Assembly Line

ASSEMBLY LINE

ASSEMBLY LINE. The assembly line is often described as a process that uses machines to move material from one place to another, but in practice, machines are not always needed. For instance, mass-market jewelers often use assembly lines in which materials are handed from one worker to another, without the benefit of machinery. At its most basic, an assembly line is a series of stations at which people or machines add to or assemble parts for a product. One of the values of the assembly line is its versatility: it can be simple, but it has the capacity to be very complex. An assembly line can begin as many different lines each devoted to a different component of a product, with the lines converging upon one another, becoming fewer until only one line is left for the final product. Automotive companies often have assembly lines that begin with raw materials and end five miles away with a completed automobile. A structure for a complex assembly line begins as one main line with stations along it that are fed by lines running perpendicular to it, with each of these side lines feeding components for the finished product. Although the assembly line has occasionally been considered outmoded, it has survived by repeatedly changing its form.

Foundations of the Assembly Line

The idea of the assembly line has many parents. In the scientific revolution of the eighteenth century, scientists, especially mathematicians tried to quantify what made an industry productive and tried to find ways to make industries more productive. The goal was to create an industry that functioned without human labor. The most important people of the time for the development of the assembly line were the Americans Oliver Evans and Eli Whitney and the Frenchman Gaspard Monge. Evans is known for his invention of the first motorized amphibious vehicle, but his most influential achievement was to design a flour mill. During the late eighteenth century, he used steam engines to power mills that used belt and screw conveyors, as well as moving hoppers, to move grain through the process of becoming flour and then to move the flour to where it could be packaged. While his equipment was not exactly an assembly line, all the basic components were there.

Best known for creating the cotton gin, Eli Whitney also contributed to the development of the assembly line with his invention of interchangeable parts. Whitney created machine tools that could create parts so closely resembling each other they could be substituted for one another without harm. In 1798, the United States government ordered 10,000 muskets, and in a preview of the assembly line, Whitney set his employees to work on manufacturing parts that were assembled bit by bit into muskets. A Whitney musket could be repaired in the field with spare parts.

Gaspard Monge made his contribution while in Italy during the Napoleonic era. He took the principals of descriptive geometry and applied them to machinery. By breaking a machine down into its component parts, Monge found that he could show how each part related to the others; this would evolve into technical drawing, which

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allowed people to make machines they had never seen, machines that would share interchangeable parts with any other machine made with the same diagrams.

Henry Ford

Making automobiles was a hobby for many Americans, and Henry Ford began as a hobbyist, but he brought to his hobby an unsurpassed ambition. In 1899, he started his own automobile manufacturing company; he wanted to produce cars in large enough quantities to make them available to everyone. In 1908, he divided up the tasks involved in manufacturing an automobile; he broke these tasks down to the function of each autoworker, conceiving of each worker as a part of a machine that made cars. At first, he tried having chassis pulled along factory floors with towropes. Men walked alongside the chassis to stations, at each station parts were added. Manufacturing time for a single automobile decreased from twelve hours to five and one-half hours. In 1913, he installed conveyor belts in his factories. With these, workers stood at their stations, each doing the same repetitive task over and over again. Manufacturing time for one car fell to around an hour and a half. At such a pace, Ford could make a small profit on each car but could make much more money from selling the cars in the millions. By The end of 1914, his employees were the highest paid industrial workers in the world; a worker performing the simplest of tasks could, and some did, become rich.

World War II

When the United States entered World War II, its heavy industries were charged with manufacturing the matériel for the armed services. The assembly line was crucial to this production. In March 1941, Ford began building a factory and, by the end of 1942, was taking in raw materials at one end, processing them, and producing B-24 bombers. By The end of the war, Ford's factory was producing B-17 bombers at the rate of one every sixty-three minutes.

