Rapid Prototyping Glossary - Appendix C

From "User's Guide to Rapid Prototyping"


RP book cover


Abbreviation for 2-dimensional. Often applied to the description of CAD systems (e.g. 2D CAD) indicating that the resulting file is a flat representation that has dimensions in only the x and y axes.


Abbreviation for 3-dimensional. Often applied to the description of CAD systems (e.g. 3D CAD) indicating that the resulting file is a volumetric representation that has dimensions in the x, y and z axes.


See 3D printing.

3D Keltool®

An indirect rapid tooling process where powdered metals are formed against a pattern and sintered . This technology is owned and licensed by 3D Systems.

3D printing

1) Rapid prototyping processes that use systems that are low cost, small in size, fast and easy to use. Often suitable for an office environment. Original process and terminology developed at MIT (Massachusetts Institute of Technology); now commonly used as a generic term. 2) Collective term for all rapid prototyping activities.


Devices that have simultaneous motion in the x, y and z axes.


Devices that have simultaneous motion in the x, y and z axes and two rotational axes.

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(Accurate Clear Epoxy Solid) Stereolithography build style that offered increased accuracy and improved surface finish, when compared to earlier build styles.

additive manufacturing

See rapid prototyping or rapid manufacturing.

alpha test

In-house testing of preproduction products to find and eliminate the most obvious design deficiencies. See also beta test.


(additive rapid prototyping) See rapid prototyping.


Coding system for representing characters in a numeric form. ASCII (pronounced "asskee") files are text files that can be displayed on a screen or printed without special formatting or specific software program requirements.

aspect ratio

Relative relationship between height and width. Expressed in integer form (not percentage) as the ratio of height to width, where each is divided by the width to yield a ratio of X:1.

associative geometry

Placing and controlling graphic elements based on a relationship previously defined graphic elements. Elements placed associatively maintain the relationship an element is manipulated.


Operating under a single, integrated database structure. Allows changes in any application (i.e., design, drawing, assembly, mold, etc.) that are then reflected instantly throughout all associated applications as well as in every deliverable (e.g. drawings, bill-of-materials, NC tool paths)

axis (CAD)

Imaginary line segment upon which all measurements are made when creating or documenting a CAD model in 3D space. The complete Cartesian coordinate system is comprised of an x, y and z axis.

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Break-away support structure. A style of support structure for the fused deposition modeling process that is manually removed after prototype creation.


For shop floor or model making operations, the process of finishing a part or prototype, typically with manual operations and hand tools. Examples: sanding, filing, joining and bonding.


(boundary representation) CAD software methodology that defines the model as a set of vertices, edges, and faces (points, lines, curves and surfaces).


(bi-cubic spline) Sequence of parametric polynomial curves (typically quadratic or cubic polynomials) forming a smooth fit between a sequence of points in 3D space.

beta test

External operation of pre-production products in field situations to find those faults that go undetected in controlled in-house tests but may occur when in actual use. See also alpha test.

bezier curves

Quadratic (or greater) polynomial for describing complex curves and surfaces.

binary system

Numbering system in base two, using ones and zeros.


Single digit number in base-2, or binary notation (either a 1 or zero). The smallest piece of information understood by a computer.


Matrix of pixels representing an image.

blow molding

Manufacturing process in which plastic material, in a molten state, is forced under high pressure into a mold, causing the plastic to conform to the shape of the tool with a consistent wall thickness. Often used to produce hollow items such as bottles.


(bill of materials) Listing of all subassemblies, intermediate parts and raw materials that go into a parent assembly, showing the required quantity of each.


(Ballistic Particle Manufacturing) Rapid prototyping process where wax materials are deposited with a multi-axis, ink jet print head. Process is no longer available.

bridge tooling

Relating to molds or dies intended to fill demand between early prototype, or soft tooling, and production tooling.

build time

Length of time for the physical construction of a rapid prototype, excluding preparation and post processing time. Also known as run time.

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(computer-aided design or computer -aided drafting) Software program for the design and documentation of products in either two or three dimensional space.


(computer-aided engineering) Software method using the design data of CAD for the analysis of mechanical and thermal attributes and behavior. This is accomplished through the use of finite element analysis (FEA) software for determining mechanical strength and thermal analysis.


