Many properties of products have to be modeled, including form, dimension, tolerance and structure. In all of these areas geometry, images and spatial manipulation are very important. For this reason, CAD is founded on computational geometry and computer graphics.
The role of modeling and communication
It is important to distinguish between models of the design process, which essentially attempt to describe the pattern that designers follow in the design of products and models of the designs themselves.
Models of the design are used for a variety of purposes. They are used to record and manipulate ideas and to evaluate the design. The models have a major role in the communication of the design between participants in the process, and to those involved in the manufacture, development and subsequent use of the product.
Types of design model
In practice, the designer uses a host of different models depending on what property of the design is to be modeled, and who or what is the target, or receiver, for any communication. The designer has to model the function of a design, its structure, the form of the component parts, and the materials, surface condition and dimensions that are required. He may also wish to form mathematical models, or other computer-based representations, to assist in the evaluation of design.
For any particular combination of modeled property and receiver there will be a type of model and a technique for its generation that will be the most appropriate.
Of all the modeled properties, form and structure are of particular importance in engineering, and the most appropriate method of representing these has traditionally been graphical, by drawings of form, by a system engineering approach, or by diagrams showing structure, or system arrangement.
The target receiver for the communication influences in particular the technique that is used for the generation of the model. In order for any communication to be successful, the “language” that is employed must be agreed and understood by all those involved.