Kindly clarify the PFMEA.

Hi,
I have one basic question. In PFMEA, PROCESS/FUNCTION indicates which process?
a. Process that directly involved with product alone.
b. All the process includes machine movements also.

example, Consider the following process.
Input: Part with M5 nut engaged manually,
PFMEA for "M5 nut torquing(2.2Nm) with electronic nut runner unit mounted on cylinder, LM slide (Z axis) arrangement".

Option 1:
Process/Function = A) M5 nut torquing alone
(Failure modes: i) Torque out of spec (Low/High) ii) Angle out of spec (Low/High)
Option 2:
Process/Function = A) Nut runner movement to work position (Z axis)
(Failure modes: i) Nut runner not moved ii) Nut runner stopped in-between iii) Nut runner socket miss.
iv) Nut runner socket not aligned with nut

Process/Function = B) M5 nut torquing
(Failure modes: i) Torque out of spec (Low/High) ii) Angle out of spec (Low/High)

I feel option 1 is enough for PFMEA. What is your opinion?

It reads like there are different failure modes identified under option 2 which won't have controls identified for them if option 1 is pursued.

Option 2 contains more failure modes which are not directly affects the product. Still do we need to include them in PFMEA?

Currently we are following Option 2 only, which makes PFMEA bit complicated in automated assembly lines.

Anyway, following option 2 gives much clarity about the process meanwhile it confuses a lot while preparing PFMEA.

Deciding to stick with option 2. Thanks for your reply

I think option 2 is correct. (If you work at an automotive industry)

The reason for recommending option 2 is based on AIAG-VDA FMEA handbook.
According to the handbook, failure effects are analyzed with 3 categories.
One is 'Your plant', another is 'Ship-to plant' and the other is 'End user'.

If you have a look at examples of 'Your plant' failure effect, examples are 'Line shut down', 'Operator safety risk' and 'Tact time decreased' and so on.
Failure mode of nut runner movement could affect on 'Your plant' failure effects.
For example, if nut runner not moved, tact time could be decreased.
If nut runner socket miss, line could be shut down (If there is no substantial process for the failure)

I hope this helps you.
Thank you.

Kim from Korea said:

If you have a look at examples of 'Your plant' failure effect, examples are 'Line shut down', 'Operator safety risk' and 'Tact time decreased' and so on.
…
For example, if nut runner not moved, tact time could be decreased.

Click to expand...

Since Takt time is the time interval for meeting product demand any decrease in takt time means that more product must be completed in a given time interval. This doesn’t make sense in your example - can you elaborate?

Bev D said:

Since Takt time is the time interval for meeting product demand any decrease in takt time means that more product must be completed in a given time interval. This doesn’t make sense in your example - can you elaborate?

Click to expand...

Sorry. That was my bad. Tact time is wrong.
Let me correct a sentence from my previous reply.

For example, if nut runner not moved, tact time could be decreased. → For example, if nut runner not moved, production amount could be decreased.