Test Fits 

Our project involved both 3D printed and laser cut pieces. Before printing and cutting all of our parts, we made some test pieces to determine the best sizing for shaft and bearing holes. 

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In our attempts to fabricate the timing belt loop to get successful rotation transfer between the shafts, we noticed that the torque requirement and belt tension were big issues. The torque requirement to raise and lower the finger assembly was large, and the torque being provided by the small gears was not enough which resulted in the rotation stalling and gear teeth skipping at times. To provide more torque, we replaced the second gear (gear on the finger wagging shaft) with a larger gear which solved the torque problem. This provided adequate torque to raise and lower the finger assembly, but the belt was no longer a 1:1 timing belt (it had a 3:1 ratio). Additionally, without the right belt tension rotation did not transfer between the shafts. To address the tension issue, we created a makeshift tensioner using an allen key to pull the belt to the correct tension. The final timing belt assembly with a 3:1 ratio and tensioner is shown below. 

Final Assembly

Once we had all our pieces 3D printed and laser cut, we began the final assembly. The team also took some time to look at the design of the final layout of the mechanism to determine the shaft lengths needed and cut these in the machine shop. We used wood glue to attach all the platform pieces to one another and attach the motor mount and supports to the platform. Super glue was used to keep the bearing cups and shafts in place in links to ensure that the attachments were rigid. Some images of the final assembly are shown below.

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