Rapid Prototyping/Manufacturing: “Tomorrow Is Just a Day Away”

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By Miki Fairley

When midday approaches, does the convenience of fast food beckon? Well, you can forget the drive-through. Just turn on your printer-your 3D printer, that is. The number of items that have been produced by 3D printing or rapid prototyping from an astonishing array of materials, including such quirky ones as chocolate, cheese, sugar, and household silicone-rubber caulk, staggers the imagination.

Blake Young, new product development specialist for TechHelp at Boise State University, Idaho, displays prototypes produced by the College of Engineering's 3D Systems Viper si2 SLA machine. TechHelp, a tri-university initiative to assist Idaho manufacturers, has used this machine to help Coyote Design find solutions to design challenges. Photograph courtesy of the College of Engineering at Boise State University.

On a more serious note, rapid-prototyping and manufacturing technologies have been playing an important role in the aerospace, marine, architectural, automotive, medical, dental, and consumer-products industries, to name just a few. Could these technologies also play a part in advancing O&P manufacturing? The consensus seems to be "Not today, maybe not tomorrow-but maybe the day after tomorrow."

Although there are formidable barriers to widespread use at this point, some industry experts are beginning to explore the possibilities. First, though, let's take a look at the technologies.

Rapid Prototyping: What Is It?

Also called additive fabrication (AF), three-dimensional (3D) printing, solid freeform fabrication, and layered object manufacturing, rapid-prototyping (RP) technologies add and bond materials in layers to form physical objects directly from computer-aided design (CAD) data sources. Geometrically complex, intricate designs can be made without an elaborate machine setup or final assembly.

Some of the more widely used rapid-prototyping technologies include stereolithography apparatus (SLA), fused-deposition modeling (FDM), selective laser sintering (SLS), laminated object manufacturing (LOM), three-dimensional printing (3DP), and inkjet methods including thermal-phase-change inkjet and photopolymer-phase-change inkjet.

RP in Action

To see some examples of RP in action, visit www.youtube.com/watch?v=uAt2xD1L8dw&feature=related or www.dimensionprinting.com/3d-printers/3d-printing-uprint-video.aspx

For more information about rapid prototyping, including a description of each process described above, as well as their comparative advantages and disadvantages, see "Rapid Prototyping" on the Ferris State University (Big Rapids, Michigan) website, www.ferris.edu/cot/accounts/plastics/htdocs/student/westerdale/fdm.htm or www.efunda.com/processes/rapid_prototyping/intro.cfm

Rapid manufacturing (RM) is similar but involves the actual production of series products or the use of the prototyped part in the production of other parts, as opposed to simply producing a 3D illustration of a design concept. Often the two terms are used interchangeably. Rapid manufacturing is sometimes referred to as direct digital manufacturing (DDM) or simply digital manufacturing.

What Are Its Advantages?

Creating a 3D model quickly enables design teams and other stakeholders to better analyze a part for flaws, ergonomic considerations, and suitability for manufacture, notes the Foundation for P2P Alternatives (www.p2pfoundation.net). Designers can analyze how effectively multiple components work together. With advancements in materials, parts can be built for functional testing before production begins.

Mike Hudspeth, IDSA, describes the tedious, expensive prototyping process used in the "good ol' days" in his article "Low-Cost Rapid Prototyping" in the February 2, 2008, issue of Cadalyst (www.cadalyst.com). "You would need to make fully detailed drawings and send them out to a machine shop to produce models. It took weeks to get them back only to find that changes needed to be made. It would take several iterations before you could gain enough confidence to sign off on the design and begin preliminary tooling. Then you had to have enough prototypes for testing. The tooling would give you that ability, but by then if changes needed to be made, it was both hideously expensive and time consuming."

TechHelp is a university initiative that provides technical assistance and training to Idaho's manufacturers, processors, and inventors. Conducted through a partnership between Boise State University, Idaho; the University of Idaho, Moscow; and Idaho State University, Pocatello, part of TechHelp's mission is to demonstrate the dramatic difference rapid prototyping can make in design-process time and cost savings. One of a lengthy list of Idaho firms that have accessed TechHelp is O&P manufacturer Coyote Design, Boise.

The FDM process used in the Statasys Fortus 360 production system is used commonly in the medical community for prototyping medical devices, surgical tools, and orthotics, just to name a few. Photograph courtesy of Stratasys.

TechHelp has utilized an SLA rapid prototyper to help Coyote meet various design challenges. The machine "allows us to design and test alternate iterations easily," Steve Hatten, TechHelp new-product development manager, explains on TechHelp's website, www.techhelp.org. "The SLA machine helps us stay focused on solving the design problem, rather than on manufacturing small and intricate parts."