(computer -aided manufacturing) Software program that uses the design data of CAD to build tool paths, and similar manufacturing data, for the purposes of machining prototypes, parts, fixtures or tooling.


1) Components of a design instance in a product structure tree. Also referred to as parts. 2) Nodes in a database tree structure that have a parent. 3) Also refers to features in parametric modeling. These features are dependent on others for establishing location in space. If the parent features are changed drastically, the children can become "orphans", or unassociated.


Line segment that connects two distinct points on an arc.

chord height

Distance from the chord to the surface that the chord approximates. One of several terms that relate to the control and tolerance of the STL file.


(coordinate measuring machine) A device that determines 3D spatial coordinates from a physical part. The output is typically used for inspection and can be used for reverse engineering.


(computer numerical control) Numerical control (NC) system in which the data handling, control sequences and response to input is determined by an on-board computer system at the machine tool.


Geometry that occupies the same spatial location. For example, coincident lines can have differing lengths while one occupies the same location as the other.


Process of compacting digital data to reduce file size for electronic transmission of data archival.

computer model

Set of computer data representing a product or process and capable of being used to simulate the physical product or process behavior.

concept model

Physical model intended primarily for design review, not meant to be sufficiently accurate or durable for full functional or physical testing. Examples foam models, 3D printed parts, rapid prototype parts.

concept optimization
/ concept study

Research approach that evaluates how specific product benefits or features contribute to a concept's overall appeal to consumers. Product development tasks that help determine unknowns about the market, technology, or production processes.

concurrent engineering

Organization of product design, development, production planning and procurement that occurs in parallel rather than in series. The use of a project oriented team structure to include input from all concerned parties.

conformal cooling

Water lines in tooling that follow the geometry of the part to be produced, which creates higher cooling rates and lower cycle times. Unattainable prior to rapid prototyping techniques, significant research and development efforts are being made to understand and device optimal cooling strategies.


Mold component that forms the exterior or external surface of the closure.


Mold component that forms the internal surface of the closure.


(constructive solids geometry) CAD modeling technique that uses a hierarchical representation of instances of solids and combination operations (union, intersection, difference).


(computed tomography) 1) Scanning system based on X-Ray technology used to reverse engineer or dimensionally verify physical parts. 2) X-Ray based volumetric scanning used for solid objects (e.g. bone in humans, but also industrial components) with internal features.

cycle time

Period between the start of an operation and the start of the next occurrence of the same operation.

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Penetration depth. Variable for photocurable materials that specifies the depth of solidification at a known level of power input. Combined with Ec, these variables identify the photo speed of a resin.

design for

Process to insure that a product or its components can be manufactured. The objective is to maximize the process rate and minimize the cost to produce.


(design for assembly) Application of a design philosophy to insure that parts and part designs are optimized for use in the assembly process. This step is important when automated assembly equipment is used to insure parts can be handled, oriented and positioned accurately.


See design for manufacturability.

die casting

Manufacturing process that produces metal components through the pressurized injection of molten alloys into a metal tool (die). Typically used for high volume production.

digital modeling

The concept of holding the master product design definition in purely digital form; the total information set required to specify and document the product. Related terms include virtual prototyping, virtual product development, soft prototyping and electronic product development.


When applied to rapid tooling and rapid manufacturing applications, the production of a tool or part from a rapid prototyping devices without secondary manufacturing operations.

Direct AIM

Injection-mold tooling produced directly from a stereolithography process, where AIM stands for ACES Injection Molding. See ACES.

direct digital

Application of additive technologies (rapid prototyping) to the production of finished goods without the use of tooling or secondary processes.

direct digital tooling

Application of additive technologies (rapid prototyping) to the creation of molds or dies without the use of secondary or intermediary steps.

Direct Metal
Deposition (DMDTM)

Proprietary rapid tooling process from Precision Optical Manufacturing (POM). Laser-based technology that produces fully dense metal tools. Often applied to tool restoration.

Direct Metal
Laser Sintering (DMLS)

Rapid prototyping and tooling process from EOS GmbH that sinters metal powders.

