Using RP Methods for Production Parts

Terry Wohlers Wohlers Associates, Inc.

This paper was presented in December 2000 at EuroMold in an event titled "RP - Rapid Production: An International Conference."


Industry consultant Terry Wohlers discusses a number of industries and applications that are ripe and ready to use RP for the production of final manufactured parts. Among them are parts for business jets, helicopters, racecars, high-end consumer and industrial automobiles, antique cars, sports gear, hearing aids, surgical implants, and prosthetics. Wohlers will also provide an update on some of the companies that have pioneered the idea of "rapid production" including Specific Surface, Therics, and Align Technology. In the future, RP will mean rapid production.


Industry consultant Terry Wohlers is president of Wohlers Associates, Inc., a consulting firm he founded in 1986. Wohlers' highly sought after views and opinions come from years of collecting and analyzing market data, coupled with his work as an advisor to major organizations in the U.S., Europe, Asia, and South America. He has authored nearly 250 books, articles, reports, and technical papers on engineering and manufacturing automation. In 1992, Wohlers led a group of 14 individuals from industry and academia to form the first association dedicated to rapid prototyping. In 1998, he co-founded the Global Alliance of RP Associations (GARPA) involving 14 member nations around the world. Wohlers is serving as the chairman of this conference.


Rapid production is the use of methods of rapid prototyping (RP) to manufacture final end-use parts. Manufacturing companies are beginning to explore this idea as they seek methods and strategies of producing finished products more quickly than has been possible in the past. Delays in tooling translate into lost market share when a company's competitors move swiftly, so rapid production can help reduce, or in some cases, eliminate these delays. Indeed, when only hundreds or a few thousands parts are needed, methods of rapid production may prove to be a viable replacement to injection molding. The use of RP patterns for the production of metal castings for finished products is another important strategy that companies are now considering.

Several factors will determine whether it makes sense to consider methods of RP for manufacturing. Companies that make parts that are relatively small and in relatively low quantities will be the first to embrace it. Also, when the cost to produce parts is high, it may be less expensive to use methods of RP to manufacture the parts. Parts that do not require a high quality surface finish and are hidden from view are also good candidates. In cases where tens or hundreds of thousands of parts are required, it may be feasible to produce and deliver finished parts using methods of rapid production in parallel with the creation of tooling. This approach would permit the company to sell and gain valuable feedback on the product while waiting for the tooling and injection molded parts.


The cost of individual parts for the aerospace industry is high. Consequently, this is an industry that could benefit from rapid production. However, the demands of this industry are quite high. Rigorous testing and certification is necessary before one can use materials and processes for the manufacture of aircraft parts. Even so, Boeing's Rocketdyne has successfully used RP technology to manufacture hundreds of parts for the International Space Station and the entire space shuttle fleet.

Using DTM's Sinterstation, Rocketdyne has produced parts in glass-filled nylon, as well as a super alloy that was developed in-house. The company is also manufacturing parts for military applications, such as the F-18 fighter jet.

Laser sintered glass-filled nylon part 
used in the International Space Station, 
courtesy of Boeing Rocketdyne.

The manufacture of business jets is another market that could benefit from RP for the production of finished parts. Individual part cost is high and quantities are low. Potential parts include custom interior plastic pieces and metal parts that would otherwise be manufactured using investment casting. Helicopters, for both recreation and industrial use, would benefit similarly. 


The racecar industry is already benefiting from RP technology for the production of metal castings. C.R.P. Technology, a division of the Cevolini Group of Italy, is using laser sintered CastForm PS from DTM to produce patterns for titanium castings. Parts include uprights, suspension supports, clutch boxes, steering boxes, and gear boxes. The Minardi Team of Italy is using these parts directly on its Formula 1 racecars. While this is not a direct manufacturing process like Rocketdyne's application, it is none-the-less an application of rapid production using RP.

Replacement parts for antique cars will also benefit from rapid production. For hard-to-find parts, owners will turn to RP to custom manufacture plastic and metal parts. As the technology improves, companies that produce high-end cars and trucks will take advantage of RP to produce custom parts specified by the buyer, giving automobiles a touch of personality that has not been affordable in the past.

Medical Applications

Several interesting medical applications are in the early stages of development. In the field of orthodontics, Align Technology is pioneering a new way of straightening teeth using stereolithography technology from 3D Systems. Using Align's proprietary Invisalign process, patients no longer wear conventional metal braces. Instead, they wear custom-fit clear plastic aligners that straighten the teeth. The company is in the process of purchasing and installing 10 SLA 7000 machines. The list price of the SLA 7000 is about $800,000, so this is a serious investment on the part of the company. The SLAs are used to produce patterns that are in turn used to manufacture each custom aligner. The patient receives 12 to 48 aligners, depending on the particular case. The individual wears each aligner for about two weeks, removing them only to eat, brush, and floss. As they replace each aligner with the next, the teeth moves little by little. Invisalign was launched in July 1999, and already, more than 6,000 patients are in treatment.

Plastic aligner created using
 the Invisalign process, 
courtesy of Align Technology

  Companies that specialize in implants and surgical reconstructions have benefited from RP for some time, although its use has been limited. In the future, RP will become popular for the manufacture of custom knee and hip implants. Surgeons will increasingly rely on the technology to produce custom pieces for reconstructions, such as cranial facial surgeries. In the short term, companies will use 3D Systems' QuickCast and ThermoJet, DTM's CastForm, and EOS's DirectPattern to produce the patterns for the investment castings. Long term, companies will directly manufacture metal parts using the growing list of machines that fabricate metal parts directly.

