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Qwestrum Engineering360 · Automotive & Manufacturing · Automotive Quality Systems

FMEA and Control Plan

FMEA identifies and prioritizes risk, while control plans define process controls and response actions.
Exam tip: keep SI units consistent end-to-end, write the governing relation symbolically before substituting, and sanity-check magnitude and sign.

Key formulas & points

Skim these first — then read the full notes below.

  • Prevention controls reduce occurrence
  • Detection controls catch before shipment
  • Special characteristics in control plan

Topic details

Introduction

B.Tech examiners expect clear linkage between PFMEA failure modes and control-plan checkpoints. Automotive quality systems influenced by Bosch and AIAG-VDA now prefer action priority logic over blind RPN ranking.

Key relations & formulas

RPN=S×O×DRPN = S \times O \times D
(legacy ranking)

Formulas (Indian textbook notation)

  • actionpriorityAPfromS,O,Dmatrix(new)action priority AP from S,O,D matrix (new)

Formulas (Indian textbook notation)

  • reactionplanwhenout−of−controlreaction plan when out-of-control

Notation and sign conventions

Relation 1 —
RPN=S×O×DRPN = S \times O \times D
RPN=S×O×DRPN = S \times O \times D
(legacy ranking)
Write this relation with symbols exactly as in Iatf16949 Handbook — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 2 —
actionpriorityAPfromS,O,Dmatrixaction priority AP from S,O,D matrix

Formulas (Indian textbook notation)

  • actionpriorityAPfromS,O,Dmatrix(new)action priority AP from S,O,D matrix (new)
Write this relation with symbols exactly as in Iatf16949 Handbook — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 3 —
reactionplanwhenout−of−controlreaction plan when out-of-control

Formulas (Indian textbook notation)

  • reactionplanwhenout−of−controlreaction plan when out-of-control
Write this relation with symbols exactly as in Iatf16949 Handbook — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Concept in depth

Risk analysis should begin with functional intent, then map failure effects, causes, and control effectiveness. Control plans convert high-risk items into measurable controls with frequency, method, and reaction rule so production teams can respond consistently.

Assumptions and validity limits

State assumptions explicitly before using any relation for fmea and control plan — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.
Wrong assumptions invalidate the entire solution even when the formula is correct. In Automotive Quality viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

Step-by-step problem approach

1. Read the question and list given data with SI units (common in Automotive Quality papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to fmea and control plan.
4. Use equation 1:
RPN=S×O×DRPN = S \times O \times D
.
5. Use equation 2:
actionpriorityAPfromS,O,Dmatrixaction priority AP from S,O,D matrix
.
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

Applications & exam relevance

FMEA and Control Plan appears in supplier quality and OEM audits. In Indian automotive curricula this topic is tested because it connects theory to APQP, PPAP, and IATF 16949.
GATE and semester exams often combine fmea and control plan with earlier units — revise prerequisites before attempting mixed problems.
Industry interview panels sometimes ask: "Where did you use fmea and control plan?" — answer with a lab, mini-project, or plant visit example if possible.

Common mistakes in exams

Students commonly increase detection controls only, without prevention actions at source. Another mistake is presenting RPN ranking as sufficient even when severity is very high.

Quick revision checklist

Before attempting fmea and control plan problems, confirm you can:
1. Prevention controls reduce occurrence
2. Detection controls catch before shipment
3. Special characteristics in control plan
Revise the solved examples in Iatf16949 Handbook — Standard reference and one previous-year GATE or university paper for this unit.

Worked examples

Try the problem first — open the solution when you are ready to check.

Legacy RPN computation

Problem

A failure mode has Severity 8, Occurrence 5, Detection 4. Compute RPN.

Solution

RPN = 8 × 5 × 4 = 160. Action should be prioritized further using AP matrix, especially if severity is high.

Conceptual check — FMEA and Control Plan

Problem

In a Automotive Quality semester or GATE paper you are asked: "State the main assumption, the governing relation, and one practical consequence of fmea and control plan." What should a complete answer include?

📖 Standard books (India)

  • Iatf16949 Handbook — Standard reference

    Read: Syllabus unit

    Referenced in Indian B.Tech syllabus

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