By adding programmable control devices to machines used in manufacturing, industry was able to retain much of the flexibility provided by skilled workers while automating production.
Numerical control
Significant social and technical factors lay behind the development of N/C technology. Among these factors was a hazardous work environment in manufacturing. Between 1940 and 1945, according to one estimate, eighty-eight thousand workers were killed and more than eleven million were injured as a result of industrial accidents, eleven times the total U.S. casualties in combat during World War II.
Labor unrest and the disruption of work by strikes also motivated management to find technology to replace workers. The end of World War II marked the beginning of the greatest industrial crisis in American history, industrial relations expert Neil W. Chamberlain has written. The years 1945 and 1946 saw the biggest strike wave in the history of a capitalist country. Between 1945 and 1955, there were more than forty-three thousand strikes, idling some twenty-seven million workers.
A third factor in the development of N/C technology was a shortage of skilled machinists. As early as 1947, the Bureau of Labor Statistics had warned that the pool of skilled machinists was drying up. A 1952 study verified this assertion and named retirement, reduced immigration from Europe, and a shortage of apprenticeships as the causes. The military was developing aircraft and missiles that required extremely tight tolerances and advanced machining skills to produce, and in the absence of workers with such skills, it became necessary to rely upon machines. Finally, management had a desire for greater control of manufacturing processes in order to achieve technical and economic objectives.
In the environment outlined above, it is not surprising that labor replacement technologies were of great interest to industrialists. Wide use of automation technology in industry began with “continuous-flow” processes, in which elements of a product are combined continuously. By the late 1950’s, the first industrial operations to be controlled by analog computers
Soon, steel rolling mills, blast furnaces, and various chemical processing plants around the United States went under full computer control. Companies such as International Business Machines and Honeywell began to design computer systems specifically for manufacturing operations in the 1950’s. By 1964, approximately one hundred systems were operational or on order in the petroleum-refining industry alone. This technology, however, was special-purpose in nature and only effective at replacing unskilled workers performing extremely repetitive tasks.
The greater challenge in replacing labor with machines was the development of a means of nonhuman control of general-purpose equipment that otherwise required skilled operators. The challenge of automating machine tools was how to render a general-purpose machine tool (such as a lathe or drill press) self-acting, or acting automatically according to prespecified instructions without human intervention. Adding to the challenge was the desire to retain versatility, which was required for short-run production and small batch jobs.
Essentially, the problem was one of of programmable automation, of temporarily transforming a universal machine into a special-purpose machine through the use of variable programs. With programmable automation, a change in the product being manufactured required only a switch in programs rather than reliance upon machinists to retool or adjust the configuration of the machine itself. Programmable automation would not simply render automatic operation flexible; it would also give management more direct control over the machinery of production and undermine the power of machinists on the shop floor.
A variety of approaches to programmable automation were considered. These included record-playback, or motional, control (with a machine recording the movements of a human worker and then playing them back), tracer control, plugboard controls, and numerical control. The N/C technique ultimately became the industry standard by meeting the challenge of automating general-purpose machine tools and providing management with greater control of production.
With both record-playback control and N/C, the motional information required to manufacture a part was stored on a permanent medium, such as paper tape or magnetic tape. In this way, the record-playback system served to enhance or multiply a machinist’s value; this may have contributed to management’s lack of complete satisfaction with this approach. With N/C, however, the need for machinists’ skills was reduced. The motions of the machine tool required to produce a particular part were described in detail mathematically, corresponding to the blueprint specifications for the part, and were recorded as numerical information. The entire process of producing a part, including the skill of the machinist, was reduced to formal, abstract description. That description was then translated (usually by a computer) into commands to activate machine controls. Numerical control was an abstract synthesizer of skill, circumventing the need for the machinist; an N/C tool acted as an “automatic machinist.”
The widely recognized father of numerical control was John T. Parsons. Parsons was a machinist who was in search of a means of manufacturing a particular type of wing for the Air Force. His initial designs used extensive hand computations and made use of drilling equipment that was automated, by use of commands recorded on tape, to make specified parts by drilling holes tangent to the surface of the part to be manufactured. The remaining excess material was then to be sanded down in order to bring the part into specification.