The production of hearing aids is another interesting area that is being explored. As early as 1989, one major manufacturer of custom-fit hearing aids investigated the idea extensively. Since then, RP machines, materials, computers, and laser scanners have improved dramatically, making the idea much more feasible today. A number of hearing aid manufacturers are currently evaluating RP and related technologies for the manufacture of custom-fit shells that fit in the ear canal. A non-contact scanner digitizes a silicone impression of the ear and custom software prepares the data for fabrication on the RP machine.

Left: Believed to be the first fully functional hearing aid
produced from a stereolithography shell. 
Right: Hearing aid shell produced with Fused 
Deposition Modeling (FDM).

Therics has produced a machine called TheriForm for medical applications. It is based on the Three-Dimensional Printing (3DP) technology invented at the Massachusetts Institute of Technology (MIT). TheriForm is used to manufacture time-release "designer pills" by printing binders and medicine onto the surface of a powder. The process builds up one voxel at a time, creating microdose tablets that can release one or more drugs in a series of controlled stages. The Series 3200 TheriForm machine, which uses a print head consisting of either 16 or 32 nozzles, is capable of printing up to 60,000 oral dosage forms per hour.

Therics also uses the technology to produce resorbable tissue scaffolding and implants for cartilage, tendon, and bone substitutes. They are built from powdered natural or synthetic bones, with the latter being either bioceramic or bioglass, and could include drugs, growth factors, and gene fragments to promote cell regeneration. The process has been FDA validated in the USA, although the products themselves are still under development.

Consumer Products

In the future, companies will manufacture customer products, such as footwear, using non-contact scanners and methods of RP. Over the past few years, this idea has been discussed and evaluated repeatedly and some have even tried to make a business of it. Companies that manufacture expensive shoes, such as those worn by professional athletes, will be the first to use RP for rapid production.

One can also envision the use of RP to produce custom-fit eyeglasses and safety goggles. The cost of purchasing and operating RP machines will need to drop significantly before this approach makes economic sense, although it is likely to happen.

Makers of scuba and snorkeling gear will also benefit from rapid production. Dive masks must fit perfectly, yet it is not easy to obtain a good fit. The result is a mask that fills with water—something that divers prefer to prevent happening when diving deep below the surface. Dive fins also fit poorly because they come in standard sizes. Even a size that is supposed to fit well often does not. For this reason, divers would pay a premium to get fins that fit comfortably.

Other Applications and Industries

In the USA alone, organizations spend an unbelievable amount of money on professional and college sports. Yet American football players, for example, are at great risk due to the brutalities of the sport. At any time on the field, the season can come to sudden end for a top athlete. Consequently, teams take every precaution necessary to reduce the risk of injury. Helmets and shoulder pads come in standard sizes, but they don't always fit as well as they should. Using non-contact scanners, software, and RP machines, it is possible to manufacture helmets and pads that are custom-tailored to the specific needs of the athlete.

Museums are looking for less expensive ways of reproducing bones and valuable artifacts. With technology that is available today, it is possible to reproduce replicas in an efficient and affordable way. A few museums have discovered the benefits of RP, but many more will use it in the future for the rapid production of items that would be impossible to replace if lost or destroyed. 

Specific Surface is another company that has licensed MIT's 3DP technology. The company has developed a process, called CeraPrint, for rapidly producing high performance ceramic filters for industrial and diesel exhaust applications. Using CeraPrint, the company claims that it can efficiently produce filters and substrates in quantities of 10 to 100,000. Over the past year, Specific Surface has been working on the development of recrystalized silicon carbide filters for particulate removal from diesel engines. The company also produces filters for liquids. For example, Kikkoman in Japan has been using its CandleStac products for the filtration of soy sauce. The modules clarify high viscosity soy sauce (10,000 cps) removing particles 15-20 microns in diameter at 1000 ppm.

Ceramic filter produced using the CeraPrint process, 
courtesy of Specific Surface

Companies that produce electrical connectors are exploring ways in which they might use RP technology to manufacture products. The fine resolution offered by some stereolithography processes in the USA and Japan makes it possible to manufacture connectors and other electrical components in configurations that would be impossible to produce any other way.


The idea of rapid production conjures up questions and issues such as "how would designs change if one could manufacture parts without the constraints imposed by tooling?"  Using this approach, one could design and manufacture parts without regard to draft, die lock conditions, or even assembly. Historically, these problems have created a need to reduce the complexity of part geometry and have stifled the imagination and creativity of designers. This, in turn, has made it difficult to manufacture some products that may have broad market appeal. In the future, companies will pay a premium for the flexibility of machines that can produce quantities of production parts quickly and economically, without the need for tooling.

Part of the challenge for companies to move toward the idea of rapid production is the long-established traditions and cultures within organizations. Some companies may appear to be well suited for this new approach to manufacturing, but the "thinking" within the organization may prevent it from happening. The best candidates are companies with progressive thinkers and individuals willing to take risks, push the limits, and try new ideas and technology.

Copyright 2000 by Terry T. Wohlers