BACK TO BASICS
It's Fun To Work With an F-M-E-A
Prevent defects, enhance safety and increase customer satisfaction
by Kristen Johnson, assistant editor
A failure mode and effects analysis (FMEA) is a systemized group of activities intended to recognize and evaluate the potential failure of a product or process, identify actions that could eliminate or reduce the likelihood of the potential failure occurring and document the entire process.1
FMEAs help manufacturers prevent defects, enhance safety and increase customer satisfaction. Most are conducted in the product design or process development stages, but conducting an FMEA on an existing product and process can also be beneficial.2
The main objective
An FMEA looks for all the ways a process or product can fail. For example, a toaster could fail in several ways:
There is a short in the power cord.
The coils burn the bread no matter which setting is used.
The pop-up mechanism is too sensitive and flings toast onto the counter.
Failures can also occur when the user makes a mistake, and it is wise to include both types of failures in an FMEA. Anything that can be done to assure the product works correctly, regardless of how the user operates it, will move the product closer to 100% satisfaction.3
A product/design FMEA can uncover problems that will result in safety hazards, product malfunctions or a shortened product life. They key question to ask here is, "How can the product fail?" A process FMEA uncovers process problems related to the manufacture of the product. The key question to ask here is, "How can process failure affect the product, processing efficiency or safety?"4
10 steps for an effective FMEA
1. Review the process: Gather a team of four to six (be sure to include people with various job responsibilities and levels of experience) and give each member a copy of the product's blueprint. Also, have the team operate the product so all members can become familiar with the way it works.
2. Brainstorm potential failure modes: Look at each component of the product and identify ways it could potentially fail.
3. List potential effects of each failure mode: List the potential effect of each failure next to the failure. If a failure has more than one effect, write each in a separate row.
4. Assign a severity rating for each effect: Give each effect its own severity rating (from 1 to 10, with 10 being the most severe). If the team can't agree on a rating, hold a vote.
5. Assign an occurrence rating for each failure mode: Collect data on the failures of your product's competition. Using this information, determine how likely it is for a failure to occur and assign an appropriate rating (from 1 to 10, with 10 being the most likely).
6. Assign a detection rating for each failure mode and effect: List all controls currently in place to prevent each effect of a failure from occurring and assign a detection rating for each item (from 1 to 10, with 10 being a low likelihood of detection).
7. Calculate the risk priority number (RPN) for each effect: Multiply the severity rating by the occurrence rating by the detection rating.
8. Prioritize the failure modes for action: Decide which items need to be worked on right away. For example, if you end up with RPNs ranging from 50 to 500, you might want to work first on those with an RPN of 200 or higher.
9. Take action to eliminate or reduce the high risk failure modes: Determine what action to take with each high risk failure and assign a person to implement the action.
10. Calculate the resulting RPN as the failure modes are reduced or eliminated: Reassemble the team after completing the initial corrective actions and calculate a new RPN for each failure. Then you may decide you've taken enough action or you want to work on another set of failures.
- Chrysler, Ford and General Motors, Quality System Requirements, QS-9000, third edition (Southfield, MI: AIAG, 1998).
- Robin E. McDermott, Raymond J. Mikulak and Michael R. Beauregard, The Basics of FMEA (New York: Quality Resources, 1996).