計算機輔助設(shè)計外文翻譯---cadcam的應(yīng)用范圍(文件)
【正文】 f 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。 the increased demand far durable 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 studied. Taylar also condueted meatalcutting experiments at the Midvale Steel Campai1y that lasted 26 yeaIS and produced 400 tans af metal chips. The result af Taylar39。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 in this simple fixedveIsus variable cost relationship, are usually the result of different manufacturing procedures transferline techniques for highvolume items veISUS jobshop procedures for lowvolume items. The U. S. Department of Commerce has poin
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