Failure mode, Process Excursion and Failure mode cause

[Quality Engineer]

I have a process risk assement in which I have fields "PROCESS EXCURSION" and "FAILURE MODE". I had to covert it to the new format which have fields "FAILURE MODE" and "FAILURE MODE CAUSE".

I am confused in understanding Process excursion and failure mode cause. How should input he information in new format from the old process risk assessment?

The instructions in the new format states that Failure mode cause categories include, but are not limited to:
Machine
Material
Man
Measurement
Method
Environment (Mother Nature)


Example from old Process risk assessment:


1. Process excursion: Incorrect program
Failure mode: Leak not detected
2. Process excursion: Incorrect pressure - too low
Failure mode: Leak not detected

3. Process excursion: Part A not seated properly on Part B
Failure mode: Inadequate bond -Bond failure
4. Process excursion: Missing / too little/ expired/ inadequate cure / wrong adhesive in the part A and B
Failure mode: Inadequate bond -Bond failure

5. Process excursion: Stop cock opened too fast/suddenly
Failure mode: welds damage
6. Process excursion: Stop cock already opened before starting the test
Failure mode: welds damage

In example 3 and 4 the parts are same, the process is the apply adhesive and then place one part onto another.

I will really appreciate if being explained in simple wordings. Thank you.

 

[Bev D]

It sounds like the “process excursion” is causing the failure mode?
there are usually many causal steps to a failure (like dominoes falling)
typically it is best to list the most immediate cause of any failure mode in an FMEA for the level of the FMEA.

When I lead FMEAs, I typically list the function, the ways in which the function can fail (failure modes), the ’local’ or first effect and then the system or final effect on the User/Customer. I then list the potential immediate causes of the specific failure mode.

process excursion is not a typical phrase for a FMEA…

 

[Quality Engineer]

It sounds like the “process excursion” is causing the failure mode?
there are usually many causal steps to a failure (like dominoes falling)
typically it is best to list the most immediate cause of any failure mode in an FMEA for the level of the FMEA.

When I lead FMEAs, I typically list the function, the ways in which the function can fail (failure modes), the ’local’ or first effect and then the system or final effect on the User/Customer. I then list the potential immediate causes of the specific failure mode.

process excursion is not a typical phrase for a FMEA…

So I the Failure mode cause should be defined as "Operator error", "Equipmnent failure" or the process excursion is actually another wording for the failure mode cause?

As I shared that what my industry defines the failure mode cause.
I am too confused in this.

 

[I_Moy]

The easiest way I find to keep these straight in my head has always been: Failure Mode - what could be wrong, Failure Mode Cause - how could it go wrong. So from one of your simpler examples: Failure Mode - inadequate bond, Failure Mode Cause - too little adhesive.