DJN said:
When is MSA appropriate? I have been asked to perform MSA on a new custom built gauge. However, the characteristic the gauge is measuring is neither significant nor critical.
Why have a custom-built gage for an insignificant characteristic?
DJN said:
Do I need to do MSA on this gauge? I can find nothing about when MSA needs to be performed.
It depends on customer requirements and common sense, although not necessarily in that order. If you are working under the AIAG PPAP requirements, MSA is required "...for all equipment used for new or modified gages, measurement, and test equipment" (page 8, PPAP 3rd Edition). There is also a requirement (page 6) for MSA to be performed on gages used in PPAP capability studies. Your customer(s) may have other specific requirements.
As for the common sense part of it, if you've spent good money on a custom gage it stands to reason that you'd want to know if it will work as intended, so MSA is a good idea even in the absence of customer requirements.
DJN said:
I also have several custom gauges which are the same. i.e. perform the same function and built the same. Now, I know that MSA can be performed on families of gauges. Do I need to do each gauge, or would one study be sufficient.
Assuming that you've verified that each was "built the same," a "family" GR&R would be appropriate under most circumstances insofar as customer requirements are concerned, but again, you should decide for yourself whether or not it would make sense to do MSA on each one.
DJN said:
And finally, when does MSA need to be re-done? My understanding is that MSA should be re-done after the gauge has been moved, after repair and when a new operator is using the gauge. Would that be correct?
There are no hard-and-fast rules in the absence of customer-specific requirements. Movement of a gage from one place to another shouldn't be reason in itself. New operators should be qualified the same way as present or former operators were qualified, and re-analysis might be appropriate, especially if previous analyses indicated an issue with operator error .