fmea-process

name	fmea-process
description	Process FMEA (PFMEA) — failure mode identification, RPN calculation, severity/occurrence/detection ratings, AIAG-VDA FMEA handbook, control plans, mistake-proofing (poka-yoke), FMEA linkage to design FMEA and control plans.
metadata	{"priority":7,"promptSignals":{"phrases":["process FMEA","PFMEA","AIAG FMEA","RPN calculation","failure mode effects analysis","poka yoke"],"minScore":3}}

Process FMEA (PFMEA) — Complete Skill

PFMEA Overview

Purpose: identify potential process failure modes; assess effects, causes, and controls; prioritize action Scope: manufacturing and assembly processes; service processes; not product design (that is DFMEA) Standards: AIAG-VDA FMEA Handbook (2019); IATF 16949 requirement; AS9100 (aerospace); FDA 21 CFR 820 (medical devices)

PFMEA team (cross-functional): Manufacturing engineer + Quality engineer + Process engineer + Design engineer + Supplier (if applicable) Facilitator: experienced FMEA practitioner; minimum 4 hours per process step typical

PFMEA Seven-Step Approach (AIAG-VDA 2019)

Step 1: Planning and Preparation

Define scope: boundary diagram (process flow); level of analysis (operation, sub-operation) PFMEA header: project name, process, FMEA number, responsible engineer, revision date

Step 2: Structure Analysis

Process structure tree: Process step → Work element → Process characteristics Example: "Welding station → Arc initiation → Wire feed speed, Arc voltage"

5T Analysis: Team, Timing, Tasks, Tools, Timing (schedule)

Step 3: Function Analysis

Process function: what the process step is supposed to do Product characteristic: dimension, surface finish, torque, property the process is intended to achieve Process characteristic: input variable (wire feed speed, temperature, force) that drives product characteristic

P-diagram (Parameter diagram): Control factors → [Process] → Product function Noise factors (uncontrolled: ambient, material variation, machine wear) Error states (failure modes)

Step 4: Failure Analysis

Failure Mode: how the process could potentially fail to perform its function

• Dimensional: undersize, oversize, out of round
• Surface: scratches, burrs, contamination
• Missing: missing component, missing weld, missing torque
• Wrong: wrong part, wrong orientation, reversed assembly

Effect of Failure (downstream and customer): Effect on next operation, end customer, vehicle safety Multiple effects possible (local operation + downstream + end user)

Cause of Failure: Process input characteristic variation (root cause at process level) 4M analysis: Man, Machine, Material, Method, Measurement, Environment (6M) Use "Is/Is Not" analysis for each cause

Step 5: Risk Analysis

AIAG-VDA Severity (S) — 1 to 10:

S	Effect Description
10	Affects safe vehicle operation, without warning
9	Affects safe operation, with warning
8	Major disruption to downstream production
7	Minor vehicle performance loss; customer very dissatisfied
6	Minor vehicle performance; customer dissatisfied
5	Comfort item degraded; customer somewhat dissatisfied
4	Customer notices; minor fit/finish/squeak
3	Customer may notice
2	Very minor effect; rarely noticed
1	No effect

AIAG-VDA Occurrence (O) — 1 to 10:

O	Probability of Occurrence
10	≥ 1 in 2 (CPKP ≤ 0.33)
8–9	1 in 8 to 1 in 20 (CPK = 0.51–0.67)
6–7	1 in 80 to 1 in 400 (CPK = 0.83–1.0)
4–5	1 in 2,000 to 1 in 15,000 (CPK = 1.17–1.33)
2–3	1 in 150,000 to 1 in 1,500,000 (CPK = 1.5–1.67)
1	< 1 in 1,500,000 (CPK > 1.67)

AIAG-VDA Detection (D) — 1 to 10:

D	Detection Ability
10	No detection method; defect passes undetected
9	Visual check only; unreliable
8	SPC chart; operator check; low effectiveness
6–7	Attribute gauging; CMM sampling; moderate
4–5	Error proofing; 100% inspection
2–3	Error proofing (poka-yoke) + 100% gauge check
1	Error proofing prevents failure entirely

Risk Priority Number (RPN — Legacy Method)

RPN = S × O × D [range: 1 to 1000] Legacy threshold: RPN ≥ 100 → mandatory action Limitation: RPN non-unique (5×5×5 = 125 = 1×5×25); doesn't distinguish high-severity low-RPN cases

AIAG-VDA Action Priority (AP — 2019 Replacement)

Action Priority (AP) table replaces RPN threshold: AP = H (High), M (Medium), L (Low) based on S, O, D combination Key rule: S = 9 or 10 → mandatory action regardless of O and D High (H): must take action to reduce risk Medium (M): action strongly recommended Low (L): action at team discretion

Step 6: Optimization

Recommended actions: Reduce O: change process, add error proofing, improve process controls Reduce D: improve detection method, add verification step, 100% inspection Reduce S: requires design change (DFMEA involvement)

Poka-Yoke (Error Proofing): Level 1 — Prevention: physically prevents wrong action (guide pins, asymmetric slots, foolproofing jigs) Level 2 — Detection: detects error before it becomes defect (limit switches, sensors, camera inspection) Level 3 — Warning: signals operator of potential error (light curtains, alarms) Level 4 — Correction: automatically corrects error (adaptive feedback, servo control)

Action responsibility: assign responsible person + target completion date for each recommended action

Step 7: Results Documentation

Control plan linkage: PFMEA → Control plan (reaction plan for each control characteristic) Control plan columns: part number, operation, control characteristic, spec/tolerance, measurement method, sample size/frequency, reaction plan

PFMEA linkage to DFMEA: DFMEA: failure mode at product level → PFMEA failure mode at process level Special characteristics (SC): DFMEA identifies SC → PFMEA shows how process controls SC

Special Characteristics

Significant characteristics (SC): diamond symbol; require statistical control Critical characteristics (CC): star symbol; affect safety or regulatory compliance; require 100% verification or error proofing (D ≤ 3) Key characteristics: significant impact on customer satisfaction; require special process control

PPAP (Production Part Approval Process): PFMEA required in PPAP submission package (AIAG PPAP 4th Edition Level 3+)

PFMEA for Non-Automotive Industries

Medical devices (FDA 21 CFR 820 + ISO 13485): Risk management: ISO 14971; PFMEA is primary risk tool Severity linked to patient harm: S=10 → death; residual risk (after controls) must meet acceptable risk limit

Aerospace (AS9100 + SAE ARP4761): Systems FMEA + PFMEA; safety assessment process (SAP) Catastrophic effect: probability ≤ 10⁻⁹ per flight hour (FAR 25.1309)

Process pharma (21 CFR Part 211 cGMP): PFMEA for manufacturing process qualification; process characterization → FMEA → design space

Standards

Standard	Scope
AIAG-VDA FMEA Handbook (2019)	Automotive PFMEA — current standard
IATF 16949:2016	Automotive QMS — FMEA required
SAE J1739	Potential failure mode and effects analysis
IEC 60812	FMEA general standard
ISO 14971	Risk management for medical devices
AS9100 Rev D	Aerospace QMS — FMEA requirements

Output

Provide: process name and step analyzed, team members, top 5 failure modes by AP (High priority first), for each: failure mode description, effect (S rating), cause (O rating), current controls and detection method (D rating), AP (H/M/L) or legacy RPN, recommended action (reduce O/D/S), poka-yoke level (1–4) if applicable, responsible person and target date, revised AP/RPN after action, special characteristic designation (SC/CC), control plan linkage (measurement method, frequency, reaction plan), and applicable standard (AIAG-VDA 2019, IATF 16949).