assembly line, manufacturing technique in which a product is carried by some form of mechanized conveyor among stations at which the various operations necessary to its assembly are performed. It is used to assemble quickly large numbers of a uniform product. Henry Ford is often credited with establishing the first assembly line for his Model T. So long as an assembly line's output is high, the cost per unit is relatively low. It is somewhat inflexible, however, as it must be designed and installed for a particular product. Also, the operations on the product usually must be performed in a sequence that is strictly ordered. A malfunction or shortage of parts that shuts down a single assembly station necessitates shutdown of the entire line. Traditional assembly lines had come under criticism from those concerned with their effects on workers, but industrial robots now perform many of the repetitive tasks. Recent variations on the assembly-line process, such as teams of workers responsible for multiple steps, have increased productivity and employee interest.

Industrial arrangement of machines, equipment, and workers for continuous flow of workpieces in mass-production operations. An assembly line is designed by determining the sequences of operations for manufacture of each component as well as the final product. Each movement of material is made as simple and short as possible, with no cross flow or backtracking. Work assignments, numbers of machines, and production rates are programmed so that all operations performed along the line are compatible. Automated assembly lines (see automation) consist entirely of machines run by other machines and are used in such continuous-process industries as petroleum refining and chemical manufacture and in many modern automobile-engine plants. Seealso Henry Ford, interchangeable parts, Taylorism.

Learn more about assembly line with a free trial on Britannica.com.