专业英语翻译.docx

1、专业英语翻译翻译资料：Computer-aided designComputer-aided design is the use of computer systems to facilitate the creation, modification, analySIS, and optimization of a design. In this context the term computer system means a combination of hardware and software. Computer-aided manufacturing is the use of a c

2、omputer system to plan, manage, and control the opemtion of a manufacturing plant. An appreciation of the scope of CAD/CAM can be obtained by considering the stages that must be completed in the design and manufacture of a product, as illustmted by the product cycle shown in Fig. 5 . 8. The inner lo

3、op of this figure inludes the various steps in the product cycle and the outer loop shows some of the functions of CAD/CAM superimposed on the product cycle . Based on market and customer requirements, a product is conceived, which may well be a modification of previous products. This product is the

4、n designed in detail, including any required design analysis, and drawings and parts lists are prepared. Subsequently, the various components and assemblies are planned for production, which involves the selection of sequences of processes and machine tools and the estimation of cycle times, togethe

5、r with the determination of process parameters, such as feeds and speedsCJJ. When the product is in production, scheduling and control of manufacture take place, and the order and timing of each manufacturing step for each component and assembly is detemnned to meet an overall manufacturing schedule

6、. The actual manufacturing and control of product quality then takes place according to the schedule and the final products are delivered to the customers. Computer-based procedures have been or are being developed to facilitate each of these stages in the product cycle, and these are shown in the o

7、uter loop of Fig. 5 . 8. Computer-aided design and drafting techniques have been developed. These allow a geometric model of the product and its components to be created in the computer. This model can tlIen be analyzed using specialized software packages, such as those for finite element stress ana

8、lysis, mechanisms design, and so on. Subsequently, dmwings and parts lists can be produced with computer-aided drafting software and plotters. Computer-aided process-planning systems, including the prepamtion of NC programs, are available that produce work plans, estimates, and manufacturing instruc

9、tions automatically from geometric descriptions of the components and assembliesCll ror scheduling and production control, large amounts of data and numerous relatively simple calculations must be carried out. One example is the determination of order quantities by subtmcting stock levels from forec

10、asts of the number of items required during a particular manufacturing period. Many commercial software packages are available for scheduling, inventory control, and shop floor control, including materials requirements planning (MRP) systems. At the shop- floor level computers are used extensively f

11、or the control and monitoring of individual machines. There is a difference in the time scale required for processing data and the issuing of instructions for these various applications of computers in the product cycle. For example, design and process-planning functions are carried out once for eac

12、h new product and the time scale required is on the order of weeks to years for the competion of the task . Scheduling and production period cusually one week,throughout the year .at the machine-control level in-structions must be issued continually with a time scale of micro-or nanoseconds in many

13、cases. One of the major objectives of CAM is the integration of the various activities in the product cycle into one unified system, in which data is transfened from one function to another automatically. This leads to theconcept of computer-integrated manufacture ( CIM), with the final objective be

14、ing the paperless factory. Several developments have taken place, but no totally integrated CIM systems have yet been achieved. Since the design and process-planning functions are carned out once in the product cycle, these are the most suitable functions for integration. This integration is particu

15、larly desirable because the geometric data generated during the design process is one of the basic inputs used by process plannipg when determining appropriate manufacturing sequences and work plans. Consequently, various activities in desilSll and process planning can share a common design and manu

16、facturing data base, as illustrated in Fig.5 .9. With such a system, geometric models of the products and components are created during the design process. This data is then accessed by various downstream activities, including N C programming, process planning, and robot programming. The programs an

17、d work plans generated by these activities are also added to the data base. Production control and inventory control programs can then access the work plans, time estimates, and parts lists (bill of materials file), in preparing the manufacturing schedules, for example.1 Computer-Aided DesignCompute

18、r-aided design, or CAD as it is more commonly known, has grown from a narrow activity and conceI;t to a methodology of design activities that include a computer or group of computers used to assist in the analysis, development, and draw-ing of product components. The original CAD systems developed a

19、nd used in industry could more realistically be classified as computer-aided drafting systems. However, the benefits, of using basic geometric information for structural analysis and planning for manufacturing were quickly recognized and included in many CAD systems. Today, as in the past, the basis

20、 for CAD is still the drafting features or interactive computer graphics (ICG) that these systems were originally designed to perform. However, the scope of these systems has taken on a new meaning. In general, there are four basic reasons for implementing CAD systems. 1 . A reduction in design time

21、. The total time required from inception of an idea to its complete specification can be reduced by an order of magnitude by using easily alterable geometric models. Design perturbations/ changes can be completed in minimal time. Whole scenarios of design possibilities can be constructed quickly. 2.

22、 Improved product design. Because CAD systems allow the designer to alter the product without major redrav-ring with considerable time commitment, many final designs can be constructed in a reasonable period of time. Similarly, these designs can be automatically analyzed for stlUCtural characteristi

23、cs by using computer-aided engineering (CAE) software such as finite-element modeling (FEM) . 3 . Improved information access. Because CAD drawings are stored in a large computer database, they can be accessed quickly and easily. Parts can be coded on the basis of geometric shape, and similar parts

24、can be called up to assist in the design and specification of new parts. Standard parts can be employed whenever possible, rather than having to re-invent the wheel over and again. 4. Manufacturing, data creation. With the advent of numerical control (NC) carne the need to automatically generate the

25、 tool path required for machining. Since the part geometry dictates the machining required, kno,-ing the part shape can allow for (semi-)automatic part-prograrn preparation. CAD data can also be used for automated process planning. It is interesting to note that twenty years ago if a part of reasona

26、ble geometric and manufacturing sophistication was created, hundreds of design and drafting hours would be required. After the part was specified, marlufacture would begin. ll1is planning would normally require some minor design changes (back to the designer and draftsman), and might take as long as

27、 the original design process. Special tooling, fixturing, etc., might also be specified during the plarming for manufacture. In all, the entire process of product and process design could take several weeks or months. With todays CAD systems, designing (againg a rea.onably sophisticated component) a

28、nd generating manufacturing plans, preparing paIt programs and producing the pm is possible in days rather than weeks. In general, the tatal en!?ineering aI1d manufacturing time has been markedly using integrated CAD/CAM methodalogies. 2 Computer- Aided lVIanufacturing The scientific study of metal-

29、cutting and autamatian techniques are pnxlucts af the twentieth century. Two. pianeers of these techniques were Frederick Taylar and Henry Ford. During tl1e early 1900s, the improving U. S. standard af living brought a new high in penlOnal wealth. Ille majar result wa; the increased demand far durab

30、le goods. This increased demand meant that manufacturing cauld no. longer be treated as a blacksmith trade, aIld the use af scientific study was emplayed in manufacturing analysis. Taylar pianeered studies in scientific ITlaI1agement in which methods far productian by both men and machines were stud

31、ied. Taylar also condueted meatal-cutting experiments at the Midvale Steel Campai1y that lasted 26 yeaIS and produced 400 tans af metal chips. The result af Taylar s metal-cutting experiments was the develapment af the Taylar tool-life equation that is still used in industry today. This toollife equ

32、atian is still the basis af detennining ecanamic metal cutting and has been used in adaptive canhulled machining. Henry Fords contributions took a different turn from Taylors. Ford refined and developed the use of assembly lines for the major component manufacturer of his automobile. Ford felt that

33、every American family shd have an automobile, and if they could be manufactured inexpensively enough then every family would buy one. Several mechanisms were developed at Ford to accommodate assembly lines. The automation that Ford developed was built into the hardware, and Ford realized that significant demand was necessary to offs