Here at Abacus Design Studio we can take a 2D drawing and import the data into selected sketch planes to produce a working 3d model part. We do this by extracting views into separate sketches for extruding into a base feature, whilst also continuing to add the features of the modelled part.
The 2d to 3d conversion process is usually faster and more reliable than redesigning the part from scratch once the 2d data as been converted into a 3d model the model can then (if required) be used in the rapid prototyping process to produce the modelled part.
The process of a 2d to 3d conversion is also very affective in assemblies of the parts and can be used to check for correct fit, clearance, and tolerance,
Another advantage of a 2d to 3d conversion is that assembly can easily be shown in any varied configurations that many be required.  

Also see our page on Simulation for a demonstration of how video simulation can be used as a training aid in the assembley of components built in their correct order and orirentation for manufacture.
Also provides a great training tool