General Motors made an impressive innovation with its production of chassis for combat tanks. Despite being a big and heavy machine, a tank needed to be tight in its joints and fluid in its reactions to the men operating it. With early tanks, the impact of an enemy shell might not breach the American tank's armor but would blow bolts loose in the interior, killing the people inside. The management at General Motors was not alone in realizing that the bolts had to be replaced by welds, but it was their engineers who came up with the assembly line innovation that helped make the welds succeed. Instead of using machines to do the welding, they employed human welders as craftsmen; they created an enormous machine that could pick up a tank chassis and tilt it quickly to any angle the welders wanted. The assembly line station became a craftsman's shop, with the line responding to the workers rather than the workers just being parts of the machine. Decades later, the Japanese manufacturer Toyota would use a similar machine to weld its automobile chassis, and a similar concept for the work stations. General Motors did them both first.

The assembly line affected the lives of American women. Women fit into many assembly line jobs previously only done by men. The assembly line was successful enough at relieving workers of the tasks requiring brute strength. Historians note the millions of American women who left their jobs when American servicemen returned to civilian life; not so often noted is that women workers were so good at their tasks that aircraft manufacturers and auto makers kept many of them employed to handle tasks such as wiring.

Wounded but Still Alive

The wear and tear on workers created by relentlessly repetitive physical motions on assembly lines became increasingly public after World War II. Further, factories that relied on an assembly line seemed to have become inefficient. When Japanese automakers began to make inroads into American markets in the 1970s, American industry seemed less than up to the challenge. Toyota had introduced a concept called kaizen, meaning "continuous improvement." The idea was to have assembly line workers participate in the development of a product and to suggest changes even during the production process. This idea harkened back to when Ford and Chevrolet encouraged worker suggestions, back in the late 1910s and early 1920s, saving the companies millions of dollars by pointing out inefficiencies. By the 1980s, it was known as the Toyota Production System.

Although General Motors began using robots on the assembly line in the 1960s, it was not until the 1980s that robots were extensively used on the industrial assembly line. Robots could be very efficient at doing certain repetitive jobs, and Japanese manufacturers soon led the world in using them on their assembly lines. Station workers' costs were cut, because fewer workers were needed. Yet, the overall use of robots was by 1990 becoming a failure. Many people were required to maintain the robots and program the computers that directed them. In the 1990s, Ford and Chrysler developed "value engineering," a process by which the basics of a design were kept simple, allowing them to be repeated for several different products; about 70 percent of the parts for a new car would be shared with a previous design. This allowed for quick responsiveness to the public's desires, since a plant did not have to completely retool for each different car model. This development was combined with ergonomic workstations. By Asking workers on the assembly line for ideas, manufacturers discovered that something as basic as moving a convey or belt from the floor to waist height could increase productivity and decrease injuries. With robots proving not to be complete substitutes for human beings, the comfort and care of workers became ever more important. By Creating work stations that were comfortable and by combining work stations into groups, communication among workers increased. Most manufacturers found this led to increased productivity and improvements in quality. The fundamental concept of the assembly line still remains the basis for the most efficient mass production of manufactured goods.

BIBLIOGRAPHY

"The Arsenals of Progress." The Economist (US) 330, no. 7853 (5 March 1994): M5–7.

Chow, We-Min. Assembly Line Design: Methodology and Applications. New York: Marcel Dekker, 1990.

De Camp, L. Sprague, and Catherine C. De Camp. The Story of Science in America. New York: Charles Scribner's Sons, 1967.

Hapgood, Fred. "Keeping It Simple." Inc. 18, no. 4 (19 March 1996): 66–70.

Nof, Shimon, W. Wilhelm, and H. Warnecke. Industrial Assembly. New York: Chapman & Hall, 1996.

Scholl, Armin, and A. Siedenberg, eds. Balancing and Sequencing of Assembly Lines. New York: Springer-Verlag, 1999.

Womack, James R., Daniel Roos, and Daniel T. Jones. The Machine That Changed the World: The Story of Lean Production. New York: Rawson Associates, 1990.

Kirk H. Beetz

See also Automobile Industry ; Industrial Revolution ; Mass Production ; Robotics .