The Jidoka principle in production and logistics
The Jidoka principle describes the ability of a machine, a facility or an entire system to shut itself down in the event of errors, quality and production problems. Alongside the just-in-time principle, Jidoka is the second mainstay of the Toyota Production System (TPS) and is an important factor in lean management and in quality assurance. Using sensors, limit switches or other devices, malfunctions or errors that occur are detected, which leads to the aforementioned automatic shutdown of the machine. This increased degree of autonomy of the facility is referred to as autonomation (automation + autonomy); it is also described as intelligent automation or automation with a human touch.
Jidoka in production
The crucial aspect of Jidoka is that it checks the manufactured materials during the production process, instead of detecting possible defects only afterwards. This enables a thorough search for the cause of the problem and may result in a short-term loss of productivity, but in the long term it increases reliability and thereby also profits. Jidoka functions as a cost-efficient intermediate step towards complete automation, in which errors that occur are not only detected by the machine itself, but also eliminated. Certain components, such as sensors, are used to enable the facility to do this. All deviations from normal operation (anomalies) are detected and, if possible, automatically corrected; if the latter is not possible, the machining process is also automatically stopped and visually signaled to the responsible employees.
The Toyota term “jido” is applied to a machine with a built-in device for making judgments, whereas the regular Japanese term “jido” (automation) is simply applied to a machine that moves on its own. Jidoka refers to “automation with a human touch,” as opposed to a machine that simply moves under the monitoring and supervision of an operator.
Toyota-Global
Advantages in production
- In the context of quality assurance, 100% control is no longer necessary, since defects are automatically detected in advance.
- Scrap and rework are reduced or even eliminated altogether, since faulty parts processing is detected immediately; as a result, no defective parts are passed on to downstream processes.
- Machines no longer wear out due to faulty processes and parts.
- Facilities and individual machines no longer have to be monitored by employees; pure monitoring is seen as a waste, specifically: a waste of time. This allows one employee to operate several facilities at the same time, safe in the knowledge that no defective parts will be produced (Multi Process Handling).
The Jidoka principle in intralogistics
The Jidoka principle also applies in intralogistics, only differently. For example, the aim is to avoid waste in the warehouse. The corresponding types of waste can be as follows: unnecessary transport due to excessively long distances, unnecessary stocks due to incorrect planning, rework due to picking errors or waiting times due to missing information, employees, materials or items. In the context of Lean Warehousing, Jidoka is a method that pushes quality management, cushions increasing cost and efficiency pressure, supports the growing share of value added services and expands the use of materials handling and automation technology.
Examples include automation processes within goods receipt, picking, stocktaking and the processing of returns. Within a warehouse management system, individual work steps are automated and computer-controlled on the basis of stored information. For example, in the goods receipt area, the goods inspection begins with the notification (the advice) of the goods. Based on the notification information, the process steps in the goods receipt area are automatically defined before the actual delivery. The receipt of the goods into the logistics center or distribution center describes not only the storage but also a comparison of the available data: article, weight, quantity, item number. Using a dialog, the employee can quickly see what exactly has been entered and whether the goods (delivery note data) match the information in the notification (usually supported by systems such as ERP and WMS). To complete the goods receipt process step, the data must be confirmed; only then is the inventory of the goods complete. These control mechanisms usually take effect at the so-called identification point (I-point) and automatically follow a specific process if the employee triggers it via a scan, for example.
There are several ways in which the inventory that has been or is to be stored can be checked during picking. On the one hand, the picking method pick-by-vision offers the possibility of guiding the employee error-free by providing detailed information (graphics, photos, text); on the other hand, picking processes such as pick-by-scan, pick-by-light and pick-by-robot are designed in such a way that the warehouse management system itself shows the employee exactly which item needs to be picked – during the picking process, quantity checks are carried out automatically. If the system quantity does not match the actual quantity in the compartment, the compartment is automatically assigned to a clarification case. A clarification case can also trigger the replenishment.
Editor’s note: In contrast to the Jidoka principle in production, intralogistic materials handling equipment, such as a pocket sorter or general sorters within a picking zone, are not switched off if, for example, product defects are detected. The defective products have to be removed from the actual material flow and handled separately.
Manual processes offer flexibility
The expansion of the jidoka principle in intralogistics is counteracted by the chaku-chaku principle, which is also part of the TPS. In this case, system performance is made more flexible by increasing the number of personnel, while at the same time avoiding complicated materials handling technology. If a distribution center relies for example on a wide range of items, but also faces fluctuating demand (seasonal), chaotic storage is also favored, and manual work steps often make more sense than using automated technology (see manual sorting-picking).
Summary of the Jidoka principle
The application of the Jidoka principle enables machines and software to recognize errors that occur in the running process and, if necessary, to correct them or to stop the current process. This prevents production errors from spreading through the entire downstream process, which in turn avoids the need for subsequent rework or shifts in the production sequence. This autonomous and automatic quality assurance is an important element of lean manufacturing, which originated in the Toyota production system. Similar, mostly software-based control mechanisms are implemented in warehouse management systems or ERP systems within logistics centers. Unlike in production facilities, there is no need to stop facilities in intralogistics.
If you are interested in lean management, then read the articles Lean method Heijunka and Kanban system.