Common 3D Printing Mistakes and How to Fix Them

Warping happens when the bottom layers of a print cool and contract faster than the layers above them, pulling the corners upward off the build plate. It's most severe with ABS and ASA, moderate with PETG, and rare with PLA. Large flat parts are the highest risk — the more surface area, the more cumulative contraction force.

Stringing happens when the nozzle oozes molten filament as it travels between two separate parts of the print without extruding. The result is a web of thin plastic threads connecting features that should be clean and separate. It's primarily a temperature and retraction problem, and it's one of the most straightforward issues to tune out.

Under-extrusion means the printer is laying down less material than it should — resulting in gaps between perimeters, weak and porous walls, holes in top surfaces, or layers that don't fully fuse. It's one of the more involved issues to diagnose because it has multiple possible causes that look similar on the surface.

Good layer adhesion requires each new layer to be deposited hot enough to partially re-melt and fuse with the layer below. When that doesn't happen — due to temperature, speed, or cooling — layers bond weakly and can split apart under any stress. This is a structural failure that isn't always visible until the part breaks.

Elephant foot is when the first layer (or first few layers) of a print flares outward, creating a wider base than the rest of the part. It looks like the bottom of the print has been sat on. The cause is almost always the nozzle being too close to the bed, squishing molten filament outward rather than depositing it cleanly. A hot bed also contributes — the bottom layers stay soft and spread under the weight of layers above.

If the first layer doesn't bond to the build surface, the print will either fail immediately or produce a mess of spaghetti plastic within the first few minutes. Good first-layer adhesion is the foundation of every successful print — and it's almost always fixable with a clean bed and correct Z-offset.

A clicking or skipping extruder is the printer's way of telling you it can't push filament through. The extruder gear is grinding or slipping on the filament rather than driving it forward. This can be a full clog (nothing comes out), a partial clog (reduced flow and under-extrusion), or a mechanical binding issue in the hotend or Bowden path.

Layer shifting produces a distinctive staircase offset — the top portion of the print is shifted sideways relative to the bottom, as if the printer lost its position on one axis. It's a mechanical issue: either the motion system skipped steps or was physically obstructed during the print. It doesn't damage the printer but usually ruins the part entirely.

Pillowing creates a rough, uneven top surface — the top solid layers sag slightly between the infill lines below them, creating a bumpy, pillow-like texture instead of a flat smooth finish. It's a slicer settings issue, not a hardware problem, and it's one of the quickest fixes on this list.

Blobs and zits are small raised bumps or surface imperfections on the outer walls of a print — usually appearing at the seam where the nozzle starts and ends each perimeter loop. They're caused by pressure buildup in the nozzle chamber that doesn't fully release before the nozzle resumes movement. Cosmetically annoying; on precision parts, they can affect fit.