Knowledge Base · Critical Thinking
What does a 5 Whys look like on a machine breakdown?
A factory machine kept jamming, the operator was blamed and put on notice, and a 5 Whys traced the cause through a worn part and a missed service to a maintenance schedule never updated when the plant moved from one shift to three. The book uses the story to show blame stopping one question too early.
Chapter 9 of the book tells it from a factory floor. A critical machine kept jamming and stopping the production line, and the first explanation was ready-made: operator error. The operator was officially put on notice. Then the team asked the questions properly instead:
- Why did the machine stop? Because a specific part kept jamming.
- Why was the part jamming? Because it was worn out and misaligned.
- Why was it worn out? Because it had not been serviced according to the recommended schedule.
- Why was the schedule missed? Because the maintenance plan had never been updated when the plant moved from one shift to three.
The root cause was a stale plan, written for a factory that had tripled its operating hours, not a careless worker. The schedule was adjusted, the part serviced properly, and the breakdowns stopped entirely. The operator, who had been blamed for a system fault, became a valuable part of the solution.
The book's lesson from the story is the critical-thinking one: the most convenient explanation is usually the least examined. Any time a team's first answer names a person, treat it as a hypothesis to be tested, not a conclusion. Run the Whys past the person and into the system, and you will find the cause you can actually fix.
Related questions
Source: Continuous Improvement in the Workplace, Ch. 9 (Harnessing the Power of Critical Thinking).