The Cord Anyone Could Pull

Above the assembly line hangs a cord. Any worker who sees something wrong, a loose bolt, a missing part, a scratch in the paint, can reach up and pull it.

A light comes on above their station and a short tune begins to play. A team leader walks over at once. If the problem cannot be put right within a minute or so, the whole line stops.

In most car factories of the twentieth century, this would have been unthinkable. Stopping the line cost money, and ordinary workers were not trusted with that power. At Toyota it became part of everyday work. The man who did most to build that way of working was an engineer named Taiichi Ohno.

A loom that stopped itself

Ohno was born in 1912 in Dalian, in north-eastern China, to Japanese parents. He studied mechanical engineering in Nagoya, and in 1932 he joined Toyoda Spinning and Weaving, a textile company run by the Toyoda family.

The family's fortune had begun with looms. Sakichi Toyoda, the founder, had invented an automatic loom that stopped by itself when a thread broke. A broken thread meant spoiled cloth, so instead of carrying on and weaving bad fabric, the machine halted and waited for a person. One worker could then look after many looms, because the machines told them when something was wrong.

That simple idea, stop as soon as something goes wrong, would stay with Ohno all his life.

Sakichi's son, Kiichiro Toyoda, began making cars and founded the Toyota Motor Company in 1937. He had an idea of his own: each part should arrive just in time to be used, not weeks early, piling up in a store. Ohno moved to the car company in 1943.

Poor and small

After the Second World War, Japan was poor. Toyota made only a small number of vehicles and had very little money. In 1950 the company came close to collapse, there was a bitter strike, and Kiichiro Toyoda stepped down.

American car makers like Ford and General Motors built huge numbers of the same model on enormous lines, with vast stocks of parts. Toyota could not afford to work that way. It had to make many different vehicles in small numbers, with little space and little cash.

Ohno, now in charge of a machine shop, began to experiment. He asked why parts were stored in big piles, why machines were set up to make one thing for days on end, and why a worker stood and watched a single machine all day.

The supermarket

Ohno had read about American supermarkets, and in 1956 he saw them for himself on a visit to the United States. What struck him was how they worked. A shopper took what they needed from the shelf, and only then did the store put more on the shelf to replace it.

He carried the idea back to the factory floor. Instead of each workshop making as much as it could and pushing it forward, each later stage would take only what it needed from the stage before. A simple card, called a kanban, travelled with the parts. When the parts were used, the card went back as a signal to make more.

Less stock meant less money tied up and less waste. It also meant something harder. With no big piles to hide behind, every problem showed up at once.

That is where Sakichi Toyoda's loom came back. When a problem appeared, the line should stop, the way the loom had stopped, and people should fix the cause before carrying on.

Asking why

Ohno taught his teams to ask "why" again and again when something broke, often five times, until they reached the real cause rather than the first excuse. A machine stops: why? A fuse has blown. Why? The machine was overloaded. Why? And so on, until the true fix appears.

He was known as a demanding boss. He is said to have drawn a chalk circle on the factory floor and made a manager stand inside it for hours, simply watching the work, until they saw the waste for themselves.

The changes took years, and many people resisted them. Workers worried that stopping the line would get them blamed. Managers worried about lost output. Slowly the results spoke for themselves. Toyota's vehicles became known for being well made, and the company was building them with fewer faults and far less stock than its rivals.

Beyond the factory

The wider world began to take notice in the 1970s. After the oil crisis of 1973, many companies struggled, but Toyota recovered quickly, and people started asking how.

Ohno wrote a short book about the system, published in Japan in 1978. In 1990, a well-known study from the Massachusetts Institute of Technology, The Machine That Changed the World, compared car factories across the world and made popular a new name for the Toyota approach: lean production.

Its ideas spread to factories of every kind, and then to hospitals, airlines, offices and software teams. Many of them now have their own version of the cord: a way for anyone to say, this is wrong, let us stop and fix it.

Taiichi Ohno died in 1990, at the age of seventy-eight. He never claimed to have invented it all alone. He built on the Toyoda family's ideas and on the work of thousands of people on the factory floor. His great step was to trust them to stop the line.

Want to read more?

Taiichi Ohno's own Toyota Production System explains the method in plain words. The Machine That Changed the World tells how the rest of the world discovered it, and Jeffrey Liker's The Toyota Way sets out the principles behind it.