MSA Study Type 1 (CMM)


Hello everybody,

We bought a new CMM. And now I am supposed to prove that the KMG is capable. I have a few questions about this.

1-For MSA Study Type 1 I will use the CMM-Check as a test standard. Which tolerances should I enter in the evaluation? According to MPE values or the smallest manufacturing tolerances (0.002 mm). The manufacturer uses the MPE values to calculate the tolerance. Because the manufacturer wants to prove that the device is capable according to catalog values. Or should I evaluate the tolerances separately for both?

2- Assuming the device has successfully passed the MSA exam. And now we want to regularly check (control card) whether the accuracy of the device is under control. For this I need a certified standard. I will be using my CMM check again. With this CMM check, the U-value is usually evaluated monthly (monitoring with rotary table function). The problem here is that the U-value is no comparison to a certified target value. Should I only have the U-value (monthly) evaluated? Or should I proceed as with SPC and have the CMM check measured regularly 5 times every month and have the results entered on the control chart. Because I don't want the employees to do both on a monthly basis (for reasons of workload). In short. By what evaluation method should I control whether the device is under control?

thanks in advance


Forum Moderator
  1. Let's look at the intent behind a Type 1 gage study. It is intended to determine whether the measurement device is repeatable enough to determine whether a product meets the "customer" requirements, not the CMM's stated MPE. If you were to perform this study on a pair of calipers, would you use the customer requirements or the caliper manufacturer's stated accuracy? In both cases the answer is the same, use the customer requirements.
  2. I would recommend using a stability study (i.e., control chart) for this.


I know i'm late on this.
1) you can't verify your cmm unless you have a certified ball bar at the correct temperature. you may get close but not microns.
2) you can prove repatability
3) What you can do is after getting it certified make or use something made from a stable material (not effected by temperature) and create a master part program. Run that part program from time to time between machine calibrations. Do your spc from that data.
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