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  17025, Guide 25, A2LA (Cal., Meas., and Test)
  How do I do a GR&R study if there is no specified tolerance?

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Author Topic:   How do I do a GR&R study if there is no specified tolerance?
kristin
unregistered 		posted 28 June 2001 01:46 PM           Edit/Delete Message   Reply w/Quote
I am writing a proposal for a supplier to include GR&R and Cpk data with shipments. One very important specification for this material invloves only a lower limit (example, >50 MPa). All of the formulas I have seen for EV and AV involve using the specified tolerance. Since I don't have a tolerance specified for this parameter, is it possible to calculate the %R&R? Is it possible to do a GR&R study without changing this spec?


I would appreciate any suggestions. I will be performing a process capability analysis (Cpk) for this particular parameter and I know this is possible when only one limit is specified.

Thanks!!

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Al Dyer
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Posts: 814
From:Lapeer, MI USA
Registered: Oct 2000

posted 28 June 2001 07:31 PM     Click Here to See the Profile for Al Dyer   Click Here to Email Al Dyer     Edit/Delete Message   Reply w/Quote
Kristin,

I'm not sure about formulas for your situation, but I pose this:

As the customer, could you set an upper limit for your supplier?

i.e. >50 ----- < 300

I guess I would have to ask why there is no upper limit? I don't know your process.

Only you or your company has the knowledge to know what that upper limit would be.

ASD...

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aysan
unregistered 		posted 14 July 2001 11:46 PM           Edit/Delete Message   Reply w/Quote
Hi
there are three types to calculate EV%, AV% and R&R%:

EV%=EV/RF
AV%=AV/RF
R&R%=R&R/RF

where, Reference Figure is one of these parameters:
- Tolerence(USL_LSL)
- Process Variation (6 sigma)
- Total Variation(TV=PV+R&R)

If you don't have Tolerence, you can use two types else to calculate those parameters.

Aysan

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Dave Stauffer
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Posts: 3
From:O'Fallon, MO, USA
Registered: Jul 2001

posted 18 July 2001 09:41 PM     Click Here to See the Profile for Dave Stauffer   Click Here to Email Dave Stauffer     Edit/Delete Message   Reply w/Quote
Contact AIAG and request an MSA Manual.
Look for the forms that utilize process variation rather than tolerance for finding the percentage R&R. ANOVA does this.

------------------
Dave Stauffer

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Al Dyer
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Posts: 814
From:Lapeer, MI USA
Registered: Oct 2000

posted 18 July 2001 10:03 PM     Click Here to See the Profile for Al Dyer   Click Here to Email Al Dyer     Edit/Delete Message   Reply w/Quote
Good call!

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