I recently received several printed models. They look great in general, but the base of each is a little warped (especially at each corner) by a few millimeters (please see attached "Warped Base.pdf"). I assume this is due to the printing process and perhaps where and how the piece was oriented in the machine. It appears that there is permanent shrinkage causing this warping.
Any suggestions on how to minimize this warping would be appreciated. The bases are very stiff, but not printed flat as modeled. Would printing this in smaller pieces and gluing back together help?
It looks like the warpage may be from the top shrinking as it cools down. Try adding a bottom flange to the outside edge like you did down the center of the piece to stabilize it. Adding diagonal cross-ribs to the ends will give it additional stiffness.