The Elsmar Cove Wiki More Free Files The Elsmar Cove Forums Discussion Thread Index Post Attachments Listing Failure Modes Services and Solutions to Problems Elsmar cove Forums Main Page Elsmar Cove Home Page
Google
  Web Elsmar.com
*Please be aware that SOME RECENT forum threads may not yet be indexed by Google.

View Full Version : MSA (Gage R&R) vs. Capability Cpk Study - Helium Leak Check Station


BenBB
29th January 2009, 12:14 PM
Trying to decide if I need to do a GR&R or Cpk study on Helium Leak Check Station. I know the basics on how to do either/both a GR&R and Cpk capability study but am not sure if I need both.

I don't have a lot of experience on the meaning of the studies only what is good and bad and how to do them.

Can someone explain what a GR&R would tell me that a Cpk would not and vesa-visa?

Also, if I should do both for our Helium leak check station? It is essentially a gauge that takes a hermitic leak rate measurement and physically does nothing to the part under test.

Jim Wynne
29th January 2009, 12:23 PM
Trying to decide if I need to do a GR&R or Cpk study on Helium Leak Check Station. I know the basics on how to do either/both a GR&R and Cpk capability study but am not sure if I need both.

I don't have a lot of experience on the meaning of the studies only what is good and bad and how to do them.

Can someone explain what a GR&R would tell me that a Cpk would not and vesa-visa?

Also, if I should do both for our Helium leak check station? It is essentially a gauge that takes a hermitic leak rate measurement and physically does nothing to the part under test.

The two types of analysis have different purposes and aren't interchangeable. If you were to do a gage study it would be because you want to know something about measurement error, and how it affects the process. On the other hand, a capability (what you refer to as "Cpk") study is intended to tell you how well-centered your process is, and give you some idea of the likelihood of nonconformance.

Another analysis you don't mention, but which should be done prior to MSA and capability study is calibration--comparison of the gage to a traceable standard, and understanding measurement uncertainty.

BenBB
29th January 2009, 12:54 PM
What type of study would I do with to understand "measurement uncertainty".

Thank you,


BenBB