Direct Shell Production
Casting (DSPC)

Rapid prototyping and tooling process from Soligen based on MIT's 3DP technology. Ink jet deposition of liquid binder onto ceramic powder to form shell molds for investment casting.


Trademarked rapid tooling process from EOS GmbH for the production of metal tools using the company's Direct Metal Laser Sintering technology.


See Direct Metal Laser Sintering

drop-on-demand (DOD)

Ink jet methodology now incorporated in rapid prototyping systems, where the material is deposited in a non-continuous stream. Drops are produced and deposited only as required.


(design of experiments) Methodology for running a statistically significant battery of tests (or computer simulations) on a design to determine its sensitivity to, or robustness for, design or manufacturing variations.


(dots per inch) Measure or resolution common to computer monitors and also applied to some raster-based rapid prototyping technologies where dots are equated to pixels or a single droplet of material.


See Direct Shell Production Casting.


(drawing exchange file) File format that allows for transfer of CAD data among dissimilar systems. Originally devised by Autodesk for the AutoCAD software program.

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Critical energy. A variable for photocurable materials that specifies the energy required to solidify a given thickness of material. Combined with Dp, these variables identify the photo speed of a resin.


(electrical discharge machining) Electric current passed through a graphite or copper alloy electrode that machines metal with spark erosion. The electrodes have the same geometry as the intended part or profile to be produced (machined).

early adopters

Customers who, relying on their intuition or vision, buy into new product concepts or new manufacturing processes very early in the product life cycle.

economies of scale

Achieving low per-unit costs by producing in volume, permitting fixed costs to be distributed over a large number of products.

economies of scope

Achieving low-per unit costs by computerizing production; allows goods to be manufactured economically in small lot sizes.

Electron Beam Melting

Proprietary rapid prototyping and tooling process from Arcam AB that solidifies metal powder with an electron beam.


The basic building block used in geometric modeling. Elements include points, lines, curves, surfaces, and solids.

enterprise prototyping

Rapid prototyping devices characterized by higher throughput, larger physical size, increased operator control, improved accuracy and enhanced surface finish. Often operated by a dedicated staff in a lab-like setting.

epoxy tooling

Indirect rapid tooling process where the mold is created by casting an epoxy resin, usually mixed with aluminum powder, against a pattern. Suitable for injection molding in low quantities.


Interaction of technological and work situations with the human being. Also called human factors.


Process where material, often in a molten or semi-molten state, is forced through an orifice that gives the material shape.

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family mold

Tool that has cavities for two or more different parts.


Polygonal element that represents the smallest unit of a 3D mesh. These elements can be either three or four sided. The mesh represents an approximation of the actual geometry. Three-sided (triangular) facets are used in STL files. Both three and four sided elements are used in finite element modeling.

facet deviation

Maximum distance between the triangular element of an STL file and the surface that it approximates. See also chord height.


See fused deposition modeling.


See finite element analysis.


Discrete attributes of a model or prototype that include holes, slots, ribs, bosses, snap fits and other basic elements of a product design.

feature-based modeling

CAD modeling method defined by a series of rules that are used to describe how features interact with each other to construct a specific solid. Example, the through-hole feature understands the rule that it must pass completely through the part and will do so no matter how the part changes.

finite element analysis

Method used in CAD/CAE for determining the structural integrity of a part by mathematical simulation of the part and its loading conditions. Also used to predict the behavior of parts under a thermal load.


Initial product that creates a new product category.


Used to hold and position the workpiece for a manufacturing operation.

form & fit

Shape and size of a component and its relationship to mating components. Often used in the context of design analysis of the adequacy of a part in terms of its size, shape and conformance to constraints imposed by mating or nested components.

free-form fabrication

Alternative description of rapid prototyping. Intended to describe a broader base of application where components are generated directly from digital data. See rapid prototyping.

free-form surface

Contours that cannot be defined with simple linear or quadratic mathematical equations. Many natural shapes, such as the human face, are examples.


(file transfer protocol) Communication standard for transferring data over the Internet or internal networks.

functional testing

Evaluation of a prototype, in conditions similar to those that the product will experience, to determine its ability to operate as specified.

fused deposition

Rapid prototyping process by Stratasys Inc. The process extrudes a thermoplastic material and deposits it on a layer by layer basis to form a part.

