AIAG PFMEA (3rd edition) Severity Rankings - Define a "portion of the product"

[GBGYMDAD]

I recently facailitated a PFMEA for a new product and used the AIAG 3rd edition FMEA book severity rankings. A lot of confusion arose over what is meant by "the product" or a "portion of the product" (see right column of table on page 43). Does a portion of the product mean part of an assembly or does it mean part of a lot that was produced in a given time period? If it means part of a lot in a given time period, how would you rank something where you are only scrapping part of an assembly (i.e., the wire in a wound motor stator but not the metal core)? If it means part of a lot, what happens with one piece flow where the lot is one? In this case, a 2 or 3 would never apply because they say "A portion (less than 100%) of the product may have to be rewoked". You would never have less than 100% in a lot of one. Help! Any ideas?

 

[Ron Rompen]

I have found the AIAG FMEA Guide to be a useful starting point, but because it was written to cover so many circumstances, it becomes less and less useful when you try and refine it down to your own process.

To make this a little easier, I would strongly recommend that you develop your OWN scoring guidelines, and use them for developing your PFMEA scores. Base it on your own processes, part and process history, and a knowledge of what you are capable of (or likely to do).

You mentioned a lot size of 1.....it does indeed make a 2 or 3 unattainable under the 'regular' scoring system, so make sure that your system reflects this.

If you have a limited customer base, it would also be a good idea to have their input; since I use a non-standard scoring system, I am frequently defending it to my customers, but after over 6 years using it, I have had only one customer absolutely reject it, and insist that I use the AIAG scores.

 

[Bill Ryan - 2007]

Welcome to the Cove GBGYMDAD

I interpret the "portion of a product" as a lot but that's only because we are a die caster and we (currently) have "no such thing" as one piece flow. (It's very tough to see how we could have such a thing - but that's for another discussion)

I agree with Ron that you should probably use an internal ranking system when using the "right hand column" (which are questions regarding your production lines). However, using the "left hand column" addresses the impact to your customer should you ship a nonconforming part(s). In my experience, unless a Severity is a 9 or 10, the ranking is normally a bit higher when addressing the Effect to our customer when compared to the Effect on our operations.

 

[Howard Atkins]

I am go to see if I can explain it. Bear with me.

Severity 7 "Or product may have to be sorted and a portion (less than 100%) scrapped, or vehicle/item repaired in repair department with a repair time between half an hour and an hour. "

After sorting the lot/quantity/amount some will be scrapped

Severity 6 "Or a portion (less than 100%) of the product may have to be scrapped with no sorting, or vehicle/item repaired in repair department with a repair time less than half an hour."
Parts rejected by the existing controls

Severity 4 "Or the product may have to be sorted, with no scrap, and a portion (less than 100%) reworked. "

The sorting is to decide which needs rework

Does this make sense?