Using a CAD package (such as AutoCad or ProEngineer, ...) a lot of the trial and error steps can be taken out of the design process. Usually engineering models will only have as much detail as is required to complete the design. The advantage of designing in full 3D is that all parts of the device can be created in the CAD software "full-size". (A 20 foot long beam will be drawn 20 feet long, and the software will zoom the structure to make it fit on the screen.) This allows parts to be fitted and checked for interference with other parts. This is especially useful for complicated linkages: the linkages can be modeled and then animated to see how they will interact with each other in motion. Using the 3D model, shop drawings can be generated. Calculating dimensions to be listed on the drawings is no longer necessary: Since all the parts are drawn at their actual size, the software can determine locations and dimensions.
When all of the conflicts have been resolved, the 3D parts can be loaded into a finite element analysis package to do stress/thermal/magnetic checking. (Of course, manual verification of some of the key values is still required. Numbers calculated by software should NEVER be taken as gospel!)
Some of the CAM (Computer Assisted Manufacturing) files can then also be created from the 3D model for use on CNC (Computer Numerical Control) equipment.
Eventually a working prototype will still have to be made, but a lot of the trial-and-error prototypes can be short circuited! In some cases a prototyping machine can create plastic mock-ups of the parts directly from the 3D model ...
Another CAD advantage is the ability to load the models into a rendering software (such as 3D-Studio Max or Alias WaveFront, ...) and generate still images or animations for use in (test-)marketing or in the final advertising campaign.
To get some more information about 3D modeling in general, look at our Animation page.