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(Global Alliance of Rapid Prototyping Associations) Alliance of rapid prototyping associations, such as RPA/SME, from around the world that fosters the transfer of information related to rapid prototyping.

gradient material

Graduated displacement of one material with another that yields a gradual transition between two materials.

gross profit

Financial measure that equals sales revenue less variable expense.

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(Initial Graphic Exchange Specification) Standard format for the exchange of 2D and 3D CAD data between dissimilar CAD software systems.


When applied to rapid tooling and rapid manufacturing applications, the production of a tool or part from a rapid prototyping devices where secondary manufacturing operations are required between the rapid prototyping operation and the production of the desired item.

injection molding

Manufacturing process where molten plastic is introduced into a tool or die with the use of pressure. Commonly applied to both prototype and production requirements.

interference checking

CAD capability that automatically examines the intersection of objects within a 3D model.

investment casting

Manufacturing process, which utilizes an expendable pattern (the investment), to produce metal parts. A ceramic mold is made by repeatedly dipping the pattern in a ceramic slurry solution followed by fine grain silica sand. The pattern is then burned out in an autoclave or furnace, which simultaneously sinters and strengthens the ceramic shell. Molten metal is then poured into the shell. After cooling and solidification, the shell is destroyed to reveal the final metal part.

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See 3D Keltool


Low melting point metal used in the casting of large mold and form tools to produce low quantities of parts. This material is generally used to make large parts.

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Laminated Object

Patented rapid prototyping system, originally from Helisys Inc. and now offered by Cubic Technologies, that uses a laser to cut a cross-section from sheet material. These cross-sections are stacked and bonded together to create an object.


Derived from concept of fusing. Rapid prototyping and tooling process from Concept Laser GmbH that produces fully dense metal parts from powders that are fused with a high energy laser.

laser sintering

Rapid prototyping processes that use heat, often from a laser, to fuse powdered materials, including plastics and metals.

layer (CAD)

A logical separation of data to be viewed individually or in combination. Similar in concept to transparent acetate overlays.

layer (RP)

A thin horizontal slice of the STL file used to fabricate a rapid prototype. Typically between 0.001 and 0.010 in. (0.025 and 0.25 mm) in thickness. Also see slice.

layer thickness

Vertical dimension of a single slice of an STL file. Smaller dimensions often lead to smoother surfaces but may increase build time.


See rapid prototyping or rapid manufacturing.


(Laser Engineered Net Shaping) Rapid prototyping and tooling process that injects metal powder into a pool of molten metal created by a focused laser beam. Originally developed at Sandia and later commercialized by Optomec, Inc.


See Laminated Object Manufacturing.


See laser sintering.

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General term for all manufacturing processes that produce parts or tools through the removal of material.


Extent to which a product can be easily and effectively manufactured at minimum cost and with maximum reliability.

mass customization

Method of production that stresses the manufacturing of small lots of customized goods rather than large volumes of standardized products.

mass production

Large-scale, high-volume manufacturing of standardized parts. Relies on "economies of scale" to achieve low per-unit costs.

mass properties

Characteristics of a solid that includes volume, weight, center of gravity, and moments of inertia.


See Multi Jet Modeling.

mold inserts

1) Components of a mold core or cavity used to change geometry features in the mold. Provides alternatives to making multiple molds. Or, it is used in the repair of hardened molds to prevent degradation of the surrounding metal if welding was used for the repair. 2) Used in insert molds to insert a complete core and cavity complete with ejector mechanism and cooling into a frame, which is then installed into a molding machine.


(magnetic resonance imaging) 1) used to generate cross sectional images of a solid part. Typically used for reverse engineering parts when 2D or 3D documentation is not available. 2) Used medically to can patients as a non-evasive method to check internal structure. 3) Process uses magnets to "align electrons" before creating a computer image. This image can be used to generate a 3D file then used to generate a rapid prototype. 3) Technique similar to CT scanning to examine internal geometry or structures.

Multi-Jet Modeling

Rapid prototyping processes from 3D Systems that use ink jet technology to deposit materials.

