New AIAG FMEA Process - How to complete the new format

alsat

Dipl. Ing.
i was thinking about trying a separated format in a smaller scope
in a vertical layout, (1) system analysis (2) failure and risk analysis (3) optimization
instead of an endless excel database, this could result in an analysis sheet for a focus element
more like an action sheet or report than a compliance focused ecxeeeeeeeeeel sheet
it is a work in progress
 

alsat

Dipl. Ing.
or, we could make a separate and complete system, function and failure analysis somewhere else for the entire process, the resulting focus elements could then be analyzed and reported one by one
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
What I have found is it easier to prepare using the spreadsheet (using the C,L,R approach), but easier to review with just the columns of like color together.
 

Bill Levinson

Industrial Statistician and Trainer
I am composing a presentation on process FMEA (Design is a little more challenging and I have not worked in that field), and the new manual actually makes sense. The concepts are pretty much the same but it stresses that you start with the failure mode as the focus element, and go from there to the failure effect (consequence) and the failure cause (why the failure mode happens, formerly known as the mechanism). One improvement is that the Occurrence rating is based on the process step's prevention controls as opposed to an estimate of the probability of failure, which is often hard to obtain unless you have an established process with a known process performance index. And Ppk doesn't account for assignable causes that result in nonconformances.

They also use an action priority matrix which is better than the risk priority number (the product of three ordinal numbers). And they also look at three classes of failures: (1) poor quality, the traditional one, (2) failures that affect continuity of operations and (3) failures with occupational health and safety issues. I am actually starting to like it.

One drawback (my opinion) is that the work elements considered are normally only four of the six traditional categories of a cause and effect diagram, with Method and Measurement omitted. I found an example in which the Method (drill speed and feed rate) might in fact be instrumental in preventing the failure in question, namely broken drill bits (which result in undrilled parts which can be detected before they leave the workstation). I am working off a Shigeo Shingo case study in error-proofing.

Another is that it is possible to get a Low action priority for a 9-10 severity failure and occurrence and detection ratings greater than 1 (1=the failure cause cannot cause the failure mode, period, for the Occurrence rating), which should not be possible, but that is just my opinion.

In any event, I really like the manual and it is definitely an improvement on how things were done 20 years ago.
 

Bill Levinson

Industrial Statistician and Trainer
This is an adaptation of a Shigeo Shingo case study in which a process spot-faced four hole positions, and then drilled small holes. The problem was that the small drill bits often broke and parts left the workstation (one worker was minding ten drill presses) without the holes. The solution was to have four rods that moved up and down with the drill press go through the part that had just been drilled; if they didn't, the tool stopped and alerted the operator. This improves the detection rating and reduces the action priority from High to Medium.

Another course of action might be to change the drilling parameters (tool speed and feed rate) to reduce the frequency of breakage, which could reduce the prevention rating and therefore the action priority rating.
 

Attachments

  • pfmea_example.xlsx
    13.4 KB · Views: 1,464

Bill Levinson

Industrial Statistician and Trainer
Here is an Excel template I put together. It has not been rigorously tested - so any improvements are appreciated.

"machine stops before reaching final position"

Shingo, Shigeo. 1986. Zero Quality Control: Source Inspection and the Poka-Yoke System. Productivity Press has numerous (similar) examples, e.g. the drill press one I am using. What happens if the machine trips a limit switch when it reaches the final position? If it doesn't, the process stops and a visual control alerts the operator? This is a jidoka/autonomation control that should probably earn a detection rating of 3. It WILL detect the failure mode in-station and prevent the part from leaving. It will not however prevent the failure mode from being produced which is required for D=2. (not engineering advice)

This, by the way, looks like the tool illustrated in the AIAG/VDA manual:
(I looked up "bearing press" to try to get an idea of what is happening).
 

akdeniz

Registered
Hello all,
I have been working on new PFMEA, I want to ask your opinion for a potential change/improvement
Item 2 of Step#4, Failure analysis describes the Failure Mode for Focus element/step.
However If you consider 4M elements though they altogether make the focus element/step but there are different failure cause for each 4m elements.
What I would suggest to write failure mode of each work element rather than failure mode of focus element/step or add additional column to describe failure cause. this will give more insight for the Work element Failure Cause. Otherwise one must always keep in mind work element function & potential failure. In case you have 4M or 6M, that makes the study even more difficult.

What is your opinion?
 

sagai

Quite Involved in Discussions
Quick feedback on this new revision coming from applying in an automotive electronics project.

Seems the structure breakdown in essence is a great approach however I found rather difficult to apply to electronics.

My sneaking suspicion at the moment, unless I am utterly wrong, that it is more likely for mechanical structures where the connection of components kind of straight forward due to the obvious sequential nature by physics, for electronics however representing the physical structure blows up a horrendous 3D spider net to represent in those 3 columns.

Finally I have dropped the structural approach and follow the journey of electricity on the schematics to nail this structure.

Also, word of caution is to use fmea in conjunction with FTA or other approach that provides more functional insights as a complementer to dfmea.

Ratings for severity/occurance/etc seem academic as usual for designs, we can use that, adds little to none to design analysis.
 
Top Bottom