Successful 1st Gage R&R Study...but

[Sean Kelley]

We have had our first succesful gage R&R study using micrometers, calipers, tapes and profileometers. We are a steel mill planning to supply automotive and ar pursuing TS 16949 with a goal of this Dec. for full implementation. Micrometers have 1.6% error mostly due to instrument error with tapes and calipers being similar

We have run into one possible issue with our gage r&r study and that is our profileometers which measure surface roughnes of steel are over the 10 % acceptable criteria according to AIAG MSA manual page 77. They do state that between 10-30% may be acceptable based upon importance of application, cost of measurement device, cost of repair, etc. We are a stainless steel mill with the intent of supplying our steel mainly for exhaust systems. There may be other applications that I am not sure of yet. Possibly engine components like I know Ford has used our steel for Mustang wheel covers, fuel injectors and fuel filters. There are likely others that I do not know about. We also produce long products such as round rod, a possibility for shafts on water pumps, altenators, etc.

My question is we have 11.67% error with our profileometers which measure surface roughness (or smoothness) depending on how you look at it. Generally it is used on out polished finish which is used for kitchen sinks, stove tops, etc. The profileometer study showed most of the error being instrument error with around 1% operator error. Can we justify using these devices. We may not even sell polished material to automotive. Thanks to all for your help.

 

[noboxwine]

Go For Ot !

Sean K.: If I had profileometers reading 11.67%, I'd be thrilled ! I see nothing wrong with this R & R based upon your given information. For added confidence, go ahead and conduct a couple more studies and see whatcha come up with. Let us know and have a day !

 

[Atul Khandekar]

Sean,
Congratulations! Overall the results look very very good to me and 11.67 looks like a borderline case. I would go with noboxwine's suggestion of conducting one or two more studies, and see what you come up with.

 

[Bill Ryan - 2007]

Sean,

Congrats!!!!! Just a quick question - Did you perform the profilometer study on a standard or or the steel?

Bill

 

[Sean Kelley]

We used our steel samples which are definitely not as good as a standard but are more like our typical results in the mill. I believe using our steel does yield more errors than a standard probably would but think it would be more like what we do day to day.

 

[Sean Kelley]

This brings me to another point. We conducted our study in a laboratory or office setting at a table but with the actual inspectors who do this job of measuring our steel. However this does differ from the their daily job of measuring steel in the factory environment. Is this acceptable for TS certification and by automotive industry or not?

 

[Bill Ryan - 2007]

We used our steel samples which are definitely not as good as a standard but are more like our typical results in the mill. I believe using our steel does yield more errors than a standard probably would but think it would be more like what we do day to day.

I certainly agree with you and noboxwine's comment of being thrilled with <12%. My reason for asking is that using a profilometer on a casting can be/is considered a "destructive" test as the material actually gets etched and when we perform an R&R on the part, the results are, typically, well over 20%. Don't know if it's the same thing on a steel surface.

This brings me to another point. We conducted our study in a laboratory or office setting at a table but with the actual inspectors who do this job of measuring our steel. However this does differ from the their daily job of measuring steel in the factory environment. Is this acceptable for TS certification and by automotive industry or not?

I honestly don't know if ambient temperature affects a profilometer as it does just about every other gage (my guess would be that it does). FWIW - We have done comparisons (not with profilometers) and found the end result didn't vary that much whether the study was performed in the metrology lab or out on the floor.

Bill

 

[Bob_M]

We used our steel samples which are definitely not as good as a standard but are more like our typical results in the mill. I believe using our steel does yield more errors than a standard probably would but think it would be more like what we do day to day.

My BASIC understanding of Gage R&R tell me you SHOULD be using production stock/material/parts during the test.
Not knowing what a profilmeter is exactly, are you CALIBRATING the gage as well against a standard? Was the calibration results prior to the R&R within tolerance?

 

[noboxwine]

Just a little more work

As someone mentioned, you should be conducting the R & R under real conditions. Ideally, the 10 pcs used should somewhat vary across the tolerance range and at least one (or two) should be out of spec. This will give you the best picture of how good your meaasurement system is. Let us know and keep up the good work !

 

[Bob_M]

As someone mentioned, you should be conducting the R & R under real conditions. Ideally, the 10 pcs used should somewhat vary across the tolerance range and at least one (or two) should be out of spec. This will give you the best picture of how good your meaasurement system is. Let us know and keep up the good work ! !

Shoulld some REALLY be out of spec? Would the AIAG MSA manaul really tell me to make BAD parts on purpose just for R&R? To be honest, some of our parts couldn't possibly be made "bad" unless the die broke or the wrong material thickness was used... *shrug* Maybe our real conditions are better than the "typical" user.