Customer Print Specifications on PFMEA

[vailmij]

Hello, I hope you all would be willing to help clarify something for a me:

Should ALL customer print specifications and notes be included as Requirements on a PFMEA?

For example, a drawn metal component that has print specs such as OD, ID, OAL, Radii, Pierce Hole Diameters, Angles, Chamfers, etc. and notes such as "burrs no larger than X" or "parts must be free from cracks splits...". There are typically 20 - 40 specs on each print - many of which are only measured at set-up (first piece) because they are what we consider "tool-controlled."

 

[Jim Wynne]

The PFMEA should be based on the process steps shown in the process flow diagram. For each process step, potential failure modes (of the process, preferably) should be considered. There is no need or requirement to base the PFMEA on drawing dimensions/requirements.

 

[vailmij]

There is no need or requirement to base the PFMEA on drawing dimensions/requirements.

Thank you for your reply, Jim. Couldn't it be said though that an oversized OD, for example, is a potential failure mode of the stamping process? I guess I'm just having a hard time understanding the distinction between product specifications and process requirements.

I did some research before posting and found this thread from last year. They seem to interpret that product specifications are the Requirements.

How to fulfill PFMEA "requirement" column?

In such a case, it would seem that we would need to list all product specifications on a PFMEA. I personally do not agree with this interpretation, but there is obviously some confusion.

Edit: Added link to a previous thread.

 

[Jim Wynne]

Thank you for your reply, Jim. Couldn't it be said though that an oversized OD, for example, is a potential failure mode of the stamping process? I guess I'm just having a hard time understanding the distinction between product specifications and process requirements.

I take a different approach, one that to me makes more sense in defining failure modes. I think it's best to define failure modes as failures of the process (as opposed to part defects), with the effects being the manifestation of process failures. The thing is called, after all, Process Failure Mode and Effect Analysis. So--the process failure mode might be "Worn punch" with one of the possible effects being ".150 ±.005 hole oversized."

You don't necessarily list all print specifications--you determine what the possible process failure modes are and the potential effects.

 

[optomist1]

remember PFMEA/DFMEAs are a team sport, a diversity of inputs from team members usually yields a better outcome...a collaborative effort...

 

[vailmij]

So--the process failure mode might be "Worn punch" with one of the possible effects being ".150 ±.005 hole oversized."

So, using this example, your PFMEA would read:

Process Step: Stamping

Requirement: Fully Formed Part​

Potential Failure Mode: OD Oversized​

Potential Cause of Failure: Worn Die​

Potential Failure Mode: ID Undersized​

Potential Cause of Failure: Worn Punch​

Potential Failure Mode: Missing Pierce Hole​

Potential Cause of Failure: Broken Punch​

​

........ etc.

rather than:

Process Step: Stamping

Requirement: OD .150 ±.005​

Potential Failure Mode: OD Oversized​

Potential Cause of Failure: Worn Die​

Requirement: ID .120 ±.005​

Potential Failure Mode: ID Undersized​

Potential Cause of Failure: Worn Punch​

Requirement: Pierce Hole .020 ±.001​

Potential Failure Mode: Missing Pierce Hole​

Potential Cause of Failure: Broken Punch​

remember PFMEA/DFMEAs are a team sport, a diversity of inputs from team members usually yields a better outcome...a collaborative effort...

Hi, yes we are pretty good about getting several people involved in the development of our PFMEAs. We recently had a minor non-conformance from our IATF audit in regards to some discrepancies on our PFMEAs. That sparked the conversation about whether or not we are creating the PFMEAs correctly.

 

[Jim Wynne]

So, using this example, your PFMEA would read...

I should have asked this before, but are you using the traditional AIAG FMEA form, or the new AIAG/VDA form?

 

[vailmij]

I should have asked this before, but are you using the traditional AIAG FMEA form, or the new AIAG/VDA form?

AIAG FMEA, 4th ed.

 

[Golfman25]

Vailmij, you can do both ways. We do family PFMEAs (old form) so we use "generic" terms like OD oversized/undersized. We actually call out the operations, such as "Trim" and then identify the failure modes such US/OS dim., burrs, etc. Then identify effects, usually assembly issues, and then causes and controls.

One note, even if something is tooling controlled it should go on the FMEA as a failure mode. It wouldn't be part of your in process controls on your control plan.

Good luck.

 

[vailmij]

Hi Golfman,

That is an interesting idea. So say, an operation is "piercing" but there are multiple different-sized pierce holes, one of which is a CC. How do you identify and score the CC item separately on such a PFMEA?