What is Rapid Prototyping?

Ablative plastics
A material which absorbs heat (while part of it is being consumed by heat) through a thermal decomposition process known as pyrolysis, which takes place in the near surface layer exposed to heat.

ABS
Acrylonitrile/butadiene/styrene (an amorphous copolymer)

Absolute Accuracy
Defined as the difference between an intended final dimension and the actual dimension as determined by a physical measurement of the part. In addition to those for linear dimensions, there are accuracy specifications for such features as hole sizes and flatness.

Absorption
(1) The penetration into the mass of one substance by another. (2) The process whereby energy is dissipated within a specimen placed in a field of radiation energy. Since processes other than absorption occur, for example, scattering, only a fraction of the energy removed from a beam is retained in the specimen.

Accelerator
A substance that hastens a reaction. For example, sulfur-containing compounds which speed up the vulcanization of rubber. Also known as promotor. Often used to denote a substance that hastens the action of an initiator or catalyst.

Acid
Chemical substitute that yields hydrogen ions in aqueous solution.

Acronyms
For commonly used RP acronyms, click here.

Acrylic Resin
A synthetic resin prepared from acrylic acid or from a derivative of acrylic acid.

Accura Bluestone
An engineered,non-settling nano-composite stereolithography (SL) material manufactured by 3D Systems.[also known as Bluestone]. For more information, click here.

Adaptive Slicing
The use of variable layer thickness in an additive fabrication process, generally thinner layers being used where part detail is greatest.

Additive Fabrication
Fabrication of a part by adding materials to a substrate or previously formed portions of a part. The most common additive fabrication methods utilize a layered approach, but other geometries are possible. The term is also used generically as a synonym for rapid prototyping.

Addition Polymer
A polymer formed by a chain reaction, for example, polyethylene and polystyrene.

Addition Polymerization (chain-reaction polymerization)
Chemical reaction in which polymers are formed from monomers by breaking the double bond (C=C); can be initiated by free radicals, ions and certain polymerization organometallic catalysts.

Adiabatic
An adjective used to describe a process or transformation in which no heat is added or allowed to escape from the system under consideration. It is used, somewhat incorrectly, to describe a mode of extrusion in which no external heat is added to the extruder, although heat may be removed by cooling to keep the output temperature of the melt passing through the extruder constant. The heat input in such a process is developed by the screw as its mechanical energy is converted to thermal energy.

Advanced Digital Manufacturing (ADM)
3D Systems' trade name for direct manufacturing or direct fabrication. Often used in conjunction with the company's OptoForm technology.

Aggregate State
For plastics, either solid or liquid (plastics decompose before they attain the gaseous state).

Air Cover
When a senior manager agrees to take the flak for an unpopular decision, while someone lower in the chain of command does the dirty work. As in: "The CFO will provide air cover, while you reduce staff by half." (A term borrowed from the military.)

Alkyd Resin
Polyesters made from dicarboxylic acids and diols, primarily used as coatings, modified with vegetable oil, fatty acids, etc.

Alloy
Composite material made by blending polymers or copolymers with other polymers or elastomers under selected conditions, for example, styrene-acrylonitrile copolymer resins blended with butadiene-acrylonitrile rubbers. See polyblend.

Alternating Copolymer
Copolymer in which the molecules of each monomer alternate in the polymer chain. See also block and random copolymers.

Alpha Pup
A market research term referring to the "coolest kid in the neighborhood." As in: "If the alpha pups go for it, we'll sell millions of them."

Amino
Indicates the presence of a - NH2 group.

Amorphous
Without (regular) form, glassy, noncrystalline, a condition of great disorder or absence of structure. Having no order, or crystallinity.

Amorphous Phase
Devoid of crystallinity, no definite order. At processing temperatures, a plastic is normally in an amorphous state. anisotropy Condition in which properties depend on direction (i.e., properties are different in different directions).

Anisotropic
Refers to the fact that parts may have different physical properties depending on which direction measurements are made, and such differences can also arise if the exact same part is made in a different way. This can happen if the building orientation of the part in the machine is changed, and also from the sequence in which the part's elements are fabricated.

Annealing
A process of holding a material at an elevated temperature below its melting point to permit stress relaxation without distortion of shape. It is often used on molded articles to relieve stresses set up by flow into the mold. antioxidant Substances which prevent or slow down oxidation of a polymeric material exposed to air.

Antistatic Agents
Agents which minimize static electricity in plastics. Such agents are of two basic types: (1) metallic devices which come into contact with plastics conducting the static to earth. Such devices give complete neutralization at the time, but because they do not modify the surface of the material it can become prone to further static during subsequent handling; (2) chemical additives which, when mixed with the compound during processing, give a reasonable degree of protection to the finished product. arc resistance Time required for a given applied electrical voltage to render the surface of a material conductive because of carbonization by the arc discharge.

As-built
A model which captures the exact physical shape of an object.

ASCII (or ASC)
A point cloud file in text format.

ASTM TESTS

PERMANENCE
Specific Gravity D-792
Mold Shrinkage (in/in) D-955
Water Absorption (%) D-570

MECHANICAL
Impact Strength,Izod (Ft-Lb/In) D-256
Tensile Strength (Psi) D-638
Tensile Elongation (%) D-638
Tensile Modulus (Psi x E+6) D-638
Flexural Strength (Psi) D-790
Flexural Modulus (Psi x E+6) D-790
Compressive Strength (Psi) D-695
Hardness, Rockwell (Rockwell R) D-785

ELECTRICAL
Dielectric Strength (V/Mil) D-149
Dielectric Constant D-150
Dissipation Factor D-150
Arc Resistance (Sec) D-495
Volume Resistivity (Ohm-Cm 10E X ) D-257

THERMAL
Deflection Temperature (F) D-648
Flammability UL-94
Linear Thermal Expansion (In/In/F) x E-5 D-696
Thermal Conductivity (BTU/Hr/Sq.Ft/F/In) C-177

WEAR
Wear Factor (Cu.In/Min/Ft/Lb/Hr) x E-10 D-3702
Coefficient of Friction D-3702

COLOR
Yellow Index ASTM E313

Atactic
Lack of structural regularity. Random placement of side chain substituents with respect to a vinyl polymer backbone. autoacceleration The increase in rate of polymerization and molecular weight of some vinly monomers polymerized in bulk or concentrated solution. Due to increase in viscosity of the reaction medium as the reaction proceeds. This impedes termination but does not appreciably affect propagation. Often called the Trommsdorff effect. average molecular weight Most synthetic polymers are a mixture of individual chains of many different sizes; hence, a molecular weight assigned to such a mixture is of necessity an average molecular weight.

Austenitising Temperatures
Austenitising temperatures normally are 980 to 1010°C, well above the critical temperature. As-quenched hardness increases with austenitising temperature to about 980°C and then decreases due to retention of austenite. For some grades the optimum austenitising temperature may depend on the subsequent tempering temperature