Coyote Director of Marketing Matt Perkins says, "The TechHelp team is fast, efficient, and we get to view the product on screen and make improvements before a physical part is ever made."

Rapid prototyping/manufacturing provides "green" advantages over conventional methods as well, according to blogger Tim Thellin (blog.stratasys.com/blog/stratasys-inc). Stratasys, Eden Prairie, Minnesota, holds a large market share of the rapid-prototyping/manufacturing market and uses patented fused-deposition-modeling technology. According to Thellin, rapid manufacturing includes these eco-friendly attributes: just-in-time manufacturing, fewer hazardous materials, and less materials waste.

The best ROI situation for additive fabrication technology is "when volumes are relatively low and complexity is high," says noted RP/RM expert Terry Wohlers, author of the annual Wohlers Report, in an interview with RAPID-Today online. The size of parts is important as well, since an additive process is less cost-effective for large parts, Wohlers points out. "Let's take an example of one that's been really successful-custom in-the-ear hearing aids. That's where volumes are low-in fact, you could argue they are a volume of one because there is no two alike. They are highly complex in shape, and they're small. And because they are small, they build quickly and inexpensively. Hearing aids are close to the best-case scenario when considering ROI criteria for manufacturing using an AF process."

What Are Its Disadvantages?

Currently, for O&P applications, the disadvantages of rapid manufacturing include cost and time, as well as durability, quality, and surface finish of the product. At this point, rapid-prototyping/manufacturing equipment is simply too expensive and time consuming, and it doesn't produce the materials-quality results to make it practical for clinical and central fabrication application in the United States, according to O&P industry experts.


Despite being called "rapid," the process can take several hours to several days depending on the method used and the project. Therefore, rapid prototyping/manufacturing is a much better fit with healthcare systems in which the average length of stay is more than a few days post-amputation, John Michael, MEd, CPO, FAAOP, FISPO, of CPO Services, Portage, Indiana, points out.

For instance, in the United Kingdom, amputation patients routinely have long hospital stays for rehabilitation, contrasting sharply with the situation in the United States, where hospital stays for patients with amputation generally range from three to ten days. Thus, for the United States, a new rapid-manufacturing process that is estimated to reduce socket fabrication time from about 25 days to 18, shorten hospital stays by seven days, and save about €2,000 (US $3,000 in 2009) per patient would just not be relevant. (Author's note: These estimates were taken from Eureka magazine online, June 24, 2009: www.eurekamagazine.co.uk/article/17503/Rapid-manufacturing-applied-to-human-prosthetics.aspx)

"Healthcare in the USA has already accomplished the cost and time savings they're just now considering," Michael says.


Both Michael and Brad Mattear, MA, CFo, general manager of O&P1, Waterloo, Iowa, point out how quickly conventional methods, including current CAD/CAM, can get the job done. Michael mentions a proof-of-concept prosthesis on display at the recent World Congress of the International Society for Prosthetics and Orthotics (ISPO) in Germany that was made in one piece from foot to socket, except for one or two small parts, out of the same plastic material by rapid-prototyping technology. "It proved the technical feasibility, but I think it took dozens of hours of continuous operation to create. With conventional materials and methods, I can create the test socket the same day, assemble the other components in an hour or so, and have the patient walking for initial dynamic alignment shortly thereafter."

Mattear agrees. For instance, for patients needing a foot orthosis, "We can see the patient, scan him, identify what he needs, fabricate and modify it, insert it in his shoe, and he's out the door in about an hour," he says.

However, Mattear emphasizes that the O&P industry needs to continually look for new and better ways to fabricate. He asks rhetorically, "Are we seeing patients the same way we did 50 years ago? The healthcare structure is dictating to clinicians to see more patients faster and for clinicians to focus on patient management rather than fabrication. "We can't just change one side of the coin and not change the other side; we have to change both sides of the coin: clinical and fabrication.

"Rapid prototyping is obviously one way of accomplishing that change, but right now it's still an unproven science and cost and time prohibitive," Mattear continues. "However, rapid prototyping is a great opportunity for the future of orthotics and prosthetics-some way, somehow, this method of fabrication will be important."

RP/RM: Getting Better

Stratasys Dimension uPrint 3D printer.

