Reading [reprap.org] gave me the impression that it is possible to extrude ABS without a heated bed with somewhat good results. It mentions that the main option for ABS on a non-heated bed would be acrylic, since ABS sticks to that well. What kind of warping/lifting would I be looking at with this kind of setup (acrylic bed, ABS extrusion)?

If you need more info on the size of the parts, just think of the Mendel model files; I'll mostly be making more Mendels to sell to (hopefully) make back my investment, and ABS parts tend to be of higher quality than PLA parts (less brittle, higher temp threshold, etc).

I have successfully printed ABS mendel parts on an unheated acrylic bed. I did have to print some of the bigger mendel parts several times. I discovered that I got better results with the uncolored ABS than with the black ABS.

The temperature of an unheated bed still makes a difference. If you have problems with the raft lifting and the bed is cold to the touch, you should try to warm it up slightly (no warmer than the belly of a cat, though). The bed only has to be warm like this while the raft is being laid down. I have discovered that wiping the bed's surface with acetone will make the raft stick to it better. This has the advantage over slight heating in that you can selectively wipe the parts of the bed that will have the edges of the raft. This means that removing the raft will not be so hard.

I have also slightly modified some of the bigger mendel files to break up the longest dimension of the bottom surface with a notch a millimeter or so deep. I do this with Art of Illusion.

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