FMEA and PFMEA: catching the defect before it exists
It is the only tool on this list that works on a defect that has not happened yet. Which is why it is the one most often filled in out of obligation and least often actually used.
FMEA, failure mode and effects analysis, is a structured method for identifying the ways a process or product can fail, scoring the risk of each one, and prioritizing action before the failure reaches the customer. Applied to a manufacturing process it is called PFMEA; applied to the design it is DFMEA.
The three numbers that set priority
- Severity
- how serious the effect is for the customer. This one rarely comes down without a redesign.
- Occurrence
- how often the cause is expected. This is where poka yoke and process control hit.
- Detection
- how likely you are to catch the failure before it ships. Improving only this is the most common mistake.
- 01 Build the team before the form An FMEA written by one person is an opinion in a table. You need process, quality, maintenance and someone from the floor.
- 02 Describe the failure mode in plant language Not "dimensional nonconformity". Instead: "the part comes out 0.3 mm long and will not seat in the assembly".
- 03 Score against written criteria, not against a feeling If your severity scale is not defined in a table everyone reads the same way, the numbers are not comparable across lines.
- 04 Attack occurrence before detection Lowering detection only means you will find more defects. Lowering occurrence means you will make fewer.
- 05 Reopen it whenever something changes New supplier, new tooling, new shift, new volume. An FMEA untouched for two years does not describe your current process.
- Filling it in the week before the audit and filing it the week after.
- Using different scales on each line, which makes risk impossible to compare.
- Listing actions with no owner and no date, the most common way an FMEA dies.
- Forgetting that a closed 8D should come back as an FMEA update. That is where the loop closes.
I run it tied to problem solving, never as a standalone document. Every 8D your team closes should modify the FMEA, and every high risk failure mode should have a real action behind it, usually a poka yoke or a control change. That linkage is what turns the form into a system.
This lives inside Problem solving and continuous improvement
What is the difference between FMEA, PFMEA and DFMEA?
FMEA is the general name. PFMEA analyzes the manufacturing process. DFMEA analyzes the product design. On the plant floor you are almost always working PFMEA.
Is RPN still used?
Plenty of plants still use it, and the AIAG-VDA standard replaced it with action priority, which weighs severity, occurrence and detection together instead of multiplying them. I work with whichever one your customer asks for.
How often should it be reviewed?
Whenever something in the process changes, and at the close of every 8D. If your only review date is the annual audit, the document is permanently behind reality.
What is holding your operation back today?
Tell me the concrete problem. I will tell you whether it is mine to solve or someone else’s, and what I would do first.