Print Failure Troubleshooting Guide
Match what you're seeing to the likely cause, then go fix that specific thing instead of changing five settings at once.
Quick reference
| Symptom | Likely cause |
|---|---|
| Thin hair-like strands between parts | Stringing — temp too high or retraction too weak |
| Corners lifting off the bed | Warping — cooling too fast or too uneven, no enclosure |
| A visible horizontal offset partway up the print | Layer shifting — lost steps from a belt, pulley, or collision |
| Bottom layers flare out wider than the rest | Elephant's foot — first layer squished too flat or bed too hot |
| Gaps, holes, or weak thin walls | Under-extrusion — partial clog, wrong flow rate, worn nozzle |
| Blobs, dimensional inaccuracy, oozing | Over-extrusion — flow rate too high, wrong filament diameter setting |
Stringing
Thin wisps of plastic dragging between separate parts of a print, most visible on models with lots of small isolated islands (miniatures, lettering). Usually caused by nozzle temperature running slightly too hot for the filament, or a retraction distance/speed that isn't pulling the nozzle's ooze back far or fast enough between moves. Drop nozzle temp in 5°C steps and increase retraction distance slightly (direct-drive extruders need much less retraction than Bowden setups) until it clears up.
Warping
Corners or edges lifting off the bed mid-print, from unequal cooling as the bottom of the part shrinks faster than the top. More common on materials prone to shrinkage (ABS, ASA, nylon, PC) and on large flat parts with sharp corners. Fixes in order of effectiveness: increase bed temperature, add a brim, eliminate drafts (an enclosure or even a cardboard box helps more than people expect), and round sharp corners in the design if the part allows it.
Layer Shifting
A clean horizontal offset appearing at one specific height and staying shifted for the rest of the print — this is a lost-steps problem, not a temperature or cooling problem. Check belt tension, make sure nothing is catching on a cable or the print itself as the head passes, and confirm pulley grub screws are actually tight on the motor shafts. If it happens at the same height every time on the same model, look for a physical obstruction at that specific layer.
Elephant's Foot
The bottom few layers bulge out wider than the rest of the part, from the first layer being squished flatter than intended or the bed running hotter than the plastic can hold its shape at while still soft. Reduce first-layer squish (see the First-Layer Squish Guide), lower bed temperature slightly, and if your slicer supports it, enable an elephant's-foot compensation setting that shrinks the model slightly at the very bottom layers to counteract the bulge.
Under-Extrusion
Visible gaps between lines, weak or holey top layers, or thin/fragile walls despite the settings looking right. Common causes: a partial nozzle clog (see the Nozzle Maintenance Guide), a flow rate or extrusion multiplier set too low, a worn nozzle with an enlarged or damaged orifice, or a filament diameter setting that doesn't match the actual filament.
Over-Extrusion
Blobbing at corners, rough surface texture, dimensionally oversized parts, or a nozzle that's audibly grinding against too much plastic. Usually a flow rate/extrusion multiplier set too high, or a filament diameter setting entered as smaller than the filament actually is (telling the slicer to push out more plastic than needed to hit its target flow).
Change one thing at a time
It's tempting to adjust temperature, retraction, speed, and cooling all at once when a print fails, but that makes it impossible to know which change actually fixed it — and just as likely to introduce a second problem while chasing the first. Pick the single most likely cause from the symptom above, change only that, and reprint a small test before moving to the next variable.