Strengths, Weaknesses, Benefits

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The Failure Mode and Effects Analysis (FMEA) methodology assesses risks from the standpoint of susceptibility, occurrence, and detection. The methodology has both strengths and weaknesses.

Quick reference

Strengths, Weaknesses, Benefits

The Failure Mode Effects Analysis has strengths and weaknesses.  Understanding these will ensure that it is applied correctly for maximum benefits.

When to use

The strengths, weaknesses and benefits of the FMEA methodology are inherent in the methodology and apply whenever it is used.

Instructions

FMEA is a structured and documented analytical technique for identifying technical risk in a product or process design, analysing that risk, scoring it, and prioritizing the risks.  With this analysis, a design team can decide upon the needed design improvements.  Also, if this analysis has been completed, a problem solving team can review the analysis to gain insight on likely root causes for the problem they are solving.  The structured process asks the question, “What?” in a a variety of ways.

  • What could go wrong?
  • What is the effect if it goes wrong?
  • What could cause that?
  • What counter measures exist?
  • What can be done to improve?

This analysis starts with the function of the product or process step.  It identifies the failure modes associated with that function.  Then it analyses the failure mode from three perspectives: the severity of the failure, the likelihood of that failure occurring, and the ability of the user/operator to detect when the failure is about to occur and to take an appropriate action to prevent or control the failure.  Each of those three attributes are scored from 1 to 10 with the higher the score, the worse the failure mode.  The three scores are multiplied together to create a Risk Priority Number (RPN) which is used to prioritize all the failure modes.  A business can then decide if the risk is too high and mitigation should be done, or if the risk is acceptable.

The analysis follows this pattern:

Like any technical analysis, there are strengths and weaknesses or limitations to its use.  These strengths and weaknesses are summarized in these tables:

The use of an FMEA provides significant benefits for a business.  Businesses do not have infinite resources, so this allows them to prioritize the failure risk mitigation actions based upon which failures have the highest RPN score.   The RPN can also provide a means of doing a relative assessment of the benefit of implementing mitigation actions.  While the primary benefit is during product or process design, an FMEA can also help after a product or process goes in production.  If a problem arises, the FMEA indicates likely causes and a Lean Six Sigma team can use this during the Measure Phase to know where to look and collect data.  Likewise, whenever product or process changes occur, such as during a Lean Six Sigma Improve Phase, the changes can be used to update the FMEA and a quick assessment can be done of any unintended consequences.

