Development of Final Prototype
Following our first prototype, we moved on to make adjustments based on what we learned, starting with updating our CAD model in Solidworks to reflect the changes we hoped to make for our final design. The first and most readily apparent of these changes is the size of our final prototype. The size increase revolved around being able to use a life-size pan in our linkage, so our final mechanism turned out to be roughly two and a half times the size of our initial prototype discussed above.
Other changes to the design of the mechanism include the addition of two saddled links, doubling the thickness of each of the non-saddle links, changing the design of the pan, designing a mount for a new motor, and adjusting the design and placement of the link anchors as well as the base plate to reflect changes to the links making up the mechanism.
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As discussed previously in the First Prototype Reflection section, we had an issue with not generating enough linear velocity in our first prototype. As a result, we knew we wanted to extend the distance between the location of our egg to the linkage arm. Thus, we created a longer detachable pan arm design which connected with bolts and nuts. This allowed us to iterate on the design, such that if we wanted to increase the pan arm length or adjust pan geometry, we could print each part while reutilizing the other part that didn’t need changing. We also made slight adjustments to the pan geometry itself, decreasing the thickness of the walls and increasing the curve radius to improve flipping motion.
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Having learned our lesson with regard to the importance of determining tolerancing ahead of time to make the manufacturing process smoother from building our first prototype, we spent time taking data for the tolerance of one of the laser cutters available at TIW. We found each laser cutter to be slightly different in terms of the tolerance they would cut parts to, so we made sure to cut our parts for the final prototype on the same laser cutter for which we took all our measurements for determining the tolerances. We determined the tolerances for square cuts as well as circular cuts for both wood and acrylic on our chosen laser cutter by cutting multiple small squares with circular cutouts in the middle.
After determining all required tolerances for our mechanism, we proceeded to laser cut all of the components, including the links, anchors for the mechanism, and base plate. We then took these components and assembled them together with the 3D printed pan and motor mount, using bearings, shafts, and shaft collars at each joint. Finally, we wired and integrated our electrical components (arduino, motor controller, motor, and power source) into the assembly with a laser cut acrylic cover providing protection for the arduino, motor controller, and the wires between them.
After initially assembling the final mechanism, our motor struggled to power the weight of our system, resulting in it outputting a non-constant angular velocity of the motor shaft. This meant that we were able to achieve our targeted motion profile, but not the ideal velocity profile. In order to attempt to counteract this, we decided to remove half of the input link (connected to the motor shaft) and the ternary link, since both of these were acrylic and removing the extra thickness lowered the overall weight of the system. After halving the thickness of these two links and reassembling, our motor continued to struggle to power the system, albeit to less of an extent as before.
Final Prototype and Demonstration
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