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

[energy]

Seen one used a couple of times

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?

The Profilometer? has a stylus that moves back and forth over a surface and measures surface finish. It kind of looks like those things on a polygraph moving back and forth on chart paper. Anyway, the instrument is calibrated against a know standard. I wasn't aware that it leaves marks on the surface. We requested profilometer results on polished Stainless seamless piping and it was on the actual part we purchased. No evidence of "etching".

 

[noboxwine]

Msa

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.

Metal B: I believe (only one coffee so far today..) the MSA says the parts must be selected from the process itself and represent the entire operating range. I have always done that but found it not a bad idea to have at least part outside one limit just to further quantify the system. Never had a customer or auditor question it and most importantly, I like the additional assurance. (Wish I could only make a bad part when a die explodes...... )

 

[Bob_M]

Metal B: I believe (only one coffee so far today..) the MSA says the parts must be selected from the process itself and represent the entire operating range. I have always done that but found it not a bad idea to have at least part outside one limit just to further quantify the system. Never had a customer or auditor question it and most importantly, I like the additional assurance. (Wish I could only make a bad part when a die explodes...... )

OK that makes sense. I've typically taken the ten randoms parts from production (or from a 100 pc PPAP sample run). I was not trying to brag, but we make basic metal stampings that typically do not deviate much (thus we need stuff like SPC readings to often). If instructed to, we still couldn't make too many bad parts on purpose without risking die destruction (well not the ones we COULD use for R&R studies).

 

[Bill Ryan - 2007]

Although this is off the original profilometer question, we don't produce parts out of tolerance specifically for a Gage R&R either. I have taken parts for attribute studies and physically altered them (with a BFH ) so I did have "bad" parts to show on the form. I have done the same thing for a variable study, but rarely. The whole intention of a Gage R&R is to prove out that the gaging methodolgy, as well as the gage itself, are adequate to tell you what you need to know about a particular feature (good data in = good data out). It's just as important (if not more important) that the gage "tells" you when you have a nonconforming part as it is when "telling" you it is conforming. Therefore, the more of your tolerance you can cover (even out of tolerance) during the study, the more confident you would be in your measurement "system".

Wow, that's way too much for me to be writing on a Friday

Bill

 

[cslauenwhite - 2009]

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.
Bill

Bill.

Profilometers and surface finish testers in general are considered a destructive test for C1010-C1020 steel. The point of the gauge which is measuring is a sharp diamond being dragged across the surface. Now don't get me wrong the damage is very minimal but for the sake of accuracy the first reading and the last reading in the same spot will be effected by this dragging. Will you see this as error in a GR&R sure. Will it be a contributing factor to the outcome; probable not.
My only advice is that for TS keep a good record of the GR&R failing the 10% but have the validation stating that 12% was evaluated and found to be acceptable in this circumstance.

 

[cslauenwhite - 2009]

Re: Seen one used a couple of times

The Profilometer? has a stylus that moves back and forth over a surface and measures surface finish. It kind of looks like those things on a polygraph moving back and forth on chart paper. Anyway, the instrument is calibrated against a know standard. I wasn't aware that it leaves marks on the surface. We requested profilometer results on polished Stainless seamless piping and it was on the actual part we purchased. No evidence of "etching".

Energy,

The stylus does not move back and fourth like a record player but rather A diamond stylus is moved vertically in contact with a sample and then moved laterally across the sample in a stright line for a specified distance and at specified contact force.
Also the stilus does leave a mark as it is a diamond and harder always marks softer material but the radius of diamond stylus ranges from 20 nanometers to 25 μmso the mark left will be very narrow, shallow and short. Unless you know the location of the inspection it will be very hard to find.