AUTOMATIC PROBING, COMPENSATION, AND ADJUSTMENT OF A FLEXIBLE FIXTURE FOR A CNC MACHINE

• US 20120239181A1
• Filed: 03/16/2011
• Published: 09/20/2012
• Est. Priority Date: 03/16/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Gu, Jie, Deeds, Paula J., Kurgin, Sheri K., Agapiou, John S., Owen, Michael J.
• Granted Patent: US 8,761,920 B2
• Time in Patent Office: Days
• US Class Current: 700/176
• CPC Class Codes: B23Q 17/22 for indicating or measuring existing or desired position of tool or work B23Q16/005 takes precedence
• CPC Class Codes: G05B 19/4086 Coordinate conversions; Other special calculations
• CPC Class Codes: G05B 2219/37203 Compensate probed values as function of reference plane of fixture, clamp
• CPC Class Codes: G05B 2219/37221 Probe fixture to know datum points

Abstract

A method for properly locating a flexible fixture on a CNC machine comprises probing a plurality of locators on a flexible fixture to determine a locator position on a coordinate system for the CNC machine. The position for each of the plurality of locators is analyzed to determine if all of the plurality of locators are within a predetermined offset limit from a nominal position. A controller is programmed with an offset compensation amount based upon the probed position for each locator when each of the plurality of locators is within the predetermined offset limit. The locator positions are adjusted if one of the probed locations is not within the predetermined offset limit. The CNC probing programs are generated by a computer language to accommodate various fixture configurations.

Claims

1. A method for properly locating a flexible fixture to a CNC machine comprising:

mounting a flexible fixture on a table of the CNC machine;

probing a plurality of locators on the flexible fixture to determine a locator position on a coordinate system for the CNC machine for each of the locators;

determining if each of the plurality of locators is within a predetermined offset limit from a nominal position; and

programming a controller with an offset compensation amount based upon the probed position for each locator when all of the plurality of locators are within the predetermined offset limit.

2. The method of claim 1, further comprising:

adjusting the position of at least one of the plurality of locators to adjust a position of the flexible fixture when the probed position for any of the plurality of locators is not within the predetermined offset limit.

3. The method of claim 2, wherein adjusting at least one of the plurality of locators to adjust a position of the flexible fixture further comprises calculating an amount that the at least one of the plurality of locators must be adjusted in each direction with the controller, based upon the probed position for the respective one of the plurality of locators.

4. The method of claim 2, wherein adjusting the position of at least one of the plurality of locators further comprises one of shimming the respective one of the plurality of locators, grinding the respective one of the plurality of locators and adjusting a spacer associated with the respective one of the plurality of locators.

5. The method of claim 4, wherein adjusting at least one of the plurality of spacers to adjust a position of the flexible fixture further comprises adjusting a spacer to reposition one of:

a primary locator relative to one of a first and second axes, a secondary locator relative to one of a first and second axes, and a tertiary locator relative to a third axes of the coordinate system.

6. The method of claim 1, wherein probing a plurality of locators on the flexible fixture to determine a locator position for each of the locators further comprises using the probed locator positions to determine a normal vector for a plane passing through the three tertiary locators.

7. The method of claim 1, wherein probing a plurality of locators on the flexible fixture to determine a locator position for each of the locators further comprises measuring at least a primary locator, a secondary locator and three tertiary locators.

8. The method of claim 7, wherein probing the primary and the secondary locators provides a xz-position for the primary and secondary locators when the flexible fixture is a horizontally mounted fixture, and probing the tertiary locators provides a y-position for each tertiary locator when the flexible fixture is a horizontally mounted fixture.

9. The method of claim 7, wherein probing the primary and the secondary locators provides a xy-position for the primary and secondary locators when the flexible fixture is a vertically mounted fixture, and probing the tertiary locators provides z-positions for each tertiary locator when the flexible fixture is a vertically mounted fixture.

10. A method for properly locating a flexible fixture to a CNC machine comprising:

probing a primary locator, a secondary locator and at least three tertiary locators on a flexible fixture mounted to the CNC machine to determine a locator position on a coordinate system for the CNC machine for each of the locators;

determining if each of the primary locator, the secondary locator and the at least three tertiary locators is within a predetermined offset limit from a nominal position;

programming a controller with an offset compensation amount based upon the probed position for each of the primary locator, the secondary locator and the at least three tertiary locators when all of the primary locator, the secondary locator and the at least three tertiary locators are within the predetermined offset limit; and

adjusting the position of at least one of the primary locator, the secondary locator and the at least three tertiary locators to adjust a position of the flexible fixture when the probed position for any of the primary locator, the secondary locator and the at least three tertiary locators is not within the predetermined offset limit.

11. The method of claim 10, wherein adjusting the position of at least one of the plurality of locators further one of shimming the respective one of the plurality of locators, grinding the respective one of the plurality of locators and adjusting a spacer associated with the respective one of the plurality of locators.

12. The method of claim 11, wherein adjusting at least one of the plurality of spacers to adjust a position of the flexible fixture further comprises adjusting the spacer to move one of:

the primary locator relative to one of a first and second axes, the secondary locator relative to one of a first and second axes, and any of the at least three tertiary locators relative to a third axes of the coordinate system.

13. The method of claim 10, wherein adjusting at least one of the plurality of locators to adjust a position of the flexible fixture further comprises calculating an amount that the at least one of the plurality of locators must be adjusted in each direction with the controller, based upon the probed position for the respective one of the plurality of locators.

14. The method of claim 10, wherein probing a plurality of locators on the flexible fixture to determine a locator position for each of the locators further comprises using the probed locator positions to determine a normal vector for a plane passing through the three tertiary locators.

15. The method of claim 10, wherein probing the primary and the secondary locators provides a XZ-position for the primary and secondary locators when the flexible fixture is a horizontally mounted fixture, and probing the at least three tertiary locators provides a y-position for each of the at least three tertiary locators when the flexible fixture is a horizontally mounted fixture.

16. The method of claim 10, wherein probing the primary and the secondary locators provides a XY-position for the primary and secondary locators when the flexible fixture is a vertically mounted fixture, and probing the at least three tertiary locators provides a z-position for each of the at least three tertiary locators when the flexible fixture is a vertically mounted fixture.

17. A method for properly generating a CNC machine program comprising:

inputting a nominal location for a primary locator, a secondary locator and at least three tertiary locators on a flexible fixture mounted to the CNC machine to determine a locator position on a coordinate system for the CNC machine for each of the locators;

inputting nominal locations for each of a plurality of spacers, where each of the plurality of spacers are associated with one of the primary locator, the secondary locator and the at least three tertiary locators; and

creating the CNC program based upon the nominal locations for the primary locator, the secondary locator, the at least three tertiary locators and the associated spacers.

18. The method of claim 17, wherein creating the CNC program based further comprises using at least one of:

table position information, fixture position information, probe calibration information, and probe length and height data.