3D Printing Troubleshooting Guide

The 10 most common 3D printing issues — what causes them and how to fix them.

Stringing & Oozing

Common

Thin wisps of filament left between parts of the print, creating a cobweb-like effect. Almost every printer owner encounters this at some point.

What It Looks Like

  • •Fine hair-like strings between separate parts of the print
  • •Blobs or zits on the surface where the nozzle travels
  • •Messy surface finish on detailed prints

Common Causes

  • !Retraction settings too low — filament continues to ooze during travel moves
  • !Nozzle temperature too high — melted filament is too runny and drips
  • !Wet/moisture-absorbed filament — steam creates bubbles and oozing
  • !Travel speed too slow — more time for filament to leak during moves

How to Fix

  • 1.Increase retraction distance (start 5mm Bowden, 1–2mm direct drive) and speed (40–60mm/s)
  • 2.Lower nozzle temp by 5°C increments until stringing stops
  • 3.Enable Combing / Avoid Crossing Perimeters in slicer
  • 4.Increase travel speed to 150–200mm/s
  • 5.Dry your filament (45–55°C for 4–6 hours)

Material Notes

PETG strings more than PLA — a heat gun cleans it up. TPU should have retraction nearly disabled (0–1mm) to avoid jams.

Pro Tip

Print a retraction tower — dial in perfect retraction distance and temperature in a single print.

First Layer Not Sticking (Bed Adhesion)

Common

The first layer lifts, slides, or doesn't bond to the build plate. Getting the first layer right is the single most important factor in a successful print.

What It Looks Like

  • •Filament doesn't stick and gets dragged by the nozzle
  • •First layer peels up at the corners during printing
  • •Print detaches completely and creates a spaghetti mess
  • •First layer too squished or too high and not bonding

Common Causes

  • !Bed not level — nozzle too far from or too close to the bed
  • !Bed not clean — oils, dust, or residue preventing adhesion
  • !Bed temperature too low for the material
  • !First layer speed too fast
  • !No adhesion aid on a smooth surface

How to Fix

  • 1.Re-level — paper test: slight drag under nozzle at all corners
  • 2.Clean bed with IPA before every print
  • 3.Use correct bed temp: PLA 50–60°C, PETG 70–80°C, ABS 100–110°C, TPU 40–60°C
  • 4.Slow first layer speed to 20–25mm/s
  • 5.Apply glue stick, hairspray, or painter's tape for extra grip
  • 6.Add a brim (5–10mm) in your slicer for small or tall prints
  • 7.Fine-tune Z-offset — lower by 0.02mm increments until first layer is nicely squished

Material Notes

PETG bonds too aggressively to bare glass — use a glue stick as a release agent. PLA works great on PEI sheets with just IPA cleaning.

Pro Tip

Watch the first layer. Lines should be slightly squished flat — not round, no gaps. If you can see through the first layer, the nozzle is too high.

Warping & Lifting

Common

Corners or edges curl upward off the bed during printing. Caused by uneven cooling and material shrinkage as the plastic cools.

What It Looks Like

  • •Corners of the print lift off the bed
  • •Base is curved or banana-shaped
  • •Print detaches mid-print and fails
  • •Cracks appearing in lower layers

Common Causes

  • !Temperature differential — hot plastic shrinks as it cools, pulling corners up
  • !Drafts or cold ambient temperature causing uneven cooling
  • !Bed temperature too low
  • !No enclosure (critical for ABS)
  • !Large, flat prints with lots of surface area are most susceptible

How to Fix

  • 1.Use an enclosure — even a cardboard box helps significantly
  • 2.Increase bed temperature by 5–10°C
  • 3.Disable part cooling fan for the first 3–5 layers
  • 4.Add a brim (8–15mm) for maximum bed grip
  • 5.Use a raft for very warp-prone prints
  • 6.Eliminate drafts — close windows, move away from AC vents
  • 7.For ABS: try ABS slurry (ABS dissolved in acetone) on the bed

Material Notes

ABS warps the most — an enclosure is essentially mandatory. PLA rarely warps. PETG warps moderately. TPU almost never warps due to its flexibility.

Pro Tip

For PLA and PETG, warping is usually a bed adhesion issue, not temperature. For ABS, it's almost always enclosure and bed temp.

Layer Shifting

Moderate

Layers suddenly shift horizontally mid-print, creating a staircase effect. This is a mechanical issue — not a slicing or temperature problem.