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(numerical control) Method of controlling the cutter motion of a machine tool through the use of numeric data and standardized codes. In contrast to CNC devices, NC tools offer automation with limited programming ability and logic beyond direct input.

neutral file

Format for electronic data that can be both imported and exported by dissimilar software programs. Examples include DXF, IGES, STEP and STL.


(Non-Uniform Rational B-Spline) Mathematical description of a surface created by two or more b-splines.

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(original equipment manufacturer) Company that uses product components from one or more other companies to build a product that it sells under its own company name and brand.


To subcontract services, such as prototyping, design or manufacturing, to an organization that is independent of the buying (requesting) organization.

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Paper Lamination
Technology (PLT)

Rapid prototyping process from Kira Corporation that laminates paper and then cuts the layer profile with a computerized knife.

parametric CAD

Type of CAD methodology that relates the geometry of different elements of a part such that the change of one element changes related features. The association is based on a predetermined correlation.


Physical representation of a design that is used to produce molds, dies or tools. Also called master pattern.


(product data management) Technology for managing and controlling all engineering and manufacturing data.


Proprietary rapid tooling process developed by Procter & Gamble that was granted to The Milwaukee School of Engineering for further process development and refinement.


Liquid resin material that utilizes light (visible, ultra-violet) as a catalyst to initiate polymerization, in which the material cross-links and solidifies. This technique is used by various rapid prototyping techniques.

pipeline management

A process that integrates product strategy, project management, and functional management to continually optimize the cross-project management of all development-related activities.


Individual dot placed on a cathode-ray tube that, when combined with neighboring dots, creates an image (e.g. television or computer monitor).

plaster mold casting

Process for creating small quantities of metal parts in aluminum, zinc or magnesium. Often used as a prototype method for the simulation of die castings. The mold is created from a pattern, with several intermediate steps. Metal is cast into the mold, as with investment casting, the mold is destroyed to yield the metal casting.


Rapid prototyping process from Objet Geometries that deposits photocurable materials through an ink jet process.

post processing

Common practice required with rapid prototype systems that refers to clean-up and finishing procedures on RP models after they are removed from the RP machine. May include mechanical or chemical removal of support structures, powder removal and surface finishing.

pre-production unit

Product that looks and works like the intended final product, but is made either by hand of in pilot facilities rather than by the final production process.


Lowest state of a solid model. A solid of surface that is not derived from other elements, such as a cube, cone, cylinder, or sphere.

product data

All engineering data necessary to define the geometry, the function, and the behavior of a product over its entire life span, including logistic elements for quality, reliability, maintainability, topology, relationship, tolerances, attributes, and features necessary to define the item completely for the purpose of design, analysis, manufacture, test, and inspection.

production tooling

1) Hardened tooling intended to create large volumes (quantities) of parts. The molds should last the life of the products produced. Typically machined from steel, it is used for the mass production manufacturing of wax, polymer or metal components.


Rapid prototyping and tooling process commercialized by Extrude Hone, Inc. that is based on the MIT 3DP technology. The process generates a "green" part by solidifying metal powder with a binder. The green part is placed in a furnace to burn off the binder, sinter the powder and infiltrate with an alloy.


Physical model of a part or product during the product development process. Depending upon the purpose, prototypes may be non-working, functionally working, or both functionally and aesthetically complete. Derived from Latin term for "first form".

prototype tooling

Short life molds and dies used in the fabrication of molded, stamping and dies and other parts. This approach has a low life expectancy compared to hardened production tooling. May yield from one to as many as 50,000 parts depending on methods and materials utilized.

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A trademarked process of 3D Systems for a stereolithography build style that reduces the mass of the pattern to accommodate the investment casting process.

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rapid manufacturing

Production of end use parts-directly or indirectly-from a rapid prototyping technology.

rapid prototyping

Collection of technologies that are driven by CAD data to produce physical models and parts through an additive process.

rapid tooling

Production of tools, molds or dies-directly or indirectly-from a rapid prototyping technology.


