Why does this happen? Thoughts, I'm out of them.

Any idea why, at exactly the same number or rows up in everything I print, this happens?

it’s fine before these layers, and fine after them … I just can’t figure it out.

Thanks for any help you can give (sorry i had to attach the file, stuck using iPhone at the moment).

First off, is that part supposed to have a slant to it? If not, tighten the belt and the motor pulley in whichever direction that is.

As for the layer change issue, there are a couple of things going on. For starters, you have some lifting. I’d try bumping the bed temperature up about 6-8 degrees above where you have it The lifting is causing the first layers to get closer to the nozzle, which cause it to extrude less than it thinks it is, which causes backpressure. that will generally slowly decrease as the model goes up, but if you have enough excess pressure in the nozzle chamber, when you transition from a larger surface area to shed excess, to a smaller one, it can cause surface roughness and overextrusion until the printer can normalize.

You are probably overextruding a bit. Check your actual fillament diameter with calipers in 3 places, take the average, and then use that number as the filament width setting inside of your Slic3r program. It’s usually 3.00 by default, which can be good or bad depending on which fillament you are using. they vary in width dramatically sometimes.

If that doesn’t take care of it, you may need to adjust the esteps of your extruder slightly. to do that, look up “3d printer calibration” and follow the guidelines. Generally you end up measuring 110 mm of filament up from the top of the extruder body, then extrude 100mm, and measure how far your mark is from the point you measured from the first time. It should be exactly 10mm. if it is more or less, you do some math, then adjust the value in the firmware, etc. there are a couple of guides with links for how to do that in the forum here. Generally the lulzbot printers are pretty well dialed in from the factory, so you probably won’t have to do that part.

Other things to check for, make sure your extruder is solidly mounted to the X carriage. There should be very little play there up or down. if there is, you may have to move the rail bearings on the back in or out to ensure they are in full contact with the rails themselves.

You might also want to check your starting layer height. If you are too close, you can get an excess of plastic from the first layer out. Since you are getting lifting on that small of a part, i’m guessing thats not the case here, but it could be. Post a picture of that same print but stopped after the first layer and we’ll be able to tell for sure.