What is Rapid Prototyping?

Gel Coat
Resin layer (usually colored) that protects the underlying resin/glass fiber laminate from external influences such as impact, UV light, chemicals, etc.; the side of the molded part that remains most visible or external after demolding, hence the gel coat is the first layer applied to the mold.

Geometric
Standard shape features such as planes, lines, circles, cylinders, spheres, etc.

Glass Transition
The change in an amorphous polymer or in amorphous regions of a partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one. This transition generally occurs over a relatively narrow temperature region and is similar to the solidification of a liquid to a glassy state; it is not a phase transition. Not only do hardness and brittleness undergo rapid changes in this temperature region, but other properties such as thermal expansibility and specific heat also change rapidly. This phenomenon has been called second-order transition, class transition, rubber transition, and rubbery transition.

Glass Transition Temperature (Tg)
The temperature region in which the glass transition occurs. See

Glass Transition.
The measured value of the glass transition temperature depends to some extent on the method of test.

Graft
Is usually transplanted tissue, either from the host (as in dermal autografts for burns), from another of the same species (homograft, allograft), or from another species (xenograft, heterograft).

Granulate
Plastic starting material for primary processing; particles are usually in the form of lentil-shaped cylinders

Green Part
A part that has been formed by a rapid prototyping process, but is in a loosely-bonded state. For example, metal or ceramic parts formed by some selective laser sintering systems are in a "green" state when removed from the machine. They are then sintered by a secondary operation to a "brown" state.