What Is FMEA (Failure Mode and Effects Analysis)?
Also known as: failure mode and effects analysis, DFMEA, PFMEA
Definition
FMEA (Failure Mode and Effects Analysis) is a structured risk assessment that identifies how a product or process can fail, the effects and causes of each failure, and existing controls, then prioritizes actions to prevent the highest-risk failures.
FMEA (Failure Mode and Effects Analysis) Explained
An FMEA proceeds function by function. For each function the team lists potential failure modes, the effects those failures have on the customer or next operation, the potential causes, and the current prevention and detection controls. Each row is then rated on Severity of the effect, Occurrence of the cause, and Detection capability of the controls, each on a one to ten scale with ten always being worst. Design FMEA addresses the product; Process FMEA addresses the manufacturing process that builds it.
The traditional prioritization multiplies the three ratings into a Risk Priority Number from 1 to 1000. RPN has a well-known flaw: a severity 10 item with low occurrence and good detection may score below a severity 3 item with mediocre ratings across the board, even though the first can kill someone. The AIAG and VDA harmonized FMEA published in 2019 replaced RPN with Action Priority, a lookup table that returns High, Medium, or Low and explicitly weights severity, which is the direction most aerospace and defense programs have followed.
FMEA earns its cost only when it is done early and kept alive. Performed before design freeze or before process validation, it redirects cheap decisions. Performed after launch to satisfy an auditor, it becomes a document nobody reads. It should be revisited whenever the design changes, the process changes, a new failure appears in the field, or a similar product enters development, and the same failure modes should propagate into control plans and work instructions.
The most valuable output is the link to controls. Every high-priority failure mode should trace to a specific prevention control, ideally a poka-yoke that makes the failure impossible, or to a detection control with demonstrated capability. An FMEA whose control column says only inspection or operator training for its top-ranked items has identified risk without reducing it, which is the most common reason FMEA programs get characterized as paperwork.
Why It Matters
- Moves quality effort upstream, where a design or process change costs a fraction of a field failure or recall.
- Creates an auditable, structured risk record required by IATF 16949, expected under AS9100, and increasingly requested on defense programs.
- Drives specific control plan and work instruction content instead of leaving risk mitigation to individual judgment.
- Captures institutional failure knowledge so hard-won lessons survive the departure of the engineers who learned them.
In Practice
A PFMEA on a connector assembly rates a reversed-polarity failure at severity 9, occurrence 3, detection 4, giving an RPN of 108, which falls below the team's action threshold of 120. Under Action Priority logic, severity 9 with any meaningful occurrence lands in the High band and demands action regardless of the product. The team adds a keyed housing that physically prevents reversed insertion, occurrence drops to 1, and a failure that the RPN threshold would have waved through is eliminated by design.
Frequently Asked Questions
What is the difference between a DFMEA and a PFMEA?
A DFMEA analyzes the product design and asks how the design itself can fail to perform its function, assuming it is built correctly. A PFMEA analyzes the manufacturing and assembly process and asks how the process can fail to build the design correctly. They are complementary, and DFMEA outputs such as key characteristics should feed directly into the PFMEA.
Is RPN still used in FMEA?
Many organizations still use it, but the 2019 AIAG-VDA harmonized method replaced RPN with Action Priority tables that rank risk as High, Medium, or Low and give severity dominant weight. The change addresses RPN's core weakness, where a high-severity failure could score below an unimportant one. New programs should generally adopt Action Priority.
Related Terms
PPAP (Production Part Approval Process)
PPAP (Production Part Approval Process) is a standardized supplier approval package, originating in the automotive industry, that demonstrates a supplier's production process can consistently produce conforming parts at the quoted rate before shipments are authorized.
Poka-Yoke
Poka-yoke is a mistake-proofing technique that designs a process or fixture so a human error either cannot occur at all or is detected immediately, before it becomes a defect passed to the next operation.
Six Sigma
Six Sigma is a data-driven improvement methodology that reduces process variation and defects using statistical analysis, targeting a capability level of 3.4 defects per million opportunities, typically executed through the five-phase DMAIC cycle.
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