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The final four steps of the Process FMEA are where the assessment happens. These steps do the original analysis and manage the mitigation of high risk failures.

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Process FMEA Analysis.docx
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Quick reference

Process FMEA Analysis

The last four steps of the Process FMEA process are the ones where the analysis is accomplished.  These are the steps that determine the technical design risk in the process.

When to use

Whenever a Process FMEA is conducted, the analysis steps must be completed.  After the first three steps are done, the remaining four steps can be completed.  These steps must be completed in the order indicated.

Instructions

The heart of the Process FMEA is the analysis and these steps provide direction for how to do that analysis.  These steps complete each of the columns on the Process FMEA form.

Step 4. Identify functions and failure modes

Use the Process Map from Step 3 to list all the process steps that are included in this Process FMEA.  These are entered into the first column on the left side of the form.  Subsequent entries will be entered in the next sequential column. Each step should be on a separate line.  For each step, list all the functions that occur at the step.  Each function should be on a separate line.  For each function, list all applicable failure modes.  There should be one failure mode on each line of the Process FMEA form.  If a function has multiple failure modes, add additional lines below the line listing the function.

Step 5. Analyse failures

For each failure mode, describe the effect of that failure on product or process performance.  Then score the severity of that effect.  Next list the possible causes of that failure mode.  If there is more than one cause, list each cause on a separate line.  Now score the probability of occurrence of that cause for this process, using actual data if possible.  Finally, describe the prevention or detection control that is used on the function with respect to the failure listed.  Score this detection capability.

Step 6. Implement mitigation plan

The three scores from Step 5 are multiplied together to get a Risk Priority Number or RPN.  When this value exceeds the organizational threshold, a mitigation action should be taken. Typical actions are:

  • Product design change to lower the severity (safety covers, or less volatile materials)
  • Process improvement change to lower the frequency of occurrence (improved yield)
  • Process change to improve prevention or detection (use of statistical process control)

After a mitigation is completed, the failure mode is rescored.  Depending upon the product or process change, new failure modes may have been introduced and these should also be analysed.

Step 7.  Document analysis

The Process FMEA is placed under revision control and maintained as part of the process design and control documentation.  It should be revised whenever there is a change to the process, a change to the way the process is managed or controlled, or if new information becomes available concerning the probability of occurrence for failure modes.

