DFMEA & PFMEA - Special Characteristics Identification

[tcastelino]

Hello Everyone,

I'm a quality consultant, working in many industries, but mainly automotive, aerospace and consumer goods. I have some specialist experience in FMEAs, but would like to clarify the following:

A) Can anyone advise on what criteria are used to identify the following Special Characteristics in a DFMEA and PFMEA, in terms of Severity, Occurrence and Detection rankings?

1. Critical Characteristic
2. Significant Characteristic
3. Major Characteristic
4. Standard Characteristic

This information would normally be shown in the 'Classification' columns of the FMEAs. Attached are what I believe to be the normal criteria used by Ford and Visteon. Are these correct, or does anyone know of amendments to these?

B) Does anyone know the significance/meaning of of the 'Y' and 'V' prefix for YS (potential significant characteristic) and VS (confirmed significant characteristic).

I would really appreciate your feedback on these points

 

[Stijloor]

Hello Everyone,

I'm a quality consultant, working in many industries, but mainly automotive, aerospace and consumer goods. I have some specialist experience in FMEAs, but would like to clarify the following:

A) Can anyone advise on what criteria are used to identify the following Special Characteristics in a DFMEA and PFMEA, in terms of Severity, Occurrence and Detection rankings?

1. Critical Characteristic
2. Significant Characteristic
3. Major Characteristic
4. Standard Characteristic

This information would normally be shown in the 'Classification' columns of the FMEAs. Attached are what I believe to be the normal criteria used by Ford and Visteon. Are these correct, or does anyone know of amendments to these?

B) Does anyone know the significance/meaning of of the 'Y' and 'V' prefix for YS (potential significant characteristic) and VS (confirmed significant characteristic).

I would really appreciate your feedback on these points

Any feedback?

Thank you!!

Stijloor.

 

[joker33]

Can anybody reply to the above question of tcastelino?

 

[adamsjm]

A) Can anyone advise on what criteria are used to identify the following Special Characteristics in a DFMEA and PFMEA, in terms of Severity, Occurrence and Detection rankings?

1. Critical Characteristic
2. Significant Characteristic
3. Major Characteristic
4. Standard Characteristic

Special Characteristics are based upon risk. Ford (and therefore Visteon) use a severity / occurrence table for this (see FMEA ver 4 ref. manual). Per your attached spreadsheet, if the "potential effects of failure" severity rating is a 9 or a 10 then the potential failure mode is critical and corrective action / re-design must be taken to reduce the severity. [Check with Ford's or the Visteon Supplier Quality Engineer to see if an occurrence of a 1 is acceptable.}

DFMEA: If the "potential effects of failure" severity rating is a 5, 6, 7 or 8 and the occurrence of the potential cause is a 4 or greater then the potential cause is "Significant" and requires re-design / improved and/or improved design tools to be proven in the recommended section of the DFMEA. If this cannot be accomplished in the DFMEA (such as part tolerance), then it may be passed to the PFMEA for risk reduction (again via the recommendation section). If Manufacturing can prove acceptable Cpk, then they have proven "occurrence reduction" which can be fed-back to the DFMEA. But keep the "Significant"characteristic on the PFMEA as a reminder as to why SPC or proof of tolerance compliance is required on that dimension.

 

[Richard Pike]

Not quite in agreement there.

Special Characteristics have many meanings. Look at all the different definitions in TS / VDA / AIAG etc etc.

A common auditor "nuance" is to state that if a severity factor is 9/10 then we must have corrective action. not true -- only if it "relies on detection". I will ALWAYS have 9/10 and no amount of corrective action (other than a process/productdesign change) will fix it.

One of the better definitions of Special - is if it needs special control. This applies especially to charecteristics that cannot be verified easily - and therefore the Process Charecteristic controling the product charecteristic becomes "special".

In essence my best advice is to define them according to your own needs -- and then to see if the use of those definitions - assist you in applying resources to the areas that need them.

If the definitions do no assist you in applying resources where needed - then the definitions are wrong. Hence they cannot be generic (as some auditors advise) but must be customised to suit the organisation.

 

[tcastelino]

Adam & Richard,

Thanks for your replies. My understanding of the Critical and Significant Characteristics is the same as yours, but the Major and Standard Characteristics is new to me. I was wondering whether you have any idea as to the numbering criteria (ref attached spreadsheet) that apply to the DFMEA (if applicable) and PFMEA to define these two characteristics.

 

[adamsjm]

... but the Major and Standard Characteristics is new to me. I was wondering whether you have any idea as to the numbering criteria (ref attached spreadsheet) that apply to the DFMEA (if applicable) and PFMEA to define these two characteristics.

It appears that Visteon is separating DFMEA from PFMEA Characteristics. They are also appear to be basing their risk category solely upon severity.
I would check the Ford (& Visteon) FMEA manual or contact the SQE for your product.

Per Richard Pike

Not quite in agreement there.

I was addressing the question as viewed by the AIAG members FORD / Visteon. Not all possibilities.

 

[cmi001]

Visteon is one of our customers. Generally, I cannot see this method deviated to the TS-16949 requirement (at least for 7.3.2.3).

 

[IngridD - 2012]

Visteon is one of our customers. Generally, I cannot see this method deviated to the TS-16949 requirement (at least for 7.3.2.3).

Hi,

I looked at your sheet SC.pdf

Could you please clarify the abbreviations: VC, YC, VM, VS??

Thanks!!!!

 

[Miner]

This is going from memory and it may have changed as I have been out of the automotive industry for a few years.

I believe that Y and V referred to different levels of pre-release engineering drawings.

C referred to CRITICAL characteristics that could affect safety or regulatory items.

S referred to SPECIAL characteristics that could affect customer satisfaction.

M is new since my involvement in automotive.