How to complete a Design FMEA

Design Failure Mode and Effects Analysis (DFMEA) is a structured analysis of how a product design could fail to meet its intended function or requirement. The design-responsible organization owns it; manufacturing, quality, suppliers, service, and test specialists provide essential input.

Choose the method before you start: Use the FMEA format and method required by your customer and organization. A traditional AIAG-style form commonly uses Severity, Occurrence, Detection, and Risk Priority Number (RPN). The AIAG & VDA FMEA method uses a structured seven-step approach and Action Priority (AP). They are not interchangeable templates.

Traditional DFMEA: what belongs in each column

Item / function: Identify the component, interface, or design element, then state what it must do. Include the operating condition and requirement. “Housing” is an item; “seals fluid at the specified pressure and temperature” is a useful function.
Potential failure mode: State how the function could fail: leaks, cracks, deforms, has insufficient output, loses retention, or produces an incorrect signal. Do not enter the cause here.
Potential effects of failure: Describe the consequence of the failure at the next level, vehicle, manufacturing operation, or end user. Use factual language: loss of braking assist, fluid leak, assembly interference, customer complaint, or regulatory nonconformance. This is the basis for Severity.
Severity (S): Assign the required rating based on the effect, using the customer or organization’s approved criteria. Do not reduce Severity because a control is strong; controls affect occurrence or detection, not the consequence if the failure occurs.
Potential causes / mechanisms: State the specific design reason the failure could occur: insufficient wall thickness, incompatible material, tolerance stack-up, inadequate heat dissipation, incorrect requirement, or interface mismatch. “Poor design” is not a cause.
Occurrence (O): Assign the required rating based on the likelihood of the cause or mechanism. Use evidence from analysis, testing, comparable designs, and lessons learned—not a preferred target score.
Current design prevention controls: List what prevents or reduces the cause: design standards, calculations, tolerance analysis, material selection rules, requirements reviews, or design rules. Planned controls should be identified as planned until complete.
Current design detection controls: List what can detect the cause or failure before release: design review, simulation, verification test, prototype test, or validation test. A detection control does not prevent the cause.
Detection (D): Use the approved rating criteria for the likelihood that the listed detection controls will find the problem before release. Do not rate a control that has not been performed.
RPN / recommended actions / responsibility / due date: Where your form uses RPN, calculate it from the approved ratings and follow your organization’s escalation rules. Define a specific action, accountable owner, due date, and completion evidence. The action should reduce the cause or improve detection; then reassess the affected ratings.

AIAG/VDA DFMEA: what changes

The AIAG & VDA approach organizes the work into seven steps: planning and preparation; structure analysis; function analysis; failure analysis; risk analysis; optimization; and results documentation. Instead of treating the worksheet as a list of independent rows, it traces a chain from structure to function to failure to cause to prevention/detection control.

Structure analysis: define the system, subsystems, components, and interfaces. This answers “what is being analyzed?”
Function analysis: define functions and requirements for each structure element and interface. This answers “what must it do?”
Failure analysis: connect failure effects, failure modes, and failure causes in the proper direction. This answers “what can go wrong, and why?”
Risk analysis: assess Severity, Occurrence, and Detection using the applicable criteria, then use the AIAG/VDA Action Priority table rather than automatically relying on RPN ranking.
Optimization and results: document prevention or detection actions, responsible owner, due date, evidence of completion, revised assessment, and communication to the next APQP activity.

Practical DFMEA workflow

Freeze the design scope, current requirements, interfaces, assumptions, and revision level being analyzed.
Bring design, test, manufacturing, quality, supplier, service, and reliability knowledge into the review at the right time.
Write functions before writing failure modes. Weak functions produce generic, unhelpful FMEAs.
Use historical failures, warranty data, test results, simulations, design rules, and lessons learned as evidence.
Assign and close actions with objective evidence. A “completed” action with no design change, analysis, or test result is not evidence.
Communicate relevant product characteristics, interfaces, and residual design risks to the PFMEA and Control Plan owners.

Build and maintain linked FMEAs

QA Assistant Studio MAX supports Design FMEA, Process FMEA, process flow, Control Plan, and work-instruction documents, with linked-information reviews and controlled document history.

Explore linked APQP documents

For the PPAP-specific DFMEA completion guide, see DFMEA deliverable guide. Use the current customer-required FMEA method and licensed reference manual for ratings, action priority, and form requirements.