Gage R&R/MSA for PPAP - Our product has no variance

[christinaparkway]

I work for an injection molding company. I am doing all he documentation and studies required for a PPAP. Our product has no variance. I am "failing my studies because I do not have any parts under my nom. Has anyone had to deal with this issue? Do I have to hand make parts so they look good in the study?

 

[Jim Wynne]

Re: Gage R&R/MSA

Welcome to the Cove.

I suspect that it's not that your product has no variation; it's that your measurement system isn't sensitive enough to detect it. Tell us more about what you're measuring (characteristic, nominal, tolerance) and what you're measuring with.

 

[christinaparkway]

Re: Gage R&R/MSA

It is a small 8mm ball that we check with a micrometer. 8mm +/- 0.025. Last study parts measured 8.013 to 8.018. The study is being kicked back due to lack of variance in process. They kicked back the study stating lack of variance. Guessing it's because we are not 25% low, 25% high, and 50% nom. I haven't ran across an issue like this before.

 

[christinaparkway]

Re: Gage R&R/MSA

reply wouldn't work earlier. See below for my response. I forgot to add it's the O.D

 

[Jim Wynne]

Re: Gage R&R/MSA

It is a small 8mm ball that we check with a micrometer. 8mm +/- 0.025. Last study parts measured 8.013 to 8.018. The study is being kicked back due to lack of variance in process. They kicked back the study stating lack of variance. Guessing it's because we are not 25% low, 25% high, and 50% nom. I haven't ran across an issue like this before.

From here it's hard to say what they might be complaining about. I assume it's a customer who rejected the study. They might be concerned about the process not being centered on the nominal, but that's not an MSA issue. Did you also do a capability study on the feature?

 

[christinaparkway]

Re: Gage R&R/MSA

Yes, the document submitted was contained MSA, R&R, and the capability results.

 

[christinaparkway]

Re: Gage R&R/MSA

also, we are using the anova graph in mintab to track everything.

 

[Jim Wynne]

Re: Gage R&R/MSA

Yes, the document submitted was contained MSA, R&R, and the capability results.

How do the capability results compare (mean, ranges, etc.) with the MSA data? Are you sure you used parts for the R&R that were representative of the process spread?

 

[Matt33]

When you gathered your parts (8mm balls) for the study, did you gather them across the typical production process? (As opposed to consecutively produced.)

 

[Sean Kelley]

I have worked in injection molding in the past and there was some variation in that process. We used what was called a microview which basically was a micrscope on a monitor with calibrated rotary micrometers that were much more accurate than a handheld micrometer. A toolmakers microscope would also work well. Taking parts at the startup when it was a little colder would yiled different variation than when it warmed up and even different than if it ran for 8 hours. Also fiberglass in some plastics will wear certain types of molds if they are made of aluminum or soft steel vs hardened steel. Not sure if this helps but just some thoughts.