On 3/7/01 8:23:16 AM, Dorothy Brown wrote:
>Is there a generally
>acceptable accuracy range
>between two very different
>CMMs? My question comes from
>trying to correlate readings
>from our Zeiss Eclipse running
>U-Soft to a supplier's old
>Coordax machine. So far the
>difference between
>measurements have been around
>0.03 mm on the CMM training
>block that came with my CMM.
>Is this acceptable or is it up
>to my company to decide?
>Thanks for any help or advice.
>
>Dorothy Brown
>Quality Technician
>CME Mitsuba Corporation
>Mt. Pleasant,MI
>brown_d@cmecorp.com
>
Dorothy,
I'm not certain if such a range exists between two machines but my thoughts would be no. I'm only aware of the acceptable guaranteed measurement of uncertainties at 65 to 71 (deg) F. Our customers require 10% or less gage error. So if you are seeing more than a 10% difference, then yes you have problems and should verify both machines. At times I have experienced this same amount of variation that you have seen. Many times this can be attributed to a change in temperature or vibration. I've found this to be quite common between different inspection times, especially from separate CMM. Assuming both CMM were in the same environment and points taken were from the exact same location on your training block, this may be cause for alarm on parts having a tight tolerance. Understanding you need to know for sure. Many times my company's engineers will make the call. Our specification requirements are generally not much smaller than +/- 0.5mm and 0.03mm at only 0.001" would not raise any concern. We at LMS deal primarily with the automotive industry. What type of products are you measuring? The gage R&R variation of our Zeiss DB900 CMM with ST probe system has never gone outside 0.009mm in any axis. Are you finding variation in all axis or just one in particular? If your Zeiss eclipse has passed calibration then I would except the results and stand my ground against any other CMM not to mention an older Coordax. If you are still concerned, please click here > http://www.zeiss.com/imt/Service_Support/service_quotation.htm It never hurts to re-calibrate. I recommend Jeff Maksymowski for any service on our CMM.
Best regards,
Geoff
Sr. CMM Programmer
Lapeer Metal Stamping
LMS Metrology Lab
Lapeer, MI