After I put together Mr. Squiggles, I started examining the economics of 3d printing. Owning a 3d printer gives you the ability to manufacture things on a small to medium scale, but there are certain things the technology is better suited for. It’s not great for cranking out thousands of something, and the build area of most printers pretty much rules out large items. What the 3d printer really excels at is making small batch or one off, specialized parts. It’s perfect for prototypes, and it’s even more perfect for robots. So, I decided to start building some robots. The first robot I decided to have a go at was a polargraph.
An English cat named Sandy Noble has spent a huge amount of time and effort on this drawbot. He’s got some excellent tutorials on building it, and has put together some impressive software to control it. The mechanism is simple. There are two stepper motors attached to some ball chain and a pen holding apparatus called a gondola. The steppers change the lengths of the chains attached to the gondola and in doing so, slowly drag the pen along the desired path to create a picture. The process is totally mesmerizing.
It was easy to find most of the parts. The only hitch is that the steppers Noble uses aren’t readily available in the states. Being new to the world of electronics, and a headstrong idiot, I got some that pulled way too many amps, and would have fried my motorshield. Thankfully, I had the sense to check the specs, and eventually located a set that would work. I ended up buying these. They work, but I think there are probably steppers out there that would be better suited to the task.
I printed up some ball chain sprockets using this design from thingiverse. I took the default sprocket to the hardware store. They didn’t have a ball chain with the correct pitch and ball size, so I bought the smallest stuff they had and printed up new sprockets that fit.
Oddly enough, I didn’t like the gondola design that actually introduced me to the polargraph, so I designed and printed my own. It’s a pretty simple affair, actually inspired by the gondola in this video. I like it because I can quickly and easily pull the pen out of the gondola. It also holds pens and markers of varying thickness.
Once I had all of the parts, I followed Noble’s instructable and stuck my polargraph to a scrap of MDF I had. I guess I was feeling greedy, because I was not content with the drawing area of my little test polargraph. Bigger is better right?
I got a hold of an old cart made to display those pull down maps that you see in schools. It was on its way to the dumpster, and thankfully I was there to save it. The cart is a little over 6 feet tall, and about 4 feet wide. I decided to mount a 4 foot by 4 foot board on it as my drawing surface. I couldn’t fit a board that big in my bitchin’ grand am, so I joined together two boards to make the the same dimensions. I did it the same way I joined the Frankenstrument’s top, except instead of tape, I used nylon straps. That worked surprisingly well. I glued some scraps perpendicular to the joint on the back to brace it. I stuck a 2×4 shelf at the bottom on the front, so that the bot could double as an easel, in case I ever learn how to paint.
I hung the board on the cart with hose clamps and strapped some shelves to it the same way. This also worked surprisingly well.
The crossbars on the cart are perfect for holding a 3 foot roll of paper, I couldn’t find paper that size locally, so I bought some 2 foot paper and rolled it over the top. I slapped on some nylon straps to hold the paper taught, and I was ready to draw.
Gaze and be amazed at the monolithic Dr. Scratchy. I doubt if he’s the biggest polargraph out there, but he’s certainly no wimp.
I get a huge kick out of running this machine. It’s not really built for speed or precision drawing, though with some tweaking it can probably be done. Operating it is really more of a zen exercise, sort of like watching a plant grow. I really like to drop the speed way down and run it at night. It makes soothing scratching noises as the pen slowly drags along, and I feel content knowing that it’s busy drawing incredible digital patterns as I sleep.