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  Destructive Tests gage R&R

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Author Topic:   Destructive Tests gage R&R
Orlando Guillory
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posted 24 February 1999 01:17 PM     Click Here to See the Profile for Orlando Guillory   Click Here to Email Orlando Guillory     Edit/Delete Message   Reply w/Quote
How do you do a gage R&R when the sample is destroyed or modified during the test? I have several tests such as a rupture test that we want to define the errors but cannot repeat the test with the same samples. Suggestions?

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Batman
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posted 24 February 1999 06:26 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
Up until two days ago, I would have said no way. However, I just finished reviewing the PPAPall.xls file - found in the PDF Zone elsewhere in this site. On one of the pages, near the 'regular R&R' page, it has a fill in the blanks form with calculations. While I am NOT any type of math wiz, I do have some objection to this philosophically. However, I believe it is blessed by Delphi, so have at it.

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Don Winton
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posted 27 February 1999 10:34 AM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
The spreadsheet Batman mentioned appears to be statistically sound. Destructive testing could also be R&R'd as attribute data, but the attribute portion of the same spreadsheet appears to be somewhat 'lacking.'

Regards,
Don

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Batman
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posted 03 March 1999 12:29 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
Sorry for the delay, been having trouble logging into the site.
So Don, to answer Orlando's question, CAN you legitimately perform a Gage R&R in destructive testing? Even though there is a form in that PPAPall spreadsheet? As you pointed out, the calculations are 'lacking,' so could one get in trouble using it? Trouble with auditors, trouble using the data to make decisions?

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Don Winton
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posted 03 March 1999 03:20 PM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
Yea, I guess I should expound upon my last post. Sorry about that.

quote:
·the calculations are 'lacking,' so could one get in trouble using it? Trouble with auditors, trouble using the data to make decisions?

Using logic, if the portion of the spreadsheet for attribute R&R is somewhat Īlackingā (IMHO), then an argument could be made that other portions of the same spreadsheet may be lacking as well, thus you must be able to justify the use of the calculations to your assessors (assuming the question is even asked) and yourself. My particular problem with the attribute page of PPAPall.xls was that is did not consider marginal samples. The samples either had to all pass or all fail for the gage test to be considered acceptable (100% same results per sample. Plueeeeeeze. Does differentiate ring a bell?). BUT, I did not design nor have input to its design. Therefore, an argument could be made that the authors had a legitimate reason for the calculations, but I cannot explain these reasons to my assessors, nor myself.

If Delphi accepts the destructive portion (or any portion, for that matter) and the calculations of PPAPall.xls, that should satisfy most assessors. But, I would not be willing to gamble my registration on it. I would want to be able to explain how if the subject came up. How I came to the conclusion that the R&R was acceptable, etc. and PPAPall.xls offers no derivations on the calculations involved. Perhaps they may be available from the source, perhaps not. Do not get me wrong, I am neither accepting nor rejecting PPAPall.xls nor its authors. They obviously put a lot of good work into it. And, I applaud Marc for providing it to the public. These are just my thoughts on this matter.

quote:
CAN you legitimately perform a Gage R&R in destructive testing?

Having reviewed the destructive portion of PPAPall.xls, these are my particular issues, other than those outlined above. Under the assumption that the test was tolerance based, you could use that if you wished. Under the assumption that the test was attribute based, you may not be able to. Therefore, I humbly propose an alternative. Use process capability.

Process capability tests are available for both variable data and attribute data. Process capability does not require use of the same sample. AND process capability is something that should be acceptable as a measure of R&R, designed correctly. You perform capability on the gage, not the process. However, if the assessors do not want to accept process capability numbers, translate process capability numbers into R&R numbers. I have the method laying around here somewhere, if anyone is interested.

In short, my answer to Batmanās question is yes, assuming you are willing to work outside the normal paradigm.

Regards,
Don

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Marc Smith
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posted 05 March 1999 08:33 PM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
I'd like to see the interpolation from capability to R&R.

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Don Winton
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posted 05 March 1999 09:04 PM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
Will send by e-mail this weekend. Format is Word 6.0.

Enjoy and critical analysis welcome.

Regards,
Don

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Orlando Guillory
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posted 09 March 1999 05:11 PM     Click Here to See the Profile for Orlando Guillory   Click Here to Email Orlando Guillory     Edit/Delete Message   Reply w/Quote
Thanks for all the input. I would like to see the method to translate process capability into R&R.

I have been using control charts and cpk for the approvals of destructive methods at this time. The charts must be in control and cpk greater than 1.3 to accept the gage and part. This makes the assumption a bad gage R&R will not allow a cpk of 1.3 or greater. Of course if the part varies widely you are condemning the gage as well.

I cannot download the PPAPall.xls file mentioned. Is their a trick? By the way I cannot get to the listing through the Cayman system. For some reason I have to go straigt to it via a bookmark to "index of /pdf_files".

