Does the PFMEA Severity have to match the DFMEA Severity?

Does the PFMEA severity have to match the DFMEA severity? Does anyone know if Ford has anything specific to say about that subject as that is who I'm working with.

Re: DFMEA vs PFMEA severity

Simple answer is Yes.

The severity is determined at the DFMEA level. Severity does not change when design is improved either.

For example, a brake function failure for a vehicle will always have a severity of 10, no matter the design, capability and poke yoke in place.

Re: DFMEA vs PFMEA severity

Kales Veggie said:

The severity is determined at the DFMEA level. Severity does not change when design is improved either.

For example, a brake function failure for a vehicle will always have a severity of 10, no matter the design, capability and poke yoke in place.

Click to expand...

Most of the time this is a correct statement. However, in some circumstances the potential failure mode can be designed out by eliminating the cause, or designing it to fail in a safe mode. I admit that it is an exception to the rule, but it is possible.

Re: DFMEA vs PFMEA severity

Kales Veggie said:

Simple answer is Yes.

The severity is determined at the DFMEA level. Severity does not change when design is improved either.

For example, a brake function failure for a vehicle will always have a severity of 10, no matter the design, capability and poke yoke in place.

Click to expand...

But the DFMEA for the brake assembly will be different from the process FMEAs for the components, so the severity factor can't just be transferred. It can't be assumed that if component "A" fails that the whole assembly will fail, or that the severity of the failure of any component will be equivalent to the failure of an assembly. Nonetheless, if the DFMEA for an assembly has been done properly (good luck with that!) the components will be considered individually wrt their impact on the failure of the assembly.