1) A two-dimensional array of pixels which, when displayed, form an image or representation of an original document. 2) A scan pattern (as of the electron beam in a cathode-ray tube) in which an area is scanned from side to side in lines from top to bottom. Antonym - vector.

reaction injecting

Manufacturing process where thermoset resins are injected into rigid tools.


1) Facility for annotating on-screen documents by transmitting overlaid comments and sketches. 2) Process of marking documentation for requested changes to part, tooling or specification documentation.


Process of adding shading, colors, reflectivity, textures, and other visual elements to a solid model to make it appear realistic.


General classification of non-metallic materials and compounds. For rapid prototyping, the term is most often associated with the liquid state of stereolithography photopolymers. For molding operations, the term is a reference to any thermoplastic or thermoset material.

reverse engineering

Process for the capture of the geometric definition of a physical part through scanning technologies. Resulting data, often a set of discrete points that are spatially oriented, is imported into a CAD system and used for further product refinement, prototype creation, tooling creation or manufacturing.

return on investment

Financial calculation that illustrates the value of an investment in a specific period of time. ((financial gain - cost)/cost) x 100%.


(request for proposal) Bid package, submitted to potential vendors, that solicits price and delivery information for a program or project.


(request for quotation) Similar to an RFP, but generally used when requesting individual parts.


See reaction injection molding.


Term applied to the fused deposition modeling process that describes the extrusion of material in a single pass.


See return on investment.


See rapid prototyping.


(Rapid Prototyping Association of the Society of Manufacturing Engineers) Association dedicated to the collection and sharing of information on rapid prototyping. tooling and manufacturing.


(Rapid Prototyping Mailing List) Internet forum for the online discussion of topics related to rapid prototyping.

RTV molding

See silicone rubber molding.

rubber molding

See silicone rubber molding.

rubber plaster molding

See plaster mold casting.

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sand casting

Manufacturing process for the production of metal, including gray iron, castings. Sand is packed against a form (tool) to create each half of the tool. After combining the tool halves, metal is cast into the cavity and allowed to cool. To remove the metal casting, the sand tool is destroyed.

Selective Laser Melting

Rapid prototyping and tooling process from F&S GmbH that produce 100% dense metal parts by melting a power with an infrared laser.

selective laser

Rapid prototyping process, originally developed by DTM Corp and now owned by 3D Systems, which uses a CO2 laser to fuse powdered materials, including plastics and metals.

service bureau

1) Company or group of companies providing engineering, prototyping or manufacturing support to other companies who do not have the capability. 2) For rapid prototyping, a commercial entity that specializes in providing rapid prototyping and peripheral services to a customer base.


See Solid Ground Curing.

short run tooling

Molds created for low volume (e.g. less than 100 samples) production.

silicone rubber tooling

Soft tooling technique that utilizes room-temperature vulcanized (RTV) rubber material to form molds that are cast from machined or rapid prototype patterns. Commonly used to produce small lots (25 to 100 pieces) in urethane materials.


Heating a material to a temperature below its melting point to causes it to fuse to create a solid mass.


See stereolithography.


(StereoLithography Apparatus) A trademarked name by 3D Systems for the machines that use the stereolithography process. Also used interchangeably with SL.


Single layer of an STL file that becomes the working surface for the additive process.


See selective laser melting.


See selective laser sintering.

Solid Ground Curing

Rapid prototyping process that solidifies photocurable materials through a photo-mask. The use of the mask allows curing of a complete layer with one flash of UV light. Process is no longer available.

solid imaging

An alternative term for rapid prototyping.

solid freeform

An alternative term for rapid prototyping.

solid modeling

3D CAD technique that represents all physical characteristics of an object; including volume, mass, and weight.

Solid Object Ultraviolet
-Laser Printer

Stereolithography process offered by CMET.


See Solid Object Ultraviolet-Laser Printer.

spin casting

Process that uses rubber molds to create metal castings in low melting temperature alloys. The mold is rotated and material is poured into its center. Centrifugal force fills the mold with molten material.


A trade name and technology owned by the Ford Motor Company. This process uses wire arc spray of metal alloy onto a ceramic mold pattern to generate tooling.

spray metal tooling

Process for creating prototype or bridge tooling through metal deposition onto a pattern using wire arc spray, vacuum plasma deposition or similar techniques. After creation of the metal tool face, epoxy or other materials are used to backfill the tool to add strength. Often used for injection molds.


