed axis control parts of a determination result when it is determined that the oscillation amplitude of the oscillation command is smaller than the predetermined threshold, and
the determination part of each feed axis control part uses at least one of a determination result of whether or not the oscillation amplitude of the oscillation command is smaller than the predetermined threshold value and a result of the determination notified from the determination part of another feed axis control part to determine whether to both turn off the learning control and set the oscillation command generated by the oscillation command generation part to zero or to only turn off the learning controller.

5. The control device according to claim 1 , wherein the position command generation part calculates the predetermined threshold value from the feed speed and the position command of the feed axis and notifies the determination part.

6. The control device according to claim 5 , wherein the position command generation part is configured to notify the determination part of the feed speed and a threshold value for the feed speed, and the determination part uses at least one of a determination result of whether or not the oscillation amplitude of the oscillation command is smaller than the predetermined threshold value and a determination result of whether or not the feed speed notified from the position command generation part is smaller than the threshold value for the feed speed to determine whether to both turn off the learning control and set the oscillation command generated by the oscillation command generation part to zero or to only turn off the learning control.

7. The control device according to claim 1 , wherein the oscillation command generation part generates the oscillation command by subtracting the oscillation amplitude from a reference axis of a cosine wave as an offset value.

8. The control device according to claim 1 , wherein the oscillation command generation part generates an oscillation frequency of the oscillation command such that the workpiece or the tool is shifted by a half-cycle each time the workpiece or the tool makes one revolution based on the rotation speed, and generates the oscillation amplitude of the oscillation command based on the rotation speed and the position command.

9. The control device according to claim 1 , wherein the oscillation command generation part generates the oscillation frequency and the oscillation amplitude such that the torque of the at least one feed axis does not exceed a predetermined value.

10. The control device according to claim 1 , wherein the oscillation command generation part generates the oscillation frequency and the oscillation amplitude based on a control band of the learning controller so that learning converges.

11. The control device according to claim 1 , wherein the oscillation command generation part generates the oscillation frequency and the oscillation amplitude based on a desired length of swarf generated by the tool processing the workpiece.

12. The control device according to claim 1 , wherein the workpiece comprises a corner portion which is not continuous with the radially outermost portion of the workpiece on the side which is more radially inwards than the radially outermost part in a cross-section along the central axis thereof.

Assignees

• Fanuc Corp

Inventors

• Yamamoto Kenta

Classifications

• B23Q15/14 Primary

  Control or regulation of the orientation of the tool with respect to the work · 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

• G05B19/4147 Primary

  characterised by using a programmable interface controller [PIC] · CPC title

• B23Q15/013

  Control or regulation of feed movement (B23Q15/12 takes precedence) · CPC title

• B23Q15/12

  Adaptive control, i.e. adjusting itself to have a performance which is optimum according to a preassigned criterion · CPC title