Pfmea Process

Process FMEA (PFMEA) — AIAG-VDA 2019

Goal

Identify and prioritise process risk before production — using the AIAG-VDA 2019 7-step approach — so that high-priority failure modes are eliminated or controlled before they reach the customer, and the result feeds directly into the Control Plan and Work Instructions.

Required Execution Checklist

• Scope defined: process step boundaries, model year, team assembled with cross-functional representation
• Process Flow Diagram (PFD) available and used as Step 2 input
• All process steps in the PFD have a corresponding entry in Structure Analysis (Step 2)
• Every process step has at least one Function defined in Step 3
• Failure chain complete for each function: Effect → Mode → Cause (in this direction — not reversed)
• All Failure Causes are evidence-based — no unverified assumptions used as final causes
• S/O/D ratings agreed by the cross-functional team and documented
• All Special Characteristics have S=9 or S=10
• Every H-AP item has a named owner, target date, and is tracked to closure
• PFMEA detection controls match the Control Plan; prevention controls match Work Instructions

When to use

• New process development (pre-production)
• Existing process change or transfer
• After a quality escape (update to reflect failure mode)
• Periodic review (IATF requires annual review or at change)
• Customer-specific requirement (Ford, GM, Stellantis, BMW, VW all require PFMEA)

Prerequisites

• Process flow diagram (PFD) — required for Step 2
• Product drawings with special characteristics identified
• DFMEA (if applicable) for effect severity reference
• Team: process engineer, quality engineer, production supervisor, maintenance

The 7-Step AIAG-VDA 2019 Approach

Step 1 — Planning and Preparation

Define the scope:

• FMEA header: part number, part name, model year, process step scope, revision, date, team
• Analysis boundary: which process steps are in scope (start point and end point)
• Timeline: new PFMEA or revision of existing?

Prepare:

• Process Flow Diagram (PFD) — this drives Steps 2 and 3
• List of Special Characteristics (SC) from the drawing (symbols: ◆ ★ ⬟ vary by customer)

Step 2 — Structure Analysis

Map the process hierarchy:

Process Item (e.g., Steering Column Assembly Line)
└── Process Step (e.g., Station 3 — Torque tightening)
    └── Work Element (e.g., Pneumatic driver, torque wrench)

For each process step, identify the 4M inputs: Man, Machine, Method, Material.

This structure becomes the "what can go wrong" framework in Step 4.

Consistency check: Every Process Step defined here must have at least one Function defined in Step 3. A process step with no function is incomplete — it cannot be analysed for failure in Step 4.

Step 3 — Function Analysis

For each process step and work element, define:

• Process function: what should happen? (verb + noun + measurable characteristic)
  • Example: "Tighten bolt M8 to 22 ± 2 Nm"
• Product characteristic: what product feature results from this step?
  • Flag all Special Characteristics (SC) — these get highest attention in D/O/D ratings

Functional chain:

Work Element function → Process Step function → Product Characteristic
(tool applies torque) → (bolt is tightened to spec) → (joint meets strength requirement)

Step 4 — Failure Analysis

For each function, identify the failure chain: Failure Effect → Failure Mode → Failure Cause

Work in this direction (Effect first, then Mode, then Cause):

Failure Effect (FE): what is the impact on the customer (internal or end user)?

• End-user effect (most severe): safety, regulatory non-compliance, loss of function
• Manufacturing effect: rework, scrap, line stoppage, warranty

Failure Mode (FM): how does this process step fail to perform its function?

• Example: "Bolt torqued too low", "Part installed backwards", "Incorrect material loaded"

Failure Cause (FC): what causes the failure mode?

• Machine: "Torque wrench not calibrated", "Air pressure drop"
• Man: "Work instruction not followed", "Untrained operator"
• Method: "Incorrect torque value in WI", "No torque verification step"
• Material: "Wrong bolt grade loaded", "Lubrication not applied"

Multiple causes per failure mode are normal — each FC gets its own row.

Failure Cause validation: Failure Causes must be supported by objective evidence or structured root cause analysis (e.g., 5-Why). Unverified assumptions — "probably," "may be," "could be" — must not be entered as final Failure Causes. For post-escape PFMEA updates, the FC must match the validated root cause from the 8D or CAPA, not a revised opinion.

Step 5 — Risk Analysis (Action Priority)

For each FC row, assign three ratings:

Severity (S) — impact of the Failure Effect on the customer

Severity rates the EFFECT, not the mode or cause. S=10 or S=9 means you must act regardless of O and D.

Occurrence (O) — likelihood the Failure Cause leads to the Failure Mode

O considers prevention controls already in place (poka-yoke, SPC, incoming inspection of material).

Detection (D) — effectiveness of detection controls before product reaches next customer

D considers detection controls already in place (gauging, inspection, poka-yoke).