A design failure mode and effects analysis: a structured review of how a product's design could fail to do its job, the effects, the design causes and the controls, rated for severity, occurrence and detection so the highest risks are acted on before release.

What is the difference between a DFMEA and a PFMEA?

A DFMEA looks at failures of the design, assuming the part is made to the drawing. A PFMEA looks at how the manufacturing process could fail to make it to the drawing. Design risks feed the process FMEA through special characteristics.

How is the RPN calculated?

RPN = severity × occurrence × detection, each rated 1 to 10, so it runs from 1 to 1,000. It ranks risks for attention; it is not a pass mark, and every severity of 9 or 10 needs attention whatever the RPN.

What is action priority (AP)?

The AIAG-VDA FMEA handbook replaced ranking by RPN with action priority tables that give each combination of S, O and D a high, medium or low priority. The template has a column for it if your customer uses the AIAG-VDA method.

Who should be on a DFMEA team?

Design engineering, test or validation, manufacturing, quality, and someone who knows how the product is used and fails in the field. Suppliers of key components can join for their parts.

Free template

Design FMEA (DFMEA) template

A design FMEA (DFMEA) is a structured look at how a product's design could fail to do its job, what the effect would be, what would cause it, and what the design and its verification do to prevent or find it, before the design is released. Each failure mode and cause is rated for severity (S), occurrence (O) and detection (D) from 1 to 10, and the highest risks get actions. It assumes the part is made to the drawing; how the process could fail to make it to the drawing belongs in the process FMEA. This template has the worksheet with a class column for special characteristics, item and function, failure mode, effects, causes in the design, prevention and detection controls, S, O, D, RPN (S × O × D) and action priority, the recommended action with owner and date, and S, O, D and RPN again after the action. Page 2 has more rows and a general rating guide for design risks. The Excel version works out the RPN, flags every severity of 9 or 10 and any RPN at or above your review level, and counts open actions.

Free to use: print it, copy it and edit it for your team. Enter your name and work email once to download.

Page 1 of the design FMEA template: fields for the system or part, part number, DFMEA number and team, a key for S, O, D, RPN, AP and class, and a wide worksheet with columns for item and function, failure mode, effects, severity, causes, occurrence, controls, detection, RPN, actions and ratings after action. — Item, function and requirementFailure modes and effectsDesign causesPrevention and detection controlsS, O, D, RPN and APActions and ratings afterDesign rating guide

When to use it

When to use a design FMEA

On a new product or a new use of an existing one, while the design can still change cheaply.
When a design changes: new material, new supplier of a key component, a new operating condition.
When your customer asks for one, as in an automotive PPAP where you are responsible for the design.
After a field failure, to find the other failure modes the same weakness could cause.

How to fill it in

1
Set the scope
The system, subsystem or part, the design responsibility and a cross-functional team: design, test, manufacturing, quality and someone who knows the field.
2
List the functions
What each item must do, with the requirement: holds 200 N, seals to 2 bar, runs at 60°C. Failure modes are the ways each function is not met.
3
Work out effects and causes
For each failure mode, the effect on the user or the product, and the design causes: wrong material, tolerance stack, too little clearance.
4
Rate S, O and D
Use the rating guide, or your customer's tables. Severity rates the effect, occurrence the cause with today's prevention, detection how likely verification is to catch it before release.
5
Act on the highest risks
Every severity of 9 or 10 first, whatever the RPN, then the highest RPNs or action priority H. Give each action an owner and a date.
6
Rate again
Once the action is proven, rate S, O and D again. Keep the DFMEA as a living document and update it with every design change.

A filled-in example

Illustrative, not a benchmark

An example: one line from a DFMEA for a hose connector (illustrative).

Function: seal the joint at up to 2 bar. Failure mode: leaks at the joint. Effect: fluid loss, the product stops working. S = 8.
Cause: O-ring groove too shallow for the O-ring's tolerance. Prevention: design rule for squeeze. O = 5.
Detection: pressure test on prototypes after design freeze. D = 7. RPN = 8 × 5 × 7 = 280.
Action: tolerance stack on the groove and O-ring, groove depth changed, pressure and temperature test on the first samples.

After the change and the early test: S stays 8, O = 3, D = 3, RPN = 72. Severity stays the same because the effect of a leak has not changed; only a design change that removes the leak path would lower it.

Common mistakes

Mixing design and process causes
"Operator fits the wrong O-ring" is a process cause. Keep it for the PFMEA, and assume the part is made to the drawing here.
Treating the RPN as a pass mark
An RPN of 120 can hide a severity 10. Deal with high severity first, whatever the number.
Filling it in after the design is frozen
A DFMEA done to satisfy a customer after release changes nothing. Start it while the design can still change.
Lowering severity with a test
A test finds a problem; it does not make the effect less severe. Only a design change lowers severity.

Download the template

Free to use: print it, copy it and edit it for your team. Enter your name and work email once to download.

Run this template in LeanSuite

In LeanSuite defects are logged as tags, ranked in the QA Matrix, and systemic ones become CAPA projects with approvals, root cause analysis and an action plan.

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