What Is an Assembly Line?

An assembly line is a production process that breaks the manufacture of a good into steps that are completed in a pre-defined sequence. Assembly lines are the most commonly used method in the mass production of products. They are able to reduce labor costs because unskilled workers could be easily trained to perform specific tasks. Rather than hire a skilled craftsman to put together an entire piece of furniture or vehicle engine, companies would hire a worker to only add a leg to a stool or bolt to a machine.

History of the Assembly Line

The introduction of the assembly line drastically changed the way goods were manufactured. Credit Henry Ford, who set up an assembly line in 1908 to manufacture his Model T cars. Before, workers would assemble a product (or a large part of it) in place, often with one worker completing all tasks associated with product creation. Assembly lines, on the other hand, have workers (or machines) complete a specific task on the product as it continues along the production line rather than complete a series of tasks. This increases efficiency by maximizing the amount a worker could produce relative to the cost of labor.

When to Use an Assembly Line

Determining what individual tasks must be completed, when they need to be completed and who will complete them is a crucial step in establishing an effective assembly line. Complicated products, such as cars, have to be broken down into components that machines and workers can quickly assemble. Companies use a design for assembly (DFA) approach to analyze a product and its design in order to determine assembly order, as well as to determine issues that can affect each task. Each task is then categorized as either manual, robotic or automatic, and then assigned to individual stations along the manufacturing plant floor.

Companies can also design products with their assembly in mind, referred to as concurrent engineering. This allows the company to start the manufacture of a new product that has been designed with mass production in mind, with the tasks, task order and assembly line layout already predetermined. This can significantly reduce the lead time between the initial product design release and the final product roll out.