I decided to re-build the arm machine now that the funding can cover it. I plan on starting the production of the new machine in the next few weeks.
I don't have much code or plans yet because I am still deciding on the materials I will use.
As for the technical side. I plan to fabricate my own unique PCB that will run the stepper motors. The machine runs on the arduino language so It would be very easy to use other systems for this purpose. For example, my first machine was made using an Arduino Duemilanove in conjunction with an Adafruit Motor Shield. (This may be the cheapest way to get started) If you try my code, you may need to change the stepper motor controls for your specific setup. Other boards used in 3axis cnc systems (like the reprap or makerbot) may also be used but I have not tested them.
I have received a good amount of interest in the code for the wall mount model. I have included a link to the code required for the arduino and Processing.
The wall machine works by converting each incoming coordinate into a Polar system. It does this by running the Pythagorean theorem for each point. This figures out how long each belt needs to be to arrive at that point.
The machine is designed to be flexible. I have included a Processing Sketch that will take Vector SVG files and send one point at a time to the machine. (you will need the Geomerative library to use this sketch http://www.ricardmarxer.com/geomerative/ )
If you take a look at the code, you will see that the machine can work with just about any program that can send serial message in the correct format.
the format for sending coordinates to the machine is as follows, Ten digits, the first 5 being the X values and the second 5 being the Y values. If your sending a small number, add leading zeros so it will always be 10 digits. An asterisk will reset the previous buffered coordinate and expect a new set of coords after it.
sending "+" or "-" to the machine will alternate the servo to lift the pen off of the page.
I have tested it with Max/msp and Processing only, but I imagine that whatever language you prefer should work fine.
Let me know if you have questions. This is by no means a plug+play type system and you will need to develop the mechanism first. My coding skills are meager at best so if you have any suggestions I would be happy to hear them.