Actions Taken - Updating a FMEA for the addition of a downstream poke yoke

[qcman]

I have a question about updating a FMEA for the addition of a downstream poka yoke to detect the presence of a feature made upstream. Our FMEA's are arranged by process steps. Do you normally put the action taken ( poka yoke installed) on the FMEA where its installed or where the feature is made? In other words if step #1 makes a hole and I poka yoke that hole on step #2 do I document this action taken on process step #2?

 

[Zbigniew Huber]

IMO

Put the "recommended action" and then "action taken" in the "row" for operation #1 (where failure occurs). The poka-yoke at downstream is a "post processing" detection method. If the poka-yoke prevents further processing then detection ranking is 4 according to AIAG FMEA Rev.4

 

[Grimaskr]

I'm not sure I follow the question, but usually the action is tied to the step that is error-proofed.

For example:
Step 1 is "Create Hole", Failure is "No Hole Created".
Step 2 is "Stick something in Hole", Failure is "No Hole Available".

If I were to error-proof Step 1, we could never get a part where no hole was created. The poka-yoke action would be at Step 1. You could then remove "no hole available" as a failure mode in Step 2, if it can no longer occur in Step 1.

If I were to put in a vision system at Step 2, so that I could never fail Step 2 because we catch "no holes" before we try to stick something in them... that would be poka-yoke for Step 2. I could still have failures at Step 1, they just wouldn't cause failures at Step 2.

 

[Zbigniew Huber]

IMO

FMEA sheet should looks like it:

Step #1
----------------------------------------------------------
Process step: #1 Drill hole
Function/Requirement: "Drill hole, dia. XX etc"
Failure mode: "no hole"
...
Cause: tool broken
...
Detection controls: 100% visual inspection at step #1 (7)
Det: 7
...
Recommended action: Install mistake-proof (poka yoke) at step #2
Actions taken: Poka-yoke installed at step #2. 03/03/2015
Sev: same as before
Occ: same as before
Det: 4
RPN: recalculate
----------------------------------------------------------

As a general rule in PFMEA assume incoming material and products from upstream as "conforming" when analysing downstream step. So in step #2 you should not consider "no hole drilled in step #1",because it is a failure mode in step #1.

Of course the FMEA team may decide to include some failures from upstream as causes in downstream step but it is exemption from the rules and can be used only for known, hard to solve issues in upstream or at suppliers.

During analysis of step #1 detection controls - include all detection controls for cause and failure mode at the station (at source) and failure mode detection in subsequent stations (post processing). Put rank for each controls (as a part of the description) and record the lowest ranking in detection (Det) column.

Example:

Step #1 (when poka-yoke is already "current" controls)
----------------------------------------------------------
Process step: #1 Drill hole
Function/Requirement: "Drill hole, dia. XX etc"
Failure mode: "no hole"
...
Cause: tool broken
...
Detection controls: 100% visual inspection at step #1 (7), poka-yoke at step#2 (4)
Det: 4
...


Please note that Poka-Yoke could be "mistake-proofing" (detection device) or "error-proofing" (prevetion device). In you case it detects failure mode from step #1 in post processing (at next station) and block it. According to AIAG FMEA it is detection level = 4.

Prevention type poka-yoke (error-proofing) is a solution that prevents failure mode from occurring because it prevents the cause from occurring. When it prevents cause then in must be in the FMEA row where given (prevented) cause is stated.

Hope it helps.