1、附录 1 英文原文 Scope of CAD/CAM Computer-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 comput
2、er 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 loop of
3、 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 then des
4、igned 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, together wit
5、h 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. The
6、 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 outer
7、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 analysis
8、, 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 instructions
9、 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 forecasts
10、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 for th
11、e 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 each new
12、 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 cases
13、. 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 the concept of computer-integrated manufacture ( CIM), with the final objective being
14、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 particularly desirable because the