As with many new technologies, as more equipment manufacturers use rapid manufacturing, the barriers to its widespread adoption are slowly coming down. Its reliability, speed, and quality are improving; costs are decreasing; and the range and durability of materials are increasing. Some machines now utilize tougher plastics and even metal. For example, Dimension 3D Printing Group's uPrint® desktop personal 3D printer debuted in 2009 at $14,900. Mattear notes that such printers cost upwards of several hundred thousand dollars when the technology was in its infancy. According to Dimensions, the uPrint uses ABSPlus™, a production-grade thermoplastic, and the products it prints "are tough enough for functional testing under real-world conditions. They can be drilled, machined, sanded, painted, and even chrome-plated. They're perfect for proof of concept, functional testing, product mock-ups, and even making jigs, fixtures, and vacuum-forming molds." The printer was a DeskTop Engineering Editor's Pick in February 2009.

Z Printer 150. Photograph courtesy of Z Corporation

Two other recently introduced lower-cost 3D printers are Z Corporation's ZPrinter® 150 (monochrome, $14,900) and ZPrinter® 250 (multicolor, $24,900). Leslie Langnau, managing editor of MakePartsFast Digital Manufacturing Resources (www.makepartsfast.com), notes in a July 2010 article that both are easy to use out of the box. They print five to ten times faster than other 3D printing systems, according to Z Corporation, and can print multiple, stacked models simultaneously.

O&P: Views from the Field

In spite of the obstacles, various industry experts see a possible future for rapid prototyping/manufacturing in O&P.

"The long-term potential is that the technology can be used in all areas of prosthetics and orthotics," Bill Clover, vice president of fabrication service and technical service, Otto Bock HealthCare, Minneapolis, Minnesota, says. "The close-in applications would probably be in the areas where the loads and stress are the lowest, such as upper-limb prosthetics. As the technology progresses and the materials improve in strength, then other areas can be added to the list such as lower-limb prosthetics. Then we could move into lower-limb orthotics followed by dynamic parts like feet and dynamic AFOs."

Michael sees devices such as partial-hand prostheses and foot orthoses as being more likely candidates for rapid prototyping/manufacturing than larger structures, since the technology is more readily adaptable for smaller-scale products. However, he points out that most lower-limb orthotic applications are structurally much more challenging than prosthetic applications. "Sockets, shins, etc., are basically tubular shapes that are inherently very strong structures. Most orthoses, however, need to have full-length openings, and that dramatically weakens the structure."

Rapid Prototyping: Orthotics Research Base Grows

Although the focus seems to be more on prosthetics, the orthotics field has not been forgotten. Research involving applications of rapid prototyping in orthotics include studies presented at the 2009 Trent International Prosthetic Symposium, hosted by the United Kingdom member society of the International Society for Prosthetics and Orthotics (ISPO), and a 2008 study by University of Texas at Austin researchers explores the use of selective laser sintering to fabricate passive-dynamic AFOs.

Theory Moves Closer to Reality

At least two O&P manufacturers have rapid-prototyping/manufacturing products under way.


Ohio Willow Wood, Mount Sterling, Ohio, is working on a project titled "Standardizing Prosthetic Socket Design" that is being funded by a grant from the Telemedicine and Advanced Technology Research Center (TATRC) of the U.S. Army Medical Research and Materiel Command. "The purpose of the project is to merge the talents of prosthetic experts and rapid-manufacturing (RM) experts to develop the materials and processes necessary for fabricating improved prosthetic sockets directly from CAD designs without the need to make positive models," Jim Colvin, Ohio Willow Wood's director of engineering, explains. Specific aims of the project include the following, according to Colvin:

  • Develop standards for check sockets and definitive sockets for lower-limb prosthetics with respect to socket strength and flexibility.
  • Evaluate commercially available RM equipment and materials and identify the best option for use in prosthetic sockets.
  • Develop socket designs for RM processes that meet the strength and flexibility standards.
  • Develop new distal adapters specifically designed for RM-produced sockets.

Some European researchers are also exploring the feasibility of making test and definitive sockets via rapid prototyping, bypassing the need for positive models.

O&P1 is working with another company to develop prosthetics rapid-prototyping technology, according to Mattear. Details about the project are proprietary at this point; however, Mattear says that some patients have been fitted with trial sockets, adding that O&P1 hopes to unveil the new technology soon, possibly at the 2010 American Orthotic & Prosthetic Association (AOPA) National Assembly or the 2011 Annual Meeting and Scientific Symposium of the American Academy of Orthotists and Prosthetists (the Academy).

Pursuing Creative Innovation


Scott Summit, founder of industrial-design firm Summit ID, San Francisco, California, and chief technology officer of Bespoke Innovations, San Francisco, has long been interested in creating a rapid-prototyping-fabricated suite of prosthetic legs. The prosthetic legs do not include the socket; Summit is leaving that up to clinical experts. "The legs would range from low-cost for developing countries to higher-end versions that emphasize the materials and form," Summit explains. The firm now has enough funding to explore these areas, although not yet enough to follow through with the extensive life-cycle testing needed to offer them on the market, he says.

