Failure Mode Effects Analysis (FMEA) is a tool that helps us anticipate what might go wrong with a product or process. We can also use it to identify the possible causes and probabilities of failures.

A failure mode is a chance for a process to go wrong. Or, to look at it another way, it’s an opportunity for a defect or variation to occur in a product.

Every process has potential weak spots. If we can recognize these in advance, we go a long way toward minimizing the damage caused. That’s why FMEA is such a handy tool.

Perform a FMEA when you’re:

The analysis can be of use in all of these situations.

You can use a FMEA in the Analyze and Improve phases of a DMAIC project, which will depend on the purpose of your project.

If your project aims to find issues in an existing process, then you’ll perform the FMEA in the Analyze phase. This is to help you figure out where things are already going wrong.

If your project has another aim鈥搊ther process improvements, adding a new process, etc.鈥搕hen the FMEA’s use is a bit different. Then, you’ll use it in the Improve phase to look for issues in your solution to the problem. You’re essentially double-checking yourself.

A DFMEA focuses on a product or service. You’ll typically do these before you put a new product or service into manufacture or when you change the design of either. When you perform one, you look at potential failures, safety issues, and regulatory concerns with the end product. Then you rank the severity of these. The next step is to find causes for those potential issues.

Use a DFMEA to minimize the effects of product failure on your customers. By the end of your DFMEA, you should have strategies in place to correct all design issues identified.

A PFMEA looks at a process. Unlike a DFMEA, it looks at the end product or service only to find issues with the process that produced it. More commonly, you’ll look at the output from the process instead. Why are these two things different? Because most products and services are the result of multiple processes, not just one. For example, a digital camera has many parts, each of which is produced using at least one process鈥搊ften more. To find an issue with the shutter, for example, you’d look at processes that produce the shutter and processes that fix the shutter into the camera.

Start a PFMEA at or after the feasibility study and before production begins. Typically, you’ll perform a PFMEA after the DFMEA, as the latter is focused on design, and the PFMEA is focused on how you bring the design to life.

Also known as a functional FMEA (FFMEA). A System Failure Modes and Effects Analysis looks at the entire system on a high level. When you perform one, you look at things like the interrelationships between components and processes. An SFMEA can be useful because problems don’t just occur within processes or specific machines. They also occur between multiple processes or machines.

Perform a SFMEA before the design phase where possible. This helps you to anticipate and work through issues that would otherwise affect your DFMEA.

Further reading on SFMEAs

Your inputs for an FMEA typically come from people who know the process, product, service, or system very well. You’ll usually sit down and brainstorm potential failure points with these subject matter experts.

During the FMEA process, you’ll need to provide three key scores:

These all use a scale from 1 to 10. You’ll note that these are somewhat subjective – you can’t simply use a tool to measure any of them. If you find that your team has trouble reaching a consensus on the scorings, try taking individual scores and calculating the mean score for each.

Note: Some people use a scale of 1-5 instead. As long as you’re consistent, the scale you use isn’t too important.

The main output from an FMEA is a Risk Priority Number (RPN) for each failure mode. The RPN is an objective priority measure for fixing any failure mode or failure mode effect. The bigger the RPN, the higher the priority.

The formula for calculating an RPN is:

The first step in creating a failure modes and effects analysis is understanding your goal. We’ve listed the basic types of FMEA above; read through these and decide on what type of analysis you’ll be performing and what the end result should be.

Your preliminary work will depend on the analysis you plan to perform. Essentially, you need to ensure that the whole team understands what you’re analyzing so that you can brainstorm potential failure modes.

So you’ve created your FMEA document. Your job doesn’t finish there. Next, look at ways that your team can modify the product, service, system, or process to decrease RPN scores.

It would be overly simplistic for this article to suggest always working on the highest-scored (hence, highest priority) failure modes first. However, that can be done in a vacuum. Other sort-orders are possible. For example, ASQ recommends “The team should use their experience and judgment to determine appropriate priorities for action.” (source)

Once you’ve lowered the risks of failure modes as much as is feasible, add two more columns to the FMEA:

Then:

A company is putting together a new customer support department. As part of that process, it’s developed a number of processes for various customer queries. The Level 2 support team must complete a design FMEA for one of its processes.

The team’s process analyst puts together a flowchart of the process. It shows the team five high-level steps in the process:

The team lead uses Excel to create a spreadsheet for the FMEA.

They add the five high-level process steps to the FMEA table.

The team sits down together with the incomplete FMEA table. They discuss the process steps and brainstorm things that could go wrong. Once they’ve talked through all options, they enter the agreed failure modes.

The team record effects of each failure mode, sticking to objective measures that affect KPIs.

While some situations might require a tree diagram or other tools to chart potential causes, the team decides that this situation doesn’t need anything too complex. They record causes where the issue would reasonably originate in the customer service teams.

The team used a simple discussion method to score Severity, Occurrence, and Detection for each failure effect. Then, they calculate the RPN for each by multiplying the three scores.

The team sorts the spreadsheet from highest to lowest RPN.

Now that the team has a prioritized list of failure modes, it can get to work on mitigating them. Beginning at the top of the list, they’ll work on decreasing the RPN: by making the failure less severe or less likely to occur. On the other hand, making it harder to detect isn’t generally recommended.

Once the team has decreased the RPNs for its FMEA as much as possible, it adds a basic response plan for each failure mode.

Step-by-step guide.

Question: A Six Sigma team has been chartered to improve the way in which a company takes orders for its products. Which of the following tools should the team use to determine all of the potential pitfalls and the actual defects that occur? (Taken from ASQ sample Black Belt exam.)

(A) Process failure mode and effects analysis(B) Process map(C) Design for six sigma(D) Supplier input process output control

Answer:

Question: A black belt is developing a failure mode and effects analysis (FMEA) for the hamburger preparation station in a fast-food restaurant. The following ratings were developed for the low-heat temperature failure mode.

Severity = 9Occurrence = 2Detection = 1

What is the risk priority number (RPN) for this FMEA?

(A) 4(B) 6(C) 12(D) 18

Answer:

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