Quality at source, jidoka, and problem solving
Quality at source, jidoka, and problem solving tests whether you can stop defects at the point they occur, contain the effect, and remove the cause rather than inspect quality in at the end.
Core rules
- Jidoka gives machines and people the ability to detect an abnormality and stop. The andon cord is a response system: stop, call, contain, and fix; it is not a suggestion box.
- Quality at source means build in quality at each process, use source inspection and poka-yoke where possible, and never pass a known defect downstream.
- Problem solving follows PDCA: contain first, then define the problem with data, find root cause, choose countermeasures, verify results, and standardize. 5 Whys should be evidence-based, not a ritual of exactly five questions.
- Separate human work from machine work in jidoka design; machines should stop autonomously, and people should do judgment work.
- A countermeasure is stronger when it makes the error impossible or immediately visible, not when it asks people to be more careful.
Worked example
A customer reports three loose brackets out of 500. The team contains by quarantining the lot, checking torque on all units, and notifying downstream. The defect is traced to low torque. Why? The torque driver was out of calibration. Why? Calibration was overdue. Why? The due date was not visible at the station. Why? The maintenance schedule was not linked to the asset ID. Root cause is a missing visual calibration control, not operator carelessness. Countermeasures: color-coded calibration tags, daily torque verification with a preset wrench, and a poka-yoke fixture that rejects an uncalibrated driver. Verify with a week of torque audits.
Traps
Do not skip containment and jump to root cause. Do not accept operator error or lack of training without asking why the system allowed the error. Do not use five whys to confirm a predetermined answer. Do not confuse detection (andon, inspection) with prevention (poka-yoke).
Key points
- Contain before root cause.
- Jidoka stops at abnormality; andon requires a response.
- Poka-yoke prevents or detects errors at source.
- 5 Whys needs evidence; operator error is not a root cause.