Homebrew PCBs

>drawing the traces down the middle of the designed trace. The width
>of the trace could be controlled by using different needles on the
>dispenser or controlling the air pressure.

Mark, why not output the HPGL in 'multiline' format, with fixed pen width?

>I'm willing to rip out the electronics and make my own stepper
>drivers, but I'd like to know what software I would use to run the
>converted machine, presumably using some form of HPGL. Does anyone
>know how this would be done?

Kcam4 is free and good for controlling a standard stepper driver.
Cristian