Hi everyone!
My partner (Ludovica) and I finally finished our BIOE555 midterm project! It is humbling to say that it really challenged us and we worked on it for more than 20 hours in total. But hey, it’s done now and we are pretty satisfied with our job! We chose the mechanical movement #138 from the 507 mechanical movements book guide that was provided to us by Dr. Wettergreen. Our movement is described as “On turning the cam at the bottom a variable alternating rectilinear motion is imparted to the rod resting on it.” 
Having said this, we picked a theme for our project, which was the sea and animal creatures. So we had the idea to create a box with a rotating rod in the middle with various cams on it, which would move up and down our animals (attached to poles) as if they were swimming or jumping. We quickly realized that we needed to have not only one surface with the appropriate holes but also a second one to have a more stable rectilinear motion and avoid the poles to move in the x-direction. We followed our cardboard model, shown below, as a guide
Overall, we wanted a box inside a box, with both top surfaces in acrylic (so they would be see-through for people to analyze the mechanism), with a total of 4 holes in both top surfaces where the poles with the attached animals would be inserted. This needed to be done with such a minimal amount of friction so that the poles could move up and down even without the help of the pushing cams.
First thing first, we designed our two boxes with MakerCase.com and after properly testing the dimensions with cardboard (project gate 1-2), we moved to using the plywood sheets. We probably printed both boxes a total of 10 times, because we would always have scaling issues, kerf issues, or the inner box would not fit properly (i.e. fitting inside but being big enough to not move around) inside the bigger box. The final box sizes that worked for us were the following:
- Bigger box (outside box):
- Length 11 inches
- Width 5 inches
- Height 7 inches
- Smaller box (inside box):
- Length 10.8 inches
- Width 4.8 inches
- Height 5.8 inches
After making sure the two boxes properly fit, we started laser cutting both the acrylic top surfaces. It was very challengeable to precisely align all the 4 holes between the two surfaces, especially since they were of different sizes. After 3 or 4 trials, thanks to Ludo’s Adobe Illustrator expertise, we were able to figure it out. But…. of course there was an additional problem: the holes were slightly too big and the poles would have actually moved side to side instead of only up and down. Having said that, we proceeded to laser cut and test different hole sizes and see which one caused less friction on the wood poles. More specifically, we needed holes with an aperture of 0.180 inches in width and 0.2335 inches in height (these were the poles dimensions). So we printed 3 options, as can be seen below: 
These very small changes in dimensions could seem negligible but they really naked a difference in terms of smooth movement and friction prevention. The hole dimension that was a perfect match is the one with an aperture of 0.185 inches in width and 0.234 inches in height (hole #2 in the above figure). After discovering this, we printed once again out two top layers with the 4 holes, and snap-fit them on the two wood boxes.
After assembling the two boxes one inside the other and trying to insert the rod with our cams and test whether the poles would actually go up and down properly, we were emotionally frustrated to realize our mechanism was not working at all. The cams would “cut” on the base of the pole instead of letting it move smoothly around it and providing that up and down movement we wanted. We initially thought that maybe we should have done a different shape type for the pole base in order for it to function. Having said that, we tried various pole designs and tested each one of them, but nothing seemed to really work. 
Desperate and with no motivation left, we sought help from the TAs of the class, and Paige was actually really helpful advising us that maybe our inner box was too tall, making the height difference between the two top acrylic surfaces (where the holes are located) too little for the poles to be properly stabilized by them. So we proceeded to disassemble the inner box and try to position, by simply holding with our bare hands, the top layer some inches below its original height. We were surprised to see that by increasing the distance between the two top layers the poles would not only go up and down, but they would do so in a very smooth manner! We did not know how to thank Paige enough, as we were very demoralized and almost wanting to give up on our design and her input was really what saved us in the end, since we did not have a clue of what we were doing wrong. At this point, we had to lower the height of the inner box, so we printed its sides once again, making it 1 inch less tall. By doing so, we were able to re-test whether the cams would properly push the poles (we ended up choosing the middle pole design from figure X shown above), and it worked 🙂.
Moreover, we also had already printed the sea animal we wanted to have along with corals for decoration. We also had printed a wood layer resembling ocean waves to put in front of the bigger box, so it would seem like the animals were jumping in and out of the ocean. After spray painting all our elements, we designed a rectangular box with the same dimensions as the wave wood piece and printed it with vinyl, to then attach with school glue the three corals, as shown below. We also took the inner circle figures remained after laser cutting the adaptors/spacer and spray painted them with white color to simulate air bubbles in our ocean (i.e. the blue vinyl).
