This past Saturday a few members of the robotics team ran a booth at the Philadelphia Science carnival. We demonstrated our robot, our 3D printers, and, at the front of the exhibit, our work on prosthetic hands. Xan’s electronic setup was front and center, allowing us to place the EMG sensors on people’s forearms as they walked by to control the hand. About 300 people were able to work the prosthetic, and only few were unable to operate it.
We also heard back from the people running the research part of DuPont Nemours hospital. They have an extremely high end 3D printer, which they allowed us to print two models of our hand on. The quality of these are way beyond what we were capable of doing on our printers. One of them is currently being used by Xan on his research with the myoelectric control system, while the other is being set up for the activation energy and efficiency tests, hopefully completed towards the end of this week.
We’re in the last month of our work here, but we’re really close to finishing a working model.
It’s great to say that we’re finally beginning to see some actual results. A prosthetic hand has been printed, assembled, and attached to our testing rig. The first two rounds of tests on this model have been completed: the activation force and the efficiency at 0° of a bend. Testing will continue throughout this week until we have a baseline standard to base our improvements off of. Continue reading
I want to start this off by saying that we’ve made a significant amount progress in the way of fixing the printer. The issues with the print pieces adhering too well are in the process of resolving. After tweaking some settings on the printer related to how close the print bed is to the bottom resin tank and adjusting the thickness of the base, we are hopeful that our next print will be fully successful. This means that we can begin to print and evaluate the current prosthetics along with the one’s we’ll model as soon as we get back from break. The last major part of protocol to develop is how to do the materials analysis for the PLA and ABS from the extrusion based 3D printer and we are currently looking through industry standard protocols to see if there is one that can be adapted for our purposes.
Another aspect of the project we’ve progressed in is the conservation of print resin. When prints fail, it is common for small pieces of partially hardened, flaky resin to be in the tank. Whenever this happens, we now are going to strain the resin using a funnel and four overlapped sheets of wire mesh that has holes of about 1mm length and width. The first time we did this saved about 20 ml of resin, so over time this will begin to add up to a huge amount of prevented waste.
Last week we began the process of materials analysis, but we’ve come across some difficulties with the Form1 Printer. The prints have been sticking to the print bed too well, a change from our problems with it when it was new of the prints not sticking at all. We’ve contacted customer support and are eagerly awaiting a response so we can return to printing our test parts.
This week we had planned to meet with Joy to fit the hand, but the prosthetic we had ready to fit was knocked off of a table. Although it only fell a few feet, several parts of the hand shattered. The resin that the new higher end 3d printer uses seems to be much more vulnerable to shock. Now we must look into working on a full materials analysis and comparison of the 3d printed resin vs PLA and ABS plastics that our other 3d printers use. Tensile strength is probably the most important aspect we are going to measure, so we will test that for a variety of shapes, sizes, and densities for each material.
This week was an exciting beginning to our process of 3D modeling. Using Rhino, I created a structure that will be used to mount other finger models to for testing and evaluating their designs. I plan to print it this week and begin refining my process for the evaluation of printed models.
This week was cut short by a mix of senior work days and school days off. We were able to finish the assembly of the current hand, most of which involved cutting bolts to the proper length, getting rid of sharp edges, and getting the strings ready to tie when Joy comes in for the next fitting.
This week was a refreshing and exciting change from what we’ve been doing for the first few weeks. We met two nights this past week to be able to work in the Design and Engineering lab to bring the 3d printers back into working condition. Our goal for the week was to print and assemble a prosthetic of the current model for Joy, one of the children we are working with. Continue reading
This week saw the completion of my plan of action for the first half of the year. Among several smaller deadlines that I’ll be working to meet, the main goal is to have a mechanically driven prosthetic hand by the end of January so that we can begin further development of a myoelectrically driven prosthetic in February. Continue reading
As I continued my research, I realized that the useful articles I was coming across were all coming from the Journal of Rehabilitation Research and Development, so instead of continuing to dig through articles on a general scientific search engine, I went to the JRRD’s website and began to look there. The two types of articles I found an abundance of were research on improving the control systems for myolectrically controlled prosthetics and on different materials or finger designs to improve grip. Continue reading