"Our process has been to start with a 3D scan of the sound-side leg, run it through parametric templates that we've created, and then use a variety of RM processes to create the parts. We can create cosmetic 'fairing panels,' like the shrouds on a racing motorcycle, to give it form, that mirror the sound-side leg in order to create symmetric reference geometry for the new parts. We fab them, then wrap them in leather, metal deposition, or raw material to give them quality and style." The company has similar plans for an improved foot.

Summit is looking for volunteers with transtibial amputations living in the San Francisco Bay area to test the prostheses; however, the wearer would have to pay costs out-of-pocket since insurance does not cover them. Summit says the company is planning a test run to see if they can offer a reasonable price.

In describing the long-range goal of the project, Summit says, "The larger goal was to create an entire leg via scripted parametric templating. The thinking is that anyone with a digital camera could scan an amputee anywhere, upload the images to the site, and let the scripts do the rest. The amputee could then be sent a very high-quality leg for around $4,000."

Samples of rapidly prototyped objects produced by the Boise State University College of Engineering's SLA machine. Photograph courtesy of the College of Engineering at Boise State University.

Summit has created functional prototypes with this method. "The leg was symmetric, since it was based on a stereophotogrammetric 'scan' from the camera, the leg was light, since RM allows hollow, trabeculated parts; it featured a lockout knee and a countersprung foot that allowed dorsiflexion and plantarflexion. And every detail was calibrated to the weight and activity level of the user."

A transfemoral amputee volunteer in Truckee, California, tried the leg and told Summit it was the best leg he had ever worn. However, the prosthesis quickly broke, which Summit notes is likely with a first prototype of any complexity. Due to funding issues, Summit has shelved this project but says he is hopeful that eventually he will be able to resume development.

Echoing the experience of other inventors and innovators, Summit says, "The challenges that I found were not in the technology-it's mature and ready. It's more in the business model and insurance world."

Direct-to-Definitive Challenge

Other current and past efforts have focused on using rapid prototyping to create a definitive socket directly from a CAD model obtained via reverse engineering of MRI and CT scans and other imaging technologies. However, eliminating a test socket is a fatal flaw in clinical practice, at least at this point.

"Scanning to definitive socket has been a dream for decades, but no one is anywhere close to making that work, unless you're willing to deliver a percentage of poorly fitting sockets," Michael sums up. "MRI to definitive socket, radiograph to definitive socket, finite-element analysis to definitive socket, and related imaging strategies have also failed to surpass 'artistically fitted' prostheses. The prosthesis must function comfortably and consistently under dynamic loading across an amazing range of human activities, so it takes intuition and artistic skill to overcome the fact that no one knows how to define a 'perfect socket,' let alone measure all the variables. These challenges are good food for research, but are not yet close to workable, as best I can tell."

However, Michael notes a patient population for which a "good" socket can be sufficient: the new amputee who is barely walking and not fully weight bearing on the prosthesis. "The post-operative changes to residual-limb geometry mean that precision fitting cannot be maintained during this 'seasoning' stage," and the limited loading applied for a short time permits safe ambulation despite multiple sock plies," Michael points out. "Many practitioners start with a 'made-to-measurements' test socket for this application, which allows them to create an individually fitted socket that is sufficient for the task in a time-efficient manner, avoiding the costs and x-ray exposure of the more complex experimental imaging systems."

The Big Picture

Overall, the main potential advantages of RP/RM-if materials durability, time, and equipment costs become feasible-appear to lie in time and cost savings for larger operations, such as central fabrication facilities or multi-site facilities sharing an in-house fabrication center, rather than small-practice in-house use.


Will rapid prototyping/rapid manufacturing or other automated technologies ever replace the practitioner's art and skills? "Not likely," Michael says.

"Thus far, making the CAM file usually amounts to capturing the subjective rectified shape determined by the CPO, so all the art is still needed but a more complex fabrication process is added," he notes. "It's hard to beat what a good CPO can do!"

Jonathan Kuniholm, a mechanical engineer who helped found the Open Prosthetics Project (www.openprosthetics.org), an open-source collaboration for creating and improving prosthetic devices, echoes Michael's comments. "I don't think we can ever take the art of the prosthetist out of the business," says Kuniholm, who lost his right arm below the elbow in military action in Iraq. "Probably the most significant value in prosthetics will be the interaction of the prosthetist with the patient and the customization of a solution for that particular patient. The scanning and rapid manufacturing of components can be easily integrated with the creative process that the prosthetist uses to provide the solution for the individual user."

Miki Fairley is a freelance writer based in southwest Colorado. She can be reached at