A FMEA (Failure Mode Effects Analysis) is a tool that helps us anticipate what might go wrong with a product or process as well as identify the possible causes and probabilities of failures.
Steps of the FMEA
- Recognize and evaluate potential failure modes
- Use Risk Priorities Numbers to evaluate the modes.
- Identify the cause of failure
- Identify the actions which could prevent failures
- Document ideas of the team
Risk Priority Number (RPN)
RPN is used to weight the probability and criticality of a failure occurring.
Severity means the possible impact/effect to the system.
A Risk Priority number multiplies the severity, occurrence, and detection numbers for each failure mode.
RPN = Severity * Occurrence * Detection.
Types of FMEA
- performed at the design level to analyze how the failure modes affects the system and to minimize the failure effects.
- Used before products are released to the manufacturing process.
- All anticipated design deficiencies should be detected and corrected by the end of this process.
- started before or after the feasibility stage, prior to production tooling
- Usually after a Design FMEA, but it could be some time before production activities start up.
- Should take place before manufacturing begins.
- accounts for all manufacturing operations.
- If a defect does occur during manufacturing, you should check to see if there is an unaccounted for failure mode occurring.
- Comprised of parts.
- all of the part level FMEAs will tie together to form the system.
- Lower into the system, more detail.
- Known as a black box FMEA
- focuses on the performance of an intended portion or device rather than the characteristics of the individual parts.
- Ex. Does it work instead of color must be blue.
All types of FMEA can be applied to software systems.
Additional FMEA resources
Six Sigma Black Belt Certification FMEA Questions:
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.)
Answer: (A) Process FMEA. While a process map is a helpful tool to visualize what is going on, it just indicates the current process and does not detail all of the problems that could occur. Design for Six Sigma might detail the actual defects in a current process before designing a new one but you wouldn’t go through all of that effort just for this one task. A SIPOC diagram can be great input into such a list, but that’s not it’s main purpose.
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 = 9
Occurrence = 2
Detection = 1
What is the risk priority number (RPN) for this FMEA?
Answer: (d) A Risk Priority number multiplies the severity, occurence, and detection numbers for each failure mode. In this case, 9 * 2 * 1 = 18.