3D Printing & Simulation to Design Affordable Prosthetic Arms

prosthetic arms

While 3D printing technology has been around for more than 25 years, the recent arrival of affordable desktop 3D printers means that large companies and R&D groups are no longer the only ones with access to this powerful technology. Students, hobbyists, and makers are getting involved and using their talents to change the world.

Making an Impact on Prosthetic Arms Accessibility

One area where this impact is huge is medical prosthetics. In general, the cost of a prosthetic limb can range anywhere from $15,000 – $90,000 and must be replaced every 3-4 years due to the wear and tear of everyday use [1]. For children, these costs are compounded as they are growing and need to be fitted with a new prosthesis more regularly. Conversely, “a 3D printed prosthetic arm costs less than a reel of plastic, so about $40,” says Will Davies, a volunteer with e-NABLE – a web based community that brings together volunteers from around the world who use their 3D printers, design skills, and personal time to create free 3D printed prosthetic arms and hands for children who need them [2].

Will Will and Bruce and his father Bruce, a retired biochemist, have been involved with e-NABLE since 2013 and 2014, respectively, and have used their 3D printer to produce prosthetic arms for 22 children in their home country – the United States. The process is straightforward explains Will, “All of the designs are open source so all you need to do is buy the plastic, 3D print the arm, clean up the print, put it together with the hardware, and then customize the fit for the child.”

The child must have a functional wrist or elbow to operate e-NABLE devices properly. The prosthetic hands open and close using the flexing of the wrist or elbow to create tension so that a fist can be made. This allows the child to grasp a pencil, hold sports equipment, or balance better on a bicycle.Fitting an arm

There are a variety of hand and arm designs available: there’s the Raptor hand, the Talon hand, the Cyborg Beast hand, and the RIT arm just to name a few.

Using SimScale to Improve the Design

Will and Bruce have been working on the RIT arm, an adaptive device that was designed for those with an elbow but no wrist. They noticed that this particular arm design has a tendency to break around the same point, at the location where the extension comes off of the elbow cup. Turning to SimScale, “I was able to determine where the maximum stresses and strains were, and we then worked to add reinforcements to those weak areas,” says Will.

The RIT arm (left), The extension cup piece (geometry, mesh, stress) shown on SimScale platform

The RIT arm (left), The extension cup piece (geometry, mesh, stress) shown in SimScale

By thickening the plastic at the location of high stress and increasing the size of the fillet, Will and Bruce have created a working model which feels much stronger, however, it hasn’t yet been “battle-tested.” We look forward to hearing about the results!

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