Jidoka: the second pillar of TPS

• Jidoka: the second pillar of TPS
• Poka Yoke

Jidoka: the second pillar of TPS

The term Jidoka can be defined as “automation with a human touch”. The fundamental point of Jidoka is that quality must be built into the process so that the output is 100% quality.
This objective is the only acceptable one, and two conditions are necessary for it to be achieved:

• The plant or machine must be stopped when quality can no longer be guaranteed.
• Any work carried out on the machine or system must not alter the quality of the output in any way.
  These two conditions are guaranteed by introducing large doses of “human intelligence” into the production system to obtain “intelligent” machines.
  With Jidoka, plants and machines are equipped with appropriate stopping devices for when non-quality conditions arise.

The stop in case of poor quality also applies to manual assembly lines. Each piece is checked by the operator immediately after production, often using devices that make the process error-proof (Poka Yoke) and in the event of non-compliance, the operator is authorised to suspend production.
When the two conditions mentioned above are met, the goal of Jidoka is achieved: eliminating the rigid link between man and machine. The machine no longer needs continuous human observation, and therefore humans can devote themselves to value-added activities.
Breaking this link is one of the major contributions of the new production system, which greatly reduces or eliminates Muda due to operators' expectations.

POKA YOKE

A Japanese term that identifies a fail-safe tool or procedure that prevents defects from occurring in the order management or production process.
There are three types of Poka Yoke:

• The contact method (contact method): the physical characteristics of an object (its shape, colour, etc.) make it possible to distinguish the correct position or prevent objects from connecting to each other, thus avoiding malfunctions caused by incorrect contact.
• The fixed value method (fixed-value method) checks whether a certain number of operations have been performed.
• The work phase method (motion-step method) checks whether all the steps in a given process have been performed in the correct order.