How a Loom Inventor's Son Reinvented Manufacturing

Taiichi Ohno joined Toyota's truck plant in 1943 and spent the next thirty years reshaping how the company built cars. Two decisions defined his approach. The first was that any worker could pull a cord called the andon and stop the entire assembly line if they spotted a defect. The second was that parts should arrive at each station only when the next station was ready for them — not stockpiled in advance.

Ohno called the second idea just-in-time. He claimed he got it from watching American supermarkets restock shelves: a customer takes a can of soup, the gap signals the next can to come forward. Detroit's auto plants did the opposite, building enormous inventories of every part and pushing them through the line. Ohno's plants used kanban cards — small paper signals — to pull parts only as needed.

The other half of the system came from the founder's father. Sakichi Toyoda had invented an automatic loom in 1924 that stopped itself the instant a thread broke. His principle, called jidoka or autonomation, meant a single worker could supervise many machines because each one would call for help only when something went wrong. Ohno applied the same logic to assembly lines.

Western companies took thirty years to take the system seriously. James Womack and Daniel Jones popularized it as lean manufacturing in their 1990 book The Machine That Changed the World, after a five-year MIT study showed Toyota plants outperformed American and European ones on quality, productivity, and cost simultaneously. Toyota had not kept the system secret. It had been published in trade journals for decades. Detroit had simply assumed it was Japanese cultural quirk, not a transferable system.