What It Looks Like

  • •Sudden horizontal offset — layers shifted in X or Y
  • •Staircase pattern visible on the side of the print
  • •Usually happens at a specific height and continues for the rest of the print

Common Causes

  • !Loose belts — the most common cause by far
  • !Stepper motor skipping steps — moving too fast or hitting an obstruction
  • !Print head hitting a warped/curled section of the print
  • !Loose grub screw on a pulley
  • !Loose stepper motor cable
  • !Print speed too high

How to Fix

  • 1.Tighten belts — taut and twangy like a guitar string, not slack
  • 2.Check grub screws on all pulleys, especially on stepper motor shafts
  • 3.Reduce print speed and acceleration — try halving your speed to test
  • 4.Ensure stepper motor cables are firmly plugged in
  • 5.Check for obstructions — wires catching, filament spool tangling
  • 6.Fix any warping issues first — a curled edge hitting the nozzle causes shifts

Pro Tip

If the shift always happens on the same axis, focus there. Pluck the belt — if it sounds dull and doesn't vibrate, it needs tightening.

Under-Extrusion

Moderate

Not enough filament is being pushed through the nozzle, resulting in thin, weak, or missing layers. Prints look sparse and fragile.

What It Looks Like

  • •Gaps between lines in the top surface
  • •Thin, weak walls that crumble easily
  • •Missing layers or sections
  • •Clicking or grinding sound from the extruder

Common Causes

  • !Partial nozzle clog — filament can flow but not at the required rate
  • !Filament diameter inconsistency — cheap filament can vary in thickness
  • !Extruder tension too loose — gear can't grip the filament
  • !Print temperature too low — filament isn't melting fast enough
  • !Print speed too fast for the hotend to keep up
  • !Bowden tube gap — causes filament to pool and jam
  • !Worn nozzle — especially after abrasive materials

How to Fix

  • 1.Cold pull: heat to 200°C, push filament in, cool to 90°C, pull firmly — repeat until clean
  • 2.Adjust extruder tension — gear should mark filament but not grind into it
  • 3.Increase temperature by 5–10°C
  • 4.Reduce print speed by 20–30%
  • 5.Check Bowden tube is cut flat and seated flush against the nozzle
  • 6.Replace the nozzle — they're cheap consumables
  • 7.Calibrate e-steps — mark 100mm of filament, extrude 100mm, measure what's left

Material Notes

TPU is especially prone to under-extrusion on Bowden setups — the flexible filament compresses in the tube instead of pushing through the nozzle.

Pro Tip

Clicking from the extruder means the gear is slipping on the filament. It's always either a clog, too-cold temperature, or too-fast speed.

Over-Extrusion

Moderate

Too much filament is being pushed through the nozzle, creating bulging, blobby prints with poor dimensional accuracy.

What It Looks Like

  • •Prints are larger than designed dimensions
  • •Blobby, rough surface finish
  • •Filament bulging out between layers
  • •Nozzle dragging through previous layers, leaving scars

Common Causes

  • !Flow rate / extrusion multiplier set too high in slicer
  • !E-steps calibrated too high — extruder pushes more than requested
  • !Filament diameter set incorrectly in slicer
  • !Nozzle temperature too high — filament is too fluid

How to Fix

  • 1.Reduce flow rate in slicer — try 95% and adjust in 1% increments
  • 2.Calibrate e-steps — command 100mm extrusion and verify with calipers
  • 3.Verify filament diameter in slicer matches actual filament
  • 4.Lower print temperature by 5°C increments
  • 5.Print a calibration cube and measure walls with calipers

Pro Tip

Print a single-wall cube. If line width is set to 0.4mm but measures 0.48mm, reduce flow to (0.4 ÷ 0.48) × 100 = 83%.

Clogged Nozzle

Common

Filament partially or completely blocks the nozzle, preventing extrusion. The most common maintenance issue in 3D printing.

What It Looks Like

  • •No filament despite the extruder motor turning
  • •Very thin, inconsistent extrusion
  • •Extruder clicking, grinding, or skipping
  • •Filament curling up around the nozzle instead of laying flat

Common Causes

  • !Carbonised filament — burnt residue inside the nozzle
  • !Foreign particles or dust in the filament
  • !Printing too cold — partially melted filament jams
  • !Mixing filament types without purging (e.g. PLA residue blocking when switching to PETG)
  • !Heat creep — heat travels too far up the hotend, softening filament above the melt zone
  • !Deformed PTFE tube

How to Fix

  • 1.Cold pull: heat to 200°C, push filament in, cool to 90°C, pull firmly — repeat until clean
  • 2.Acupuncture needle: heat to printing temp, push a thin needle up through the nozzle to dislodge debris
  • 3.Soak nozzle in acetone overnight (remove from hotend first) to dissolve residue
  • 4.Replace the nozzle — keep spares on hand
  • 5.Check and replace PTFE tube if discoloured or deformed
  • 6.Prevention: always purge 50–100mm of filament when changing materials

Material Notes

Glow-in-the-dark and carbon fibre filaments are abrasive and wear brass nozzles quickly — use a hardened steel nozzle for these materials.

