[Sphynx]

First off, lets get some of the basics out of the way before we actually look at the stuff that we need to do to produce something using Rapid Prototyping.

The Basics Concepts

The very basic idea of rapid-prototyping involves the use of a descending platform in a basin containing some form or media that will either form the object itself, or a support for the object as it is built. Above the platform is a 'gun' which, depending upon each of the various types of rapid-protoyping, either fires the material or some form of energy which converts the flexible, non-fixed material in the basin to the solid walls of the object.

The 3D object being built is sub-divided inside the computer into a series of thin layers that becomes a cross-sectional pattern for the 'gun'. The gun draws the cross-section into the basin, and the platform then descends by the thickness of that particular method's cross-section. Cross-sectional thickness can vary between methods, and the smoothness of the finished product usually directly correlates to the thickness of each cross-section. In the same way as a bitmap image onscreen, the larger the layer, the bigger the 'jaggies'.

Once the platform has fully descended into the basin and the 'gun' has finished drawing each layer, the gun retracts and the platform raises up again to let the remaining material drain away (if required by that process) and allow the object to be accessed.

Again depending on the individual process, the object may then need to be cleaned and then have a further process performed on it to finalise the material - some need a second curing process to fully harden the resins, while others may need to be sprayed with an additional finish.

The materials

There are a number of materials in general use within rapid prototyping, and what lies below is a simple summary and by no means meant to be complete. It is provided here as a general guide only as I'm guessing that most people from our fraternity will actually want a reasonably solid and smooth object rather than some of the special material properies that are available.

Somos
The various Somos resins provide a range of properties including general fast production, accuracy, water-resistance, transparency, pure and clear white, and even high temperature resistance suitable for prototype testing.

Accura and RenShape
Both durable and accurate materials mimicking ABS plastic.

Polycarbonate/ABS
A mix of polycarbonate and ABS plastic. It provides both strength and durability and is widely used in the production of parts in the automotive, electronics and toy industry. It has good thermal properties and while able to produce the same detailing as ordinary ABS, it is significantly stronger.

ABS / ABSi
Reasonably strong and durable it has become an industry standard plastic. Objects made from ABS in rapid-prototyping have about 3/4 the strength of moulded ABS used in other processes, such as injection moulding. ABSi is similar to ABS, but translucent and with a significantly higher resistance to impacts (hence the 'i' suffix).

Polycarbonate / Polycarbonate ISO
Probably the strongest material available for rapid-prototyping. Like ABS, it has about 3/4 the strength of the same material used in a process such as injection moulding. The ISO version of this material meets the highest of the six standards used in ISO grading and is also suitable for sterilisation using either gamma radiation or ethylene oxide.

Plaster Powder / Starch
A plaster based powder that is infused by cyanoacrylate or epoxy resin to produce a very high resolution cross-section. It probably has the thinnest cross-sectional width available, and allows the use of multiple colours within the same object. It is invariably only used with the ZCorp and other inkjet 'inkjet' processes. Starch provides the same type of powder based media but is really not used for permanent objects - probably just temporary items which may see destruction anyway, such as in a master mould making process.

Various PolyJet Resins
Various resins providing highly detailed and smooth finishes. These materials generally provide a good impact strength as well as a slight resiliance allowing 'snap fit' capabilities.

TangoGray and Black PolyJet Resin
These materials are very similar to rubber or silicone and objects made from these materials can therefore be made to stretch over other components.

Duraform PA and GF
Duraform is a polyamide based material providing high durability. The GF version of this product incorporated glass beads.

Next: The various types of Rapid Prototyping available