In the 60's, CAD was a computer controlled plotting pen. Furthermore, CAD required a large mainframe and was so expensive that only the largest manufacturers could consider using CAD and CAE. The advances in CAD and the fall in cost has paralleled the advances in the computer industry. CAD systems are currently available for PCs at a cost of $500plus. This means CAD is now within the reach of all but the smallest manufacturing firm. Moreover, as CAD software advanced, specific programs were created applicable for each industry. (CAD software is industry specific. For example, you would not use a CAD program for mechanical design to design an electric circuit.)
Another important aspect in the advance in CAD is the continual improvement in the graphical representation of object. As computer graphics improved, designs starting with two dimensions `wire-frame' drawings advanced sequentially to three dimensional `wire-frame' drawings, two dimensional solid objects, three dimensional surfaces, to the current three dimension solid objects. In addition, vivid colors and dynamic motion were added. Today the graphic representations are of sufficient quality the CAD can be used for styling as well as design.
Computer assisted design facilitates design because an engineer can create a rough sketch and a computer program will transform the sketch into a complete engineering drawing. In architecture, the program can add standard items such as electric outlets. This transformation of sketch to finished drawing will greatly decrease the demand for draftsmen. Engineers will create their own drawings. Secondly, CAD facilitates geometric transformations. A three dimensional part can be rotated, cut by cross sections, and examined in detail by zooming in. In designing integrated circuits software programs, silicon compilers, have been created to design the circuits given the specifications.
The digital storage of CAD designs provides two advantages. First, all departments in the firm will have the most current design. Before computer stored designs, each department might have a different version creating opportunities for Murphy's law to occur. Second, in creating multiple models or making a more advanced design, the engineer can start with the existing designs and modify them. Because a substantial percent of the new parts can be obtained through modification of the old parts, great savings of time and engineering effort are obtained. Chrysler's consolidation of their product line reduced the number of parts from 75 to 40 thousand. The use of computers allows for the clustering of similar parts in design and production. Only 20%of new parts require new designs and another 40%can be created by modifications of old designs. This saving is achieved by better organization through computer use.