Printing Marvin in HIPS

Ive been trying to really dial my print settings in for HIPS using the Marvin model. It prints quite well until the loop at the top and i just cant seem to figure out whats causing the problems.

Settings:
Lulzbot Mini
Cura
Extruder: 240C
Bed: 110C
Layer height :0.09mm
shell thickness: 1.5mm
Bottom/Top Thickness: 0.18mm
Density: 20%
Flow: 100%

Minimal Layer time: 25s
cool Head Lift: enabled

Ive tried multiple settings including enabling/disabling cool head lift and layer thicknesses of 0.07 and 0.08 but nothing seems to improve the loop. Each print ive done has exhibited the same issue.

I’ve printed with HIPS and have had similar issues. It looks like the problem is heat buildup. I’ve seen this problem consistently on the left, the side opposite the fan. I suspect that the solution would be to add a second fan on the left side of the extruder. The Buda extruder has threaded inserts to help mount a fan, but you would need to design and print a shroud to mirror the right side. You would have to modify the Hex extruder to mount a fan. I’ve not tried this myself as I am now working with ABS.

Scott

Thanks for the reply. I ended up changing from Cura to Kisslicer with Pronterface and the results were much better (not perfect but better). I think kisslicer is more aggressive in slowing the printer down to enforce cooling times.