(Subtractive Rapid Prototyping) Trademarked name of Roland Corporation used to identify rapid prototyping devices that remove material for prototype creation. Antonym - ARP (additive rapid prototyping).

stair stepping

Result of additive processes where surfaces that are neither vertical nor horizontal are not smooth, since they are approximated by individual layers.


(standard for the exchange of product model data). File format standard for the transfer of data between dissimilar CAD systems. Adopted by the International Organization for Standardization (ISO) in December 1994.


Process that builds an object, a layer at a time, by curing photosensitive resin with a laser-generated beam of ultraviolet radiation. Originally applied to 3D Systems' technology, the use of the term has broadened to include all technologies that process prototypes in this manner.


Neutral file format is exported data from CAD systems for use as input to rapid prototyping equipment. The file contains point data for the vertices of the triangular facets that combine to approximate the shape of an object. The acronym is derived from the word STereoLithography.


Boundary defining an exterior or interior face of a 3D CAD model.

surface normal

Vector that is perpendicular to a surface or facet in an STL file. For the facets of the STL file, the direction of the vector indicates the outward facing side of the facet.

surfaced wireframe

Method of 3D CAD modeling that represents part geometry with bounding edges and skins that stretch between the boundaries. The CAD model is defined by its innermost and outermost boundaries and does not contain any mass between these boundaries.

support structure

Common to many rapid prototyping processes. Scaffold of sacrificial material upon which overhanging geometry is built. Also used to rigidly attach the prototype to the platform upon which it is built. After prototype construction, these are removed in a post processing operation.

surface modeling

See surface wireframe.

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(Technology Adoption Life Cycle) Business model that describes the adoption of technology through an analysis of purchasing traits.


Plastic compound that is processed (molded) in a liquid state that is achieved with elevated temperatures. This class of plastic can be repeatedly cycled through a liquid and solid state. Common applications: injection molding, blow molding and vacuum forming.


Plastic compound that is processed in a liquid state where two or more liquid components are blended just prior to molding. Upon blending, an exothermic, chemical reaction causes the liquid to change to a solid state. Unlike thermoplastics, once solidified these materials cannot be returned to a liquid state. Common applications: rubber molding and reaction injection molding.

time to market

Period to conceive, develop, manufacture and deliver a new product.


Generic term used to describe molds or dies used in the production of parts and assemblies. Examples include injection molds, blow molds, die cast dies, and stamping dies.

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Ultrasonic Consolidation

Proprietary rapid prototyping and tooling process from Solidica, Inc. that ultrasonically welds sheet metal to deliver homogeneous material properties. After welding of the sheet material, the profile is CNC machined.


Thermoset material commonly used in rubber molding and RIM molding processes. Any of various polymers that contain NHCOO linkages and are used especially in flexible and rigid foams, elastomers, and resins.


(ultraviolet) Light energy situated beyond the visible spectrum at its violet end -- having a wavelength shorter than wavelengths of visible light and longer than those of X rays Often used in the curing of photopolymer resins.

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vacuum forming

Process for producing plastic parts by heating plastic sheet and drawing it against a form when air is pulled through the form.

virtual prototyping

Computer based generation of 3D geometry for analyzing product design features. Often associated with immersive environments where the digital data is presented with realism and offers an ability to interact with the digital design as if it were real. More commonly applied to computer-based testing and analysis methods such finite element analysis.


Quantity that has magnitude and direction and that is commonly represented by a directed line segment whose length represents the magnitude and whose orientation in space represents the direction.


Volume cell. The 3D equivalent of the pixel.

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Trademarked and patented process of Stratasys, used with the FDM rapid prototyping process, that allows models (or assemblies) to be made with movable parts already assembled. The support material is dissolved in a water-based solution.


CAD modeling method that defines a part by its innermost and outermost boundaries. The model does not contain any mass between the boundaries nor any bounding surfaces.

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1. Adapted from RP Glossary. Society of Manufacturing Engineers/Rapid Prototyping Association. www.sme.org/rpa/.



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