Ok how bout some ideas on how to make a cnc 3d printer. Not that 2d 30' long paint bucket on wheels but a true paint the surface of a 3d model.
Something like these guys have.
STM (http://www.solidterrainmodeling.com/)


Donny

Replace the endmill with a paint nozzle or pen... ;)

'Rekd

The complexity of this project depends on a lot of factors:

Will the object to be printed be created by the same CNC so printing can just be another tool path?

Will the print head/nozzle need to be perpendicular to the surface or can it remain in one direction for a printing pass (say, vertical to print the topographic terrain or maybe one direction at a time to print on an object from a few angles)?

Do you want to print fine detail with a large color pallet or will an airbrush and a single color per pass be sufficient?


If you want to paint the topology, like those 3D maps, I would use a simple airbrush in the tool holder. Break down a bit mapped image into individual colors and have the CNC scan over the surface while the bitmap is used to modulate the air flow.

You could use the feed rate to synchronize scanning of the bit map but I would monitor the actual position. If your CNC has real time X,Y output then you can use that to coordinate the motion, otherwise I would tap into the encoder outputs to step through the bit map.

Now if you want to do something more like an inkjet that can print on anything, that would be an extremely complicated, but amazingly interesting, project.