Assembly line
Assembly line
An assembly line is a manufacturing system of mass production in which a finished product is manufactured in a step-by-step process involving interchangeable parts added in a sequential manner as it moves continuously past an arrangement of workers and machines. In the early years of the assembly line, each worker usually controlled one specific part of the job. Today, assembly lines may consist of workers, computers and robots, or a combination of the two. Introduced in the nineteenth century, it provided the basis for the modern methods of mass production of quantities of standardized, relatively low-cost goods available to great numbers of consumers. As one of the most powerful productivity concepts in history, it was largely responsible for the emergence and expansion of the industrialized, consumer-based system in existence today.
History
The principle of continuous movement is perhaps the simplest and most obvious fact of an assembly line, dating back to Assyrian times, where there is evidence of a system of bucket elevators called the chain of pots. Miners in medieval Europe also used these bucket elevators, and, by the time of the Renaissance, engineers were becoming familiar with some form of the assembly line. In the fourteenth century, for example, the shipbuilding arsenal of Venice, Italy, used moving lines of prefabricated parts to equip their war galleys. What may have been the first powered-roller conveyer system was introduced in 1804 with the British Navy’s automatic production of biscuits, or hardtack. It used a steam engine to power its rollers. By the 1830s, the principle of continuous processing was starting to enter the consciousness of manufacturers, although it was by no means fully embraced until the 1870s in
the United States. By then, the principles of division of labor and interchangeable parts had been successfully demonstrated by American inventors Eli Whitney (1765–1825) and Samuel Colt (1814–1862).
The assembly line was first used on a large scale by the meat-packing industries of Chicago, Illinois, and Cincinnati, Ohio, during the 1870s. These slaughterhouses used monorail trolleys to move suspended carcasses past a line of stationary workers, each of whom did one specific task. Contrary to most factories’ lines, in which products are gradually put together step-by-step, this first assembly line was in fact more of a disassembly line, since each worker butchered a piece of a diminishing animal. The apparent breakthroughs in efficiency and productivity that were achieved by these meat packers were not immediately realized by any other industry until American industrialist Henry Ford (1863–1947) designed an assembly line in 1913 to manufacture his Model T automobiles. Ford openly admitted using the meat-packing lines as a model. When the total time of assembly for a single car fell from 12.5 labor hours to 93 labor minutes, Ford was able to drastically reduce the price of his cars. His success not only brought automobile ownership within the grasp of the average person, but it served notice to all types of manufacturers that the assembly line was here to stay. The assembly line transformed in a revolutionary way the manner and organization of work, and, by the end of World War I (1914–1918), the principle of continuous movement was sweeping mass-production industries of the world and was soon to become an integral part of modern industry.
The basic elements of traditional assembly line methods are nearly all the same. First, the sequence in which a product’s component parts are put together must be planned and actually designed into the process. Then, the first manufactured component passes from station to station, often by conveyor belt, and something is done or added to it. By the last station, the product is fully assembled and is identical to each one before and after it. This system ensures that a large quantity of uniform-quality goods are produced at a relatively low cost.
When manufacturers first implemented the idea of the assembly line, they enjoyed dramatic gains in productivity, and the consumer realized lower costs. However, the nature of work in a factory changed radically. Skilled workers were replaced by semiskilled, or even unskilled, workers, since tasks had been minutely compartmentalized or broken down and each person was responsible only for assembling or adding one particular part. Manufacturers soon realized however, that not only were a great number of managers and supervisors required to oversee these laborers, but a high degree of preplanning on their part was absolutely essential. Overall operations had become much more complex and correct sequencing was essential. Thus, before actual assembly line production could begin, proper design of both the product and the assembly line itself had to be accomplished. Even the simplest tasks were critical to its overall success, and the apparently straightforward assembly line became a highly complex process when broken down and considered step-by-step.
Role of workers
Early twentieth-century assembly line systems carried the concept of division of labor to an extreme, and they usually restricted each worker to the repetitive performance of one simple task. These individuals had few real skills, and they were not required to know any more than their basic job demanded. This human element proved to be the weakest link in the entire system. For most people, assembly line work eventually entailed a physical and mental drudgery that became seriously counterproductive. Often the work itself was detrimental to an individual’s physical and mental well-being, and from a manufacturer’s standpoint, this usually resulted in diminished productivity.