In June, 1949, Parsons was awarded a contract by the Air Force to develop an “automatic contour cutting machine” that would be controlled by punched cards or tape and would be capable of making contour cuts, or cutting rounded shapes such as those found in an aircraft wing. In the pursuit of this business, Parsons subcontracted with the servomechanisms laboratory at the Massachusetts Institute of Technology (MIT) for a portion of the development. Ultimately, the MIT lab adopted and successfully developed a continuous-path contour-cutting approach beyond the scope of Parsons’s expertise and funding. The lab took over the development of N/C technology with funding from the Air Force that endured until 1959.
The development of N/C technology has been referred to as the greatest innovation in manufacturing since the assembly line. In the late 1950’s and early 1960’s, expectations for numerical control were high. Industry experts predicted sales growth of 50 percent per year for N/C systems. Others referred to the inevitability of automation. Willard F. Rockwell, chairman of North American Rockwell Corporation, linked numerical control with nuclear power and spaceflight as the three great developments of the contemporary generation.
The early expectations were too high. As late as 1973, American Machinist reported that N/C machines represented less than 1 percent of all machine tools in use and a similarly small percentage of overall industry capacity. This was true despite a doubling in the number of N/C machines in use over the previous five years and a tenfold increase over the previous ten years. The concentration of these systems was in the machine-tool industry itself, as well as in the aircraft and aircraft-engine industries. Diffusion of the technology was slower than had commonly been anticipated.
Part of the difficulty with the diffusion of N/C technology was its economic justification. Previous methods for justifying equipment purchases and previous methods for determining the cost of parts did not fit the new technology well. Programming the new equipment was another problem: Machinists were not programmers, and programmers were limited in number and lacked understanding of machining practices. Finally, the equipment developed initially was quite sophisticated, with control of five axes of movement, and offered more than many manufacturers required or were willing to pay for. As a consequence, many early adoptions of the technology were motivated by blind faith in the technology, fear of getting left behind, or faith in the advantages of automated machinery over labor rather than strict cost-benefit evaluations. N/C technology did provide industry with “islands of automation,” and there were notable successes in its use.
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Chase, Richard B., Nicholas J. Aquilano, and F. Robert Jacobs. Operations Management for Competitive Advantage. 9th ed. Boston: McGraw-Hill Irwin, 2001. This text is widely used in courses surveying the function of operations management. Chapter 3, “Product Design and Process Selection—Manufacturing,” is the most directly applicable to this topic. Includes a CD-ROM with student resources. -
Gaither, Norman. Production and Operations Management. 5th ed. Fort Worth, Tex.: Dryden Press-Harcourt Brace Jovanovich, 1992. Chapter 5 of this basic text deals with production technology. This chapter discusses types of automation, automated production systems, factories of the future, and decision-making issues related to automation in manufacturing and services. -
Greene, James H., ed. Production and Inventory Control Handbook. 3d ed. New York: McGraw-Hill, 1997. This exhaustive reference work is the authoritative publication of the American Production and Inventory Control Society. Chapter 20, “Computers in Manufacturing,” is particularly relevant to modern automation technologies. Robotics, computer-aided design, computer-aided manufacturing, group technology, flexible manufacturing systems, cellular manufacturing, and information systems are discussed. -
Krajewski, Lee J., and Larry P. Ritzman. Operations Management: Strategy and Analysis. 5th ed. Reading, Mass.: Addison-Wesley, 1999. Chapter 6 discusses technology management as applied to both the service and manufacturing sectors. Part of the emphasis in this chapter is linking technologies with strategic choices. The chapter covers such topics as electronic data interchange, office automation, and managing technological change. -
Noble, David F. Forces of Production: A Social History of Automation. New York: Oxford University Press, 1986. An extremely thorough treatment of the development of automation from the perspective of technological history. The author notes the social factors that influenced the choices made in determining the form that automation technologies would take. An underlying theme in the book is the impact of technology on the labor/management conflict. -
Schonberger, Richard J., and Edward M. Knod, Jr. Operations Management: Improving Customer Service. 4th ed. Homewood, Ill.: Irwin, 1991. Chapter 3, “Product, Service, and Process Planning,” focuses on the selection of process technologies. The chapter describes alternatives for automation and emphasizes the way in which human potential is influenced by automation.
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