Strange bulge on lower layers.

After printing a few odds and ends, I decided to push the TAZ6 to test out what it’s “high detail” settings looked like. I picked the following model and sliced it up using the easy print ABS settings in the Lulzbot Cura. It printed okay, except for a strange bulge about 10 layers up or so. I’ve attached pictures. Funny thing is, I’m seeing the same artifact on the same model that’s printing right now in PLA. Any ideas on what could be causing this? I looked at the model and the layers in Cura, and I don’t see anything amiss.

Update: the PLA model, while still having an irregularity, is much less uniform in the irregularity, and it appears to be thinner overall.

I’m wondering if your z-offset isn’t dialed in well, leaving you with extra plastic on a bunch of layers until it finally gets even enough for the next layers to print smoothly. I’ve been printing with the same first layer height as the rest of my model and 100% line width to reduce the “feet” on my prints, but it took a lot of tweaking on my z-offset to get things to stick well with those settings and I have to use a brim for models that don’t have much bed contact. Try using the fish keychain demo model and print just the first layer, if you can peel off each segment from the bed individually then you are good, if they are stuck together you are too close or have the line width too high: