Informational How to develop a Control Plan from a PFMEA (Process FMEA)
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toniriazor
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Hello all again,
I have an issue, before coming IATF 16949 audit.
In Ford health chart - Plug availability is High Impact (HI)
In Ford SCCAF - Plug availability is Significant Characteristic (SC)
In PFMEA Ford Handbook it is written that HI characteristic MUST NOT align to characteristic designated in the DFMEA as YC and YS. I understand it that way - characteristic whether is SC or HI. You can't have Plug availability characteristic - both as SC and HI.
What is your opinion about this matter ? Is my logic right or wrong ?
Please share your valuable opinion with me.
I have an issue, before coming IATF 16949 audit.
In Ford health chart - Plug availability is High Impact (HI)
In Ford SCCAF - Plug availability is Significant Characteristic (SC)
In PFMEA Ford Handbook it is written that HI characteristic MUST NOT align to characteristic designated in the DFMEA as YC and YS. I understand it that way - characteristic whether is SC or HI. You can't have Plug availability characteristic - both as SC and HI.
What is your opinion about this matter ? Is my logic right or wrong ?
Please share your valuable opinion with me.
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How is "plug availability" in the DFMEA?
It is probably best to clarify with the customer because, without additional information, you are right in that there seems to be a contradiction.
toniriazor
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Icy Mountain
Sachem
Wow, seems like last year. Once I have to go through this again with the "new" AIAG&VDA manual, I will try to update this.
Hi @Icy Mountain and all, may I kindly seek your opinion on DFMEA/PFMEA/CP linkage using below example?
Total flowrate is a significant customer requirement, and DFMEA has been done to ensure adequate design. Nonetheless, based on tolerance calculation, there could be a 2% reject from production. Management review has agreed to accept this design risk and put a test station in the production line to filter out those rejects (it's more cost effective than to further improve/control the design).
Natually this test station is recorded inside the CP as a control for total flowrate. The test station is captured in PFMEA as a process step (failure mode includes accepting bad part, rejecting good part etc.). However, it is not captured inside PFMEA as any detective control for total flowrate because the process is robust enough to prevent any error or misassembly. The assembly process could have been done as it should be easily and we still could (and expected to) get about 2% reject.
My queries are:
1. This total flowrate is a significant characteristic in DFMEA which is linked directly to CP without going through PFMEA. Is this ok? I have seen multiple responses saying that PFMEA and CP should always be linked.
2. Is it logical to lower DFMEA RPN score since there is a detection in production? It doesn't seem right to mix DFMEA and PFMEA (or CP in this example), but it does not feel right either to keep a high RPN in DFMEA whereby the risk can be mitigated before reaching customer.
Total flowrate is a significant customer requirement, and DFMEA has been done to ensure adequate design. Nonetheless, based on tolerance calculation, there could be a 2% reject from production. Management review has agreed to accept this design risk and put a test station in the production line to filter out those rejects (it's more cost effective than to further improve/control the design).
Natually this test station is recorded inside the CP as a control for total flowrate. The test station is captured in PFMEA as a process step (failure mode includes accepting bad part, rejecting good part etc.). However, it is not captured inside PFMEA as any detective control for total flowrate because the process is robust enough to prevent any error or misassembly. The assembly process could have been done as it should be easily and we still could (and expected to) get about 2% reject.
My queries are:
1. This total flowrate is a significant characteristic in DFMEA which is linked directly to CP without going through PFMEA. Is this ok? I have seen multiple responses saying that PFMEA and CP should always be linked.
2. Is it logical to lower DFMEA RPN score since there is a detection in production? It doesn't seem right to mix DFMEA and PFMEA (or CP in this example), but it does not feel right either to keep a high RPN in DFMEA whereby the risk can be mitigated before reaching customer.
Tagin
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I should probably let others more experienced in FMEA/CP answer....but here is my naive view anyway:
1. I would think your DFMEA action for this issue would be: identify issue on PFMEA where it will state to implement test station on CP. Since your solution ('test station') is a control added to the process, I would think it belongs on the PFMEA. So, the DFMEA informs the PFMEA.
2. I would think DFMEA and PFMEA RPN both get lowered due to the test station on the CP.
But are these tolerances in the design of the product, or tolerances in the fabrication of the product? If the latter, should your risk really be in the PFMEA instead of DFMEA, in the first place?
Interesting question. I'll be curious to see what the more astute FMEA'ers say.