1、外文原文：COMPUTER AIDED MANUFACTURINGThe term Computer Aided Manufacturing (CAM) covers many areas from information processing and decision making to manufacturing and machining, which makes giving a single definition for CAM extremely difficult. D. Kochan gave a very fitting definition for CAM, with its diversity and wide range of use, in his book, “CAM can be defined as computer-aided preparation of manufacturing including decision-making, process and operational planning, software design techniqu
2、es, and artificial intelligence, and manufacturing with different types of automation (NC machine, NC machine centers, NC machining cells, NC flexible manufacturing systems ), and different types of realization (CNC single unit technology, DNC group technology ).”Since CAM has such a wide range of uses, a better way to look at CAM is through CAM technologies. The CAM technologies covered are group technology, manufacturing database, automated and tolerancing. The essential role of the computer i
3、n the production function is to capture and process the data relating to a large number of transactions which continuously take place in different departments of the company. The initial research activity for CAM was Numerical Control (NC) for machine tools at the Massachusetts Institute of Technology in 1953. The first programming language was Automatically Programming Tools (APT) created at MIT, and it was the pattern for many further developments. Currently, many manufacturing functions have
4、been addressed by CAM including the following :Numerical Control (NC)Computer numerical control (CNC)Direct numerical control (DNC)Computer controlled conveyor systems Computer controlled machining processComputer aided process monitoring Computer aided fixturing design Computer aided tooling design Computer aided tolerancing analysis Computer aided cost estimatingMaterial requirement planning Computer aided process planning Computerized machinability data systems Manufacturing resources plannin
5、g Computer aided decision support systemsDevelopment of work standards Computer aided line balancing Production and inventory planning Computer aided scheduling Computer aided quality control Computer aided inspectionComputer Numerical Control. Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers, letters , and other symbols. The numbers, letters, and symbols are coded in an appropriate format to define a program is of in
6、structions for the particular workpiece or job. When the job changes, the program is what makes NC suitable for low-volume and medium-volume production, and it is much easier to write new programs than to make major alterations to the processing equipment.The principle of numerical control was first applied to the milling process, and then later to the turning process, flame cutting, drilling, and grinding. NC technology is now used more and more for other manufacturing processes, such as formin
7、g (fine forging, rolling, etc.) engraving, and laser cutting.The current NC equipment is relatively more mature. Many machines possess multiple processing functions, such as milling centers which can perform vertical and horizontal milling, drilling, boring, reaming, slotting, shaping, and turning processes. Of course, with a high capacity automated tooling library, CNC machinesfunctions can be considerably more abundant.Programmable Logic Controller . Programmable logic controller are widely us
8、ed in computer aided manufacturing. Actually , PLCs are used in virtually every segment of industry where automation is required. PLCs represent one of the faster growing segments of the electronics industry. Since their inception, PLCs have proved to be the salvation of many manufacturing plans which previously relied on electro-mechanical control system. A PLC is a solid-state device designed to perform logic functions previously accomplished by electro-mechanical relays. The design of most PL
9、Cs is similar to that of a computer . Basically, the PLC is an assembly of solid-state digital logic elements designed to make logical decisions and provide outputs. Programmable logic controllers are used for the control and operation of manufacturing process equipment and machinery. Computer sided material handling. Material handling is a very important factor in how efficiently a workshop or company can be operated. An efficient MH system will help reduce waiting time, and it may even help increase safety or the effectiveness of the entire manufacturing process.Cabbert and Brown indicated that as much as 60% of the total production cost may be accounted for by material handling. It is also evidenced that most discrete manufacturing products spend 90% of their manufacturing lead time on the duration of material handling and storage. With MH accounting for such a large amount of the total production cost, it is obviou
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