ABS Last Layer Issue On Large Flat Part

I’m having an issue where other than the last layer the part seems to print fine. I’m using a Taz 4 with a .35 extruder, and lulzbot ABS plastic. I’m using slicr, and the profile is the medium speed ABS one with slicr set to expert mode. Anyone have a suggestion on what the issue might be?

Ok that’s a weird one. You aren’t getting good adhesion to the layer below, and it looks massively underextruded just for that layer. That could just be localized extreme warping though. My best guess is that somehow the settings for the finish layer are screwed up, possibly the layer thickness is set to 0.46mm so it prints one top layer fine, goes up too far, then tries to print the next layer essentially on air, which partially adheres in some places. It’s either that or the nozzle diameter settings are switching to 0.5mm for the final layers, which I don’t even know how that could occur. If it were foing it for all layers you should see a mess sooner. Maybe fan overcooling? Are you running high fan on just the final layers?