For that top square, you either need to use a fan, or print with a one wide brim so the top layer has time to cool between layers.
…or you can try turning down the print temp slightly, but generally on small structures like that cooling (either active or passive) is what you need.
if using slic3r lower minimum print speed in filament settings / cooling tab
I have the same problem on my Simple. I think the nozzle design adds to this problem. It seems flatter at the tip than many I’ve seen. Looking closer, you seem to be too hot and/or over-extruding a bit. Did you extrude to free air to find minimum reliable temp? Did you measure filament diameter?
I’m trying to do the classic “gear cube” right now, and the corners end up distorted. I’m going to try an additional small fan next to the printer and/or a “cooling tower” tall additional piece printed at the same time.
It has been my experience that not every roll of filament has the same sweet spot for temps. The fan/active cooling suggestion for PLA is a good one too. Since it looks like it is too hot, try dropping the temps a bit if the fan alone is not the answer.
With such a small feature size, and the nozzle in constant contact, the blob never gets to cool down and set. Surface tension pulls the blob around deforming it. Slowing down by itself won’t help - it just keeps the nozzle attached. Orbiting away from the object for a minimum layer time would help, except you might have ooze issues (and with SkeinForge, exposed a divide by zero bug). Printing an extruder priming object, or printing another object at some distance away will move the nozzle off long enough to allow cooling to take place. As already mentioned, lowering nozzle temps and adding additional air flow will help, too.
Thanks for all suggestions! I will try lower temp and optimize my fan position.
