Assembly line

History

Role of workers

Resources

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