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Each of the steps identified in the process map are susceptible to failures. These failures are identified and recorded on the FMEA.

Quick reference

Process FMEA Failure Modes

The Process FMEA is structured to analyse failure modes. Therefore, all applicable failure modes for the process being analysed must be identified and entered into the Process FMEA form or spreadsheet.

When to use

The identification of failure modes will normally follow the creation of the process map.  This is step 4 in the Process FMEA procedure.

Instructions

Every process step has an action or function.  That is what is supposed to occur at that step.  If that action or function does not occur in the prescribed manner, a failure occurs.  At this point in the analysis, the FMEA analysis team brainstorms the failures for each step. 

A tool to assist the team is the Function-Failure matrix.  This matrix starts by listing each process step.  Then for each step the process step success criteria is stated.  There may be multiple success criteria elements for some steps.  Once the success criteria is known, the failures can be quickly brainstormed because those are any results from that step that is not a a complete success.   In the Function-Failure matrix, I include columns for either failure types to assist in the brainstorming process.

You may choose to use a different technique to identify the failures.  The key is to identify all failures.  Once the failures are identified, the Process FMEA form can be initialized.  The first three columns of the Process FMEA form are the process step, the step functions, and the failure modes for those functions.  The ball point pen example will continue to be used to illustrate these techniques. 