Henry Ford and his fellow industrialists soon discovered this phenomenon when they tried to speed up their assembly lines. Since the pace of the assembly line was dictated by machines, supervisors often accelerated them, forcing workers to try to keep up. When this constant pressure to increase production was combined with the essentially dull and repetitive nature of the job, the result was often a drop in quality as well as output, not to mention worker unrest and dissatisfaction. By the 1920s, industry leaders realized that they could not ignore the dehumanizing aspects of the assembly line. However, it was not until after World War II (1939–1945) that the major industries made serious attempts to make the mechanical aspects of the assembly line accommodate itself to the human physiology and nervous system.
The logical evolution of the assembly line would seem to lead to one that is fully automated. Such an automated system would ideally imply the elimination of the human element and its replacement with automatic controls that guarantee a level of accuracy and quality that is beyond human skills. In fact, this is the case today in some industries where automation has completely changed the nature of the traditional
KEY TERMS
- Automation
- —The application of self-governing machines to tasks once performed by human beings.
- Division of labor
- —The separation of a job or task into a number of parts, with each part performed by a separate individual or machine.
- Industrial robots
- —Programmable, multi-purpose, electromechanical machines that can perform manufacturing-related tasks that were traditionally done by human beings.
- Interchangeable parts
- —The production of high precision parts that are identical, as opposed to unique, hand-made parts; this standardization of size and shape assures its quality and quantity and permits low-cost mass-production.
- Mass production
- —A method of organizing manufacturing processes to produce more things at a lower cost that is based on specialized human labor and the use of tools and machines.
assembly line. Computer advances have resulted in assembly lines that are run entirely by computers controlling industrial robots of all kinds. Increasingly, such robots not only perform the repetitive, elementary tasks, but also are sufficiently intelligent (via feedback systems) to regulate or adjust their own performance to suit a changing situation. Especially in the automobile industry, assembly lines consist of machines that are run by machines. People are still needed of course, for quality control, repair, and routine inspection, as well as for highly specialized tasks. In fact, rather than minimizing the human skills needed to oversee these systems, today’s automated assembly lines require more highly skilled workers to operate and maintain the sophisticated, computer-controlled equipment.
In the 1980s, Japanese and Italian automobile manufacturers so successfully automated their assembly lines that certain of their factories consisted almost entirely of robots regularly doing their jobs. On one particular Italian Fiat, human hands did only 30 of the 2,700 welds. In principle, they are Henry Ford’s assembly lines carried to their ultimate conclusion. Starting again with the bare chassis, major components (which themselves have been automatically assembled elsewhere) are attached by robots, and the computer keeps track of exactly what is to be added to each. Each vehicle is considered unique and the central computer assures its total assembly. On the other hand, General Motors found that robots could not replace human workers and had to retrench from technology and focus on retraining workers. Final product assembly and delivery to the dealer offers the consumer, if not always the most affordable product, an extremely wide array of special options.
See also Robotics.
Resources
BOOKS
Crowson, Richard. The Handbook of Manufacturing Engineering. Boca Raton, FL: CRC/Taylor & Francis, 2006.
McNeil, Ian. An Encyclopaedia of the History of Technology. New York: Routledge, 2002.
Tilton, Rafael. Henry Ford. San Diego, CA: Lucent Books/Thomson Gale, 2003.
OTHER
“Ford Installs First Moving Assembly Line, 1913.” Public Broadcasting Service. <http://www.pbs.org/wgbh/aso/databank/entries/dt13as.html> (accessed November 9, 2006).
Leonard C. Bruno
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
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 alsoAutomobile Industry ; Industrial Revolution ; Mass Production ; Robotics .
Assembly Line
Assembly line
An assembly line is a system of mass production in which a product is manufactured in a step-by-step process as it moves continuously past an arrangement of workers and machines. Introduced in the nineteenth century, it provided the basis for the modern methods of mass production of quantities of standardized, relatively low-cost goods available to great numbers of consumers. As one of the most powerful productivity concepts in history, it was largely responsible for the emergence and expansion of the industrialized, consumer-based system we have today.
