For the midterm project I worked with Brendan Hlibok to create a machine that represents the functions of a Whac-A -Mole game using the mechanical movements of gears (24) and cams (96).
Here is the process, reflection and cost estimates in my perspective:
Process:
We started brainstorming ideas for the project and we decided upon Whac-A-Mole because we thought it was a different, never done idea and we liked the mechanisms involved.
We did a conceptual drawing our design and worked through the dimensions of the design.
Next, we created Ai file with our design to laser cut it on cardboard. Not fully included in the sketches is our cam design. We decided to move forward with a snail cam design because that would give the impression of a rise, like the moles peeping out of a hole, and then an instant drop as if the moles are trying to avoid getting hit. Most of the parts could be created using the shape-builder and other tools in adobe illustrator, but for the gears we used the website “Gear Generator” We set the number of teeth to be 16, which was a trial that we assumed would work based on the spacing of the model the website generated for us. We started building design first with our 20cm x 20cm frame, then hot gluing the pieces together and using wood rods to hold the cams and gears which created our low-fidelity prototype below:
Video of Low-Fidelity Prototype
Once completing this prototype we made a list of changes we would need to make to our Ai file before creating the medium fidelity prototype. Some of the changes we made included:
- The cam shafts were not placed in line with the holes that the moles poke out of, so we needed to ensure that they are aligned.
- The holes used to hold the moles up (not where they poke out of) are too large, and allow the moles to move too much, allowing it to get stopped by friction too easily. We needed the sides to be just small enough that the piece could slide smoothly up and down, but would not move too far out of place in the x and y direction (assuming +z is upward from the table surface).
- The cam needed to be taller. The moles were barely sticking out, so we had to make the maximum radius larger.
- We needed to design caps for the end of the cam shafts so that they would not move side-to-side.
- We needed large followers to give the bottom of the moles more surface area to glide along the cams
Needed to make the diameter of the gears smaller, so that they would fit together
From this prototype we really liked how snail cam movement, and the size of our design, not too large, almost where it feels like you’re playing with a toy.
Next, we started editing the Ai File with our changes to create our medium fidelity prototype. This prototype process really was a lot of testing and iterations which we printed and tested different pieces at separate times. We also began thinking about how we wanted to incorporate our metal piece, as well as our sign design.
Through out the process of building this prototype we tested different cams and arrangement to reduce friction between the wood-on-wood for the cams and the followers to create a smooth movement. Additionally, we still didn’t make the hole for the mole to come through small enough, and causing the moles to still get stuck on the side. To combat this, we used two long, straight pieces of wood to make the hole smaller to see if that would make the cams rise, and they did. So, we took the measurements for the distance from one rod to another and used that for the size of the mole holes.
After producing the medium-fidelity prototype, we decided that we wanted the handle to be made out of metal as it would be stronger than wood and functionally contribute to our design. We also decided that the sign would cover the front of the moles so that the user would not see them from the front as they went up and down. We decided to leave the inner mechanisms exposed so one can see how the product actually works. We also decided that we would use two snail cams for each follower, as this would still create the same motion, but would decrease the accuracy we need to get the cam directly in the middle of the follower, and allowed us to increase the size of the snail cams without them intersecting with each other by spacing them out. We test this change and the cam shafts were aligned nicely under the moles, the holes for the cam shafts were in the right place and fit the rods nicely, allowing it to spin freely, gluing the first layer to the sides did make it look nicer, and the gears moved smoothly with one another. However, we still had a couple issues with the edges of the snail cams not being smooth enough causing the followers to get stuck on the cams.
Also, we took a poor approach to assembling our medium-fidelity design, which gave us important insight on how to assemble our final design effectively. On the medium-fidelity project, we built the frame first and then tried to squeeze the cams and gears in, which caused extreme difficulty, and inaccuracy in the placement of our cams. For our final, we knew we would have to work slowly but surely from the inner workings out, placing and gluing one piece at a time.
Before going into our final prototype we did some more testing to reduce the friction. In illustrator, we printed out more snail cams, made the mole hole smaller, and we also decided to change our design for how the first layer would sit. We had a bar go across the sides of the design, and we decided we would have the first mole layer sit on that, so that it received support from our side supports, making the device more durable. Finally, the size of the snail cams were satisfactory, so we kept that same design for our final prototype.
