A form of automation in which machinery automatically inspects each item after producing it and ceases production and notifies humans if a defect is detected. Toyota expanded the meaning of jidohka to include the responsibility of all workers to function similarly, to check every item produced and, if a defect is detected, make no more until the cause of the defect has been identified and corrected.
Autonomation describes a feature of machine design to effect the principle of jidoka used in the Toyota Production System (TPS) and Lean manufacturing. It may be described as "intelligent automation" or "automation with a human touch." This type of automation implements some supervisory functions rather than production functions. At Toyota this usually means that if an abnormal situation arises the machine stops and the worker will stop the production line. Autonomation prevents the production of defective products, eliminates overproduction and focuses attention on understanding the problem and ensuring that it never recurs. It is a quality control process that applies the following four principles:
1. Detect the abnormality.
3. Fix or correct the immediate condition.
4. Investigate the root cause and install a countermeasure.
Autonomation is called by Shigeo Shingo pre-automation. It separates workers from machines through mechanisms that detect production abnormalities (many machines in Toyota have these). He says there are twenty-three stages between purely manual and fully automated work. To be fully automated machines must be able to detect and correct their own operating problems which is currently not cost-effective. However, ninety percent of the benefits of full automation can be gained by autonomation.
The purpose of autonomation is that it makes possible the rapid or immediate address, identification and correction of mistakes that occur in a process. Autonomation relieves the worker of the need to continuously judge whether the operation of the machine is normal; their efforts are now only engaged when there is a problem alerted by the machine. As well as making the work more interesting this is a necessary step if the worker is to be asked later to supervise several machines. The first example of this at Toyota was the auto-activated loom of Sakichi Toyoda that automatically and immediately stopped the loom if the vertical or lateral threads broke or ran out.
For instance rather than waiting until the end of a production line to inspect a finished product, autonomation may be employed at early steps in the process to reduce the amount of work that is added to a defective product. A worker who is self-inspecting their own work, or source-inspecting the work produced immediately before their work station is encouraged to stop the line when a defect is found. This detection is the first step in Jidoka. A machine performing the same defect detection process is engaged in autonomation.
Once the line is stopped a supervisor or person designated to help correct problems gives immediate attention to the problem the worker or machine has discovered. To complete Jidoka, not only is the defect corrected in the product where discovered, but the process is evaluated and changed to remove the possibility of making the same mistake again. One solution to the problems can be to insert a "mistake-proofing" device somewhere in the production line. Such a device is known as Poka-Yoke.