Functional testing places the rapid prototyping part in an operating assembly to see if it works. The limited range of rapid prototyping materials has restricted functional testing, but this is improving as higher temperature and more durable materials are introduced for many of the technologies. Objects made by rapid prototyping can also be transferred by means of secondary processes into final materials for testing.

Rapid Manufacturing
Industry is beginning to use rapid prototyping systems to directly produce parts which are functional end-use items. The obvious advantage is that there is no need for tooling, but in some cases items are being manufactured which can be made only by an additive process, or made at lower costs than subtractive or other forming methods would permit. In addition to parts for aerospace and medical applications, two strong present application areas, a surprisingly wide range of activity is being observed. The accompanying table is but a small sample.

Selected Rapid Manufacturing Applications Under Development
Catalyst and reactor structures. Cell culturing arrays. Complex filtration systems. Components for testing chips. Custom hearing aids. Electrodes and battery structures. Energy absorbers for crash protection. Fluid purification devices. Gas and fuel storage components.	Heat exchangers. High-strength, forged structures. Keys fabricated without blanks. Material screening arrays. Mesoscale electronic and mechanical components. Microcombustors and thermoelectric microgenerators. Motors, actuators , generators and permanent magnets. Optical fiber routing circuits, shuffles and manifolds. Optical tools for biological materials.	Personalized charms and jewelry. Photonic band gap structures, wave guides, oscillators. Product counterfeit prevention. Reinforced metal-matrix composites. Semiconductor lithography stages. Sound dampening and insulation systems. Special effects printing. Sperm sorting devices. Superconductor composite materials. Thin film devices and structures.

Metal Parts
There is strong interest in the fabrication of metal parts and many end-use items have been produced. For example, Boeing has used selective laser sintering (SLS) to make parts for the International Space Station. The company spun off its direct additive fabrication operations in 2002 as an independent company, now named On-Demand Manufacturing.

Laser powder forming technologies can also be expected to become important for metal part fabrication in the future. The wide range of applications includes large steel tools to make automotive parts, titanium parts for aerospace applications, and intricate stainless steel and alloy devices for medical implantation.

Several processes are also under development for the mass fabrication of small metal parts. Microfabrica Inc. is first to market in this area and commercializing technology developed at the University of Southern California. Stanford University's shape deposition manufacturing (SDM) process may also be competitive. SDM is actually a suite of technologies that can be adapted to produce parts in a wide variety of materials including metals, ceramics and all sorts of polymers.

Ceramic Parts
Several technologies are being utilized to produce ceramic parts for various applications. Laminated object manufacturing (LOM) has received a lot of development attention over the years, but inkjet and other RP methods are also being used. For example, MIT's three dimensional printing (3DP) technology has been used to fabricate large ceramic filters for coal-fired power plants and special filters for semiconductor manufacturing. MIT has worked with several large companies on ceramic applications such as parts for electronics over the years.

Plastic Parts
Plastic parts for end-use are being produced by fused deposition modeling, stereolithography and several other additive processes. For example, RedEye RPM, a large service bureau and a division of Stratasys, says 30% of its output of FDM-generated plastic parts is now going directly into end-use items. Another interesting example is microTEC mbH (Germany), a company that has developed a photopolymer-based technology similar to stereolithography. mircroTEC can produce up to hundreds of thousands of small parts per hour for medical, space and communication applications.

Selective laser sintering is also often used to directly manufacture high value polymer parts for applications which require good physical properties. In fact, EOS GmbH (Germany) makes parts for its own selective laser sintering machnes using the machines themselves.

Various types of inkjet-based and other rapid prototyping technologies are also being developed to fabricate electronic circuits and components, print heads, complex medical dosages and other generally small intricate items.

Rapid manufacturing applications will be driven by the development of materials that offer a broader range of mechanical properties or more closely mimic existing engineering materials, by improvements in resolution and finish, and by the development of specialized systems for diverse applications. Machines specifically designed for the production of hearing-aids and for dental applications have already been introduced, a trend which can be expected to continue as additive technology progresses.

For much more information, please see our tutorial section on rapid manufacturing or visit the rapid manufacturing directory pages.

