voids, overhangs and lips

I've found all the software, and downloaded some .stl files to review, but am still not connecting the dots on some things for 3d printing. My printer comes in this week and I've been researching the printing process while waiting and have a couple questions.

a) how does the printer work when you have a void area, like the lip on a box for both sides? or a coin with a lip? I've seen additive ideas, but is there a way to have a span that is filled over? it's like the empty space would make the abs fall or bend over a large void and if the area is small but large in volume, like a 1-3 mm height void on the underside over 10-20 mm wide empty area. I don't know how the extruded material wouldn't just fall in.
* this may seem like a commonn question, and I may not be searching the right terms so I ask for your indulgence.

b) can you print part of a job in one color and have the print start on a partially completed piece with another color? I can't figure this one out.

Thanks in advance,
Tivkin

Edited 1 time(s). Last edit at 06/04/2013 07:23PM by tivkin.

a) when it joins 2 sections that are not directly connected, it creates a bridge. You can run a search for "reprap bridge test" on youtube to see some tests.
As about overhangs, up to a certain degree, say 45 degrees, more or less depending on your printer, they can be achieved with no support material. For steeper overhangs or layers that have sections with no support at all, you can generate support material - most of the slicers have a section for this setting.

b) objects with multi-colors are actually multiple distinct objects, each object representing a color.

Edited 1 time(s). Last edit at 06/04/2013 09:49PM by MPower.

Thanks, I'll dive a little deeper with the information you game me