I bought a used MK3S(upgraded from MK3) with MMU2S on eBay. Buyer said everything is working great, however I'm having underextrusion issues. PETG and PLA both have consistent surface imperfections. I've tried a new nozzle, checking E-steps. Retraction is .5 mm, .2 mm layer height. Top handle has been painted and clearcoated, so it's a little harder to see. Top is PETG and bottom is PLA from the MK3s kit I got last week.
Check all your hardware. If all bolts are tighten.
Check all belts, check grub screws, check if belts are hitting the sides wen moving left to wright.
Clean all rods, put a little oil on them, you need to do this regular.
Check the extruder gears, clean, check also if gears are sitting straight, the steal pin(from gears) is sitting in the middle.
Try with different temperature and slower speeds.
I tinkered some more with the printer. I'm not sure it's a hardware issue since I can use the.gcode referenced in this article: https://help.prusa3d.com/en/article/the-benchy-hull-line_124745 and the print looks awesome. There are no holes.
However when I slice using Cura or Prusaslicer the holes show up again. I've tried turning retraction to 0 mm; .5 mm; .4 mm; 1 mm; slowing the print to 50% with pretty much same results. I have attached my .curaprofile I'm using.
Anyone got any ideas? I've tried several more prints with the same results. Presliced from Prusa is ok but when I slice it won't come out right.
My next steps will be trying the same gcode on my other MK3S, playing with stock PLA profiles in Prusaslicer.
Used stock PLA profile .20 mm Quality in Prusaslicer and the surface looks almost perfect.
What is causing this difference in performance?