Advancements in 3D CAD, stereolithography, and now, rapid tooling, mean that designs can get to market faster than ever before. Using 3D solids modelling, the designer is able to conceptualise almost anything on his PC. Whether that item can actually be made is another matter. Wonderfully carefully constructed ships in bottles can be designed that cannot possibly be manufactured in the real world. If they are, they may cost far more than the poor designer might actually realise.
It would be naive to assume that the designer can be expert in everything. In many cases, he is not. Understanding the intricate needs of the tooling process, for example, may still be one area that is seen as a bit of a black art.
Fortunately, there are experts that can help out on the tooling front, and they can be especially effective if they are allied to a stereolithography company. In that way, the designer can see his rapid prototypes and discuss the tooling of production parts with the same vendor, saving the hassle of working with two companies.