Building on the concept of NC manufacturing, one should ask, how are the computer instructions to the NC machines generated? If the part design and specifications can be generated on a computer, can the manufacturing instructions for NC machines be generated directly as a translation from the computer aided part design? Indeed, that is the concept of CAD/CAM, the joining of part design and processing instructions with the aid of a computer.
In the 1960s, engineers at General Motors began working with IBM programmers to develop a system of computer aided design, originally envisioned only as a sophisticated drafting system. The success of the drafting system effort is indicated by the fact that engineering drafting has been virtually eliminated in modern engineering departments. But the more far reaching effects are in the broader concepts of CAD and its connection to CAM. The data specifying the part geometry, for example, is also needed for determining how a cutting tool must move to shape the part. The specification of the cutting path must also take account of the load capacity of the machine, the material from which the part is made, the shape of the cutting tool, the speed and depth of cut, and other variables.
In currently available CAD/CAM systems, the designer sits in front of a computer console screen and can draw on a data bank of existing part designs as the part being designed may be only a variation of a previous design. Programs allow the designer to view the part in any orientation, any scale, or any cross section. Because of the efficiency of the system, the engineering analysis can be done for several alternative design solutions, perhaps analyzing the response of the part to various stresses, without building a prototype. When a design is finalized, the link to CAM is made by producing the manufacturing instructions that will control the machine to produce the part. Manufacturing issues, part of the criteria for a good design, can also be addressed as a part of the analysis.
Because of the efficiency of the CAD/CAM system, the design and manufacture of small lots, and even a custom part, can be low in cost. A CAD/CAM system for designing and manufacturing computer chips has been developed that makes custom designed chips almost as inexpensive to design and manufacture as high volume, standard designs.
Working CAD/CAM systems are now supplied by a number of software companies, and the $2.4 billion industry has been growing at the rate of 48 percent per year in the 1979 to 1984 period. While the CAD portion is more fully developed and used, the more difficult CAM link has also been developing rapidly. Siemens, a West German electronics company, recently announced a system designed to bridge the CAD – CAM gap. The system translates design information directly into the APT language that is widely used for programming NC machines.
Applications of CAD/CAM:
The early users in the aircraft industry, and indeed, some of the best known systems were created in that industry (e.g. CADAM developed by Lockheed and the AUTO system developed by McDonald Douglas). In any case, application is restricted to relatively large manufacturers because of the cost; a turnkey CAD/CAM system, including hardware and software, costs in the range of $300,000 to $500,000. However, application is now reasonably diversified in manufacturing, having spread to the largest companies in the following industries:
1. Electrical and electronic (Burroughs, Digital Equipment, General Electric, Intel Texas Instruments, Westinghouse).
2. Petroleum and refinery machinery (Exxon, Halliburton, Shell)
3. Measurement and analytical instruments (Becton Dickinson, Eastman Kodak, Xerox).
4. Transportation (Ford, General Motors, Mercedes Benz, Volkswagen).
5. Aerospace (Boeing, Rockwell, United Technologies)
6. Chemicals (Allied chemical, Dow Chemical, Dupont, Union Carbide).
7. Heavy machinery (Caterpillar Tractor, Deere & Company).