Hints & tips

  • There are many different types of FMEAs and they are tailored to the application.  We will focus on the two most commonly used, Design FMEA and Process FMEA.  The other types are special cases of these two.
  • Although the scoring is quantitative, it is based upon qualitative or subject assessment of the failure and failure conditions.  Therefore the FMEA analysis team needs subject matter expertise, but they also need to be able to interact and communicate with each other with respect.  I have seen teams where “dueling experts” could not agree on scores and the team would be stuck in arguments for hours.  A facilitator is often needed when first introducing this technique.
  • If you have a complex product or process that will likely have a long lifecycle, the FMEA is a critical design deliverable.  Over time, the people who developed the design will move on to other things and those who now have responsibility will often not have the same level of knowledge and expertise in the product.  The FMEA shows them where problems can occur and which features or process steps are most critical.
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  • 00:04 Hi, I'm Ray Sheen.
  • 00:06 So let's talk about an analytical technique for evaluating and
  • 00:09 prioritizing technical risks, the Failure Mode Effects Analysis.
  • 00:15 I'll highlight some of the strengths, weaknesses, and benefits.
  • 00:18 Let's start with a high-level description of what an FMEA is.
  • 00:24 An FMEA is a structured, systematic method, for identifying technical risks,
  • 00:28 documenting key characteristics of those risks, prioritizing the risks, and
  • 00:33 tracking any risk resolution activities.
  • 00:36 One way to think of an FMEA,
  • 00:38 is an organized way to ask questions about the product or process.
  • 00:43 What could go wrong?
  • 00:45 What is the effect on the user or the system when something does go wrong?
  • 00:49 What could cause this to happen?
  • 00:50 What counter-measures are available to react to provide protection
  • 00:54 when something goes wrong?
  • 00:55 And finally, what can we do to improve the situation?
  • 00:59 As these questions are answered, the FMEA provides a structured way to record
  • 01:03 the answers, score the answers, and then prioritize improvement opportunities.
  • 01:08 So let me illustrate how an FMEA works.
  • 01:11 We start by creating a list of functions.
  • 01:13 A product does something, or a process step performs an action.
  • 01:18 For each function we identify what could go wrong with that function.
  • 01:22 We failed to perform it, or it is performed incorrectly.
  • 01:25 Now we will take that function failure combination, and score it in three ways.
  • 01:29 First is to score the severity.
  • 01:32 If it goes wrong, so what?
  • 01:34 Do people die?
  • 01:35 Wow, that's severe, we give that a 10.
  • 01:38 Is it such a minor irritation that most people still don't even notice it?
  • 01:41 Well, in that case, we'll score it as just a 1 or 2.
  • 01:45 Next, we consider the likely causes, and
  • 01:47 score the probability of each of those occurring.
  • 01:50 If there is a high likelihood, we will score it a 10.
  • 01:53 If it never happens, we score it 1.
  • 01:56 Finally, we consider the design and application, and score it on
  • 02:00 the ability to detect a problem with time or capacity to react to the problem.
  • 02:05 If we can't detect until the damage is done,
  • 02:07 that would give us a high score of 9 or 10.
  • 02:10 If we determine the problem and can easily and immediately fix it or avoid it, well,
  • 02:15 we'll give that 1 or 2.
  • 02:16 Next, we multiply those three scores together to get a risk priority
  • 02:20 number or RPN.
  • 02:21 And normally, we're documenting all of these items in a spreadsheet or
  • 02:25 other form created by your company.
  • 02:28 Before we dig into the mechanics of setting up and
  • 02:31 scoring an FMEA, we should recognize the strengths and weaknesses of this method.
  • 02:35 Let's first look at the strengths.
  • 02:37 This is a structured approach that is focused on improving a product or
  • 02:41 process design.
  • 02:42 Through the scoring, we can establish a magnitude value for the attribute of risk,
  • 02:47 and actions required.
  • 02:48 While it is normally used with the design of new products or processes.
  • 02:53 You can also use it for
  • 02:54 evaluating the impact of changes with existing products and processes.
  • 02:59 We can use this to prioritize actions.
  • 03:02 It is also a good way to communicate cross functionally, and
  • 03:05 to communicate over time.
  • 03:07 When a problem occurs in an existing product or process, the FMEA,
  • 03:11 developed when it was first designed, can provide insight into likely causes.
  • 03:16 Another strength is that you don't have to wait until the product is fully designed,
  • 03:20 developed, and in production, to start doing the analysis.
  • 03:23 It can be done with preliminary information.
  • 03:26 But now let's look at the weaknesses or limitations of an FMEA.
  • 03:29 The tendency with an FMEA, is to focus on compensating for problem, and
  • 03:34 not the elimination of a root cause.
  • 03:37 While the scoring is numerical,
  • 03:38 the assignment of the score is a judgment call.
  • 03:41 I'll provide some guidance which is normally used in later lessons, but
  • 03:45 different people will often score a failure mode differently.
  • 03:49 Normally not major differences, but different.
  • 03:52 Large or complex products and
  • 03:54 processes, will require a lot of time to complete an FMEA.
  • 03:58 You'll need to evaluate each failure mode of each function, and
  • 04:02 all of the potential causes.
  • 04:03 An FMEA does rely on a team with subject matter expertise, so
  • 04:08 that they know how the parts in process works.
  • 04:11 If they don't have that expertise, their scoring would be meaningless.
  • 04:15 And finally, the required changes or solutions to high scoring failure modes,
  • 04:20 may be so late and difficult that they become unworkable.
  • 04:24 This becomes an issue when the FMEA is being used inflexibly late in the process,
  • 04:29 and the business is not able to make a calculated risk
  • 04:31 to accept a high-scoring failure mode.
  • 04:35 The bottom line is that the FMEA is an important and valuable technique, for
  • 04:39 improving the technical quality of new products and processes.
  • 04:43 But the limitations must be acknowledged, so
  • 04:45 that the use of the tool is appropriate and effective.
  • 04:49 So let's wrap this up with a few more of the benefits associated with using
  • 04:53 an FMEA.
  • 04:54 There are different versions of an FMEA.
  • 04:57 This allows you to pick the one that best suits your application.
  • 05:00 In this course we'll focus on the two most commonly used FMEAs, the Design FMEA and
  • 05:05 the Process FMEA.
  • 05:06 The design FMEA, is focused on features and
  • 05:08 failures from the standpoint of the customer/user.
  • 05:12 And the process FMEA looks at process steps, equipment, and
  • 05:15 procedures to consider failures to process performance.
  • 05:20 The FMEA is not only helpful in the design of the processes, it is very useful for
  • 05:24 the problem solving process for product and processes that are in production.
  • 05:29 When a failure occurs,
  • 05:30 the FMEA should be reviewed to quickly identify potential root causes.
  • 05:34 If a product has been in production for several years, the original designers may
  • 05:38 no longer be around, but their thought process is captured in the FMEA.
  • 05:43 Which means that the tool is very helpful for Lean Six Sigma projects.
  • 05:47 Both in the Measure phase when trying to decide what data to collect, and
  • 05:51 in the Improve phase to ensure that the solution does not create new,
  • 05:54 unintended consequences.
  • 05:56 You can also use the FMEA, to create a relative score for
  • 06:00 different improvement options.
  • 06:02 And by comparing those scores of the revised RPN values for
  • 06:05 the different options, select the one that best suits the situation.
  • 06:11 The FMEA is a powerful methodology for designing quality into a product or
  • 06:16 process.
  • 06:17 It does have its limitations, but
  • 06:19 if you're aware of those, you can apply this tool appropriately.

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