The Program: Jidoka, Quality at the Source
A program is an orderly set of procedures to attain a desired result.
Unless such defective work is reduced, it is difficult to assure an adequate supply for the later process to withdraw … Efforts to thoroughly stabilize and rationalize the processes are the key to successful implementation of automation. Only with this foundation can production leveling be effective. 1
Jidoka came about because of an invention by Sakichi Toyota. Before automobiles, Toyota was well known for his spinning company, called Toyota Automatic Loom Works, later Toyota Boshuku, where he developed a loom that had a new feature. At this time, each loom was operated by an individual. The operator had to watch the machine constantly in case there was a problem with the thread breaking. One operator, one machine. Sakichi’s invention stopped the loom when the thread broke or ran out. This prevented the loom from making defective cloth with broken thread. When the loom stopped, the operator would be required to correct the broken thread before continuing the operation. It was called “automation with a human element.” 2 The meaning was that the machine recognized a problem, which was normally done by a human, and stopped. This prevented the machine from making poor-quality product.
This was a big development in the loom business. What it meant was an incredible increase in labor efficiency. Instead of one operator, one machine, an operator could now operate numerous machines, because they weren’t required to stand over each one individually. This was breaking edge technology at the time. This same method was transferred to the automobile business later with the use of poka-yoke devices that sense abnormalities and help improve quality by preventing the production of poor-quality parts.
Furthermore, Toyota learned to separate machine work from human work. A simple example is that a machine is loaded with parts, a button is pushed to start the machine, and the operator moves on to the next machine. The human part is to load and start; the machine portion is to clamp, weld, and eject the part. This allows the operator to operate multiple machines.
Beyond “automation with a human touch,” an additional method used to get quality at the source is to implement quality checks in each process. This information is part of the standard work for the operator. The operator is checking for something specific, or maybe several specific checks, on each part. The sources of these checks come from several places. Some checks are done because of the inability to make the check using a poka-yoke device. In this case, there is currently no way to automatically stop the process for a defect, so the operator makes the check. This could be visual or using some sort of checking device. These checks, likewise, prevent the production of poor-quality product.
Other checks are done due to feedback from a customer downstream. It’s possible that the customer encounters a problem that is not being caught, or even known, by their supplier. The supplier checking for that failure mode would limit the chances of shipping a defect. Another source of a process quality check could be from issues arising from returned goods or warranty claims. In these instances, the defect has reached the outside customer, so these issues require urgent action.
For example, in Body, many nuts are welded onto parts using manual nut welders. Because of the nature of the machines, we were unable to install a poka-yoke device on manual nut welders. Parts sensors were in the next machine where this part was to be loaded. If a nut was left off, the machine would sense the missing nut and would not start. This required the attention of the operator to determine why. The missing nut would be discovered so that it could be attached before moving on to the next process. This is an important way Toyota prevents the passing on of poor quality to the next process.
I mentioned earlier (Chapter 7) that it was less important to implement standard work as one of the first steps in the Toyota Template, because you already had a way that things were being made. However, jidoka and visual quality checks can and should be implemented early on by adding quality checks to the current way. It’s important that no poor quality is passed on, especially when operating in a pull system. The importance of quality in a pull system is emphasized by Ohno in the six kanban rules: “Rule 5 requires 100% defect-free products (that is, do not send anything defective to the subsequent process).” 3 Remember, there’s no excess inventory to cover the problem now as there was in a push system. Additionally, it’s a good idea to have 200% checks for defects as much as possible. In all cases, implementing quality checks in the process, at the source, is critical when implementing a pull system.
Program: Quality at the source.
Culture: Quality at the source is another important aspect in building the lean culture: placing checks in the process, explaining the need to the employees, and holding them accountable to properly follow the checks. This allows them to directly contribute to the quality of the end product by improving the quality of their individual daily work. The results are visible for all to see.
1. Ohno, Taiichi. 1988. Toyota Production System: Beyond Large-Scale Production, p. 41. New York, NY: Productivity Press.
2. Ohno, Taiichi. 2013. Taiichi Ohno’s Workplace Management: Special 100th Birthday Edition, p. 61. New York, NY: McGraw-Hill.
3. Ohno, Taiichi. 1988. Toyota Production System: Beyond Large-Scale Production, p. 41. New York, NY: Productivity Press.