計(jì)算機(jī)輔助設(shè)計(jì)外文翻譯---cadcam的應(yīng)用范圍(完整版)
【正文】 tems. 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 for CAD is still the drafting features or interactive puter 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. The total time required from inception of an idea to its plete specification can be reduced by an order of magnitude by using easily alterable geometric models. Design perturbations/ changes can be pleted in minimal time. Whole scenarios of design possibilities can be constructed quickly. 2. Improved product design. Because CAD systems allow the designer to alter the product without major redravring with considerable time mitment, many final designs can be constructed in a reasonable period of time. Similarly, these designs can be automatically analyzed for stlUCtural characteristics by using puteraided engineering (CAE) software such as finiteelement modeling (FEM) . 3 . Improved information access. Because CAD drawings are stored in a large puter database, they can be accessed quickly and easily. Parts can be coded on the basis of geometric shape, and similar parts 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 reinvent the wheel over and again. 4. Manufacturing, data creation. With the advent of numerical control (NC) carne the need to automatically generate the tool path required for machining. Since the part geometry dictates the machining required, kno,ing the part shape can allow for (semi)automatic partprograrn preparation. CAD data can also be used for automated process planning. It is interesting to note that twenty years ago if a part of reasonable 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 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 today39。a more refined machine design, and new production processes. ). The early twentieth century became an era of prosperity and industrialization that created the demand necessary for massproduction techniques. In the 19?Os it was estimated that as the speed of an aircraft increased, the cost of manufacturing the aircraft (because of geometric plexity) increased proportionately with the speed. The result of this was the development of NC technology. A few tangential notes on this history include the following. As the volume of parts manufactured increases, the production cost for the parts decrease (this is generally known as economy of scale). Some of the change in production cost is due to fixed versus variable costs. For instance, if only a single part is to be produced (such as a space vehicle), all of the fixed costs for planning and design (both product and process) must be absorbed by the single item. If, however, several parts are produced, the fixed charges can be distributed over several parts. Changes in production cost, not reflected
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