The midterm project was both the most challenging and most rewarding project thus far. I had to hurdle quite a few obstacles, but overcoming them filled me with a sense of accomplishment. The device that I constructed was the mutilated pinion.

 

Essentially, it is a gear that rotates around an oblong track causing a pinion to oscillate back and forth.

The first obstacle I faced was at the very beginning. The easiest way to construct gears for laser cutting is by using an online gear generator. However, due to the unusual shape of my gear and pinion, I could not use one of these generators. As a result, I had to construct the drawing of the gear by hand. Earlier in the year, when I completed the 2D drawing project, I remembered thinking that it would be much easier to construct the gear using Solidworks than Illustrator. So that is exactly what I did. First I imported the animated image of the mutilated pinion into illustrator and then I used the measuring tool to get its dimensions. Once I had the dimensions, I made the mutilated pinion in Solidworks.

This process, though, was not one hundred percent accurate which would later pose problems for me, but I will discuss that later. As soon as I finished the gear and pinion, I decided to model the rest of my design in Solidworks so I could see how all of the parts interacted.

(I only modeled the moving parts). Now that I had a preliminary design, I was ready to begin prototype one.

Before I could laser cut prototype one, I had to decide how to mount my device. After some pondering, I ultimately decided on placing it in a small box with a handle sticking out of the box for the user to control it. This general idea actually became my final product. However, I had to make many alterations in order for it to function. For the first prototype, using cardboard, I cut out the gear and pinion, two rectangles for the top and bottom, four posts to hold up the top, and two posts with holes in the middle of them for the axle to go through. Once I cut all of the pieces, I quickly assembled the prototype.

Needless to say it did not work very well. The most significant issue it had was that the two teeth on the ends of the gear would get stuck. To remedy this, I shortened those two gear teeth in prototype two.

Prototype two was the most beneficial prototype I built. It was during this prototype that my final product began taking shape. Again I constructed the prototype out of cardboard, but this time I made an indent where the gear was located so it would stay in place and I used my new gear.

I also only attached one of the gear holders so I could inspect how the gear was working and use different gears to determine which gear was best. While doing this I realized that if I could not see the gear while testing my device, the user would also not be able to see the gear. The first solution I devised for this issue was to make the entire device larger while keep the gear holder the same width so the user would be able to see the gear around the holder. However, I liked the size of my device as it was and did not want to change it. My next thought was to make the holder out of acrylic so the user would would be able to see the gear through the holder, which is the solution that I ultimately settled on. Prototype two also showed me how fragile and finicky my device was. Because of this, I chose to completely enclose my device while having the front and top walls made out of acrylic so the user could see the device. Something else that I noticed was that the wheels of my device would not go in a straight line which caused the gear to come out of the pinion. As a result, in my next prototype I installed a track to guide the wheels. The final design flaw that I learned from prototype two was that my base was too short, and consequently the wheels would roll of the end.

In prototype three I addressed the problems that I learned in prototype two. Additionally, prototype three was my first prototype constructed with wood. Since I did not want to waste any acrylic, I did use any in prototype three. However, I did extend the length and put a guide track for the wheels in this prototype.

Additionally, I experimented with connecting the walls to the base and top using teeth.

For this prototype, I hand drew all of the teeth in Illustrator, but the teeth did not align well so for the final product I used a teeth generator. After this prototype I was ready to move onto the final device.

For the final device, I decided I was going to make the base out of metal, the front, top and gear holders out of acrylic, and everything else out of wood. First I cut everything out of wood. I wanted to make sure all of the pieces fit together before I cut the metal and acrylic. Luckily, all of the pieces fit together. However, I realized that the steel had a different thickness than the wood. As a result, I had to adjust the heights of the gear holders to account for the difference in thickness. Once I did this, I cut out all of my acrylic pieces, at which point I had all of my pieces cut and ready to be assembled except for the metal piece. This is where the roller coaster ride that is the conclusion of my blog post begins.

Monday morning, I headed into the OEDK planning to plasma cut my base and assemble my final device. When I arrived, I soon saw that the plasma cutter was out of order. My heart dropped. Without the plasma cutter I could not finish my project. After weighing all of my options, I decided that the best course of action was to finish the project without plasma cutting a piece. Luckily, I had already cut everything out of wood so the only pieces I needed to laser cut were new acrylic gear holders sized for the wood and not for the metal.

I had pretty much given up all hope for having a plasma cut piece in my device, until, while sitting in class I had an ingenious idea. When I did the plasma cutting project, I had cut two extra Pennsylvanias. I realized that I could incorporate these into my project by making a stand with them. I was back in business. As soon as I finished class for the day I rushed over to the OEDK to implement my new plan.

However, before I could build my stand, I needed to assemble the rest of my device. My first task was deciding how to finish the wood. After contemplating, I chose to stain the wood. While sanding the wood so it could be stained, I decided I liked the way it looked and felt after sanding so instead of staining all of the pieces I only sanded them. Once I finished sanding all of the pieces the real assembly began.

First, I attached the guides for the wheels and one of the acrylic gear holders. I also attached the wheels to the pinion and the gear to the axle. When I tested the gear it had two problems. First it was unstable and kept getting stuck, and second, the two end teeth were too short which caused the teeth to miss the pinion. As a result, I laser cut two identical gears with longer end teeth and glued them together. I figured a wider gear might help with the stability, and that I could sand down the end teeth of the gear until it was the perfect length. After making some adjustments I finally had a gear that worked.

Next, I attached the other gear holder. At this point, I realized that I needed to cut a hole in the acrylic sheet that was going to be the front of my device so that the axle would be able to come out. To do this, I marked where on the piece the hole needed to be and then used a drill press to drill the hole. Once I had the hole drilled I attached all of the walls of my device. Next I wanted to attach the top, but once the top was glued on I would not be able to adjust anything on the inside. So instead of gluing the top, I attached two hinges to it that allow the top to be opened. Having hinges on the top both ensures that the gear and pinion are safe and that they can be accessed if need be.

With the entire main device being assembled, there were only two more tasks that needed to be completed. The first was to attach the handle which I superglued on. The next was to build the stand. I first tried to simply glue the Pennsylvanias to the bottom of my device but they were too thin to be glued on. To fix this, I glued spare pieces of wood I had laser cut onto the backs of the Pennsylvanias to increase the surface area that was in contact with the device. This time they glued on but were very flimsy. To stabilize them, I glued more spare wood onto the Pennsylvanias and then attached the two Pennsylvanias to each other with dowels. After doing this, the base was stable and I my device was finished!

This project brought to light many aspects of prototyping and designing that I sometimes look over or neglect. The first aspect is resourcefulness. Whenever there is an obstacle, no matter how daunting it seems, there is always a way around it. For my project, the obstacle was the broken plasma cutter. Instead of giving up, I considered all of my options and in the end was able to use a part that I had plasma cut in my device. The next aspect of prototyping that played a major role in my project was planning ahead (or in my case not planning ahead). The predicament caused by the plasma cutter breaking could have been avoided if I had planned ahead and plasma cut my part sooner. The final aspect of prototyping I want to highlight was the importance of having many prototypes.

Each prototype taught me something new about my device and allowed me to improve it. Without the prototypes, there is no way I could have made a device that works. In conclusion, this project not only taught me about physically designing and making prototypes, but also about the importance of being resourceful, planning ahead, and having multiple prototypes.