Chapter 20-Rapid Prototyping

Rapid Prototyping

the rapid development of a single example of a new part that bypasses traditional manufacturing methods in order to speed the development of the product of which it is a part; it began in the mid-1980s and serves as an important tool for visualization and design verification

Destok manufactoring, digital manufactoring, solid free-for fabrication

synonyms for rapid prototyping

Prototyping

single example of a new part that is used in product design analysis and evaluation; it aids in identifying and correcting design errors; it is usually a made of polymer material but can also be made of metal or a ceramic

Subtractive Processs

general category of rapid prototyping processes that involve material removal from a workpiece that is larger than the final part; these processes are slower (taking days or weeks), and more closely resemble traditional manufacturing processes, than other rapid prototyping processes; one advantage is that often the final production material is used; it is limited to relatively simple shapes--complex geometries are not possible

Additive Process

general category of rapid prototyping processes that build up a part by adding material incrementally in layers--slice by slice--to produce the part; the slice thickness can range from 0.1 to 0.5 mm; disregarding setup and finishing operations, these processes usually take minutes or hours to produce a part

Virtual Prototyping

general category of rapid prototyping that uses advanced computer-based visualization technologies; it is a purely software form of prototyping that uses advanced graphics and virtual-reality environment to allow designers to examine a part

Fused-Deposition Modeling (FDM)

Additive rapid prototyping process in which a gantry robot-controlled extruder head moves in two principal directions over a table, which can be raised or lowered as needed, and a polymer filament is deposited to produce a part slice by slice; a machine costs between $20,000 and $300,000

Stereolithography (STL)

one of the oldest and most common additive rapid prototyping processes in which a computer-controlled laser-focusing system cures a liquid thermosetting polymer containing a photosensitive curing agent; it begins with a platform that is just barely immersed in a vat filled with liquid photopolymer; each layer is formed by focusing the laser on a portion of the surface of the liquid; the portion touched by the laser hardens and a layer is formed; once a layer is completed, the platform is lowered sufficiently to cover the cured (hardened) polymer with another layer of liquid polymer and the sequence is repeated; once the part is completed, it is subjected to a final curing cycle in an oven

Multijet modeling (MJM) polyset process

additive rapid prototyping process similar to inkjet printing in which print heads deposit a photopolymer on the "build tray"; ultraviolet bulbs, alongside the printing jets, immediately cure and harden each layer of polymer, thus eliminating the need for any additional curing

selective laser sintering (SLS)

additive rapid prototyping process in which a high-powered laser beam sinters non-metallic or metallic powders selectively in a desired pattern; the processing chamber is equipped with two cylinders--(1) a powder-feed cylinder which is raised incrementally to supply powder to the part-build cylinder through a roller mechanism and (2) a part-build cylinder which is lowered incrementally as the part is being formed; the process is similar to STL; first, a thin layer of powder is deposited in the part-build cylinder and then the computer-controlled laser beam is focused on that layer, tracing and sintering a particular cross section into a solid mass; the part-build cylinder is slightly lowered, a new layer of powder is added to the cylinder, and the process repeats; the part does not require further curing

Electron-Beam Melting

additive rapid prototyping process similar to selective laser sintering in which the energy in an electron beam is used to melt titanium or cobalt-chrome powder to make metal prototypes; the workpiece is produced in a vacuum; unlike SLS, fully dense parts are produced

Three-dimensional printing (3DP)

additive rapid prototyping process in which an ink-jet mechanism deposits a liquid droplets of inorganic binder material onto a layer of polymer, ceramic, or metallic powder; a piston supporting the powder bed is lowered incrementally, and with each step, a layer is deposited and then fused by the binder; there is considerable flexibility in the materials and binders used; it is possible to produce full-color prototypes by having multiple printheads each using a different color binder

Ballistics-Particle Manufacturing

additive rapid prototyping process related to 3DP in which an ink-jet head, guided by a three-axis robot, ejects a stream of (plastic, ceramic, metal, wax) material through a small orifice; the material ejected is the build material, so no powder is involved

Laminated- Object Manufacturing

additive rapid prototyping process in which (1) a laser beam or vinyl cutter is used to cut slices on paper or plastic sheets, (2) an adhesive is applied to each sheet, and (3) the sheets are either manually or automatically stacked to produce a part

Solid - Ground curing (SGC)

fast and expensive additive rapid prototyping process that is unique in that entire slices of a part are produced simultaneously and instantly; the process works as follows: (1) the next slice is created by computer software, (2) a mask of the slice is printed on a glass sheet (it is dark where material is not desired and transparent where it is desired) and at the same time a thin layer of photoreactive polymer is deposited on a separate surface--the work surface--where the slice will be made, (3) the photomask is placed over the work surface and a UV floodlight is projected through the mask--wherever the mask is clear, the light shines through to cure the polymer, (4) the uncured polymer is vacuumed from the surface and wax is put in its place which hardens quickly, (5) the layer is milled to achieve correct thickness and flatness, and (6) the process is repeated--layer by layer--until the part is finished

Direct (rapid) manufacturing

use of rapid prototyping as a manufacturing step in production; use of rapid prototyping processes to manufacture final parts that are used in a product; it is usually only used for small production runs if at all; parts produced in this manner tend to perform more poorly with respect to wear, fatigue, and life cycle than parts produced via traditional manufacturing methods

Rapid Tooling

production of tooling or patterns by rapid prototyping for use in various manufacturing operations; advantages include the reduction in lead time and disadvantages include the potentially reduced tool or pattern life compared to those obtained from machined tool and die materials such as tungsten carbide; an example includes the use of STL to make the "wax" (actually polymer) patterns that are used to assemble the tree pattern that begins an investment casting process

Epoxy

any of a class of resins derived by polymerization from epoxides (ring-shaped compounds consisting of an oxygen atom bonded to two other atoms, usually of carbon, that are already bonded to each other); it is used chiefly in adhesives, coatings, electrical insulation, solder mix, and castings

Sprayed-metal tooling

rapid tooling process in which (1) rapid prototyping creates a pattern, (2) a zinc-aluminum alloy is sprayed on the pattern's surface, (3) the pattern is placed in a flask that is filled with an epoxy to make a mold half, and (4) a second mold half is created using the same process; the mold can then be used for injection molding