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A question often raised is the difference between the CAD systems available on pc. In our opinion this is a simple grid.

1. Non CAD systems. Just some simple programs to build images. I guess this is out of scope. Example the drawing tool inside WinWord from Microsoft.

2. 2D Drafting package. Do you think you need 3D ? 3D is interesting if the shapes you are dealing with are unlcear on 2D or if the designs you are doing express in an easier way in 3D. Example Imagineer from Intergraph.

3. 3D and 2D mixed systems. Autocad is surely a very famous representative of this class. This type of systems are interesting if you don't have enough knowledge in design or if your design cannot fit in the parametric approach (see next category). This is very common for companys dealing with large assemblys where parts are more or less positionned in fix coordinates instead of being completly constrained one on another.

4. 3D parametric systems. A good example today is Solidworks. Parts are build from design features ( like basic shapes: holes, slots, ribs). They are then assembled by mating surfaces. Anytime you can change somepart of the design and have the new product recomputed. It is extremely powerfull but you have to be sure that it fits with your type of design.

5. Surface based 3D CAD. Many systems fell in this category like Shapes from Delcam. Here design starts with free form surfaces usually builld from section curves. Surfaces are trimmed, fileted to form a complete shape. In some cases the shape is eventually turned into a solid but it is not required. This type of system is profitable for stylist or modelmakers.

CAD Computer Aid Design. A software for design of mechanical and architecture. It will usually allow some drafting in 2D and 3D modeling capabilities.