Designing the 3D‐Printed Prosthetic Hand

Feature DESIGNING the 3D-Printed Prosthetic Hand

By Rafiq Elmansy

3D printing is remarkably affordable and lends itself to this collaborative—and philanthropic—endeavor.

Designing the

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Figure 1 Regardless of whether a traditional or a 3D-printed process is used, both the stump and the rest of the arm must be carefully measured so that the prosthetic will fit the patient’s needs and ensure maximum functionality.

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pening the first-ever Icograda conference in 1964, Britain’s Prince Philip noted, “Every day, designers of all kinds are becoming responsible for a greater proportion of the human environment. Almost everything we see and use that was not made by the Almighty has come from some designer’s drawing board.” Case in point: 3D printing. It’s taking rapid prototyping to another level and igniting hope for many product designers working with a smallscale budget, production line, process, and team. All one needs is a 3D printer and CAD software that helps to create the computer 3D model

before it is sent to the printer. Although there are still barriers to implementing this technology on a larger scale, many researchers have been motivated to explore its use in a variety of disciplines. One initiative is to design prosthetic devices that enable individuals with disabilities to live their lives with less effort and pain. Design is contributing to this project through a holistic approach that involves design thinking, as well as innovations in the development process and materials used.

Prosthetic design Prosthetic limbs have a longer history than you might imagine: A wooden toe has been discovered

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The development of prosthetic hands has seen innumerable advances through the centuries, especially in materials used; in the modern day, wood and metal have largely been replaced with… plastics and carbon fibers. on a 3,000-year-old Egyptian mummy. The development of prosthetic hands has seen innumerable advances through the centuries, especially in materials used; in the modern day, wood and metal have largely been replaced with lighter, stronger materials, such as plastics and carbon fibers. As for functionality, myoelectric devices powered by impulses generated by muscle contractions permit flexion, extension, and rotation. The design and creation of prosthetics require unique processes, since every customer is different. Devices must be customized based on the type of disability and on arm measurements. Generally, the process goes through the following stages: 1) The stump is measured and studied intensively (Figure 1, previous page) to learn more about the prosthetic to be built. Manufacturing-related details that might affect the design of the prosthetic are considered. 2) A model of the missing limb is cast based on the measurement and details collected in the Figure 2 Two friends build a prosthetic hand.

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first stage. The cast gives a preview of the final design and helps provide initial testing to make sure the measurements are accurate and workable. Plaster is generally used because it dries quickly and preserves details well. 3) A socket is created of thermoplastic that is heated and vacuum-formed around the cast to create a negative that reflects the details of the original model. The socket is made transparent to allow the model’s accuracy to be checked. 4) A prosthetic model is created—including the main shape, as well as smaller pieces, such as metal screws and joints—with a variety of materials and techniques. The model parts are then assembled to form the final prosthetic device. 5) The patient receives physical therapy training to practice using the new prosthetic so that it can become part of his or her daily life activities. In this stage, the patient learns how to take care of the device in different situations—in bed, in a car, or even how to protect it from a fall.


Figure 3 3D-printed prostheses do have a robotic look, but especially where children are concerned, the colors and “transformer-like” shapes are not so much of a drawback.

Quality control and evaluation are important to keep the development process continuous and should not stop on delivery of the prosthetic to the patient. Although, currently, there are few agreedupon standards for manufacturing prosthetic devices, the design process should include a method to evaluate the final product and get feedback from the client that can be incorporated into subsequent projects and designs.

Living with a prosthetic hand The design process described above seems to work well for general prosthetic design. Actually, the models that are currently available work well and have a fleshlike appearance that makes them reasonably acceptable to patients, and they offer many useful features and capabilities, depending on patient needs and finances. It is, in fact, finances that present a barrier for many of the disabled. Production for just one prosthetic device can cost $10,000 to $100,000 based on its type and mechanism. Not only that, but prosthetics are not adjustable—which means that as a patient grows older, his or her prosthetic may no longer fit. In underdeveloped countries where medical services are scanty, there are few options for design, customization, or repair. Another disadvantage of traditional prosthetics is their weight, especially in models that feature a complex mechanism. Myoelectric models offer advanced mechanisms, but they are also heavy. The weight may be acceptable in the short run, but using the prosthetic during everyday activities may not be workable. Although current prosthetics have been developed to enable as many functions as possible, these obstacles prevent many of the disabled from owning one.

