Thermal displacement compensating device for machine tool

• US 9,092,025 B2
• Filed: 11/08/2012
• Issued: 07/28/2015
• Est. Priority Date: 01/19/2012
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Maekawa, Susumu
• Primary Examiner(s): Fennema, Robert
• Assistant Examiner(s): Stevens, Thomas
• Application Number:
  US13/671,952
• Publication Number:
  US 20130190921A1
• Time in Patent Office: 992 Days
• Field of Search: 700177-179
• US Class Current: 1/1
• CPC Class Codes: B23Q 11/0007 by compensating occurring thermal dilations B23Q15/18 takes precedence
• CPC Class Codes: G05B 19/404 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 Class Codes: G05B 2219/49204 Control of heat to compensate for dilatation, thermal displacement

Abstract

A thermal displacement compensating device calculates a thermal displacement amount which is produced by heat generation or dissipation as a machine tool is actuated or stopped and changes with time. A thermal displacement compensation amount is calculated by multiplying the calculated thermal displacement amount by a coefficient. A position command is compensated by adding the thermal displacement compensation amount to the position command. On the other hand, a variation between a thermal displacement amount calculated last time and a current thermal displacement amount is determined for each predetermined time. A plurality of thermal displacement amount change states are identified based on comparison between the determined variation and a predetermined threshold. The coefficient is calculated based on the identified thermal displacement amount change state.

Claims

1. A thermal displacement compensating device for a machine tool, which comprises a thermal displacement amount calculation unit configured to calculate a thermal displacement amount which is produced by heat generation or dissipation as the machine tool is actuated or stopped and changes with time, a thermal displacement compensation amount calculation unit configured to calculate a thermal displacement compensation amount by multiplying the thermal displacement amount calculated by the thermal displacement amount calculation unit by a coefficient, and a position command compensation unit configured to compensate a position command for a feed shaft by adding the thermal displacement compensation amount to the position command,

the thermal displacement compensating device further comprising:

a thermal displacement state identification unit configured to determine a variation between a thermal displacement amount calculated last time and a current thermal displacement amount for each first predetermined time by means of the thermal displacement amount calculation unit and identifying a plurality of thermal displacement amount change states based on comparison between the determined variation and a predetermined threshold; and

a coefficient calculation unit configured to calculate the coefficient based on the thermal displacement amount change state identified by the thermal displacement state identification unit.

2. The thermal displacement compensating device for a machine tool according to claim 1, further comprising:

a thermal displacement compensation amount history unit configured to store the thermal displacement compensation amount calculated by the thermal displacement compensation amount calculation unit, time at calculation of the thermal displacement compensation amount, and the thermal displacement amount change state identified by the thermal displacement state identification unit into a memory for each second predetermined time;

a thermal displacement compensation amount time variation display unit configured to graphically display a temporal variation in the thermal displacement compensation amount on a screen of the machine tool, based on the thermal displacement compensation amount stored in the memory by the thermal displacement compensation amount history unit and the time at calculation of the thermal displacement compensation amount; and

a predicted thermal displacement compensation amount display unit configured to display a predicted thermal displacement compensation amount, which is calculated by applying a coefficient determined by the coefficient calculation unit to the thermal displacement compensation amount stored in the memory, on a graph displayed by the thermal displacement compensation amount time variation display unit.