Andreas Bastian shared on the e-NABLE Community his continuing experimentation into custom printed/heat-deformed mesh gauntlets for RoboHand mods that he started during the #maketheworld: Prosthetics series. He met up with John, a very savvy prosthetics user, to come up with new ideas and get real world feedback on how these variants stand up in a field test.
Check out the video below to see a few mechanical issues they discovered with this version, plus some feedback on fit and comfort. This discussion can be joined over at the e-NABLE Community, but you will have to join (quite easy!) to access the posts directly.
John and I met up yesterday afternoon in California to test the moldable PLA mesh gauntlets, floral foam molding, and 123D catching of limbs! We fitted and assembled a prototype arm and generated a lot of interesting fit and functionality feedback. I took a couple of short videos of the prototype in action to illustrate some of the problems in fit and operation that we encountered. One of the most interesting challenges is that the forearm changes shape as the hand is rotated 180 degrees about the axis extending the length of the forearm. This rotation caused the arm-piece to rotate 2-3 inches around John’s arm. Additionally, when flexing his wrist, John’s forearm changed circumference due to the muscle contractions, leading to a bit of constriction at the wrist. The arm-pieces size and shape need to be changed a bit– the leading and back edges of the mesh sheet dug into John’s arm when he flexed his wrist backwards (leading edge pressure) and when he flexed his bicep (back edge pressure into upper arm). We also found that it was important to make the hand-piece somewhat flared towards the back to make it easy to slip on and off. The Velcro was operable with one hand, but I think that we can find better methods of attachment than how I have it implemented.
The floral foam molding went well, though it was a bit difficult to transport without damaging it. We found it required a surprising amount of force to make an impression of John’s hand and ended up carving a rough approximation of John’s hand using a spoon and then taking it the final steps manually, which was easier.
I also took about 50 photos of John’s arm to test with 123D catch. I have shared the photos in case anybody else would like to try other reconstructive software.
When I get back to my printer, I will print out the reconstructed mesh and compare it to the floral foam molds to evaluate accuracy of the scan.
Finally, I’d like to thank John again for taking time out of his day to test these techniques. It was tremendously productive and exciting afternoon that has generated a lot of useful information to further inform the design of these devices.
Make The World: Prosthetics was a one month program on Google+ aimed at crowdsourcing the manufacturing and delivery of printed prosthetics to people in need, hosted by Adafruit’s Limor Fried, Matt Griffin and Phillip Torrone. The Adafruit G+ Community Adafruit’s Makers, Hackers, Artists and Engineers Community under the subsection “Make the World” continues to provide a venue for this ongoing conversation — Join us there!
Want to catch up on what you missed? Check out all four sessions of the #maketheworld: Prosthetics hangouts here!