Hints & tips

  • These steps are the focus of the Process FMEA.  They will likely take the most time and effort to complete.
  • The goal is to identify technical risk, so list all functions and failure modes, not just a minimal set in order to say you did a Process FMEA. 
  • This analysis is best done while the product is still being developed so that product changes can be easily made.  However, depending upon the development process, your organization may not start process development until after the product design is frozen.  When that is the case, the ability to impact severity is limited, so even more emphasis is placed on probability of occurrence and detection.
  • Include Process FMEA revisions in the change control process for process design documentation.  Make it a required submittal before any process design change can be approved.
  • This is an extremely helpful document to use when setting up a second manufacturing operation.  This communicates the issues that need be addressed at the new facility.
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  • 00:04 Hi, I'm Ray Sheen.
  • 00:05 Let's continue our discussion of the Process FMEA, this time,
  • 00:09 focusing on the steps where we do the analysis.
  • 00:12 So let's continue to look at the Process FMEA form and
  • 00:16 how we complete the remaining steps.
  • 00:19 In an earlier lesson, we discussed the preparatory steps 1, 2, and 3.
  • 00:21 The next step is step 4.
  • 00:25 In this step, we take the process map, and for each step,
  • 00:29 we'll review what functions are performed in that step and what failures could occur
  • 00:34 to prevent the functions from completing its work satisfactorily.
  • 00:38 Step 5 is the analysis step.
  • 00:40 We will do the analysis for severity, probability of occurrence, and detection.
  • 00:45 But in this case,
  • 00:46 we will have different definitions of the values as compared to the Design FMEA.
  • 00:51 Step 6 is similar to the Design FMEA.
  • 00:54 If the risk priority number for
  • 00:55 failure mode is above the threshold, then the failure should be mitigated.
  • 00:59 After mitigation, the failure is rescored to determine the current RPN value.
  • 01:05 The final step is the documentation step.
  • 01:08 Once the FMEA is complete and
  • 01:09 the mitigation's implemented, the revision level is updated and
  • 01:12 the former file is archived with the other process documentation.
  • 01:17 Again, this is a living document and
  • 01:18 will need to be referred to whenever there is a process change.
  • 01:23 So let's look at each step in more detail.
  • 01:25 In step 4, we identify functions and failures.
  • 01:28 The step is very straightforward.
  • 01:30 At each step, determine what the operator or
  • 01:32 equipment does, what function it performs.
  • 01:35 One of the reasons for
  • 01:36 walking the process in the previous step had been to be certain that
  • 01:40 you've identified all the functions that actually occur at each step.
  • 01:44 One thing in particular to watch for
  • 01:46 are the critical characteristics to identify in the Design FMEA.
  • 01:50 Confirm which steps are creating or modifying those characteristics.
  • 01:55 Now, for each function at each step,
  • 01:57 determine what type of failure could occur.
  • 02:00 Obviously, you should use any existing defect reports,
  • 02:03 since those indicate what failures are occurring.
  • 02:06 Keep in mind, the same failure could occur at multiple steps, so
  • 02:09 be sure to include it at each one.
  • 02:12 In addition to the failures that are already occurring,
  • 02:15 use the failure types to brainstorm other potential failures.
  • 02:18 The failure types that commonly occur in Process FMEAs are complete failure,
  • 02:23 partial failure, intermittent failure, degraded performance, and over-processing.
  • 02:29 Now, on to Step 5 and the analysis.
  • 02:31 Start by first determining the effect of each failure on both the product and
  • 02:35 the process.
  • 02:36 List that on the Process FMEA form.
  • 02:39 Now, for each failure mode and effect combination, start scoring.
  • 02:43 We use the same three categories of scoring.
  • 02:46 First, score the effect for its severity.
  • 02:49 What is the impact to the product and process?
  • 02:51 The scoring will be between one and ten, where ten being high and one is low.
  • 02:57 Now, list the cause or causes of the failure mode.
  • 03:00 It's common to have multiple causes.
  • 03:02 Each one gets a separate line and a separate score.
  • 03:05 Rate the probability of that cause occurring,
  • 03:08 which would lead to the failure.
  • 03:10 In this case, we'll be relying heavily on data for the scoring.
  • 03:14 The detection score is done a bit differently than with the Design FMEA.
  • 03:18 The detection method can be one of prevention control or
  • 03:21 detection control, and sometimes you may have both.
  • 03:25 Whichever approach you are using, annotate the method in the appropriate column, and
  • 03:29 then score the method.
  • 03:31 Step 6 is to implement mitigation.
  • 03:34 If the risk priority number for a failure mode and effect exceeds the organization's
  • 03:38 threshold value, then a mitigation action should be implemented.
  • 03:42 Depending upon the failure mode, affect, cause, or detection that's in place,
  • 03:46 the mitigation can be at a product level or process level.
  • 03:50 If done at the product level, the product undergoes a design change.
  • 03:53 Most of the time, this will change the effect and severity score.
  • 03:57 It's great when a Process FMEA can be completed before design freeze.
  • 04:01 Then it is relatively easy to make the product changes.
  • 04:04 However, most of the time, this will not be possible, or
  • 04:07 the difficulty of doing it will make another approach more viable.
  • 04:12 You can also change the process step in the way the function is accomplished.
  • 04:16 This will often change the probability of occurrence for the cause, and
  • 04:19 you have the option of changing the detection method.
  • 04:22 Whenever possible,
  • 04:23 I prefer to use a prevention approach instead of detection control.
  • 04:27 The last step is, once again, documentation.
  • 04:30 Complete the former spreadsheet including the mitigation activities, and
  • 04:34 rescore the failure modes after mitigation.
  • 04:36 That is the same as we did with the Design FMEA.
  • 04:39 Place the document under documentation control.
  • 04:42 It should be revision control and monitored just like work constructions or
  • 04:46 control plans.
  • 04:47 In fact, when one of those changes, the Process FMEA should be reviewed and
  • 04:51 updated as appropriate.
  • 04:53 And of course, share your best practices and insights with
  • 04:56 other process design teams or others doing continuous improvement projects.
  • 05:02 The analysis steps of the Process FMEA
  • 05:05 are what gives us the guidance about process risk.
  • 05:08 Make sure you do them well in order to have a viable risk assessment.

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