Here is the Ai file we used for our final prototype:
We cut out our wood parts, including the sign, and then began to consider our metal piece, and our post-processing methods we wanted to use for the wood and metal. For the metal piece, we decided on a handle that would be shaped like a mole. Brendan used the waterjet cutter to cut this part, then filed the sharp edges after the cut, and finished it a smoke gray spray paint to maintain the metal look, and keep the colors consistent with our base brown colors.
Handle after spray paint
For our final assembly, we decided to use wood glue for the frame and base, and then superglue for the inner workings, as superglue was easier to apply with accuracy in smaller spaces, such as between the cams and the cam shaft. We took a bit of time getting every cam in the correct location and using tape to measure carefully. For the wood, we sanded the frame for a nice, smoother feel to it, and specifically put extra focus into the sides of the snail cam and follower to reduce friction between them. For color, we decided to stain all parts except the inner workings (to ensure there’s no added friction) using a “classic black” but very lightly (by applying it and almost immediately wiping it off) with the vision that it would give a darker, earthy view to the product.
Staining and sanding
The sanding turned out as we expected, but the stain actually stained the top layer and the moles significantly more than the other parts that we. We considered reprinting and restaining but, it still had the earthy look to it that we wanted, and the fact that the top layer was dark almost made it feel like it represented dirt, so we liked the aesthetics of it enough to keep it as it was.
Gluing the product
Now, all of the parts were ready to assemble. As stated earlier, we took our time to assemble from the inner workings to the outside frame, we also ensured that we left enough time for the wood glue to dry, so that parts were flush and it looked like a quality assembly. We placed the gears on, then the cams one-by-one, checking it with the followers each time to ensure that they were equally centered across the middle of the mole stem, so that it would go up evenly. We also used a straight edge to ensure that the snails were at the exact same orientation. Finally, we randomly oriented the snails so that the movement of the moles would be random, like in the game.
After approximately 5 hours of careful assembly, we had all our parts glued together, and we were so happy when we found that there were no serious issues with the workings of our design. Two obstacles we encountered were that the holes on the side supports did not fit the rod, and there was one piece of wood that had a ridge which caught on the follower multiple times, stopping the machine. To fix these errors, we used 1/4″ washers (same size as the rod) on the outside of the side supports to prevent the rod from moving around, and we sanded the ridge away on the follower, and the design worked like a charm. Another small issue we had was that our device was very light and when you would turn the handle, there was not enough friction to hold the device in place. So, we placed stripes of felt tape under the device making it stable when using the handle. Lastly, we wanted to add faces to our moles with vinyl, however, it was broken when we were ready to cut.
Washer on the handle and felt on the bottom
It was one of the most satisfying feelings ever to see it finally work after putting in so many hours and late nights in the OEDK (~25 hrs each).
Here’s a video of the final product:
Reflection:
- I learned a lot about taking each step slowly and really having the patience to to test and modify and continue constantly instead of assembling everything quickly and then trying to fix the errors. This really was hard but very much worth it lesson that I saw specifically in the final design. We took our time in placing every cam and gear perfectly and it the end the mechanisms worked smoothly.
- I also learn about really preparing and taken advantage of the resources we have. Since there was a long line for the laser cutter, after the first time we waited for it I realized I need to print more than necessary of the medium fidelity to continue the testing or else we would never finish testing if we waited to print again.
- Working in a team is very useful, however, it is important to make sure everyone is on the same page or is motivated to work. I feel like I could have communicated when my energy was low and changed a meeting time because I wasn’t as productive and helpful in that state.
- Lastly, I am really glad for all the skills I have learned. I have a lot of confidence in my laser cutter skills and I am becoming better at mentally visualizing mechanical movements. I learned about my communication skills and how important it is to build a good team dynamic and motivate each other.
Cost Estimate:
Wood: 2x sheets of 1/4″ thick wood – $5.75 per
Metal: 1x sheet of Aluminum – $60.00
Overhead (OEDK Laser cutter, waterjet cutter, washers, and rods) – $40.00
Labor: 25 hours of labor at $25.00 – $625.00
Total Cost: $761.50
