Week 7: CAM Toy — Dog Chasing Fly

I created a 3D-printed mechanical CAM toy where if you rotate the lever, you can see a dog chasing an oversized fly. The designs for all objects were created with Fusion 360, sliced with UltiMaker Cura, and printed on the UltiMaker S5. Despite repeated attempts to print parts also on the Prusa i3 printer, its prints failed to produce the designs I was looking for, so only the UltiMaker was used. The rotation part of the toy is fully functional, but the tolerances between the follower and the animals can be lowered as the joint is a bit loose. Furthermore, while the toy works well with one animal, when both animals are inserted on top of the follower, the followers get de-railed from the CAM, so further improvements to that design (likely by designing a cover/slot/inward cut for the follower so it doesn't just lay flat on the wheel) would be possible in the future.

I began my CAM toy design by decreasing the size of the top (highlighted in green) by 0.2 mm and the walls by 0.5 mm after consulting with the instructional staff (Alejandro). My initial goal was to add a dog on top of the followers!

I gave the walls for printing on the UltiMaker and the top for printing on the Prusa. While the walls printed completely fine on the UltiMaker, the top did not print with holes (rather, a shell printed).

Since I gave the initial prints on Friday, I spent the weekend designing my finalized CAM toy, so I could print the remaining parts (including the top) again on Monday. After realizing that attaching a singular dog to be put on two followers at different heights did not make much logical sense, I designed an oversized fly in Fusion 360 and used the software's Assemble Joint feature to test out the joints/how big the dog and fly could be. Once finished, I lowered the bottom's tolerance by 0.2 mm and exported all my designs to Cura.

For my third and fourth prints, I again gave some parts on the UltiMaker (the dog and the fly), and I gave every other part on the Prusa to be printed. Once again, the UltiMaker parts came out perfectly, while the Prusa would not print my top with holes, and I am still not sure why that was the case. Furthermore, since the Prusa did not print with light supports (like the Ultimaker did), the filament began to scrunch up on the Prusa, so I eventually stopped that print. I then gave all the remaining parts on the Ultimaker for my 4th print, and it was turning out fine, except that with five minutes remaining, the nozzle became too close to one of the parts and sent it flying to the bottom (thus messing up the rest of the print). I stopped the print and gave it again, and it worked the 5th time!

The walls and the top/bottom fit together really well. Since I did not edit the tolerance of the CAM/shaft/lever/follower, they were a tight fit, but after some pressing, I got them to fit nice and snugly. However, I realized my 0.6 mm per side extra space on the hole I created for the follower to be inserted on each animal was too much, as the fit between the animals and the followers was very loose. Furthermore, keeping the follower on the wheel was a challenge, even though the rotation mechanism worked fine. I was eventually able to put everything together for a little while!

Attached above are current state of the CAM Toy (since the followers and animals don't stay on permanently) and the finalized CAM Toy when put together! It does look pretty when everything is attached together.

Building the toy was very fun, and I learned a lot about how tolerances can encourage snug (or not-so-snug) joints. While attaching parts like the lever to the shaft took some time, in the end, it was nicely snug (which I appreciated). In the future, I would build a small holder/wall to prevent the follower from slipping off the CAM, and I would decrease the hole size in the animals. I am also curious as to why the UltiMaker printed my designs much better than the Prusa. I assume that the light support on the UltiMaker played a role in that, but I am unsure why the Prusa would not print my top with holes regardless.