Kvalitetsfabriken

Deep Dive 03 — Overreliance on 100% Inspection

Written by

Roland Vikström

in

TL;DR

Inspection feels safe but it isn’t. Even the best inspectors miss defects, and inspection adds cost without preventing failure. The only real safety net is building quality into the process itself.

Executive Snapshot

100% inspection feels safe, but it isn’t. Humans are poor at repetitive detection tasks — fatigue, bias, and attention gaps guarantee that defects slip through. Inspection doesn’t prevent defects; it only sorts them — at high cost. The invisible factory builds quality upstream so inspection becomes a verification step, not a wall.

Why it happens

  • Prevention feels hard; “more eyes on parts” is the default.
  • Immature controls or missing capability data.
  • Cultural belief that inspection equals quality; doubling inspectors seems like doubling assurance.

How it shows up

  • Large teams at end‑of‑line; multiple re‑inspections.
  • Disputes about what was “missed.”
  • Cosmetic metric gains while scrap/rework costs skyrocket.
  • Low morale as inspectors take the blame for systemic issues.

Consequences

  • Human detection rarely exceeds 80–85% — escapes continue.
  • Costs rise; focus drifts from prevention to policing.
  • Customer trust erodes despite visible inspection “armies.”

The Fix

  • Shift from detection to prevention.
  • Invest in process capability, error‑proofing, and SPC on CTQs.
  • Use inspection selectively; keep it as verification.

Root Causes (6M+E)

DimensionTypical Issues
MeasurementInconsistent criteria; fatigue‑driven errors; subjective judgement
MethodsInspection replaces root cause elimination; redundant checks
MachinesProcess instability left uncontrolled; burden on inspectors
MaterialsIncoming variation sorted instead of improved
ManpowerInspectors blamed for escapes; training used as patch
EnvironmentPoor lighting, ergonomics, distractions during inspection

Diagnostics & Quick Checks

  • Seed known defects and measure detection rate.
  • Feed inspection data back into PFMEAs/control plans.
  • Watch for double/triple inspections — a sign of mistrust.
  • Rotate inspectors to reduce fatigue.

Acceptance Criteria

  • Automate detection or error‑proof CTQs where possible.
  • Inspection as a verification layer only.
  • Success = fewer inspectors as capability rises.

30/60/90‑Day Playbook

0–30 days

  • Map where 100% inspection is used and why.
  • Measure detection rates via seeded defects.
  • Start root cause analysis on top 2–3 defect types caught by inspection.

31–60 days

  • Mistake‑proof or automate detection for critical defects.
  • Stabilize upstream processes with SPC and capability studies.
  • Reduce redundant inspections; redeploy resources into prevention.

61–90 days

  • Audit inspection cost vs cost of poor quality; show impact.
  • Institutionalize error‑proofing checks in control plans and PFMEAs.
  • Celebrate inspector reduction as process health, not risk.

Sustain & Scale

  • Treat inspection as a temporary crutch.
  • Embed lessons into PFMEAs, control plans, and supplier requirements.
  • Audit so that processes — not inspectors — carry the burden of quality.

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References & Further Reading

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