1. Do I really need RP? Do I have other choices?

Rapid prototyping is a misnomer.
The technology is not always used to make prototypes nor is it even especially rapid in many instances. While we may speak of rapid prototyping and use the terminology without embarrassment, we are best served by thinking about these multifarious technologies in terms of their most common and defining attribute: Rapid prototyping is computer-controlled additive fabrication. Once the concept of adding materials together to make an object or a part is resolutely ensconced, it becomes easier to understand when using these technologies may bestow advantage on a particular application - and when it's best to avoid them altogether.

Additive fabrication methods are not better than subtractive ones,
nor will they become complete replacements for them. Milling, turning, EDM and other subtractive methods have reached an extraordinary level of development and they continue to evolve. They are fast, versatile, inexpensive, readily available and well-understood by large numbers of practitioners. Indeed, in many if not the majority of cases they are quite sufficient to make prototypes rapidly, and as yet have no equal when it's necessary to make very precise parts in final materials.

Additive technologies are instead complementary to subtractive ones, just as the name implies. They should be used if the situation calls for:

1. complex or intricate geometric forms,
2. simultaneous fabrication of multiple parts into a single assembly,
3. multiple materials or composite materials in the same part.

The first two item are closely related, of course. An assembly of multiple simple parts leads to an increase in geometric complexity and the stacking-up of just a few trivial individual parts can make for a difficult subtractive machining problem. RP circumvents complexity by reducing all geometries to a series of simple layers. The selection of additive technology is thus largely a matter of determining that a particular geometry demands it.

The third item, the use of multiple materials, is a subject of present day research and development. For most applications today, it's not an important consideration. Nevertheless, the capability is beginning to mature in several rapid prototyping technologies, and as it becomes more widely available more applications will take advantage of it. What's interesting about it is that additive technologies make it possible to completely control the composition of a part at every geometric location. Thus, RP is the enabling technology for controlled material composition as well as for geometric control.