Today's KNOWLEDGE Share:Prosthetic made by Filament Winding Process

Today's KNOWLEDGE Share

Steptics brings automation to the prosthetic world via the filament winding process. “We first build a mandrel which has the inner geometry of the prostheses,” says Kun. “The fiber is pulled through epoxy resin and then wound onto the rotating mandrel. The resin is typically used for vacuum infusion processes in the aircraft industry, and we use T700 type carbon fiber from Toray [Tokyo, Japan], although we could also use glass fiber or basalt or other fibers. T700 has good properties that are very well known, and it is well proven in filament winding.”

“We filament wind a long, shaped tube that we then cure in an oven,” he continues. “It’s pretty much the same curing process as with filament-wound pressure vessels. We then we cut the long tube into slices, and cut the slices into halves to get semi-finished parts. These are then individually machined to tailor the geometry and performance to the individual amputee.”

AI-assisted customization

One reason prostheses have been challenging to industrialize is the need to customize each product for the individual amputee. “That’s true,” says Kun. “We need to know the amputee’s weight and whether a left or right foot prosthesis is needed. We also want to know what they want to do with the prosthesis. Are they a walker or a jogger? And that defines the spring characteristics needed in the final prosthesis.”

For the first process, says Kun, “we have the first production line, and have made a proof-of-concept prosthesis and tested it according to ISO 10328. It performed well and withstood 2 million cycles of loading without any degradation. This first product will be a CFRP blade or sole that is a sports prosthesis, amputation level 270.”

“Our first steps were to reduce costs through automated production and development of AI for individual customization,” says Kun. “Now, we want to tackle the issue of sustainable materials. Unfortunately, carbon or glass fiber do not have the best CO2 footprint. However, many natural fibers don’t have the strength and stiffness to withstand the predominant loads. Thus, by themselves, they aren’t yet suitable for running blades or even everyday prostheses. We are still researching what reinforcements could work.”

source:steptics/compositesworld.com