As much fun as this has been to play around with, the print area is just too small! Using SketchUp I've come up with some designs for a new scaled up version using MakerBeam and pulleys (instead of threaded rods like current design).
This should give a total print area of about 250mm (as opposed to the 50mm I have now). If I put an SMD LED inside a small enclosure with a tiny 1mm hole, I should be able to decrease the width of the lines to further improve resolution as well. I figure at the moment the lines are about 3mm wide and the print area is 50mm wide. So that's a resolution of about 17x17 pixels. With 250 x 250mm bed and a 2mm wide line that will give a 125x125 resolution, or 250x250 at 1mm wide lines.
Pricing all the parts looks like it'll set me back approximately $400... which is a reasonable sum of money. Also, it occurs to me the design above is complete overkill considering the tiny payload it will carry. My thinking here is that I can adapt it to a homebrew printer or PCB mill later. After all, the whole idea of this project was to be a fun way to learn how steppers work. (As far as that goal is concerned, I could be getting a bit sidetracked here).
The other problem I will have is my camera. It can only do 15 second exposures, so I'm going to need to buy an DSLR in order for a bigger print area to be useful (unless it moves REALLY fast). Those are expensive too so will probably set me back another $400 or so unless I get a second hand one.
I'm going to leave things as they are for now while I have a think about what to do next. I might grab a SMD LED or two like this or this to see how that looks. In the meantime, more designs with current setup: