Approval of Jigs (work holding devices) for CMM

[GRISHAG]

Please let me know if precision of Jigs for measuring parts by CMM will affect measuring results, or measuring results depend of measuring method and CMM program?

In other words: must Jig for CMM be measured and approved or Jig’s deviations are absorbed during smart CMM program?

 

[Stijloor]

Measurement system variation can also be introduced by the work holding device (jig). Also, the jig often simulates datums used to verify GD&T requirements. A good MSA (measurement systems analysis) lets you know how stable your measurement system is and the dependability of measurement results.

 

[Kingsld1]

Unless the jig deforms the part, It really depends on how the CMM is being programmed. Is the coordinate system being defined by the probe touches on the part, creating a plane, line, point and using them to create an alignment. Or does the jig create the coordinate system?
If the jig creates the coordinate system, then the jig should be qualified. If it is just holding the part in the same relative spot and the program creates an alignment from points on the part then no qualification is needed. The available fixture plate and standoff systems are an example of a working holding system that does not need to be qualified. (Although double checking that the right size standoff is threaded into the right hole is a good idea.)

 

[GRISHAG]

thank for your answers!