Mass production needed one big idea. The parts had to be alike. Interchangeable parts are identical for practical purposes. So a part can be swapped for another one. Mass production became possible once machine tools could make them. Ford used large plants and standardized parts. He used the moving assembly line too. Ford's company built the Model T car. Cars are built in factories, on assembly lines. Some big factories have several buildings full of machines.

Before the moving line, Ford's team tried a test. They split one job into steps. Twenty-nine workers each added one part to a magneto. It was on a moving belt. Ford got the idea partly from Chicago meat-packing plants. There, overhead trolleys moved the work from person to person. By 1918, half of all cars in America were Model Ts. By the end, Ford had built about 15 million of them.

The industrial revolution lasted over 100 years. It had two big waves. One was about textiles and steam. One was about electricity and steel. Banks and investors helped pay for the first factories. Steam engines spread factory work across many British industries. Before that, most things were made by hand. It began in Great Britain in the late 1700s.

Toyota's founding family began with looms. Sakichi Toyoda invented an automatic loom. The Toyota Production System grew from his ideas. At Toyota, a machine or a worker can stop the line. That happens when something goes wrong. Lean thinking tries to create value with fewer resources and less waste. A product is built step by step as it moves along.

Just-in-time means making or receiving only what is needed. It also means getting it when it is needed. Robots are used in warehouses and factories. They do jobs such as moving items and packages. Many factories use a conveyor belt. It is a moving belt that carries things along an assembly line. A toy factory might have doll bodies on one. Workers add arms, legs and heads.

Words to know

• interchangeable: swappable
• standardized: made alike
• magneto: engine part
• trolleys: hanging carriers