Shape Deposition Manufacturing
Here is an example of how it would work:
The FFF process would proceed as normal, however, the software would add something like 0.2mm to the outline of the part. Then once the layer has completed printing, a very fine milling head will mill the outline of the part for superior accuracy. Once it is done, the excess material will have been removed and the part dimensions will be as they were originally intended.
- higher precision than FFF alone
- can make shapes that are impossible with milling alone. For example, milling the interior channels of a heat exchanger out of a single block of plastic.
- requires either toolhead-changing on every layer, or 2 toolheads that can move independently in the XY-plane or in Z.
Example Hardware Platform/RepStrap
It's called Shape Deposition Manufacturing. (At least by some people.)
Here's a Stanford Lab that's done a lot of work on it.
It's a very cool subject which we'd be very happy to have under the RepRap umbrella. It would mean lots of tiny gears, or gears which mesh nicely etc.
Here is a google scholar search on "shape deposition manufacturing" http://scholar.google.ca/scholar?q=shape+deposition+manufacturing&hl=en&btnG=Search&as_sdt=2001&as_sdtp=on