Common Print Quality Problems & Fixes
If you don't yet know the name of what you're seeing, check the Print Defect Visual Glossary first. This article covers the MK3S+-specific fix for each one.
First layer not sticking
Almost always a Live-Z or bed cleanliness issue, not a "bad filament" issue.
- Wash the steel sheet with warm water and a drop of dish soap — fingerprints and oils are the most common cause, more than any slicer setting.
- Re-run Calibration → First Layer Cal. and adjust Live-Z until the line is just barely see-through with faint ridges.
- If only part of the bed fails, mesh leveling may be compensating for a damaged sheet — see Mesh Bed Leveling & PINDA Probe Issues.
Stringing and blobs
See Filament & Material Guide for temperature ranges, then tune retraction: PrusaSlicer's default 0.8mm/35mm/s for the stock MK3S+ direct-drive extruder is a good starting point, not a fixed value — dry filament and a clean nozzle matter more than most retraction tweaks.
Z-wobble / ribbing
Check the Z-axis leadscrew coupler at the top of the Z motor — a loose grub screw here is the most common cause on the MK3S+, and it's a 5-minute fix with a 1.5mm hex key. Also check that the smooth rods are lightly lubricated, not dry.
Layer shifting
Almost never a firmware bug on this printer. Check:
- Belt tension (should have a firm, consistent snap when plucked, not slack)
- Print speed/acceleration too aggressive for tall or top-heavy models
- Something physically obstructing the X or Y carriage mid-print
Tip: If shifting happens at the same layer height every time, measure that height against your model — it usually lines up with a specific feature that spikes acceleration or a slicer-inserted pause.
Under-extrusion despite correct temperature
If Extruder Clicking, Grinding & Under-Extrusion doesn't explain it, check your E-steps calibration — a slipped extruder gear grub screw changes the actual steps/mm the firmware assumes, and no temperature or retraction change will fix it.