Toyota Production System: Just-in-Time and Jidoka
Toyota's production system rests on two ideas, making only what is needed and stopping when something goes wrong. Both trace back to a loom invented in the 1890s.
In this article
The Toyota Production System (TPS) is the way Toyota organises its factories. Its goals, as Toyota describes them, are to deliver vehicles quickly, at low cost and with high quality while making work easier for employees. It stands on two pillars: just-in-time, which means making only what is needed, and jidoka, which means stopping the moment something goes wrong. Both ideas have roots that predate Toyota's cars.
Pillar one: just-in-time
Toyota defines just-in-time as producing only what is needed, when it is needed and in the amount needed. A car has more than 30,000 parts, so the plants, processes and partner companies must be synchronised in a continuous flow. Each process replenishes what the next process takes, and only a minimum stock of parts is kept in advance so that orders can be filled quickly.
Toyota's own history credits Kiichiro Toyoda, the founder of Toyota Motor Corporation, with advocating this approach. He introduced flow production with a chain conveyor, and in 1938 applied it to body assembly at the Koromo Plant, now the Honsha Plant.
Pillar two: jidoka
Jidoka is loosely translated by Toyota as "automation with a human touch". When a machine or a worker detects an abnormality, such as an equipment fault, a quality problem or a delay, the line stops immediately. That prevents a defective product moving on to the next step. Because machines halt themselves, people do not have to watch them constantly.
Toyota says work is first done by hand and improved through kaizen, daily step-by-step improvement, to remove waste, inconsistency and unreasonable demands. Only after that is it automated.
The loom behind the idea
Toyota traces jidoka to Sakichi Toyoda (1867 to 1930), the founder of the Toyota Group, who invented an automatic loom to ease his mother's work on a manual one. Toyota's key dates include:
- 1896: a device that automatically stops the loom when a weft thread breaks
- 1924: the Type-G automatic loom, with a non-stop shuttle change
- 1927: chain-conveyor flow production introduced into loom assembly, at a capacity of 300 units a month
- 1938: flow production applied to body assembly at the Koromo Plant
Who built the system
Toyota names Eiji Toyoda (1913 to 2013) as the leader who ensured thorough implementation of both pillars, and Taiichi Ohno (1912 to 1990) as the engineer who, with Eiji's strong support, helped establish the system and created the basic framework for just-in-time. Wikipedia's article on the system says Ohno and Eiji Toyoda developed it between 1948 and 1975, and that Toyota published its first official description in 1992.
The supermarket story
A popular account says Ohno took the idea of a pull system from supermarkets. In a supermarket, shoppers take goods from shelves and staff restock only what has gone. Applied to a factory, a work centre withdraws parts from a store, and the process that makes them builds only enough to replace what was taken. The kanban, a card or sign that signals what to make next, is the usual tool for this.
Sources are not fully consistent about the details. Wikipedia says Toyota drew inspiration from a supermarket and also says Ohno read descriptions of American supermarkets, and it does not explicitly connect kanban to the supermarket analogy. Toyota's page on the system, the source for the dates above, does not mention kanban at all. Treat the supermarket tale as a widely told explanation, not a documented event with a date.
Waste, in Toyota's vocabulary
The system targets waste, which Japanese manufacturers call muda. Wikipedia lists eight kinds: overproduction, waiting, transportation, processing itself, excess inventory, unnecessary movement, defective products and underused workers. You may see lists of seven elsewhere, since counting practice differs between books. Toyota's own page names three related problems to remove: waste (muda), inconsistency (mura) and unreasonable demands (muri).
Why it still matters
The two pillars are simple to state, and that is the point. Make what is needed, when it is needed, and stop at once when a fault appears. Many factories outside the car industry use variations of the same ideas, though how closely any one of them follows Toyota's own methods is a separate question that these sources do not answer.
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