Weird raised, distorted corners with HIPS

I’m encountering a weird problem that only seems to happen on models with a large surface area on the bed. I’m using eSun HIPS 3mm filament at 240 degrees on a Lulzbot Mini.

During the course of a 10-14h print, the corners of the object raise off the hotbed and distort the lower layers accordingly.

I’ve tried mitigating this with a number of approaches:

Raising the bed temperature from the standard 110 degrees for HIPS to 115 helps somewhat. Further increases in the bed temperature have no discernible effect (I went up to 125 degrees).

Setting the z-index to -0.05 to increase the adhesion of the first layer again helped somewhat, but not much.

I’ve tried printing with a brim, but it turns out that this does not help: the brim stays stuck on the hotbed, but the corners of the main object still rise as the print progresses.

Resolution (low, medium, high) has no notable effect.

I’m all out of ideas and could use some good suggestions what else to try to address this.

I’ve attached an STL that exhibits the problem when printing.
box1.stl (26.2 KB)
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20160329_221152.jpg

Are you using the part cooling fan? That part appears to be large enough that the fan should not be necessary. If the part is being cooled excessively it can cause that warpage.

Interesting! Together with a mildly drafty English Victorian house, it sounds like this could be the potential culprit!

Many thanks for the tip - where would I switch the fan off? Tried googling GCode settings for this, but haven’t found anything obvious. Sorry, am a relative newbie with all this.

Bonus question: how would increasing or decreasing infill likely affect the distortion situation, if at all?

Your slicer should have a method for turning off the fan. In Cura, it is on the full setting Advanced tab, at the bottom. If you edit the gcode directly, M107 turns the fan off. M106 turns the fan on (requires extra parameters).