Like most homeowners, I have a sizeable stash of half used and expired paint cans that I know that I am never really going to use for touch ups around the house. That got me to thinking about what I might be able to use them for. I remembered reading about “motor agates” and “fordites” which are globs of paint found at old abandoned car manufacturers from the ~1940s that when cut reveal hundreds of layers of colored paint and look like agates! I started to wonder if I could perhaps build a robot to make these from my leftover paint…
My vision was of a small crane that stood in the center of several cans of paint that would rotate to the appropriate color, lower a “seed” into the paint below, lift it, turn and lower it into a drying hopper then lift it and repeat with some other color building up layers 24hrs a day.
I designed and built the mechanics of the crane which consists of two stepper motors; one that winds and unwinds a spool of line and a second which is geared to rotate the crane arm. The line travels from the spool, through an eyelet, through a hose guide and emerges inside the crane arm which is simply a bit of pvc tube.
Next I turned my attention to the electronics. Biased by experience with 3d printing and laser etching devices that follow a set of instructions in a language called G-Code I set out to design my own language and interpreter to control the crane. I did this by programming an Arduino microcontroller to interface not only to the crane but also to an SD card reader. On the SD card from my computer I can drop a text file that can contain the following commands in any sequence:
Crane Speed [SP0 speed]
SP 0 #Spool Speed [SP0 speed]
SP 1 #Crane Absolute Rotation [ angle]
AR 0 #Crane Relative Rotation [ angle]
RR 0 #Spool Relative Rotation [ angle]
RR 1 #Fan On/Off [F0 1/0]
FA 0 1
FA 0 0Wait
WT 0 1000
These commands can be combined in any way to generate a set of instructions that the crane will follow until the end and then repeat indefinitely! I could do three layers of red, then one layer of white and rinse and repeat that until I pull the plug. As far as seeds to start the process I could use a little glob of paint but I want to test other objects; I’m most interested to try a pine cone and to try a weighted balloon to make a hollow geode.
… but I waited too long to try out my device with actual paint and now it is winter, so we will have to check back next year to see how it actually works!
