My machine (http://jonathanjamieson.com/projects/electronics/drawing-machine/) is still very much working in progress but I thought I would share a MATLAB script I made for generating spirograph-like patterns. It generates coordinates (x,y) which can be saved as .csv file and used in drawing machines.

There is an infinite variety of patterns that can be generated by changing the parameters. I've explained how to use the script on the fileexchange page, basically all you need is in main.m!

http://www.mathworks.com/matlabcentral/fileexchange/38828

Just remembered that you need an account to use the File Exchange so I have uploaded the zip of the script onto my website:
http://www.jonathanjamieson.com/RotorDraw.zip

My script is real-geometry based, that is, it works it out like it's a real machine:

It's based on a real life machine:

It's funny people say these machines (polargraph style) are like spirographs because I agree, they're not. My version of polargraph causes even more confusing because initially all the coordinate sets I was using were spirograph based.

The script only took an afternoon to knock up, of course it will take significantly longer to polish off a reliable equivalent for the polargraphSD. Feel free to use the code if it's of any help for you.

I think I might buy a "Vitamin Kit" if you get them back in stock before Christmas. It wouldn't be till next summer I would have enough time to properly experiment with it.

I don't suppose you've had any time to add in a coordinate output functionality? I asked you a while ago on instructables but it (understandably) wasn't high on your priority list.