Pro Tip

Keep spare brass nozzles on hand. When in doubt, swap the nozzle — it's a 2-minute fix that eliminates the most common cause of extrusion problems.

Z-Banding (Inconsistent Layers)

Occasional

Visible horizontal lines or ridges at regular intervals on the print surface. Often called 'salmon skin' when the pattern is very fine and regular.

What It Looks Like

  • •Horizontal lines or ridges on vertical surfaces
  • •Regular, repeating pattern of thick/thin layers
  • •Surface looks ribbed or has a wave pattern

Common Causes

  • !Z-axis lead screw wobble or misalignment
  • !Inconsistent extrusion due to extruder gear issues
  • !Loose Z-axis components — couplers, anti-backlash nuts
  • !Stepper motor resonance at certain speeds
  • !Inconsistent filament diameter
  • !PID tuning issues causing temperature fluctuations

How to Fix

  • 1.Check Z-axis lead screw is straight and not bent
  • 2.Ensure the Z coupler isn't over-tightened — allow slight flex to absorb wobble
  • 3.Tighten any loose Z-axis and anti-backlash nuts
  • 4.Try changing layer height — sometimes a specific height hits a resonance frequency
  • 5.Enable Input Shaper or pressure advance if your firmware supports it (Klipper)
  • 6.Run PID autotune for hotend and bed to stabilise temperatures
  • 7.Use high-quality filament with consistent diameter

Pro Tip

If banding is very regular (every 2mm or 8mm), measure the Z lead screw pitch. If the pattern matches, the lead screw is the cause — replace it or add a flexible coupler.

Elephant's Foot (Bottom Bulge)

Common

The first few layers bulge outward, creating a wider base than designed. Named because it looks like an elephant's foot spreading under weight.

What It Looks Like

  • •Bottom of the print is wider than the rest
  • •Parts don't fit together because the base is oversized
  • •First layer squishes out past the perimeter

Common Causes

  • !Nozzle too close to the bed — first layer is over-squished
  • !Bed temperature too high — bottom layers stay soft and get squished by weight above
  • !Too much first-layer flow / line width
  • !No cooling on first few layers

How to Fix

  • 1.Raise nozzle slightly — increase Z-offset by 0.02–0.05mm
  • 2.Lower bed temperature by 5°C after the first layer
  • 3.Reduce first layer flow rate to 90–95%
  • 4.Enable part cooling fan from layer 2 onwards
  • 5.Add a small chamfer (0.5mm at 45°) to the bottom edge of your model in CAD

Pro Tip

Most slicers let you set different bed temperatures per layer. Use 5–10°C higher for the first layer (adhesion), then drop it to reduce elephant's foot.

Gaps in Top Layers

Moderate

The top surface has visible gaps, holes, or a rough incomplete finish instead of being smooth and solid.

What It Looks Like

  • •Holes or gaps in the top surface
  • •Top surface looks rough or pillowed
  • •Infill pattern visible through the top layers
  • •Top surface sags into infill gaps

Common Causes

  • !Not enough top layers — infill visible through too few solid layers
  • !Infill percentage too low — large gaps for top layers to bridge
  • !Under-extrusion — not enough material to fill the top surface
  • !Print speed too fast for top layers
  • !Insufficient cooling — top layers sag before solidifying

How to Fix

  • 1.Increase top layers to at least 5–6 (or 1.2mm of solid top thickness)
  • 2.Increase infill to 20% or higher — gives more support for top layers to bridge across
  • 3.Enable Ironing in your slicer — nozzle does a smoothing pass over the top surface
  • 4.Slow top layer speed to 15–25mm/s
  • 5.Set part cooling fan to 100% for top layers
  • 6.Check for under-extrusion issues (see Under-Extrusion above)
  • 7.Use a monotonic top surface pattern for a more consistent finish

Pro Tip

Ironing is a game-changer for top surface quality. It adds print time but produces a near-glass-smooth finish. Set flow to 10–15%.