CONTROL DEVICE FOR MACHINE TOOL INCLUDING ROTARY INDEXING DEVICE

• US 20150115514A1
• Filed: 10/21/2014
• Published: 04/30/2015
• Est. Priority Date: 10/28/2013
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: OGAWA, Yoshitsugu
• Granted Patent: US 9,527,176 B2
• Time in Patent Office: Days
• US Class Current: 269/57
• CPC Class Codes: B23Q 16/065 with a continuous drive
• CPC Class Codes: B23Q 3/08 other than mechanically-actuated B23Q3/061, B23Q3/066, and B23Q3/067 take precedence
• CPC Class Codes: G05B 19/402 characterised by control arrangements for positioning, e.g. centring a tool relative to a hole in the workpiece, additional detection means to correct position G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/39264 Torque control using hardware designed for position control

Abstract

A rotary table is rotated by a machining load. A drive motor tries to return the rotary table to a positioned target position, and increases output torque. When the output torque reaches upper limit torque Tmax or when output torque which is equal to or greater than permissible torque Tp continues for predetermined time ΔT, a target position which is sent to a drive motor is changed, thereby promoting reduction in output torque. If the output torque becomes smaller than permissible torque Tp, the target position is changed to bring position deviation of the drive motor equal to 0, and the position deviation is swiftly returned.

Claims

1. A control device for a machine tool including a rotary indexing device, the rotary indexing device comprising:

a rotary table on which a work is mounted and fixed;

a clamping mechanism for clamping the rotary table; and

a drive motor which includes a motor controller configured to control a rotation position and speed, and rotate and drive the rotary table, wherein the control device comprises drive motor output torque detecting unit configured to detect output torque of the drive motor,

a position deviation detecting unit configured to detect position deviation from the motor controller, and

a target position changing unit in which the rotary table is configured to be clamped by the clamping mechanism at a target position of a predetermined rotation angle position, and on a condition that time during which output torque of the drive motor detected by the drive motor output torque detecting unit is equal to or higher than a preset permissible torque continues for predetermined time or the output torque of the drive motor detected by the drive motor output torque detecting unit reaches preset upper limit torque while a work mounted on the rotary table is being machined, configured to change a target position such that the output torque of the drive motor is brought close to or equal to 0 if the detected output torque is equal to or higher than the permissible torque, and change the target position by increments such that detected position deviation is brought close to or equal to 0 if the detected output torque is smaller than the permissible torque.

2. The control device for the machine tool including the rotary indexing device according to claim 1, further comprising:

a target position returning unit, configured to return the target position changed by the target position changing unit, to an original target position of when the rotary table is clamped, when position deviation detected by the position deviation detecting unit is 0 and a difference between the target position changed by the target position changing unit and a target position clamped by the clamping mechanism is smaller than a predetermined value.

3. The control device for the machine tool including the rotary indexing device according to claim 2, further comprising:

a target position-change signal output unit, configured to turn on a target position-change signal indicating that a target position is changed and output this target position-change signal when the target position is changed by the target position changing unit, and turn the target position-change signal off when the target position returning unit returns the target position to the original target position of when the rotary table is clamped.

4. The control device for the machine tool including the rotary indexing device according to claim 1, wherein

the clamping mechanism clamps the rotary table at a target position of a predetermined rotation angle position, and the control device further comprises a clamping-time position deviation signal output unit configured to output a clamping-time position deviation signal when output torque detected by the drive motor output torque detecting unit becomes equal to or higher than a predetermined value before a machining operation is started.

5. The control device for the machine tool including the rotary indexing device according to claim 1, further comprising a target position excessively large error signal output unit configured to output a signal when a difference between a target position clamped by the clamping mechanism and a target position changed by the target position changing unit reaches permissible position deviation.

6. The control device for the machine tool including the rotary indexing device according to claim 1, wherein

the drive motor output torque detecting unit detects, as the drive motor output torque, a torque command which is output from a speed controller of the motor controller of the drive motor.

7. The control device for the machine tool including the rotary indexing device according to claim 1, wherein

the drive motor output torque detecting unit detects output torque by detecting drive current of the drive motor.