Moreover, we used Adobe Illustrator to design our metal piece that would act as a handle that would go attached to one end of the rod so that it can be used to move the rod, thus also moving the cams which would cause the poles with the animals to move in the y-axis. We plasma cutted our metal piece and proceeded to post process it by simply angle grinding it, sand blasting it and spray painting it blue. The bigger hole was designed for the rod to fit perfectly in it, whereas the smaller top hole is for people to insert their index finger and be able to comfortably rotate it. 
BUT THEN WE HAD TO DEAL WITH ANOTHER PROBLEM! After assembling everything together we realized that we had made the inner box so perfectly to fit inside the bigger box that when both were snap-fit together and closed, the lateral sides of the bigger box pushed the whole inner box in a manner where the 4 holes were not aligned anymore, causing the poles to not be perfectly straight through the holes of both top surfaces. Having said this, what we thought was best is to only leave the upper side of one of the lateral sides of the bigger box (which was about 1 inch), so that it would still fit and stabilize our design, but without interfering with the smaller box. The bigger/outer box lateral side was cut with the bandsaw machine, as shown below. 
For a better understanding of it, the above figure shows the rod and handle attached to one side of the smaller and inner box, with the bigger and outside box to only be that ~1 inch wood piece snap-fit only on the top side of that same lateral side. Additionally, we used the handsaw machine to cut our rod to an appropriate length and then properly placed our cams and spacers on it. One final problem we had is that our first pole, the one with a manta ray, does not move properly when we rotate the handle/rod in the clockwise directions. So, having said that, our mechanism perfectly works only in the counterclockwise direction, thus we explicitly added a direction arrow above the moving metallic handle. We believe the only thing we would have done differently if we would have had more time for our box is to ensure that it would work in both directions instead of just one working best over the other. 
Lastly, we designed and printed our name plate and pasted it to the back panel of our box with wood glue, as shown below.
FINAL RESULT VIDEO:
A picture of our clean space after finish working is also shown below:
COST ANALYSIS:
If we would like to sell our project, there are many factors we should consider first, especially given the high number of hours we worked on this and also the number of trial and errors (iterations) we had to go through. Overall, as for materials, luckily we did not have to pay for anything, as the amazing OEDK facility provided everything to us, including cardboard for the low fidelity prototype, plywood sheets, acrylic sheets, blue vinyl, metal, spray paint colors, wood rods, and wood and school glue. Thus, material costs were $0.
As for labor costs, we spent approximately between 20 and 25 hours to get our final design. We can say we charge $10/hour, so that summed and rounded up would be a total of about $200 for labor costs. Moreover, we overall made use of the EpilogPro and Epilog M2 laser cutters, the plasma cutter, the bandsaw machine, the angle grinding machine, the sandblasting machine and the vinyl cutting machine. Having said this, we can say that the operating costs can be compared to the estimated rental costs of all these machines in the Houston area.
Rental costs based on EquipmentShare.com and local hardware rental stores:
- Epilog Pro/Epilog M2 laser cutters: $50/hour
- Plasma Cutter: $75/hour
- Bandsaw Machine: $37.5/hour
- Angle Grinder: $15/hour
- Sandblasting Machine: $45/hour
- Vinyl Cutter: $30/hour
Let’s say we used the EpilogPro and EpilogM2 laser cutters for a total of 10 hours, the plasma cutter for 30 minutes, the bandsaw machine for 10 minutes, the angle grinder for 10 minutes, the sandblasting for 10 minutes, and the vinyl cutter for 30 minutes. That being said:
- Epilog Pro/Epilog M2 laser cutters: $50 x 10 hrs = $500
- Plasma Cutter: $75 x 0.5 hrs = $37.50
- Bandsaw Machine: $37.5 x (10/60) hrs = $6.25
- Angle Grinder: $15 x (10/60) hrs = $2.50
- Sandblasting Machine: $45 x (10/60) hrs = $7.50
- Vinyl Cutter: $30 x 0.5 hrs = $15
- TOTAL = $576.25
We concluded that the approximate final cost for renting all these machines and equipment in Houston, for the specific time periods we previously mentioned, is $576.25. Finally, adding this value to the approximate labor costs, would result in a grand total of $776.25.
