Unilateral Gage R&R (GR&R) - Minitab 13 - Does this study pass or fail and WHY?

[justncredible]

Yes I have went thru the other threads and they all link or say look in another thread which does not have any help at all. I only have minitab 13 which I own and I have not upgraded to 14.2 which does the unilaterail GR&R.
I tested for normaility CPK is fine, I got ahold of some sheets that another engineer said it passes, but am not sure how to read it. What exactly makes it passing. My customer looked at another excel sheet I had for 3rd ed and since it says fails he thinks it fails. Does this study pass or fail and WHY?

Thanks

Oh and first post!!!!

[justncredible]

I do not need minitab help, unless someone has the $395 upgrade laying around not being used.

I need to be able to explain WHY and HOW the GR&R is acceptable, my customer is QS/TS certified and from the rejected first submission I must be able to pass on in laymans terms how to read the reports I have.

[justncredible]

Wow first post and it gets moved to the WRONG section???????

That was not the topic title, I do NOT need minitab help, it was in the GR&R section and that is where this thread belongs. The moderators need to leave stuff alone sometimes. @@!#@!###

[Miner]

First, you may want to ponder the saying "You can catch more flies with honey than you can with vinegar." Your tone in your very first post will put a lot of people off that would normally help.

Now, to your question. The gage is not acceptable for use as an inspection device (P/T Ratio) or as a process control device (% GRR). 30% is considered the maximum acceptable limit for both measures with 10 - 15% the ideal maximum.

You gage does have adequate resolution, but the repeatability is the major source of measurement variation. This is the variation of a single operator repeating their measurements.

Since these are form measurements to a very high resolution, I assume that you are using a CMM. Is it manually controlled or DCC? The source of the high repeatability variation maybe the within-part variation in form. Using more points to define the form and defining the measurement location of each point may help.

[justncredible]

Honey and flies, after reading the other responses to the unilateral questions, I could have made a post that would have gotten links to other threads that provide nothing I seek. Now Miner your response is what I am looking for. Yet it makes me wonder if the normaility of the measurements has no bearing on the overall GR&R. And Yes it is on a CMM, DCC, with a SP600M scanning head, and the roundness is from scans. I am tweaking the settings to improve the repeatability, slowing the scan speed and increasing the point count.

One of the other threads on unilat interpetation said to test for normilaity, is there a standard PPK,CPK that should be held for gages?

Our other option is to use a talyrond, which comes at a inspection time increase.

Also Miner please note I did not ask anything about minitab, can I please get a CAR issued to the moderator that moved this thread?

Miner thanks for the respones as well......... and yes I am a noob with GR&R's

[Miner]

Originally Posted by justncredible

Yet it makes me wonder if the normaility of the measurements has no bearing on the overall GR&R.

The sample size of the measurements is really too small to define any kind of distribution. The normality of the distribution of the parts may impact your results because %GRR is a ratio of the measurement variation to the part variation. The part variation should reflect the variation of the parent distribution. If the parent distribution is nonnormal, it may be more difficult to obtain samples that accurately reflect that distribution.

Originally Posted by justncredible

And Yes it is on a CMM, DCC, with a SP600M scanning head, and the roundness is from scans. I am tweaking the settings to improve the repeatability, slowing the scan speed and increasing the point count.

Good. On a DCC, the repeatability of fixturing the product may have an influence, especially of the program starts from a reference point on the fixture versus a reference point on the part itself. To minimize the effect of within part form variation, you want to scan the same location each time. For example, if you scan a circle to check roundness of the inner diameter of a hole 1" deep, you should always measure at the same depth each time.

Originally Posted by justncredible

One of the other threads on unilat interpetation said to test for normilaity, is there a standard PPK,CPK that should be held for gages?

No. A Gage R&R is not the same as a capability study. The standard is P/T Ratio and/or %GRR should be less than 10% for an ideal gage. 10 - 30% may be okay for less critical applications, but > 30% is usually not acceptable. P/T Ratio is used if the gage is used for Pass/Fail decisions. %GRR is used if the gage is used for SPC or to make statistical decisions such as in a DOE or hypothesis test.

Originally Posted by justncredible

Our other option is to use a talyrond, which comes at a inspection time increase.

Try a study using this. If it does not improve, you may be looking at a fixturing issue or repeatablility of the starting location of the scan.

[justncredible]

Yes, I have did the talyrond, yesterday. The tol. is .0002, and the customer wants < 20%. It is beyound the cmm to pass the GR&R, it just does not have the resolution, and can not repete within the .000012 needed to pass.

We have used 3 diffrent .xls GR&R sheets, and minitab, and today I ordered the versuion 14 of minitab so we can do a true unilat GR&R study< I will also have to get a copy of the MSA to figure out how to read the results.

Attached is the study off the talyrond, the sheet is 3rd edition and says fail???? In minitab the same exact numbers give me a 10.52%, so my lack of understanding in what exactly is wrong with the study has a job on hold.

?????????????????????????????????

Thanks again miner....

[Marc]

Originally Posted by justncredible

I do not need minitab help, unless someone has the $395 upgrade laying around not being used.

Originally Posted by justncredible

Wow first post and it gets moved to the WRONG section???????

That was not the topic title, I do NOT need minitab help, it was in the GR&R section and that is where this thread belongs. The moderators need to leave stuff alone sometimes. @@!#@!###

Miner - Thanks for helping!

justncredible - As an FYI, I re-title many threads and I moved this thread. Sometimes threads can be put in different places and each place would be applicable. Were that every thread could be 'button holed' into one specific forum category. In my opinion you should be happy that so many of us care enough to look at each thread, try to put in titles that (usually) best describe the question or discussion topic (goodness knows I've seen threads with titles as simple as "Help!" which makes it difficult when people are scanning thread titles while trying to find information), and if it might better fit in a different forum move it. All in all I think we do a pretty good job at keeping things organized, all things considered.

I originally retitled this thread only adding "Minitab 13" because you are using Minitab and you are using version 13. The most recent version might be different. I put it in the Minitab forum because you're using Minitab regardless of what function, so the assumption on my end was it would be best if people familiar with Minitab functions and outputs could best help. And I felt it made more sense to put it in the Minitab forum because many people do not use Minitab at all for gage R&R. I made a judgment call.

Don't get too excited. There was a redirect in the Gage R&R related forum. A lot of people here help each other out and most questions do get answered by people who just want to help someone out. As to attitude, people here are judged by their words and actions so I really don't have a comment. Ultimately, what people do to help others is the key.