Printable Prosthetics: The design of a 3D printed swimming prosthesis (2016)
In his Master thesis, Stuart Baynes dealt with the topic of lower limb loss and how to alleviate the effect on a person’s mental and physical health. Unless you were a pirate and saw the metal-embellished leg stump as an addition to your weapons arsenal, it used to be that a lost limb was replaced with a crude imitation and often hidden in embarrassment. In our changing society augmentation is becoming an acceptable part of everyday life for some amputees, and as such not something to hide in shame, but rather wear with pride and confidence. Although our attitudes might be changing, the process of creating a new limb still and always will involve a vulnerable human being, whose enjoyment of life and welfare must be considered in the design and production process. In this particular project detailed discussions about the desired outcome for the amputee and the actual fit of the prosthesis soon resulted in a functional prototype that covered all the requirements. The ease of the process through high-resolution scanners and new printers (that can print large items in one process) not only ensures a faster end result, but also improves the whole process from the users point of view.
The amputee had expressed regret and frustration at not being able to enjoy his time in the swimming pool anymore due to the changed symmetry of his body’s movement. Another side to this was the difficulties encountered getting from the changing room to the pool itself. The prosthesis would have to be designed in a way to fully support him both outside of the pool and while he was swimming. A dual-part prosthesis was designed consisting of a removable solid outer scabbard that covered an inner swimming fin providing adequate support and movement outside of the pool and when taken off recreated/ re-established the lost anthropometric symmetry needed to swim in a straight line.
Coming to study Design at Victoria University in Wellington (New Zealand) Stuart saw that 3D printing and industrial design is becoming more and more a relevant part in the changing and challenging medical field. Throughout intensive mentoring by Bernard Guy and Tim Miller in the application of evolving 3D printing technologies he finished his studies with his thesis FreeSwim Prosthesis in 2016.
Materials and processes – close-up
Rhinoceros 5 with the Grasshopper plug-in were used for the design process.
Scanning was done with an Artec Eva and Spider scanner to get a detailed data set of measurements of the limb joint. In contrast to the traditional arduous method of making molds and multiple fitting sessions, the scanner is a discreet and fast way to accurately map out the area, where the prosthesis and the limb join and interact. Accuracy is vital to ensure a secure and comfortable fit. This accuracy is maintained throughout the whole process of collection and transferral of the data to the computer and the printer.
Printing was done all in-house on the Up Box and Big Rep One FDM printers. With assistance from his supervisor Bernard Guy, Stuart was able to use our new Big Rep One printer, making it the first project to be successfully conducted on it. The new printer has the capacity to print large objects (up to 1mᶟ) with different materials in one print run. The materials used were TPU (thermoplastic polyurethane) and PETG (Polyethylene terephthalate glycol-modified).
With supervision and guidance from NZALS (New Zealand Artificial Limb service) Sean Grey CEO, and Otto Schutte Senior Clinical Prosthetist