Outside Calibration services

[[Da...]]

In an effort to reduce costs, Management wants me to review outside cal services for our 4 micuras. 

Has anyone used CMM calibration and Service? They are based in Rockford Il.

[[Wo...]]

We've used outside calibration service before (because of scheduling issues mostly) and although we've had certs saying that the machine passed specs I wasn't confident in the machine. Couple of years ago we've had issues with bearings on one Accura. I've noticed the Masterprobe references with much higher sigma (around 0.0006mm). The machine passed outside calibration at that time. We've had the machine serviced, which brought the sigma back to 0.0001-0.0002mm on new bearings. Zeiss tech has admitted that the machine with old bearings wouldn't pass the Zeiss calibration. Another thing I've noticed was that the tech from 3rd party was using our production probes to validate the machine. There were some other things I found questionable, but I can't remember them now. In general, it looked like the savings weren't worth it.

[[Da...]]

Thanks Wojciech !

[[Ke...]]

IMO, I think that a better practice would be to invest in artifacts to perform basic dimensional checks (distances & roundness) on a monthly basis and track the trends of those dimensions; and use those results as a basis to extend the calibration frequency (say, every 18 months, instead of annually). There would be a higher up front cost, but there would be savings over time... it would also provide peace of mind between calibrations.

[[Ow...]]

Any outside calibration service I've inquired about could only tell you if the CMM was measuring within the OEM specification. They couldn't make any CAA adjustments to improve accuracy or squareness and usually was going to use the ASME B89.1 ball-bar method, not the DIN EN ISO 10360 step type of gauges Zeiss uses.

If you wanted something to just tell you if it was still accurate as prescribed, you could use one of Zeiss's calibration gauges like the CMM Check 2.0 Standard, it and the software required cost about 20K. It's a one time cost that could be used on all four of the CMM's but, I don't think any CAA adjustments can be made to improve the accuracy and if you needed to, you'd have to call Zeiss $ervice.

Or use one of the many artifacts out there like Keith Forche noted.

Long story short, you get what you pay for and the Zeiss care calibration that puts an extended warranty on some parts is generally the best cost-effective approach, especially on air-bearing CMM's. 

Edited March 10

[[Da...]]

My experience with outside services is that they are fine if you have an older machine, and are OK with calibration only down to ±.0002" (or with some machines, even .0005"). If you really need better than .0001" on your machine, call the Zeiss calibrator.

FWIW, and company that calibrates your machine with anything other than a carefully-protected "master probe" is just a hack. not only would I NOT use them again, but I'd also let other companies know about this. Too many times in this business I've encountered false "certifications", and I certainly don't need one of those for the CMM....