3D-printing technology Using technologies such as fused deposition modeling, stereolithography, and selective laser sintering, 3D printing allows designers and manufacturers to convert CAD computer

models to three-dimensional products. Bypassing the traditional heavy machinery, 3D printers use desktop printers and additive manufacturing technologies to produce a final product. Although these methods are still not suitable for bulk production volume, designing and building prosthetic devices is a customized process in which each model needs to match its user’s disability—so bulk production really isn’t an issue. The design process for 3D printing a prosthetic hand is similar to the traditional process—just more affordable and accessible. In general, the 3D-printed prosthetic process includes the following stages: 1) The stump and the rest of the arm are carefully measured so the prosthetic will fit the patient’s needs and ensure maximum functionality. (Although this step is the same for both technologies, the designer or 3Dprinting expert should consider that these measurements are expected to contribute to DMI SPRING 2015 27


modeling or modifying an existing 3D print of the prosthetic in CAD applications.) 2) Either 3D scanning or creating a mold for the prosthetic will allow testing to ensure accurate measurements for the final design. 3D scanning allows the form and function of the prosthetic model to be tested on the computer CAD application before printing. If a 3D scanner is not available, a hard mold can be made and shipped to the design team, who can then run a 3D scan. This makes for more accuracy and less expense than the traditional method. 3) Once the prosthetic is scanned and converted to a 3D model, there are other factors to consider. Although the 3D prosthetic device can be computer-modeled based on the scanned arm using various CAD applications, many of these models are available for free download on the designers’ websites in separated documents for each part of the prosthetic. These free models can be downloaded in STL format, which is readable by all the available 3D printers. In most cases, customization should be applied in order to fit with the patient’s needs; this can be done using 3D modeling applications that support exporting the files in STL or OBJ format. In contrast with the traditional process, digital 3D-modeling of the prosthetic hand contributes significantly in reducing the production cost, time, and effort required to create the model. Furthermore, the design of the 3D model or modification of an existing model does not require extensive experience with 3D modeling—and this also makes 3D-printed prosthetics more affordable. 4) Using fused deposition modeling technology, which builds the model using thin layers of filament based on the STL digital model, the model parts are printed. And herein lies another advantage of the 3D-printed prosthetic: The materials used in traditional prosthetic production significantly increase the cost of the final product, but the plasticbased filament used in 3D printing is cheap and can be modified easily, even after printing. 28 DMI SPRING 2015

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5) Assemblies are put together using cords, screws, and foam padding. In just a few hours, the entire prosthetic can be put together and ready to use. 6) The prosthesis is then installed on the patient’s arm and evaluated for functionality. Now the user begins to practice with the prosthetic hand and learn how to move the device using the remaining muscles in his or her arm. This stage gives the designer some feedback for future prosthetics development and production processes. Many individuals, organizations, and universities are mounting initiatives to build 3D-printed prosthetics that match the efficiency of traditional prosthetics. Some of this work is conducted by young entrepreneurs—for example Easton LaChappelle, the 19-year-old inventor and founder of Unlimited Tomorrow, a company that focuses on creating open-source, affordable 3D-printed fullarm prosthetics that can be controlled by the brain.

Traditional vs. 3D: Pros and cons Although the design process for 3D production is similar to that used in traditional prosthetics, 3D-printing technology clearly offers some advantages over the traditional process.


