Almost two years ago, our family was traveling back home from a seaside vacation. We were waiting for our flight in an ugly airport section and I bought my daughter a toy car to brighten up the mood. It was a small Bburago model, which is more of a detailed replica rather than a durable toy that you can give to a two-year-old child. Ironically, in a few minutes after we unboxed the car, my daughter dropped it. One wheel broke off, and since then, the car was for one year on a "to repair" shelf. For a few times, I tried to glue the wheel back in place with a CA glue and with a UV-cured resin. All my tries were complete failures. I surrendered and accepted the fact that I can't repair that wheel.
Recently I stumbled upon the car again. Of course, I remembered that I couldn't repair the wheel. But I also thought that I don't have to repair it. I can make a completely new wheel. I can 3D print it.
I had to disassemble the car a bit and remove the wheel axle. I removed the leftovers of the broken wheel, as well as the other wheel from the axel. I discovered that the other wheel was cracked as well. Thus I was going to print two new wheels. It's even better to have the same wheels on a single axle to avoid disbalance.
Then I measured the wheels and the axle, designed a simple model of a new car wheel, and printed four of them. Although I only needed a couple of wheels, I printed some extra because one of them may break, or a print may fail. Ultimately, now I have two more extra wheels in case the rest of the original wheels fail. I ended the top of the print with a silvery filament to give a disc-like shine to the wheels.
All in all, the printed wheel mostly resembled the original one. It had a bit thicker walls, to allow double perimeters of a 0.4mm nozzle. I also added reinforcing ribs between the inner and the outer walls, as I was afraid that the inter-layer adhesion would be too weak, and the inner shaft will snap off.
3D printing doesn't stop here. I could make a more detailed model: add tire treads; add more details to the tire disks; use a nozzle with a smaller diameter. I could have a separate model for tires and print them with TPU for a rubbery feel with a better grip. I will do this for other projects.
It's all about having things that work. A toy car that worked only for a few minutes and lies for a year broken on a shelf is upsetting. But it takes less than 30 minutes to design a new wheel. It takes less than 30 minutes to print four new wheels. And it's done. The car is fixed. Now the kids that throw it around and break something else. But this is another story ;)