This is a good one. Our calibration on the coordinate measurement machines start off with a six month interval. If the machine performs within 50% of the specifications then the interval can be extended up to one year. If the machine performs from 50% to 100% then we maintain the last time span and then we shorten the span if it consumes more than the 100% of the specification.

If the machine exceeds 200% of the specification, not only does the time shorten but the inspection department is required to recall all of the hardware that has been measured since the last calibration was performed and ensure that parts meet engineering specs. This is why our group has a fixed ball bar made for each machine that we run occasionally (especially when we suspect a problem), we recommend bi-monthly. In addition we maintain all report files on a network drive (including ball bar data) so we can monitor the data. We must keep our machines within specification.

My main suggestion is don’t attempt to shorten the cycle of the calibration unless absolutely necessary. A ball bar setup only cost a few hundred dollars and you can write your own routine. Contact Patricia Johnson of Bal-Tec 1-800-322-5832 for more information.


Ray Admire
Lead Quality Engineer, CMM Programming
Lockheed Martin Missiles and Fire Control - Dallas
972-603-2074