Pfmea function requirement and failure mode

WS Kang

Registered
Hello

Regarding pfmea and cp, My background knowledge is as follows.
1.Operation step in the pfmea should be based on pfd.
2. Function requirement and failure mode is relatated to product characteristic
and failure cause is related to process characteristic. Regarding this there are some
different method, but i would like to put product characteristic as a requirement and failure mode.

So my question is, Suppose that process operation step is as follows.
010 Welding
010-5 Position and secure part into fixture.
010-10 confirm setting (current and voltage)
010-15 push weld start button
010-20 take out part from fixture
010-25 Inspect weld quality.

If focused process step is high level operation like welding, Defineing product chractersistic is not difficult.
One of the product charactersistic is pull out force after welding.
But if focused step is low level like confirm setting, What is product charactersistic and process requirement?
I think there is only process chracteristic in this operation.
Consider that requirement should be product characteristic as i wrote ealier.
Please help me.

Thank you in advance.
 

John C. Abnet

Leader
Super Moderator
Hello
Consider that requirement should be product characteristic as i wrote ealier.
Please help me.
Thank you in advance.

Good day @WS Kang ;
Think of it like this....
1- Process characteristics STAY at the point of work.
For example, the "current" and "voltage", do not continue on with product. They STAY at the point of work, so are (as you have indicated PROCESS characteristics.
2- Product characteristics MOVE with the output (part).
For example, in your situation the "current" and "voltage" cause a result, which is for weld to form on the part. The WELD (result) is the product characteristic. It MOVES (continues on) with the part.

Hope this helps.

Be well.
 

Bev D

Heretical Statistician
Leader
Super Moderator
...and yet not enough detail. The important functions of welding are not listed at all.
You are also focusing on what the operator is doing (push start button) not what the weld process is doing.
 

Jim Wynne

Leader
Admin
...and yet not enough detail. The important functions of welding are not listed at all.
You are also focusing on what the operator is doing (push start button) not what the weld process is doing.
Yes. There might be something going on between 010-15 and 010-20 that could be significant. Reminds me of this:

Pfmea function requirement and failure mode
 

WS Kang

Registered
...and yet not enough detail. The important functions of welding are not listed at all.
You are also focusing on what the operator is doing (push start button) not what the weld process is doing.

Thank you for feedback.
As you mentioned , I missed some important operation. and example of operation was not proper.
But this is just example. I would like to know how to define product chraracteristic which is linked to process requirement.
Some operation is easy to define product characteristic such as get the part (product characteristic : no damage during handling or right part),
place the part to the fixture (product chracteristic : right position or right orientation, or no damaged part)
welding operation (product characteristic : pull out force),
But some operation is not easy for me to define product characteristic regarding some operation
such as setup the machine parameter, move fixture down to right position. In this case i would like to
know how to define process chraracteristic which is should be product chraceristic (output).
Or is it not proper to write down process operation in detail like this?
 

Bev D

Heretical Statistician
Leader
Super Moderator
Are you trying to do this by yourself? All FMEAs are supposed to be done by an interdisciplinary team. This would include people who understand the design and intended use of the part.

All parts of the process are supposed to be written down if they are to be performed. If a fixture is used, then yes you write down the function of the fixture. Pacing the part in teh fixture incorrectly can be a cause of failure of the fixture to properly orient or secure the part. Remember that some failures will have a very low severity and some will have a high severity.
 
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