The encyclopedia · Engineering & Operations · Technical decision · 1996–2016
Toyota decomposed every production process so defects die where they start
Toyota split each process into checkable elements so bad parts cannot reach the next step — the final water-leak test became unnecessary.
Toyota Motor Corporation
the move
Toyota has held since 1937 that quality is built into the process and defective parts must never flow to the next step: when a problem appears, stop the line, find the cause, and prevent recurrence. That discipline was the foundation of the Toyota Production System and its quality record.
But as cars became electronic and production went global in the 1980s–90s, building quality into the process quietly became a 'mindset', and plants drifted back to catching defects at downstream inspection. Jikoutei kanketsu (complete in your own process) was started in 1996 to restore the original rule.
The first project, at Tsuchiura plant, targeted zero water leaks: previously the final inspection showered every car to find leaks; the goal was to make that test unnecessary by achieving the quality in earlier processes. One process is decomposed into many elemental operations so the cause of any defect is immediately visible, and the method was later extended to design and office work, where it is known overseas by the abbreviation JKK.
why it works
- Final inspection only finds defects; it does not stop them being made.
- Decomposing work makes the cause of any defect immediately visible.
- Every worker becomes the quality gate of their own process.
- Scientific feedback is built into equipment so quality is engineered, not hoped for.
what transfers
When complexity makes final inspection unreliable, push the checkpoint into every step: decompose the work, define what good looks like, and make each handoff a quality gate.
what came after
Jikoutei kanketsu became a pillar of Toyota's TQM, spread from manufacturing to design and white-collar work, and was exported to overseas plants as 'JKK'; Toyota's technical advisor reports it has been especially well accepted in the US, and it continues to be taught through the JUSE Quality Forum.
references
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