Before Team α and Team Ω met as Team K, they independently thought of very similar ideas for their robot arm designs. Both teams felt that rounding either the shorter knotch in the robot arm or both knotches in the robot arm would be a positive way to reduce mass and redistribute forces, resulting in less stress.
After hearing about the first commercial jet liner, the De Havilland Comet, in class, neither Team α and Team Ω wanted to use sharply angled cuts. The De Havilland's square-cut windows gathered immense stress. This approach to the robot arm did not appear optimal. Hence, Team α and Team Ω used their separate design times to experiment with extruding rounded cuts.
Team α used the "spline" option to completely remove the side of the robot arm with the shorter knotch, resulting in a curved side. After experimenting with extruding arc slots, circles, and ellipses, they extruded a single ellipse. However, there was not time enough to finalize Team α's design. What resulted had a volume of 1.1 cubic inches and a displacement of .1660 mm, resulting in a scpore of .1826 mm-in³. Below is an image of Team α's final robot arm.
Team Ω had many initial thoughts when meeting. Cosmo and Seth both agreed initially that circular notches instead of squares would produce more favorable results. Other than this change, everything else was up in the air. We spent most of the given class time adjusting and testing out crazy ideas that might work and becoming more in fluent with SolidWorks. We did not come up with a finalized design before we met with the other team. With this being said, the resulting design had a volume of 1.2 cubic inches and a displacement of .1314 mm, and a final score of .159 mm-in³.
When members Seth, Cosmo, and Olivia met on Saturday morning as Team K, they initially spent time separated, experimenting individually. However, all initially agreed to keep experimenting with rounded cuts and sides.
Thinking of how circular cuts were safer, Olivia experimented further with the placement and sizing of arc slots, circles, and ellipses within the robot arm. She also determined that chamfering or filleting the edges of the cuts and of the arm itself were an easy way to reduce the overall volume of the arm.
Seth took the idea of splicing and applied it to both the long edges of the design. He also used the filleting tool to further cut down volume. His final design was simple and elegant. It had a very low mass, but it's displacement was way too big to be considered in the final design.
Cosmo's design began with understanding that the weaknesses would be at the thinnest sections of the arm, so he wanted to find ways to reduce the volume without reducing the volume or rigidity in those particular areas. Initially, he decided to go with rounded cuts at these edges but what was found was that this led to unnecessary loss of volume and therefore a larger displacement so that idea was quickly scrapped. Then he began seeking out places of great structural integrity where it seemed that the extra material was unnecessary. To remove the extra material, he used circular cuts in the beginning, remembering the lecture about airplane windows and their structural integrity. Circular cuts proved to act well under intense pressure. However, with several tests Cosmo began to realize that the equal displacement that curves provide are more effective in terms of pressures, as opposed to supporting weight. His second contention around removing circular cuts from the "joints" of the arm was the fact that the most displacement comes from areas of least width. Making the circular cuts reduced the width of the thinnest section even further, and this resulted in a large increase in displacement; therefore, square cuts proved to be a more efficient design. This idea led to Cosmo's experimentation with square cuts throughout the design, replacing all circular cuts with more rigid rectangular cuts. What was found through the tests that ensued was that these cuts were most efficient in removing unnecessary volume from the arm, because circular cuts left large corners of material that were unaffected by the stresses of the rest of the arm. Once this idea had been thoroughly tested, he began to seek out spaces within the arm that could have material removed. The only problem now was that Cosmo was lazy in saving his design and after making an error with an Extruded Cut that overlapped another, SolidWorks decided to make it impossible to undo his sketches, and he then had to redo the entire design. The second time through, Cosmo experimented with the idea of removing material without cutting through the entire design. This resulted in a long rectangular down the center that took more than half of the material out of that particular side in areas that were cut. The result was a huge reduction in volume while maintaining general structural integrity and rigidity. As a part of this idea, Cosmo toyed with the idea of placing sequential rectangular cuts instead of taking out huge areas of mass and leaving thin supports throughout the arm. However the result of this was rather odd, each thin section of the arm bent and warped a huge deal when forces were applied to them so the idea was immediately scrapped. In attempting to try this idea out a few different ways, a similar SolidWorks glitch occurred where the part was under defined but no actions could be undone so, again, the entire part had to be restarted. But the third and final reconstruction of the part was a systematic and easy process, and Cosmo could now just apply all of the most efficient ideas from previous designs and avoid any situations that would leave the part under defined. The result of this is the part shown below.
It became clear that Cosmo's work was the most developed.
Volume= .79 cubic inches Displacement= .1843 mm Score=.145597 mm-in³