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Marc Smith
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posted 09 March 1999 06:24 PM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
quote:
I cannot download the PPAPall.xls file mentioned. Is their a trick?
No trick - it's in how you set up your browser.
quote:
By the way I cannot get to the listing through the Cayman system. For some reason I have to go straigt to it via a bookmark to "index of /pdf_files".
I have no idea why, if you input the correct address, you cannot get a listing in the pdf_files directory. Works fine for me.

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Orlando Guillory
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posted 10 March 1999 04:14 PM     Click Here to See the Profile for Orlando Guillory   Click Here to Email Orlando Guillory     Edit/Delete Message   Reply w/Quote
I was able to download and open the zip file. Thanks.

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Jada
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posted 19 March 1999 12:12 AM     Click Here to See the Profile for Jada   Click Here to Email Jada     Edit/Delete Message   Reply w/Quote
I'm a fan of MSA from way back, but isn't a MSA study outside of the scope of the existing MSA manual if the measurement is not repeatable. Refer to MSA manual. By definition if we have a destructive test this infers that we cannot repeat.

From a registrar's perspective, it is impossible for them to give a NC if no MSA has been conducted on any IMTE that conducts a destructive type test because it is outside of the scope of the MSA manual.

Just my thoughts...

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Batman
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posted 19 March 1999 06:56 PM     Click Here to See the Profile for Batman   Click Here to Email Batman     Edit/Delete Message   Reply w/Quote
Yes, Jada, I agree. I just can't get past the non-repeatability of the thing. Actually, you don't even get reproducability, since the operators can't measure the same parts again.
??

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Jada
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posted 21 March 1999 06:36 PM     Click Here to See the Profile for Jada   Click Here to Email Jada     Edit/Delete Message   Reply w/Quote
Batman,

R&R on a destructive test is always intersting. When you initially think about it you might think that the majority of the error would come from the equipment(repeatability) but we found that the majority of the error was actually from the the operator(reproducibilty) because of the variation that was involved in the operator setting up the part (in this case a hardness test on a foam pad). So although the R&R study was not valid the raw data we obtained and the subsequent Exploratory Data Analysis (EDA) was very worthwhile.

Has anyone else found similar results?

Jada

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Douglas Purdy
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posted 30 April 1999 01:21 PM     Click Here to See the Profile for Douglas Purdy   Click Here to Email Douglas Purdy     Edit/Delete Message   Reply w/Quote
Don,

Where is this conversion of Process Capability to GR&R?

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Don Winton
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posted 30 April 1999 06:55 PM     Click Here to See the Profile for Don Winton   Click Here to Email Don Winton     Edit/Delete Message   Reply w/Quote
Marc was kind enough to post it here as part of a process capability paper I collected. You can find it here:

/pdf_files/CPK.pdf

You can also find it at my site below in the SQC section.

Regards,
Don

------------------
Check Out dWizard's Lair: *** Dead Link Removed ***

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Douglas Purdy
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posted 06 May 1999 01:12 AM     Click Here to See the Profile for Douglas Purdy   Click Here to Email Douglas Purdy     Edit/Delete Message   Reply w/Quote
Don,

Thanks for the information. Come to find out I had already downloaded the information back in March. I just had not used it, yet. I do have some destructive type measurement systems to work on in a fluid/batch type environment. I also enjoyed your site, and have placed it in my favorites along with Caymen Systems.

Doug

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Douglas Purdy
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posted 06 May 1999 01:15 AM     Click Here to See the Profile for Douglas Purdy   Click Here to Email Douglas Purdy     Edit/Delete Message   Reply w/Quote
P.S. I was not able to view the information from your links, but was able to download just fime.

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Bergeret
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posted 14 May 2001 04:57 AM           Edit/Delete Message   Reply w/Quote
hello,

we have recently improved an existing method to assess repeatability in destructive gauge R&R. It is based on a two time procedure
where repeatability is first counfouded with sites, and then with parts.
Solving a simple equation, it is then possible to estimate repeatabilty and then %R&R and %P/T.

A paper is going to be published in Quality Engineering before the end of the year. I can tell you more if you want.

Regards,

Francois

Bergeret, Franco

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zouzou
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posted 14 May 2001 10:56 AM     Click Here to See the Profile for zouzou   Click Here to Email zouzou     Edit/Delete Message   Reply w/Quote
i need the Atomative Industry Action Group reference manual about the mesurement system evaluation and the book of evaluating the measurement process by wheeler.
if anybody can help me to get those book.

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Marc Smith
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posted 21 May 2001 05:42 PM     Click Here to See the Profile for Marc Smith   Click Here to Email Marc Smith     Edit/Delete Message   Reply w/Quote
The AIAG book is available from www.aiag.org and the Wheeler book is probably available from www.asq.org

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