Method for compensating thermally induced displacement in machine tools

• US 5,095,788 A
• Filed: 10/25/1989
• Issued: 03/17/1992
• Est. Priority Date: 10/25/1988
• Status: Expired due to Fees

• Current Assignee: MTU Motoren- und Turbinen-Union Muenchen GmbH
• Original Assignee: MTU Motoren- und Turbinen-Union Muenchen GmbH
• Inventors: Matoni, Michael
• Primary Examiner(s): Kisliuk, Bruce M.
• Assistant Examiner(s): MARLOTT, JOHN
• Application Number:
  US07/427,331
• Time in Patent Office: 874 Days
• Field of Search: 318/568, 318/572, 364/474.34-474.35, 364/474.36, 364/474.37, 82/1.11, 82/117, 82/118-119, 82/120
• US Class Current: 82/118
• CPC Class Codes: G05B 19/4015 going to a reference at the beginning of machine cycle, e.g. for calibration
• CPC Class Codes: G05B 2219/37025 Retract, swing out of the way, measuring device during normal machining for protection
• CPC Class Codes: G05B 2219/49219 Compensation temperature, thermal displacement
• CPC Class Codes: G05B 2219/50252 Replace, change tool with tracer head, probe, feeler
• CPC Class Codes: Y10T 82/2502 with program control
• CPC Class Codes: Y10T 82/2506 And tool turret

Abstract

A method for compensating thermally induced displacement between a workpiece clamped for machining relative to a tool arranged on a tool holder of an automatically controlled machine tool, such as a lathe, where use is made of mechanical sensors to sense and correct deviations between programmed and actual tool positions relative to the workpiece. With the workpiece clamped in place, a mechanical workpiece sensor clamped in a work holder is adjusted to make mechanical contact with the workpiece in the actual position in which the workpiece is to be machined or has been previously machined. Adjustment to a thermally compensating position of a tool measuring device coupled to a mechanical tool sensor is made via the adjusted mechanical workpiece sensor.

Claims

1. A method of compensating thermally induced relative displacement between a programmed position and an actual position of a machining tool supported in a tool holder relative to a workpiece, said method comprising

securing a workpiece in a determined position,

mounting a mechanical workpiece sensor in a tool holder,

moving the tool holder so that the workpiece sensor contacts the workpiece at a reference position,

adjusting the position of a tool sensor to correspond to said reference position of the workpiece sensor by bringing said tool sensor into contact with said workpiece sensor with the workpiece sensor in said reference position,

replacing the workpiece sensor with a machining tool, and

establishing the position of the machining tool relative to said reference position of the tool holder based on the adjusted position of the tool sensor by contacting the tool with the tool sensor, with the latter in the adjusted position thereof corresponding to said reference position.

2. A method of compensating thermally induced shift of a workpiece held for machining relative to a tool mounted in a tool holder on an automatically controlled machine tool, said method comprising sensing and correcting variations between a programmed position and an actual position of a tool relative to a workpiece by the steps of clamping the workpiece to a spindle in a determined position, securing a mechanical workpiece sensor in a tool holder, positionally adjusting the sensor until the sensor makes contact with the workpiece to detect the actual working position of the workpiece and effecting adjustment of a tool measuring device coupled to a tool sensor based on the positionally adjusted workpiece sensor

the workpiece sensor being initially in a set position W₀ ;

the workpiece sensor being positionally adjusted to a new position W₁ in response to relative displacement of the workpiece and the tool holder by bringing the workpiece sensor into contact with the workpiece;

the tool sensor being positionally adjusted to a new preset value W_wz when the workpiece sensor is adjusted to its new position W₁ by contact with the tool sensor;

replacing the workpiece sensor in the tool holder by a tool;

positionally adjusting said tool by contacting the same with the tool sensor adjusted to the new preset value W_wz ; and

continuing a programmed machining operation.

3. A method as claimed in claim 2 comprising incorporating the compensation of thermally induced zero shift of said spindle, said tool measuring device and said tool holder and further relying on creating relative agreement between actual positions resulting from said zero shift.