(This blog is created together by Greg Caringer and Yuka Aoyama)
For the midterm, we worked on a music box that looks like a record player. We used Illustrator, Rhino, a laser cutter (wood and acrylic), a waterjet cutter (steel), files, sandpaper, and clear coat paint for this project. The mechanism we decided to use is #24. We used mechanism 24 by using two gears to connect a crank to another axle. This axle would rotate a music box comb over an element that would strike the comb, playing different notes.
- Low Fidelity Prototype
Body:
We used a box generator to make a finger joint box and gears for our body. We laser-cut cardboard to see what our final product would look like. We also verified that the mechanism did work as intended and was able to rotate the music box comb. The top of the box held screws that would strike the comb as it rotated.
Disk:
We mapped the music notes using arc length and distance between each note. Specifically, in Illustrator, we sketched equally spaced circles, as seen on the left, and angled lines (360 degrees/64 of 1/4 notes =5.625 degrees per 1/4 note), as seen in the middle. We first used the music notes from Canon in D but we realized that was too challenging due to the large range of notes we would have to waterjet cut and test. Therefore, we switched to ABC Song/Twinkle Twinkle Little Stars after this low-fidelity prototype. We also changed from having screws directly on the box to a disk to be able to switch between songs and also mimic a record player. To have space with no sound, we also designated a section where no notes would be on.
Ballerina:
To make our mechanism more visually appealing, we decided to create a figure that we could place above our comb that would spin as well. For this, we decided to create a 3d figure of a ballerina that could go on top of the comb. To create the 3d figure, we would have to slice a 3d model at an interval and then cut these slices on the laser cutter. When assembled, this would create the 3d figure.
To create these slices, we used the Rhino software. We imported an STL file of a ballerina and used the contour function to slice the image at an interval of 5mm (the thickness of our wood). We could then export the relevant files into Adobe illustrator to send to the laser cutter. The files had to be modified to be able to insert dowels into the different pieces so that we could connect them. From there, we could cut out the ballerina with cardboard to test how the figurine would look.
2. Medium Fidelity Prototype
Body/Disk:
We then laser-cut the box and the gears with wood to test the functionality. We chose to make our gears with 2 layers of wood for stability and increased connectivity. We also began to use square dowels to make the rotation of our mechanism easier. We also placed the dowels in bearings so that they could spin smoothly. Our wooden cut box proved to fit well, however, the living hinges we used were inadequate. The design created by the box generator worked for our design with cardboard but, when used with wood, the hinges broke. To fix this, we used the 1D living hinges found in the Prototyping Library and modified them to fit our design. These hinges worked much better when using wood to assemble the box. Also, we designed the top of the box so that the disk could be removed by making one sheet of wood only have holes big enough to fit the bearings while the sheet on top of it had a slot to fit the music disk.
We created our own washers to hold the comb in place, but our two initial designs allowed the comb to move from side to side. In order to increase stability, we designed a third washer that would wrap around the comb to prevent movement. This allowed us to use the mechanism without having to constantly re-adjust the comb.
Comb:
To start, we used waterjet cutting to create the comb, with a 1mm difference between each line. However, we soon discovered that the 0.5mm steel (located in the top left) was too flimsy and bent instead of vibrating. To fix this, we switched to a thicker 1.5mm steel (located in the bottom left) and tested the sound. While the sound was chromatic, it was producing frequencies that were too high. As a result, we created a second comb (located in the center) with longer lines, which produced a chromatic sound as well. After some testing, we ultimately decided to go with the notes on the far right of the comb. The resulting comb is located on the right, and we made slits to attach it to the square dowel using our own customized washer. We also noticed that rough edges from the waterjet cutter were affecting the sound so we filed the comb down.
3. High-Fidelity Prototype
Body/Disk:
For high fidelity, we repeated the steps we took for medium fidelity while making some minor adjustments.
After laser cutting the wood pieces, we sanded off any burn marks and applied a gloss clear coat to achieve a polished appearance. We decided to not use colors, because we liked the wood’s natural and minimalist aesthetic, especially when paired with the acrylic top.
We also switched to a thicker square dowel with a larger bearing to increase stability. To accommodate it, we re-sketched our disk and made the slit larger. We tested that people can slide out the disk through the slit.
We also created a finger tab on the disk to make the removal of the disk easier.
Cost:
Acrylic: 2 sheets of 12″x12″(3mm)= $17 (Amazon)
Wood: 3 sheets of plywood (5mm) = $20 (Amazon)
Bearings: 4 bearings = $1.6 (Amazon)
Steel: 5mm x 100mm x 100mm 304 Stainless Steel Sheet = $23.97 (Amazon)
Labor: 80 hours x $15 = $1200
Total Cost: $1262.57
