Gage R&R studies and control plan for PPAP - Critical or Significant characteristics?

[Luis Alves]

Hi

The R & R studies, should be made to all equipment's refereed in the control plane, or only the ones that measure critical or significant characterises



------------------

 

[Chad Eilers]

Only measurement systems used on the "key / sinifigant characteristics" must have Gage R&R studies done on them. However, some auditors would LIKE to see them done on all, but it is not required.

 

[Howard Atkins]

I am sorry to dissapoint you but 4.11.4
Appropriate statistical studies shall be conducted to analyze the variation.........This requirement shall apply to measurement syatems referenced in the control plan.

 

[Luis Alves]

Ok

All measurement systems referenced in the control plan, should have appropriate statistics studies, but if a study is made for a measurer system, for instance a calliper, this study is valid to that measurement system although it is use in a lot of control plans?


------------------

 

[Batman]

Hi Luis:

We have used the same results from a measurement system study for other areas, as long as we determined that the methodology was the same. Likewise, we have used one 0-6" caliper and applied the results to other areas that use 0-6" calipers, wven if they are not the exact same calipers.

You should be careful when determining when to do this. If you have 8 stations and 8 sets of identical measurement devices, measuring like features, you could decide to only use a couple of these for the R&R determination.

Also, the actual R&R result - the actual error, not the % of tolerance result - could be applied to another tolerance on another part, again if the measurement ssytem is similar enough.

 

[Lassitude]

I agree with this for EV not AV. Let's say you have a caliper with an R&R on a part dimension from part X measuring 10.0 mm. It is a flat, easy to measure dimension on a piece. Then, with the same instrument, you measure a 'hard to reach' dimension on another part of 0.5 mm. While the EV should remain approximately the same (though different part of the equipment range), AV can vary significantly.

 

[ALM]

What I am interested in, and heard a bit about at a training class for MSA...

How much stock in the Gage R&R studies can their be? I mean, for instance, if I am measuring a part that is 108mm X 25mm, and it is a pressure-sensitive fabric... it isn't REALLY possible to expect that three people using vernier calipers are going to measure each of 10 parts in EXACTLY the same spot as each has previously measured... let alone one person to the next.

Think about it... that type of "exactness" is a requirement of an effective measurement system study... or was I misinformed? If I measure the 25mm dimension on the left-third of the part on one pass, the middle on the second, and the right on the third... how does that truly impact the result?

Thoughts? Comments?

ALM

 

[Luis Alves]

What does it means EV and AV?

 

[ALM]

EV = Equipment Variation

AV = Appraiser Variation

ALM

 

[Lassitude]

In the case of the pressure sensitive cloth, measurement equipment and techniques should have been looked at during the early design phase. If the measurement is important you would pick a measurement instrument appropriate for the material and conditions. A calipers probably wouldn't be the best tool for material. The point is to find out whether it's even worth taking a measurement. Let's say the gage R&R is 25%AV and 30%EV - that's 50% of your tolerance. Now the question becomes whether your measurement means anything or not.

Gage R&Rs are a tool - no more and no less. There is also the aspect of measurement uncertainty to consider.

Don't read into this any more than is here. For example, there are alturnatives to Gage R&R - but you have to be ready to justify why you use what ever tool you use. Gage R&Rs do not make sense for every measurement condition. Automotive just happens to not know much else.