Key takeaways
  • Jidoka is automation with a human touch: equipment that detects an abnormality and stops, rather than producing defects unattended.
  • It separates human work from machine work, so one person can oversee several machines.
  • Stopping immediately is cheaper than continuing, because it caps the quantity affected at one.
Why stopping is the cheap option
A defect caught at the source affects one part

The same defect discovered at final inspection affects everything made since, plus the effort to find and sort it. Stopping feels expensive at the moment it happens, which is why it takes management commitment to make it normal.

The four steps

  • Detect the abnormality.
  • Stop.
  • Fix or correct the immediate condition.
  • Investigate the root cause and install a countermeasure.

The fourth step is where jidoka differs from simply having an alarm. Without it you have a machine that stops repeatedly for the same reason, which becomes an irritation people learn to bypass.

Detection mechanisms

  • Sensors detecting a condition outside limits: position, torque, pressure, temperature, presence.
  • Counters confirming the expected number of operations occurred.
  • In-process gauging that checks a dimension as the part is made.
  • Vision systems for presence, orientation and surface condition.
  • The operator, given genuine authority to stop and a mechanism to call for help.

Separating human work from machine work

Once a machine can be trusted to stop on an abnormality, an operator no longer needs to watch it run. That is what allows multi-machine handling and it is the productivity argument for jidoka, which is otherwise sometimes presented as a purely quality concept.

What makes it fail

  • Stops that are not investigated, so the same condition recurs and the stop becomes noise.
  • Detection with no defined response, leaving a stopped machine and nobody coming.
  • Pressure to hit numbers that makes stopping socially costly, so people find ways around the sensor.
  • Sensors that produce false stops, which reliably get bypassed within weeks.

Jidoka and poka-yoke

Poka-yoke prevents or detects the error at the point it would occur. Jidoka is the broader principle that includes stopping and responding. In practice a poka-yoke device is often the detection mechanism within a jidoka system, and the two are usually implemented together.