Nov. 29th 11am-1pm
Our team started designing and planning our project. We decided that we would go through with making a mouse trap car, so we fetched all of the materials that we would find useful in the OEDK, recorded measurements, and stored them. We designed our three gears using SolidWorks.We used MakerCam (introduced to us by Juan Borbon on Nov. 30th) to generate our g-code.
Dec. 2nd 1pm-3pm
We began to troubleshoot how to convert our 2D drawing into G-code correctly using MakerCam. At the end of this work period we had three proper NC files for our gears
Dec. 3rd 1pm-4pm
We were the first team to successfully upload a file onto the CNC machine and have it accurately cut our file. This was the first file we cut however, we needed to specify tool sizes and get a more accurate tool bit. This is how our first few cuts came out.
Yaayy, pretty flowers!
After plenty of searching and troubleshooting, we were able to get a more accurate bit and therefore a more accurate cut. The following positives are the inside edges of our gears cut out.
This left us with a negative in our wax that we then filled with a plastic molding positive. However, the mold release didn’t set well on our wax, resulting in the molded positive sticking to the wax, thus being very difficult to remove.
**Snap** “h’Oh No! I break it!” -George Zhu
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We lost our first negative
And our second negative… and third and fourth, but we yielded two successful gears. One of our smallest, another of our middle.
December 4th 1pm-2:30pm
At the end of these days we had two molded gears that meshed together almost perfectly, AND we cleaned up after ourselves.
This was our last day of class in 210, so we brainstormed how we would put together this car we had somewhere in our imagination. Sammy illustrated his idea using K’nex pieces from the prototyping cart.
During this period we also discovered that our final gear wouldn’t be able to fit on the machinable wax we had, so we began to wait for new wax to use.
Dec. 8th
More Machinable Wax Purchased!
Dec. 9th 1-2:30pm
We laser cut our largest gear only to discover that the CNC machine or Software had scaled up our gears a significant amount. (~158%)
We continued to test our concept of the gears within the car with our wooden laser cut gears. We also modified our gear files to account for the scaling by scaling our largest gear to be cut at 158% its original size. George may have made a mistake here because the large gear we would cut from this later was far larger than we expected, and wouldn’t mesh with the others.
Dec. 10th 4-6pm
Attempted to cut out our newly scaled files, but we were told to leave because it was passed time to use the laser cutter. We proceeded to use Joe’s help in the machine shop to cut centered holes into our gears.
Dec. 11th 2:30pm-6pm
We showed up to the oedk to cut the large gear out of ⅕ in acrylic, but the gear that we cut wouldn’t mesh to our molded gears. This was George’s mistake we mentioned previously.
We used the dimensions of the gears (including George’s mistake) to find the dimensions of our box, then we used BoxMaker to generate our box. The dimensions were 9×5.5×4.5 in^3. This box was bigger than we needed because of the overscaled gear, but the extra space became useful later on.
We edited our scaled file again and this time it meshed well with our gears. We used tape to wrap around our dowels so that our gears would be fixed, tight, onto the axles.
Dec.12th 3:30pm – 1:30am
We drilled the holes on the box so that the axles of the gears could pass through. However, in the first attempt, we did not realize that each side of the box was directional. If one side is flipped or rotated, it would not fit with other parts. In the second attempt, we labeled the front and back of each side, and re-drilled the holes. The axle for the smallest gear was too close to the middle gear, and everything was smooth after the third trial of re-drill.
After finishing the gearbox, we proceeded to make the wheels for the rat trap car. However, the OEDK laser cutter broke unexpectedly, and we were unable to cut the wheels due to this unforeseen happening. Since the project was due Monday morning and we could not afford waiting through the weekend for the laser cutter to be fixed, we decided to mold the wheels. We found a wood piece with circular holes in the laser cutter room, which became the negative for the wheels. We used 300Q to make 4 of the wheels and attached two together for stability.
George happened to find wheels almost the exact same size as the circular hole that we molded into, so we decided that these wheels would be a good fit for our car. The wheels would’ve made excellent rear wheels to power the car, but they had bearings inside of them, so they could not be fixed to the axle. We still used the wheels, but they operate as front wheels to keep the car on a steady path.
It was already 8:30 pm and the team had not eaten their dinner yet. So we went out to eat and buy the rat trap for the car. We went to Home Depot and purchased some mouse traps and a rat trap. After some comparison, the team decided to use the stronger rat trap.
Coming back from Home Depot, we mounted the front wheel axle to a piece of wood, attached the rat trap, and connected the wood to the front of the car.
Dec. 13th 7pm-1am
We prototyped with the small mouse traps in order to find a way to attach the string to the axle and the string to the trap so that the string pulls the axle when the trap is released. We tested the rat trap on the car, which broke the acrylic box when the trap was released. We reinforced the acrylic box using L brackets and more acrylic glue.
We tested the car with the string wrapped around the axle with the largest gear. This did not drive the car as much as we hoped. We removed the top of the box and wrapped the gear around the middle gear. This worked and drove the car in the opposite direction. Finally, we extended the string and attached it to the back axle and this worked the best to power the car.
Success!
Click on video