History
The principle of continuous movement is perhaps the simplest and most obvious fact of an assembly line, dating back to Assyrian times, where there is evidence of a system of bucket elevators called the "chain of pots." Miners in medieval Europe also used these bucket elevators, and by the time of the Renaissance, engineers were becoming familiar with some form of the assembly line. In the fourteenth century, for example, the shipbuilding arsenal of Venice used moving lines of prefabricated parts to equip their war galleys. What may have been the first powered-roller conveyer system was introduced in 1804 by the British Navy's automatic production of biscuits or "hardtack." It used a steam engine to power its rollers. By the 1830s, the principle of continuous processing was starting to enter the consciousness of manufacturers, although it was by no means fully embraced until the 1870s in the United States. By then, the principles of division of labor and interchangeable parts had been successfully demonstrated by the American inventors Eli Whitney (1765-1825) and Samuel Colt (1814-1862).
The assembly line was first used on a large scale by the meat-packing industries of Chicago and Cincinnati during the 1870s. These slaughterhouses used monorail trolleys to move suspended carcasses past a line of stationary workers, each of whom did one specific task. Contrary to most factories' lines in which products are gradually put together step-by-step, this first assembly line was in fact more of a "dis-assembly" line, since each worker butchered a piece of a diminishing animal . The apparent breakthroughs in efficiency and productivity that were achieved by these meat packers were not immediately realized by any other industry until the American industrialist Henry Ford (1863-1947) designed an assembly line in 1913 to manufacture his Model T automobiles. Ford openly admitted using the meat-packing lines as a model. When the total time of assembly for a single car fell from 12.5 labor hours to 93 labor minutes, Ford was able to drastically reduce the price of his cars. His success not only brought automobile ownership within the grasp of the average person, but it served notice to all types of manufacturers that the assembly line was here to stay. The assembly line transformed in a revolutionary way the manner and organization of work, and by the end of World War I, the principle of continuous movement was sweeping mass-production industries of the world and was soon to become an integral part of modern industry.
The basic elements of traditional assembly line methods are nearly all the same. First, the sequence in which a product's component parts are put together must be planned and actually designed into the process. Then the first manufactured component passes from station to station, often by conveyor belt, and something is done or added to it. By the last station, the product is fully assembled and is identical to each one before and after it. This system ensures that a large quantity of uniform-quality goods are produced at a relatively low cost.
When manufacturers first implemented the idea of the assembly line, they enjoyed dramatic gains in productivity, and the consumer realized lower costs. However, the nature of work in a factory changed radically. Skilled workers were replaced by semi-skilled or even unskilled workers, since tasks had been minutely compartmentalized or broken down and each person was responsible only for assembling or adding one particular part. Manufacturers soon realized however, that not only were a great number of managers and supervisors required to oversee these laborers, but a high degree of preplanning on their part was absolutely essential. Overall operations had become much more complex and correct sequencing was essential. Thus, before actual assembly line production could begin, proper design of both the product and the assembly line itself had to be accomplished. Even the simplest tasks were critical to its overall success, and the apparently straightforward assembly line became a highly complex process when broken down and considered step-by-step.
Role of workers
Early twentieth century assembly line systems carried the concept of division of labor to an extreme and usually restricted each worker to the repetitive performance of one simple task. These individuals had few real skills, and they were not required to know any more than their basic job demanded. This human element proved to be the weakest link in the entire system. For most people, assembly line work eventually entailed a physical and mental drudgery that became seriously counterproductive. Often the work itself was detrimental to an indi vidual's physical and mental well-being, and from a manufacturer's standpoint, this usually resulted in diminished productivity.
Henry Ford and his fellow industrialists soon discovered this phenomenon when they tried to speed up their assembly lines. Since the pact of the assembly line was dictated by machines, supervisors often accelerated them, forcing workers to try to keep up. When this constant pressure to increase production was combined with the essentially dull and repetitive nature of the job, the result was often a drop in quality as well as output, not to mention worker unrest and dissatisfaction. By the 1920s, industry leaders realized that they could not ignore the dehumanizing aspects of the assembly line. However, it was not until after World War II that the major industries made serious attempts to make the mechanical aspects of the assembly line accommodate itself to the human physiology and nervous system .