Manufacturing Tooling
Rapid prototyping parts are frequently used as the basis for rapid tooling. Rapid tooling is really a special case of rapid manufacturing and was a strong, early driving force behind that market segment. The RP system typically creates a positive or negative pattern which is used to generate injection molding, investment casting or other tooling for short to medium volume production runs. Numerous techniques exist for transferring patterns created by rapid prototyping systems in plastics and other soft materials into hard metal tools and products. Some methods of rapid prototyping are also capable of producing metal parts and tools directly, although still not with the complete size, accuracy and durability of subtractive metal fabrication techniques.

Selective laser sintering (SLS) can produce metal parts which can be sintered and infiltrated to essentially full density in secondary operations. This approach is taken by 3D Systems in the US for its direct metal fabrication method. In contrast, EOS GmbH (Germany) has developed a selective laser sintering process which will fabricate nearly fully-dense metal parts directly. While the choice of alloys is limited, it's possible to use injection molding tools fabricated with SLS to produce hundreds of thousands of parts. The accuracy, secondary operation requirements and materials of selective laser sintering processes have been continuously improved over the years.

Variations of selective laser sintering have also become available in the last few years, especially from European vendors. Selective laser melting (SLM) and electron beam melting (EBM) produce fully-dense parts from powder materials. See the section on European vendors for additional information.

Laser powder forming (LPF) technologies have also made much progress in the last few years. They make use of the delivery of metal powders into a high-power laser beam where they're fused into layers. Robotic or X-Y-Z controlled-platform systems are used to guide the deposition of the material and very large parts and tools can be made. Work initiated at government laboratories and universities has been commercialized in both the US and in Europe. These systems produce fully-dense metal parts with good accuracy and metallurgical properties requiring relatively minor secondary finishing operations. Laser Engineered Net Shaping^TM (LENS ®) was developed at Sandia and has been commercialized by Optomec Design Co. Other North American companies utilizing similar approaches are POM-Group and Accufusion (Canada). As with other rapid prototyping technologies, these methods can be used to fabricate novel features such as conformal cooling channels, use multiple or gradient materials, and have the added advantage of being able to modify and repair existing tools and parts.

Much more can be learned in the rapid tooling tutorial section.

Medical Applications
Rapid prototyping has become fairly common as a surgical planning tool. Surgeons may reconstruct a patient's broken or malformed bones as a tangible model from CT or NMR data in order to study, optimize and practice intervention procedures. Other related medical applications include dental reconstruction and surgical planning for tumor removal. The latter has been facilitated in some cases by the use of photopolymer resins that provide differential coloration of stereolithography models enabling surgeons to see the precise location of a tumor.

The fabrication of prosthetics has been greatly impacted by rapid prototyping. The ability to fit a prosthesis to a patient's unique proportions quickly and at relatively low cost is a considerable advantage.

Medical dosages forms which would be difficult if not impossible to make any other way are in development. Using rapid prototyping it's possible to fabricate pills with precise and complex time release characteristics or that dissolve almost instantly. The interesting possibility of combining one drug with a second compound that synchronously counteracts the first drug's side-effects within the same pill has been descibed in the literature. Medications can be made more effective and safer in this way and drug companies may be able to realize stronger revenue streams from older drugs that go "off-patent" by providing them in novel and beneficial dosage forms.

Learn more in the medical tutorial section and medical directory pages.

Jewelry and the related arts have been particularly affected. Some systems manufacturers, such as Envisiontec GmbH in Europe and Solidscape in the US, have placed much emphasis on this application. There are also service bureaus and university programs which emphasize the design and manufacture of jewelry using rapid prototyping technology. The output of an additive fabrication system is most often used as a pattern for lost-wax, or other types of casting methods in jewelry manufacture. Direct manufacture of jewelry is also a possibility.

There is some interesting work going on in the industrial design field, although higher resolution and more aesthetically pleasing output would probably allow the technology to make faster progress. The introduction of color-capable systems by Z Corporation has greatly increased the penetration in recent years, with a wide variety of items being designed from packaged goods to sneakers.

There is also much interest in architectural modeling where some complex post-modernist building forms, for example, those of the American architect Frank Gehry, are more faithfully and easily represented than they could be using traditional model construction methods. Designs with compound curves aren't a prerequisite, though. Traditional models are costly and take a long time to build which is why an increasing number of architectural and engineering firms are buying machines. Here again, Z Corp.'s color capability has allowed the company to effectively sell into these applications and related areas such as GIS-based modeling.

Learn more in the art & architecture overview section and arts directory pages.