We’re officially halfway done with the semester! The last few weeks, we (Coby and Abby) have been hard at work on our midterm project.
The first step to the project was coming up with an idea. After browsing the internet for some ideas, we decided to make a slot machine. Our design was to have a box with three rotating “reels” with images on them. The rotation would be controlled by a series of gears connected to a lever. We sketched out our design and discussed how we would control each aspect for our first project “gate.” We also used Maker Crate in order to make 2D drawings of our “reels” and external box, and Gear Generator to make drawings of our various gears.
Next, it was time to start prototyping. Because of the many gears which had to be connected and supported within our machine, it was very important for us to determine the size of holes we would need based on the size of dowels available to us. We did this by measuring the dowels and cutting holes of various sizes in a piece of wood. Then, we determined which size was ideal both for press-fit and free-rotation applications of the gears. Once this had been determined, we started laser cutting one set of the gears to ensure that they fit together inside of an open-sided version of our external casing, which we also laser cut. We were extremely grateful to find that all of the gears fit together nearly perfectly on our first try! To finish up our low-fidelity prototype, we also printed out one of our reels to make sure that we were able to attach and rotate it with the gear system. At first, we mis-measured the distance between gears and made the reel too big; however, after quickly adjusting its size, we found that our setup seemed to work quite well!
From our low-fidelity prototype, scaling up was relatively straight forward. One change we implemented in our design was eliminating two of the big gears attached to the lever, and instead just using one to rotate all of the gears on the middle dowel.
This meant that we just had to print out a few more sets of gears and two more reels, as well as a better external casing and handle, for our next prototype. Once again, everything went pretty smoothly, with the biggest problems occurring due to the laser cutting behaving inconsistently (sometimes not cutting through wood, other times burning much larger holes than we expected). We also added some small wooden “caps” to hold the various elements in place on the dowels without glue. It took some time to assemble everything and line the gears up for the ideal rotation, as well as a few iterations in order to perfect the sizing and spacing of everything, but after a few sessions in the OEDK we had a working medium-fi prototype! We were also able to incorporate an element which allowed us to push the handle inward after turning it to allow the reels to continue to spin on their own, making the machine more realistic.
Another element we decided to implement was a small piece of wood with dowels
attached which we could insert through holes on the top of the box. When the piece of wood was pressed down, the dowels would contact the top of the reels, and the pressure would cause them to all rotate so that a flat side was aligned with holes in the front of the box (preventing the reels from stopping in between two sides).
The final stages of our project involved incorporating some decorative elements and a metal component. We vinyl cut some slot machine icons, as well as outlines for text and decorative symbols we wanted to paint on the box, which was pretty straightforward and quick. We also used the water jet to cut a metal handle for our device and laser cut a second box which would attach to and stick out from the first, creating a more realistic shape for our slot machine. Finally, we engraved a decorative piece of wood to attach to the top of the box for additional effect.
Once we had all of our components, we spray painted the reels (which we also sanded down to make the sides flat) and the front of our box, and then hand-painted the symbols onto the reels and text onto the box using our vinyl stickers. This part took a lot longer than anticipated due to having to take frequent breaks to let everything dry, and the method of painting within the vinyl stickers and then peeling them off turned out to be less accurate than anticipated, requiring us to do quite a bit of touching-up by hand.
After we were satisfied with everything aesthetically, we assumed putting everything back together would be relatively straight forward. However, we almost immediately realized when putting the reels back into the box that we had painted the symbols upside down! This required me to flip the front and the back of the box, which required prying the pieces apart and lots of work with a rubber mallet. Once everything was finished, we just had to attach the back of the box, which was harder than anticipated, and the hammering misaligned the internal gears; however, we were able to reach through the windows to manipulate everything until it was working again, giving us a final product we are very proud of!
Device Videos: Outside of Box, Inside of Box
Cost Estimates:
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | ¼” wood (18” x 24” ) | $21.58 | WoodPecker’s Craft | 4 pieces | $86.32 |
| Aluminum metal | $12.58 for 6’ x 18” | Lowes | ⅓ piece | $4.20 | |
| Vinyl Sheet | $13.29 for 12” x 40 ft | Amazon | 0.6 pieces (used 24” x 12” piece) | $7.94 | |
| White Spray Paint | $6.14 | Walmart | 5% of can | $0.31 | |
| Silver Spray Paint | $5.98 | Walmart | 5% of can | $0.30 | |
| Red Spray Paint | $6.98 | Walmart | 5% of can | $0.35 | |
| Acrylic Paints | $5.99 | Michaels | 20% of paint | $1.20 | |
| Labor
|
Laser Cutter Operator | $19.17/hr | ZipRecruiter | 4 hours | $76.68 |
| Water Jet Operator | $15/hr | ZipRecruiter | 30 min | $7.50 | |
| Vinyl Cutter Operator | $20/hr | ZipRecruiter | 30 min | $10 | |
| Painter | $18/hr | ZipRecruiter | 2 hours | $36 | |
| Overhead | Facility Cost (Machine Time) | Assume 15% of labor and materials | Rockler | N/A | $66.74 |
| Quality Control | $20/hr | ZipRecruiter | 1 hour | $20 | |
| Design | Engineering and Development | $43.12/hr | ZipRecruiter | 3 hours | $129.36 |
| Misc. | Waste/scrapwood (wood we cut but didn’t use) | $21.58 | WoodPecker’s Craft | 3 pieces | $64.74 |
| Total | $511.65 | ||||
