Hello everyone!

I’m excited to share that my partner Giorgia and I have completed our BIOE555 midterm project! It was quite a challenge but we’re really proud of the results.

For our project, we selected mechanical movement #138 from the 507 Mechanical Movements guide given to us by Dr. Wettergreen. This movement is characterized by a cam at the bottom that, when turned, produces a variable alternating linear motion in the rod resting on it.

We chose to reproduce the sea and marine animals. Our concept involved creating a box with a central rotating rod fitted with various cams. These cams would raise and lower our animal figures (attached to poles) to simulate swimming or jumping movements. We soon recognized the need for an additional surface with suitable holes to ensure a more stable linear motion and prevent the poles from shifting in the horizontal direction.

We aimed to create a nested box design, featuring two acrylic top surfaces that would allow viewers to observe the internal mechanism. Each top surface was designed with four holes for inserting poles with attached animals. Our goal was to minimize friction, ensuring the poles could move smoothly up and down, even without assistance from the pushing cams.

To start, we designed both boxes using MakerCase.com. After testing the dimensions with cardboard in Project Gate 1-2, we transitioned to plywood. We printed prototypes of both boxes around ten times due to scaling and kerf issues, as well as challenges with the inner box fitting snugly within the outer box without excessive movement. Ultimately, the dimensions that worked best for us were:

• Length: 11 inches

• Width: 5 inches

• Height: 7 inches

• Length: 10.8 inches

• Width: 4.8 inches

• Height: 5.8 inches

Once we confirmed that the two boxes fit together properly, we moved on to laser cutting the acrylic top surfaces. Aligning the four squared holes between the two surfaces was hard, especially because of their different sizes. After multiple attempts, we achieved a functional result. However, we encountered another issue: the squared holes were slightly oversized, causing the poles to shift side to side instead of just moving up and down.

To address this, we decided to experiment with different squared hole sizes to find the optimal fit that would minimize friction on the wooden poles. Specifically, we needed the holes to match the dimensions of the poles, which were 0.180 inches in width and 0.2335 inches in height.

               

While the slight adjustments in dimensions might seem minor, they significantly impacted the smoothness of movement and friction reduction. We found that the ideal hole size was 0.185 inches in width and 0.234 inches in height. With this information, we laser cut the two top layers again, incorporating the four holes, and snap-fitted them onto the wooden boxes.

After assembling the nested boxes and attempting to insert the rod with our cams, we were very sad to discover that the mechanism wasn’t functioning as intended :(. Instead of allowing the poles to move smoothly, the cams were catching on the base of the poles, hindering their vertical motion. Initially, we considered that a different pole base shape might resolve the issue. We experimented with various pole designs, testing each one, but unfortunately, none provided the desired functionality.

At this point Paige gave us a great advise, suggesting that the inner box might be too tall, which reduced the height difference between the two acrylic surfaces and compromised the stabilization of the poles.

At this point, we disassembled the inner box and manually positioned the top layer a few inches lower than its original height. Finally, this adjustment allowed the poles to move up and down smoothly. Next, we adjusted the height of the inner box, reprinting its sides to make it 1 inch shorter. With this change, we tested the mechanism again using the middle pole design from the earlier figure, and to our delight, it worked perfectly!

We moved to spray-paint our sea animals and to attach our vinyl sticker.

 

Next, we designed our metal handle using Adobe Illustrator. Having a metal handle facilited the movement of the rod. Using the plasma cutter, we cut our metal piece and then we post processed.

Before the spray painting step, we used the sand blast to obtain a nice surface.

At this point we tried to assemble everything, but we sadly realised that a lateral side of the bigger box was pushing the inner box, misaligning our holes. To solve this issue, we cut 2/3 of the problematic bigger box side and we solve the problem.

Here, it is our final product! However, we encountered another challenge with the rotation of the pole because of one of the assembled sea animals. It wasn’t moving correctly when we rotated the handle and rod clockwise. As a result, our mechanism currently functions well only in the counter clockwise direction. To address this, we added a directional arrow above the metallic handle to indicate the preferred rotation. If we had more time to refine our box, we would have aimed to ensure it could operate smoothly in both directions instead of favouring just one.

To conclude our work, we designed and printed our name plate and we pasted it onto the back side of our box.

As always, we made sure that all our work spaces were cleaned properly.

Cost type		Price	Source	Quantity	Total
Materials	Cardboard	$12.19	Staples	1	12.19
	PlyWood 2ftx4ft	$10.99	Joann.com	6	$67.94
	Aluminium sheet	$14.63/y	Home depot	1	14.93
	Grinding disk	$3.99	Harbor freight	1	$3.99
	Spray paint	$5.98/can	walmart	5	$11.96
	Vinyl paper	$19.58	Amazon	1	$19.58
	Acrylic board	$18.48	Home depot	1	$18.48
	Wood glue	$5.48	walmart	1	$5.48
Labor	Laser operator	$19.26/h	ziprecruiter.com	3	$57.78
	Prototyping engineer	$22/h	Ziprecruiter.com	20	440
Overhead	Plasma cutter	$75/h		0,5	$37.50
				Total	$689.83

If we produced this item in batches of 100, the overall costs per product would significantly decrease, particularly when considering labor and overhead expenses. For instance, the costs associated with the plasma cutting operator, laser operator, and prototyping engineer would remain constant for all 100 pieces.

Conversely, material costs would increase since we’d need more raw materials to manufacture 100 units. Currently, with labor and overhead costs estimated at $535.28, the cost for producing one piece would be approximately $40. Additionally, many of the materials listed can be utilized to manufacture multiple pieces, further optimizing cost efficiency.