Finger Rehabilitation Device: Scanning and CAD Model
This week we focused on producing 3D models of a hand and the rehabilitation device. To create a computer model of a hand we used two different scanning techniques. A CAD model of the device was created in solidWorks so that we can begin printing.
Scanning:
Two different scanners were used to get a computer model of a hand. The first was the ShapeGrabber in the biomechanics lab. This is a laser scanner that can produce a 3D model when multiple scans are taken. Figures 1 and 2 show this scanner in action. The problem we ran into was with an actual hand it is very difficult to keep it in the exact same orientation between scans. Because of this we just used one scan of the top of a hand so the curvature can be followed when creating the CAD model.
Figure 1 and Figure 2. ShapeGrabber scanning Buzz’s hand
The other scanner we used was in the polymer lab. This scanner rotates an object slowly and scans it in 3 dimensions. We ordered a plastic hand model to use with this scanner as it would be near impossible to use an actual hand. This process can be seen in Figure 3 and 4 below.
Figure 3 and 4. Scanning of mannequin hand
CAD model:
A CAD model was created in solidWorks as seen in Figure 3 and Figure 4 below. This model was created without using dimensions of an actual hand but will be updated once the scan is brought into solidWorks. With the preliminary CAD model completed we will begin printing and testing different variations of the elastic section. Our plan is to use different infill densities to change the resistance of the device. We will also test a few different ways to connect the assembly together (snap fit, latch, ect.) and adjust the tolerances so the printed parts fit together correctly.
Figure 5 and Figure 6. Initial CAD design of device.
Obstacles:
During our scanning process, we ran into a couple of issues including unavailability of equipment as well as accuracy of the mannequin hand. The ShapeGrabber scanner was yielding the best results so far. However, technical difficulties occurred during the second round of scans with the scanner in the polymers lab. The system was restarted at some point and in order to function it requires an administrative login. This login information was lost and no one in the lab knew how to retrieve it. Since then, the issue has been resolved and scanning could be resumed, however this did create a delay for our project. Another obstacle that we faced was with the accuracy of our mannequin hand. We purchased a rubber hand in hopes that we could get more accurate scans of a hand without dealing with the constant motion of an actual hand. Our model did not hold the exact positioning that we wanted and the fingers seemed a little disproportional. With that in mind, we still attempted to take a 3D scan of the hand using the scanner in the polymers lab.
Initial Print:
Our first print was performed this week using the CAD models mentioned above. Different infills will be tested to get varying resistances (as seen in figure 8). Some iterations will also have to be made in order to get the snap fit end to work properly. However the first print was a success and is a good starting point for future prints in the coming week.
Figure 7 and 8. Initial prints of the resistance bar. Flexibility of bar is shown