I've always had a healthy appreciation for the pintograph, so when we were assigned this project, I knew exactly what I wanted to do.
After some research online, I discovered that I needed two stepper motors in the simplest implementation. However, I wanted to practice working with gears again, as well as give myself a bit of a challenge, making two disks rotating in opposite directions with only one stepper motor.
I used geargenerator.com to virtually calibrate my gears to the right size for one rotating at 9.7RPM and the other at 10RPM, speeds that I gathered from research. I used five gears, with two axled to each other, to make the left and right gears rotating in opposite directions.
During prototyping, I printed my designs on regular paper and roughly cut out the gears to verify my measurements and sizing, before laser cutting. Unfortunately, I don't have pictures of the process.
My medium-fi prototype was essentially the final project, but with "hack-y" pieces as shown by the representation below. I made sure to print plenty of spacers to set the heights of all my gears to the same level.
In the eleventh hour, I discovered that my stepper motor was overpowering the gears and actually rotating its own body instead of the gears. Thus, with the help of lab managers, I laser cut screw holes into my box to screw the motor in. I also recut the circles with pegs (concave-ly sanded dowels with screws super glued in). In the end, the project worked quite well, but because of the recutting, the middle gears were too close and caused some problems, and having not enough weight caused vibrations and noise. The following videos and pictures show the final project connected to a stronger power source to brute force the tight gears.