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Most important, 3D-printed prosthetic devices are cheaper than traditional devices—less than $2,000, typically, but even cheaper ($1,000 or less) depending on the quality of the 3D printing and the various parts needed. This makes it affordable for many patients in developed, as well as underdeveloped, countries. As noted above, one of the drawbacks faced by prosthetic devices for children is simply that children grow. The cheaper price for a 3D-printed device makes it easier for parents to afford a new prosthesis. The materials involved in 3D printing are easy to access from anywhere around the world. Many of them are available directly from printer manufacturers, filament manufacturers, or from ecommerce websites, such as Amazon and eBay. 3D printers are becoming cheaper and easier to buy as manufacturers race to reduce their price. Some of them go for $2,000 or even less. Some are even crowd-funded, going for less than $1,000 on such websites as Kickstarter. Having all the resources available on the Internet makes printing 3D prosthetic device production affordable for designers around the world. If the designer has a 3D printer, he or

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she can simply download the required STL files for the prosthetic, customize it to the patient amputee, and 3D-print and assemble it. Another advantage for the 3D-printed prosthetic hand is its light weight. The plastic materials and low number of components makes them light compared with many of the traditional prosthetics—even for myoelectric versions. Whereas traditional prosthetics are hard to adapt, 3D-printed devices can be modified. Some parts can be replaced by the patient themselves. In some cases, prosthetic hands are so simple to assemble that this work can be done by schoolchildren (Figure 2). It’s important to remember, however, that 3D-printed prosthetics are still under development and have not yet been taken to a large production level. Most of them are made by volunteers who want to help the world’s disabled. And 3D-printed devices have some other disadvantages. Most of them have a robotic look—more like a wire frame than flesh and blood (Figure 3, see page 27). The cords and the screws are visible and can easily be cut or damaged accidentally. This is an issue that needs to be addressed by designers, especially when they are designing for children, who are in motion so much of the time.

Figures 4a, 4b, and 4c One of the e-Nabling 3D prosthetic hands before and after assembly.

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Figures 5a and 5b Boy and girl scout troops assemble 3D-printed prosthetics for Syrian refugees.

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Feature DESIGNING the 3D-Printed Prosthetic Hand Rafiq Elmansy is a design lecturer at the American University in Cairo. His experience includes more than 17 years in the design industry, working with clients from around the world. He is the founder of Designorate.com, a magazine devoted to the strategic use of design.

Elmansy’s work is on exhibit in many locations, including Croatia, South Africa, and Spain. He is also a jury member and mentor in acknowledged design competitions, including the A Design Award, the Adobe Design Achievement Awards, and Poster for Tomorrow. He is the author of several books, including Teach Yourself Visually

SEO, Illustrator Foundations, Photoshop 3D for Animators, and Quick Guide to Flash Catalyst. He also writes and manages content for the Interaction Design Foundation, with a focus on user experience research. Elmansy is an Adobe-certified instructor and education leader.

Figure 6 The e-Nable project provides a unique model for an open-source design process to improve prosthetic-hand production and reach many people in need around the world.

3D-printed devices can be created by anyone around the world. That is a strength, but it can also be a drawback. If measurement or printing mistakes happen, it may affect the patient and cause discomfort. And because 3D-printed prosthetics are available as an open-source product, there may be issues of quality control.

created social-media websites on Google Plus and Facebook that act like a virtual workshop hub for designers, volunteers, and patients to communicate and exchange experience and results with 3D-printed devices (Figure 6). (For more information, see www.enablingthefuture.org.) This project not only helps designers to start creating 3D-printed prosthetics in their e-Nabling the Future project own countries, but also lends its strength to the No discussion of 3D-printed prosthetics would be development of this new technology. Because complete without a mention of the e-Nabling the e-Nable is handled totally online, with design Future initiative. This story started in 2011, when teams that must meet virtually to collaborate, an American prop maker and a carpenter from creativity and brainstorming are enhanced as they South Africa came together to create a prosthetic become a big part of the design process. hand device for a small child in South Africa who Design and innovation are baked into this had lost four of his fingers. development process—solving many of the Then they gave the plans away—for free. affordability and adaptability problems that face That was the beginning of a project that now traditional production. The very nature of 3D involves more than 1,500 engineers, makers, printing invites designers to collaborate with students, parents, occupational therapists, each other and with other disciplines from around designers, and garage tinkerers, among others the world. (Figures 4a-4c, see page 28). It triggered an avalanche of suggestions, requests for help, and donations from around the world (Figures 5a and 5b). As the requests increased, the e-Nable group DMI SPRING 2015 31