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What is a Control Plan?

A control plan (also called a manufacturing control plan or process control plan) is a document that defines:
  • What to measure — Characteristics linked to design requirements and failure modes
  • How to measure — Specific inspection methods, gauges, and acceptance criteria
  • How often — Sampling frequency and lot/batch sizes
  • What to do — Reaction plan when a part exceeds control limits
Control plans are required by IATF 16949 and APQP (Advanced Product Quality Planning) for automotive suppliers. In TestAuto2, control plans are integrated with your FMEA risk controls and design characteristics, ensuring traceability from hazard analysis through production verification.

Control Plan Workflow Overview

diagram

Key Concepts

Control Plan Items

A control plan item is a single row in your control plan risksheet, representing one characteristic or parameter that needs production verification. Each item specifies:
  • Process Step — The manufacturing step where the control occurs (e.g., “Solder Wave Reflow”)
  • Characteristic — The design characteristic being monitored (linked to FMEA failure mode)
  • Control Method — The measurement technique or inspection type
  • Sample Size — How many parts per batch are inspected
  • Sample Frequency — How often samples are collected
  • Reaction Plan — What happens if the control fails

SC/CC Classification

Control plan items must align with SC/CC (Special Characteristics / Critical Characteristics) classification:
  • S (Special Characteristic) — Characteristic critical to safety, emissions, or regulatory compliance
  • C (Critical Characteristic) — Characteristic critical to fit, function, or customer satisfaction
  • Regular — Characteristic important but not critical
In TestAuto2, control plan items link to design requirements that have SC/CC classification, ensuring that all safety-critical characteristics (S-class) are covered in the control plan.

Sampling Strategies

Common sampling plans include:
StrategyUsageExample
100%Critical characteristics, first-run partsEvery sensor output value measured
AQL (Acceptance Quality Limit)Repeating production runsANSI/ASQ Z1.4 AQL 1.5
Statistical Process Control (SPC)High-volume, stable processesEvery 50th part for trend analysis
Skip-LotVerified suppliers with perfect track recordEvery 5th lot (not every part)

Common Tasks

Standards & Compliance

Control plans are required by:
  • IATF 16949 — Automotive quality management system (Section 8.5.1)
  • APQP — Advanced Product Quality Planning (Phase 4: Product and Process Validation)
  • ISO 26262 — Functional safety; control plans provide evidence of manufacturing risk mitigation
In TestAuto2, control plans are integrated with your FMEA (failure modes and risk controls) and characteristics management, providing complete traceability from hazard analysis through production verification.
Control plans are living documents — update them as production experience reveals new risks or as design changes affect critical characteristics. Always link changes back to your FMEA for full traceability.