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Harish Jose


The Toyota House

Why jidoka and JIT?

Published: Monday, October 19, 2020 - 12:03

Today I’m looking at the “house” of the Toyota Production System (TPS). The illustration below shows the two pillars of the TPS house, jidoka and just in time (JIT).

I’ve been thinking about why jidoka and JIT are the two pillars, and why they’re not kanban or kaizen.

Jidoka was developed from the ideas of Sakichi Toyoda, father of Kiichiro Toyoda. Kiichiro Toyoda founded Toyota Motor Corp. Sakichi Toyoda invented an automatic loom that stopped immediately when the thread broke. He viewed it as automation with human intelligence. Jidoka in Japanese means “automation,” but Toyota’s jidoka includes a human character in the written script, and although it’s still pronounced “jidoka,” it now means “autonomation.”

Figure 1: The TPS house (Source: Toyota Europe website)

The emphasis of jidoka is on quality. We can view jidoka as preventing defects from being passed along or ensuring that the quality of the product is maintained as it flows through the line.

The second pillar of the TPS house is JIT, which was the brainchild of Kiichiro Toyoda. The idea of JIT is also quite simple: have only what is needed, only in the right quantity, and only when it is needed. Perhaps one might attribute these two pillars of the TPS house as a way to show respect to the Toyoda elders. However, I think there is more to it than this.

One way to explain the two pillars is to view them as two lofty goals. Jidoka calls for maximizing quality, and JIT for minimizing inventory. I again think there is more to this. In its 1998 little green-and-white book, Toyota explained jidoka:

“The principle of stopping work immediately when problems occur and preventing the production of defective items is basic to the Toyota Production System. We call that principle jidoka... we design equipment to detect abnormalities and to stop automatically whenever they occur. And we equip our operators with means of stopping the production flow whenever they note anything suspicious. That mechanical and human jidoka prevents defective items from progressing into subsequent stages of productions, and it prevents the waste that would result from producing a series of defective items.... The most fundamental effect of jidoka, though, is the way it changes the nature of line management: It eliminates the need for an operator or operators to watch over each machine continuously—since machines stop automatically when abnormalities occur—and therefore opens the way to major gains in productivity. Jidoka thus is a humanistic approach to configuring the human-machine interface. It liberates operators from the tyranny of the machine and leaves them free to concentrate on tasks that enable them to exercise skill and judgment.

Similarly, Toyota explained JIT as “doing it all for the customer,” noting:

“JIT is making only what is needed, only when it is needed, and only in the amount that is needed. JIT production eliminates lots of kinds of waste. It eliminates the need for maintaining large inventories, which reduces financing costs and storage costs. It eliminates the waste that occurs when changes in specifications or shifts in demand render stocks of old items worthless. It also eliminates the waste that occurs when defects go undetected in the manufacturing of large batches. JIT production, though simple in principle, requires dedication and careful, hard work to implement properly. Once managers and employees have mastered the basic concept, they learn to devise various tools and techniques for putting this concept into practice... (e.g., leveled production, pull system, continuous-flow processing, and takt time).”

The two principles also link to another Toyota house called the Toyota Way. The two pillars for the Toyota Way are continuous improvement and respect for people. This is explained very well by the architect of the Toyota Way, Fujio Cho:

“Toyota is planning and running its production system on the following two basic concepts. First of all, the thing that corresponds to the first recognition of putting forth all efforts to attain low-cost production is ‘reduction of cost through elimination of waste.’ This involves making up a system that will thoroughly eliminate waste by assuming that anything other than the minimum amount of equipment, materials, parts, and workers (working time), which are absolutely essential to production, are merely surplus that only raises the cost. The thing that corresponds to the second recognition of Japanese diligence, high degree of ability, and favored labor environment is ‘to make full use of the workers’ capabilities.’ In short, treat the workers as human beings and with consideration. Build up a system that will allow the workers to display their full capabilities by themselves.”

The Toyota Production System is a result of decades of trial and error to find solutions for unique problems faced by Toyota. The company didn’t have luxury to operate state-of-the-art machines or carry large inventory to support the then-prevalent mass production system. Taiichi Ohno, the father of TPS, was able to come up with a framework that incorporated the principles of jidoka and JIT to ensure that Toyota could keep the cost low for its customers, increase productivity, and yet also provide them with high-quality products. Jidoka and JIT are aligned very well with the principles of continuous improvement and respect for people.

Ohno was famous for asking people to do more with less (less people, less inventory, etc.). He created conditions where the human capital was nurtured such that everyone learned to see wastes and came up with ingenious ways to remove them. Ohno created a framework for cultivating capable leaders and providing employees with necessary practical skills. The idea of jidoka ensures that quality isn’t compromised; quality is built in. Operators can take pride in what they are doing and ensure that it is value-added. The work of the machine is separated from operators so they can focus on using their creative skills to remove further waste.

Toyota Production System’s framework can be viewed as a closed system, in the sense that the framework is static. At the same time, the different plants implementing the framework are dynamic due to the simple fact that they exist in an ever-changing environment. In a cybernetic sense, information can be processed (i.e., meaning can be generated) only in a closed system. And yet viability requires an open system. Thus, you need to be closed and open at the same time.

The basic concepts of the Toyota Production System are unchanging. But companies implement those concepts differently. One of the great advantages of TPS is its adaptability. Yet common threads are apparent in the experience of the companies that have implemented the system successfully. Just-in-time manufacturing and other elements of TPS work best when they are a common basis for synchronizing activity throughout the production sequence. This an egalitarian arrangement in which each process in the production flow becomes the customer for the preceding process, and each process becomes a supermarket for the following process.

I’ll finish with some strong words from Taiichi Ohno:
“Those who decide to implement TPS must be fully committed. If you try to adopt only the ‘good parts,’ you will fail.”

First published Sept. 7, 2020, on Harish’s Notebook blog.


About The Author

Harish Jose’s picture

Harish Jose

Harish Jose has more than seven years experience in the medical device field. He is a graduate of the University of Missouri-Rolla (U.S.), where he obtained a master’s degree in manufacturing engineering and published two articles. Harish is an ASQ member with multiple ASQ certifications, including Quality Engineer, Six Sigma Black Belt, and Reliability Engineer. He is a subject matter expert in lean, data science, database programming, and industrial experiments. Harish publishes frequently on his blog harishnotebook. He can be reached on LinkedIn.