【正文】 n made. The instantaneous updating of productioncontrol data permits better planning and moreeffective scheduling . Expensive equipment, therefore, is used more productively, and parts move more efficiently through production, reducing workinprocess coats. Product quality, too, can be improved. Not only are moreaccurate designs produced, for example,but the use of design data by the qualityassurance department helps eliminate errors due to misunderstandings. People are enabled to do their jobs eliminating tedious calculations and paperwork—not to mention time wasted searching for information—the puter not only allows workers to be more productive but also frees them to do what only human being can do: think creatively. Computer integration may also lure new people into manufacturing. People are attracted because they want to work in a modern, technologically sophisticated enviroment. In manufacturing engineering, CAD/CAM decreases tooldesign,NCprogramming, and planning times while speeding the response rate, which will eventually permit inhous staff to perform work that is currently being contracted out. 二 、 Numerical Control One of the most fundamental concepts in the area of advanced mannufacturing technologies is numerical control(NC). Prior to the advent of NC, all machine tools were manually operated and controlled. Among the many limitations associated with manual control machine tolls. Perhaps none is more prominent than the limitation of operator skills. With manual control, the quality of the peoduct is directly related to and limited to the skills of the operator. Numerical control represents the first major step away from human control of machine tools. Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instrutions. Rather than operating a machine tool, an NC technician writes a program that issues operating a machine tool, an NC technician weites a program that issues operational instructions to the machine tool. 機(jī)械專業(yè)中英文文獻(xiàn)翻譯 Numerical control was developed to overe the limitation of human operators, and it has done so. Numerical control machines are more accurate than manually operated machines,they can produce parts more uniformly, they are fastre, and the longrun tooling costs are lower. The development of NC led to the development of several other innovations in manufacturing technology: discharge machining. cutting. beam welding. Numerical control has also made machine tools more versatile than their manually operated predecessors. An NC machine tool can automatically produce a wide variety of parts, each involving an assortment of widely varied and plex machining processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible form an economic perspective using manually controlled machine tools and processes. Like so many advanced technologies, NC was born in the laboratories of the Massachusetts Institute of Technology. The concept of NC was developed in the early 1950s with funding provided by the Force. The APT(Automatically Programmed Tools)language was designed at the Servomechanism laboratory of MIT in 1956. This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the further development of NC technology. The original NC systems were vastly different form those used today. The machines had hardwired logic circuits. The instructional programs were written on punched paper, which was later to be replaced by magic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. Together, all of this represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development. A major problem was the fragility of the punched paper tape medium. It was mon for the paper tape containing the programmed instructions to break or tear during a machining process. This problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instuctions had to be rerun through the reader. If it was necessary to produce 100 copie