I think this is a pretty good indicator. Both prints using the same spool of ABS (which my friend Tyler at filabot dropped off for playing with because of the nonuniform color). Right without a chamber, left with chamber. The right one also suffers from cracking problems because it was about 7% under-extruded, but I don’t think that would have helped the warp much.

The left one might need a little less extrusion — you can see where the top layers of the bolt stuck to the bottom of the nut and broke away. (I think I’d like to be able to edit the g-code right there and insert a blast of fan cooling for just that layer.)

I’m using a honeycomb infill pattern for this, and I need fairly high infill, because otherwise some of the top shells just get cantilevered over empty space and slump down. But I worry that the strength of the hexagons contributes to warping. Does anyone else use, say, concentric infill for situations like this where strength is not an issue?

Oh, and thanks to Creative Tools for putting this one up.