Method for synchronously interlocking feed axes of a lathe

• US 5,181,441 A
• Filed: 07/03/1991
• Issued: 01/26/1993
• Est. Priority Date: 07/05/1990
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Okada, Kiyoshi
• Primary Examiner(s): Bilinsky, Z. R.
• Application Number:
  US07/725,118
• Time in Patent Office: 573 Days
• Field of Search: 82/1.11, 82/118, 82/142, 364/474.11, 364/474.17, 364/474.18
• US Class Current: 82/1.11
• CPC Class Codes: B23B 3/06 Turning-machines or devices characterised only by the special arrangement of constructional units B23Q37/00 takes precedence; such features of general applicability B23Q
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/42186 Master slave, motion proportional to axis
• CPC Class Codes: G05B 2219/45125 Four axis, spindle lathe
• CPC Class Codes: G05B 2219/50216 Synchronize speed and position of several axis, spindles
• CPC Class Codes: Y10T 82/10 Process of turning
• CPC Class Codes: Y10T 82/2502 with program control
• CPC Class Codes: Y10T 82/2552 Headstock

Abstract

A method for synchronously interlocking feed axes of a lathe is disclosed. In particular, a numerical controller (NC) controls the operation of a lathe by sending position command signals to servo amplifiers. The lathe turns a long workpiece chucked by two opposed headstocks which are driven synchronously. The servo amplifiers send signals to corresponding directional servo motors for moving the headstocks in respective directions. The present invention overcomes the problems of mechanical and workpiece displacement developed as loads on the servo motors by compensating for the positions of the feed axes by means of position offset values determined from the displacement of the machine or workpiece. Specifically, the displacements are detected in accordance with a difference between the torque of the two feed axes to be controlled for synchronous interlocking. In this manner, the displacement of the machine or workpiece is compensated for by moving the headstocks, which are synchronized in the corrected positions.

Claims

1. A method of synchronously interlocking first and second opposing headstocks of a lathe coupled to first and second feed axes of said lathe and linked by a workpiece for performing synchronous interlocking control of said first and second opposing headstocks in accordance with position command data, comprising the steps of:

obtaining a first torque associated with a first motor coupled to said first headstock and a second torque associated with a second motor coupled to said second headstock;

determining offset values of headstock positions attributable to machine or workpiece displacement based only upon a torque difference between said first and said second motors;

converting said torque difference into a distance difference; and

compensating for at least one of said position command data of said first and said second opposing headstocks in accordance with said distance difference obtained in said converting step.

2. A method for synchronously interlocking said first and second opposing headstocks of the lathe defined in claim 1, wherein either of said first and said second opposing headstocks coupled to said first and second feed axes is employed as a master headstock, and the other is used as a slave headstock, wherein a slave headstock servo amplifier receives compensated position command data.

3. A method for synchronously interlocking said first and second opposing headstocks of a lathe as defined in claim 1, wherein said first and second opposing headstocks are only compensated for in an interlocking mode and said offset values are canceled when said interlocking mode is reset.

4. A method of compensating for displaced positions of two opposed headstocks in a lathe comprising the steps of:

driving said two opposed headstocks which are linked via a workpiece to achieve synchronous interlocking control of said two opposed headstocks;

determining displacement of positions of said two opposed headstocks based only upon a torque difference between first and second motors associated with said two opposed headstocks, respectively; and

moving at least one of said two opposed headstocks to compensate and eliminate said displacement.