Hints & tips

  • Use historical quality records to determine what types of failures have occurred in this process or similar processes. 
  • Assign the failure mode to the step in which the failure occurred, not the step where it was found.  Many failures are found in test and inspection steps, but the actual failure occurred in a previous step.  The types of failure that occur at test and inspection steps are the incorrect application of test and inspection methods leading to a wrong assessment of product or process quality.
  • It is OK to have lots of potential failure modes, that does not mean you have a bad or risky process.  Once we start to score those modes, we will determine then if any of them are significant.
  • Only place one failure mode per line in the Process FMEA.  That may mean that one step or function has multiple failure modes and multiple lines.
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  • 00:04 Hi, I'm Ray Sheen.
  • 00:06 Now, let's discuss identification of the failure modes.
  • 00:09 And it's no surprise that the failures we will be looking at are the failures of
  • 00:13 each step in the process.
  • 00:16 Let's start with some basic principles about process failures.
  • 00:20 First, every process step is an action.
  • 00:23 It is not a state of being, something is happening there.
  • 00:27 Make sure when you write you process steps you have clarified what the action is.
  • 00:31 Failures will occur when the action does not complete as it is expected to be
  • 00:36 completed.
  • 00:37 Also, a failure would occur if the step does some unexpected and undesired action.
  • 00:42 So we can see that every step has at least one failure mode.
  • 00:46 It's virtually impossible to imagine a step where something unexpected and
  • 00:51 undesired could not happen.
  • 00:52 So just because it hasn't happened yet,
  • 00:54 it doesn't mean that you should exclude a failure mode from the analysis.
  • 00:59 To help us determine the failure mode,
  • 01:01 it's sometimes easier to start with the success criteria for that process step.
  • 01:05 If the process step is performing its action as intended, what happens?
  • 01:10 Now, just take that success criteria and negate it, that is a failure mode.
  • 01:15 Or the failure mode might be an intermittent.
  • 01:17 The step meets success criteria sometimes and yet not all the time.
  • 01:22 Another type of failure we discuss earlier was too early too late,
  • 01:26 processes has sequences that is why we put the errors on the process map.
  • 01:30 If a process step is submitted or forgotten that is a failure,
  • 01:34 if the steps get out of sequence we have another failure mode to analyze.
  • 01:38 And sometimes we get stuck in a process step and repeat it again and again,
  • 01:43 which can create an excessive performance or over processing failure.
  • 01:47 So how do we determine the failures?
  • 01:49 Well, just like what the Design FMEA, I create a function failure matrix.
  • 01:53 In this case, I format it a bit differently and
  • 01:56 start with the process step.
  • 01:58 I find that listing the success criteria makes it easier to both identify failures
  • 02:03 and communicate with the team what is really happening at each step.
  • 02:06 Then I have the failure types listed, we covered these in an earlier lesson, and
  • 02:11 I use these as idea starters to brainstorm a list of failures.
  • 02:15 And one thing worth mentioning, any quality defect or
  • 02:18 customer complaint from the process should be included in the list of failures.
  • 02:22 Just assign it to the correct step.
  • 02:24 In this example, we're working with our ball point pen assembly.
  • 02:27 The first step is to review the kit of materials on the shop floor traveler,
  • 02:31 which has our work instructions in it.
  • 02:33 The success criteria is to make sure that we have the right parts.
  • 02:36 And we have identified two failures.
  • 02:38 The first one is to misidentify parts and
  • 02:41 the second is to damage the parts while handling them.
  • 02:44 Notice we don't have a failure of the wrong parts.
  • 02:48 The reason is that failure would have actually occurred at the stock
  • 02:51 room when they created the kit.
  • 02:53 It would be found at this step, but not caused by this step.
  • 02:57 So we only include at this step the failures that are caused here.
  • 03:01 The misidentification of parts could happen here and it could be a complete or
  • 03:05 partial failure.
  • 03:06 The damage to the parts could be due to excessive handling or over processing.
  • 03:10 We're doing some unwanted action that allows damage to occur,
  • 03:14 such as spilling a cup of coffee on the kit.
  • 03:17 The next step was to clean the bottom barrel.
  • 03:19 The success criteria is to remove dirt and
  • 03:22 contaminations and the failure is just the opposite, to not remove everything.
  • 03:26 In addition to complete and partial failure,
  • 03:29 we considered two other failure types.
  • 03:31 Those were intermittent failure, sometimes clean, sometimes not, and over processing,
  • 03:36 the wasted time and effort of cleaning things that were already clean.
  • 03:40 A second success criteria for this step is that the barrel is prepped and
  • 03:44 ready for the application of the decal.
  • 03:46 We've already talked about a dirty surface, the other concern for
  • 03:50 prepping is a damaged surface.
  • 03:52 This could be due to an unwanted action that damages the part, or
  • 03:55 excessive cleaning that creates the damage.
  • 03:58 The third step is to apply the decal.
  • 04:01 The success criteria is to align the decal correctly,
  • 04:04 and bond the decal to the pen barrel.
  • 04:07 The alignment failure is easy to understand, it's placed incorrectly.
  • 04:10 This could be a complete failure or a partial failure.
  • 04:13 I annotated degraded performance to indicate the alignment starts
  • 04:17 drifting out of tolerance and the unwanted performance would
  • 04:20 be the application of a decal in a totally incorrect location on the pen.
  • 04:24 With respect to bonding it could be a complete failure of partial failure where
  • 04:28 the bonding process could damage the barrel.
  • 04:31 The failure types for complete and partial bond are obvious except for
  • 04:34 the out of sequencing failure for the partial bond.
  • 04:36 This is because if the bonding is attempted before the cleaning and prep,
  • 04:40 the bond will only be a partial bond.
  • 04:42 The damage barrel failure associated with the bonding process would include crushing
  • 04:47 the barrel while trying to set the bond, or
  • 04:49 taking some other action to improve the bond that actually damages the barrel.
  • 04:54 The final step in the failure I wanna discuss at this time is
  • 04:57 the decal inspection step.
  • 04:59 Now, notice failures in the decal alignment and
  • 05:03 bonding were discussed at that step.
  • 05:05 You want to make sure that you assign failures to the step where it actually
  • 05:10 occurs, not where it's found.
  • 05:11 The failure at this step is that an incorrect assessment is made concerning
  • 05:16 the correct placement of the decal.
  • 05:18 Essentially, failing good parts and passing bad ones.
  • 05:22 And there are numerous ways that this type of failure could manifest itself.
  • 05:27 Now, we'll take the results of the Function - Failure matrix and
  • 05:31 enter those into the Process FMEA form or file.
  • 05:34 As you can see, the first column is the process step.
  • 05:37 The second column is the functions that are performed at each step.
  • 05:40 And the third column is the failures that are associated with those functions.
  • 05:44 Just to be clear, when completing the Process FMEA,
  • 05:48 I would include all of the steps.
  • 05:50 I've abbreviated it here for training purposes.
  • 05:52 But you want to have every step included.
  • 05:56 The failures in the Process FMEA are based upon the functions to be performed
  • 06:01 at each of the steps in the process.
  • 06:03 Clarify the function, and the failure modes will typically become obvious.

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