The logical evolution of the assembly line would seem to lead to one that is fully automated. Such an automated system would ideally imply the elimination of the human element and its replacement with automatic controls that guarantee a level of accuracy and quality that is beyond human skills. In fact, this is the case today where automation has completely changed the nature of the traditional assembly line. Computer advances have resulted in assembly lines that are entirely run by computers controlling industrial robots of all kinds. Increasingly, such robots not only perform the repetitive, elementary tasks, but also are sufficiently intelligent (via feedback systems) to regulate or adjust their own performance to suit a changing situation. Especially in the automobile industry, assembly lines consist of machines that are run by machines. People are still needed of course, for quality control, repair, and routine inspection, as well as for highly specialized tasks. In fact, rather than minimizing the human skills needed to oversee these systems, today's automated assembly lines require more highly skilled workers to operate and maintain the sophisticated, computer-controlled equipment.
In the 1980s, Japanese and Italian automobile manufacturers so successfully automated their assembly lines that certain of their factories consisted almost entirely of robots regularly doing their jobs. On one particular Italian Fiat, only 30 of the 2,700 welds were done by human hands. In principle, they are Henry Ford's assembly lines carried to their ultimate conclusion. Starting again with the bare chassis, major components (which themselves have been automatically assembled elsewhere) are attached by robots, and the computer keeps track of exactly what is to be added to each. Each vehicle is considered unique and the central computer assures its total assembly. On the other hand, GM found that robots could not replace human workers and had to retrench from technology and focus on retraining workers. Final product assembly and delivery to the dealer offers the consumer, if not always the most affordable product, an extremely wide array of special options.
See also Robotics.
Resources
books
How in the World? Pleasantville, NY: Reader's Digest Association, Inc., 1990.
McNeil, Ian. An Encyclopaedia of the History of Technology. New York: Routledge, 1996.
Periodicals
Rae, John B. "The Rationalization of Production." In Technology in Western Civilization Vol. 2, edited by Melvin Kranzberg and Carroll E. Pursell, Jr. New York: Oxford University Press, 1967.
"Who Says the Assembly-Line Age Is History?" U.S. News &World Report (July 16, 1984): 48-49.
Leonard C. Bruno
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Automation
—The application of self-governing machines to tasks once performed by human beings.
- Division of labor
—The separation of a job or task into a number of parts, with each part performed by a separate individual or machine.
- Industrial robots
—Programmable, multi-purpose, electromechanical machines that can perform manufacturing-related tasks that were traditionally done by human beings.
- Interchangeable parts
—The production of high precision parts that are identical as opposed to unique, hand-made parts; this standardization of size and shape assures its quality and quantity and permits low-cost mass-production.
- Mass production
—A method of organizing manufacturing processes to produce more things at a lower cost that is based on specialized human labor and the use of tools and machines.
Assembly Line
ASSEMBLY LINE
Developed in the early twentieth century, assembly line methods greatly increased the efficiency and productivity of manufacturing. The moving assembly line is a highly mechanized process that breaks manufacturing tasks down to the smallest detail. A product moves along a conveyor belt that is lined with workers. Each laborer performs one simple operation in the production process, so that by the time the product reaches the end of the line, it has undergone many different operations and is completely finished.
This method of mass product manufacturing can be done by largely unskilled laborers. It is an early example of the growing interaction between human laborers and machines in the workplace. The increased production and efficiency not only allowed businesses to put more of their product on the market, but it also lowered the costs of production. This, in turn, decreased the cost of the product to consumers.
The assembly line was first used by the brewing, canning, milling, and meatpacking industries. The most successful early use of the assembly line is in the automobile industry. In 1913, Henry Ford (1863–1947) began to use the assembly line at his Ford Motor Company in Highland Park, Michigan. Ford used the method in the assembly of the flywheel magneto, a part of the automobile's electrical system. It showed such promise that a year later, in 1914, Ford introduced an electrically driven endless-chain conveyor to move entire auto chassis down the line for production. It was a success. Production increased from 475 cars in a nine-hour day to over 1200 cars in an eight-hour day. By using the moving assembly line, Ford Motor Company tripled production and reduced labor time per vehicle by almost 90 percent.
Since Henry Ford's success, the assembly line process has continued to grow. One development is the modular assembly. This process strives to increase efficiency by having parts of a whole product produced on subassembly lines before joining the main line for final production. For example, in the automobile industry the chassis, interior, and body would each be produced on their own subassembly line before joining together at the final stages of production.
The new assembly line methods being developed all aim to refine its original goal—to improve the production process by reducing the amount of time workers and machines spend on specific tasks.
See also: Automobile Industry, Colt Manufacturing, Ford Motor Company