Built an aluminum gantry-crane type arrangement that
supports a Dremel tool.
Tried to keep mass and friction low as possible. Connected it to the plotter
with a pantograph arrangement.
Anybody else have some mechanical alarm bells going off at the notion of a
dremel on the end of a pantograph?
I would maybe use some parts from existing printers and or scanners, but
this sounds like a build from scrap project, not adapt a old plotter. Basic
problem is just what you mention, you are going to need to rewrite control
software, which for a basic x/y plotter can't be too awfully tough.