CAD can be defined as any design activity that involves the effective use of computer to create, modify, and document an engineering design. There are four phases of CAD:
- Synthesis (geometric modelling).
- Analysis and optimization (engineering analysis).
- Evaluation (design review and evaluation).
- Presentation (automated drafting).
The first phase is geometric modelling. It is concerned with mathematical description of the geometry of an object. The mathematical description called a model is contained in computer memory. The image is displayed on graphics terminal to perform certain operations on the model. There are various types of geometric models in CAD—wire frame and solid models, coloured and animation, two-dimensional and three-dimensional drawing.
The second phase is engineering analysis which includes the stress–strain calculations, heat transfer analysis, dynamic simulation, and optimization. The CAD system increases the designers analysis ability.
The third phase is design evaluation and review procedures. Some CAD features which are helpful in evaluating and reviewing a proposed design include:
- Automatic dimensioning routines.
- Interference checking routings.
- Kinematics routines.
The fourth phase where CAD is useful in the design process is presentation and documentation. CAD system can be used as automated drafting machines to prepare highly accurate engineering drawing quickly. It is estimated that a CAD system increases productivity in the drafting function by five times the manual preparation of the drawing.
Objectives of CAD System: The objectives of CAD system are to increase the productivity of the designer, improve the quality of the design, improve the design documentation, and create manufacturing database.
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