That is classic Z height problems and overextrusion.
Two things you have to do.
- Use your calipers and measure the diameter of the filament in 4-5 spots and average the 5 diameters. Put this diameter into Filament diameter box. If you haven’t measured your filament correctly, it will cause overextrusion and give you that print defect. Most 2.85mm filament isn’t actually 2.85mm. 2.83, 2.87, 3mm isn’t uncommon.
After you’re sure you have EXACTLY the correct diameter:
- Print a new test part with a skirt. Get out your digital calipers and measure the thickness of the skirt. This is the initial layer thickness. Does your measured initial layer thickness match what your initial layer thickness is set for in cura? I’m guessing no.
You can modify your Z height of your nozzle under expert mode: machine: machine settings: Z-offset. Ex: If you measure your skirt thickness to be 0.3mm, and cura initial layer height is set to 0.425mm, add about half the difference into Z-offset (~0.06mm). Print the part again and measure the skirt. Maybe it measures 0.36mm this time. Add half the difference between 0.36mm and 0.425mm (~0.03mm) and add that to the previous Z offset (New Z offset would be 0.06 + 0.03 = 0.09mm). Print again and measure your skirt thickness and compare against initial layer thickness setting. Repeat until measured skirt thickness matches initial layer thickness in cura.
If you can’t find your Zoffset settings, contact Lulzbot support and they can point it out to you.
3. If you’ve done steps 1 and 2 correctly, you should see improvement. If you haven’t ever calibrated your printhead, then it’s possible you’ll need to reduce your flow % a few % to really dial it in.
If you complete steps 1 and 2, print a test cube and post a picture of the bottom side of the print and it will be easy to diagnose whether we need to mess with your flow %.
Classic problem, easily fixed. You just need to dial in your printer a bit.