Conclusions - JG

Overall, the mechanism effectively completes the function that was desired. We wanted a controllable quick return, and as we can see from the available pictures and videos, we were able to achieve this. A few notes on what could be improved or added upon:

One of my original goals was to create a motor driven mechanism. My idea involved replacing my input link with a gear, and having that gear be driven by another gear attached to a motor. The idea was to attach a small gear to the motor, and use a larger gear for my input link. This would allow me to create a gear ratio where the mechanism rotates at a controllable speed while having a large enough output torque. Unfortunately, I was unable to return to campus with enough time to design or locate usable gears that fit with my design. I instead attempted to use a DC motor I had at home to directly drive the link, however while testing I accidentally burned out the motor as it did not have sufficient torque to power the mechanism without the assistance of a proper gear train.

A potential improvement I had considered was machining all of the components from metal, and using a combination of bolts, bearings, and sleeves to fully optimize the smoothness of its movement as well as increase the mechanism’s strength. This idea became less valid as it became apparent that I would not be on campus as often as I would have hoped. However, by sanding down my links and joints, and adjusting the dimensions appropriately, I was able to achieve a smooth motion through a full input rotation. By using a combination of ¼” wood and highly filled ABS 3D prints I was still able to achieve a high strength mechanism that was still lightweight and easy to handle.

The only major point of error came from my output link and grounding component connection. The sliding joint I created worked well in terms of the sliding tolerances, however was just a bit too short in comparison to my output link length. This caused my output link to want to turn or bend when at its maximum extension. By increasing the length of the sliding ground joint by about 1-2 inches on both sides, we would see a much more stable output motion. This may have slightly increased the overall friction at this point, but I believe this would be minimized by the additional sanding I completed.

Another consideration was the actual speed of the quick return. I knew from the beginning that I wasn’t looking for the absolute maximum quick return, as this would likely lead to an unstable and high-stress mechanism, especially if I had succeeded in creating a motor driven input. I knew that the closer my O2 and O3 joints were, the larger my quick return velocity would be. The length of my input link 2 was also a big consideration, as the longer the input link, the larger the ratio between the quick and slow return velocity would be. If stronger materials were used, and I was able to properly ground the mechanism in a way that could ensure it wouldn’t move, then I could have designed the mechanism to have a larger velocity ratio.

At the end of this project, I was very pleased with the design and outcome of my mechanism. It follows the proper pattern, moves very smoothly, and is able to hold up against the stresses it experiences. It has given me great insight into the beginnings of robotic mechanism design and has allowed me to get a feel for all of the considerations that need to go into prototyping and manufacturing. I wish I had been able to complete the motor driven goal, however I believe I learned a great deal from my failure to do so, and hope to gain more experience with motor driven robotics in the future.