drawing machine. woo.

there were several different ways we proposed possibly making a drawing machine.

this was a planetary gear drawing machine

this was a similar design where the gears would change directions

this was a fixed gear design where all gears are fixed instead of being floating in a planetary configuration.

the direction changing gears presented a problem, in that certain gears would need to be fixed, defeating the purpose of the planetary configuration, also if the gears didn’t move continuously in the same direction, nothing could be drawn (if there would be something it would be uninteresting)

the  non-direction changing planetary drawing machine was attempted and prototyped, but the drawing arms created too much torque on the system, to the point where the gears wouldn’t stay meshed and would slip and fall out of the assembly

the issue we found with a 3 gear fixed drawing machine was that it wasn’t particular complex. it could be build fairly easily and wouldn’t require much thought.

enter: non-circular gears

a smooth parametric sinusoidal function was selected, as a fixed distance would be obtained between the axles of 2 meshed gears at all points

this is the final gear design

The issue with noncirculars gears like this, (or any gears of exactly the same size) is they rotate over the same path over and over again, so if we desire a drawing, it would just draw over the same path over and over again as well

this issue will be addressed later

heres the milling of our wax mold, and as we can see here

because of the size bit we used on the cnc machine, the teeth weren’t as sharp as we had designed them to be. we milled the mold before we got the smaller bits in anyways.

also, holes were drilled in the mold, filled with play dough so we could poke out the finished piece without breaking the mold

the gears ended up meshing fine in the end, so we didn’t need to mill another mold

the plan was to to have 3 of the noncircular gears in a row, with the outer 2 connected to arms that would control a drawing implement

we then designed a driving gear assembly which allowed us to spin a separate gear to allow the system to start spinning

so the issue of our gears is that they would trace over the same path over and over, so we fixed this problem by rotating the drawing surface as well

this allowed us to make a radial pattern on the drawing surface that looks much more interesting that the hersheys kiss shaped design that we would draw without a rotating canvas

here’s the finished device

also, we laser cut a few wooden prototypes, but i forgot to take pictures, and they are now in the trash i think

🙁

there are 2 problems with the final prototype

1. we used machine screws and nuts to secure the gears to a base, and the nuts have a tendency to either loosen or tighten, despite double nutting

a solution would be to either use some sort of thread locker or use non-threaded axles and glue stoppers to either side.

2. the acrylic we cut the rest of our assembly from was very subtly warped, so some of the holes in the middle of the gears are lopsided and some of the gears themselves don’t sit flat

this creates excess friction. as it is, it’s pretty difficult to turn smoothly because of this problem, but if we were to recut on non-warped material, we would likely solve this problem.

 

despite these problems, we were still able to get it to draw an interesting radial pattern. since the drawing gears are fixed, the only way to change the pattern would be to change the length of the arms holding the drawing utensil.