3D Printing Troubleshooting: 15 Common Problems and Fixes

I have a folder on my computer called "print failures" with over 400 photos. Every failed print I have ever produced is documented with a photo, the settings I used, and the diagnosis. It started as a troubleshooting reference for myself and has become the basis for this guide. After three years of printing almost daily, I can diagnose most problems by looking at a failed print for about five seconds. Not because I am gifted, but because the same 15 problems cause 95% of all 3D printing failures, and once you know what to look for, the patterns are unmistakable.

This guide is organized by frequency, the most common problems first. For each issue, I will describe what it looks like, what causes it, and the systematic steps to fix it. If you are new to printing and want to master the foundational skill that prevents most of these issues, start with our first layer guide before diving into this troubleshooting reference.

Problem 1: Stringing (Oozing Between Travel Moves)

What it looks like: Thin wisps of filament stretched between separate parts of your print, like spider webs. Ranges from barely visible hairs to thick strings that ruin the print surface.

What causes it: Molten filament oozes from the nozzle during travel moves (when the printhead moves between print areas without extruding). The nozzle is hot, the filament is liquid, and gravity plus residual pressure push material out.

Systematic fix:

Step 1, Enable retraction: Retraction pulls filament back into the nozzle before a travel move, reducing pressure and minimizing ooze. If retraction is disabled in your slicer, enable it. Default retraction distance for direct-drive extruders is 0.5-2.0 mm. For Bowden setups, 4-7 mm. Start with the default and adjust from there.

Step 2, Increase retraction speed: Faster retraction pulls filament back before oozing begins. Try 25-45 mm/s for direct-drive, 40-60 mm/s for Bowden. Too fast can cause filament grinding, so increase in 5 mm/s increments.

Step 3, Reduce nozzle temperature: Lower temperature means more viscous filament that oozes less. Drop by 5°C and test. Repeat until stringing stops or you start getting under-extrusion (which means you have gone too low).

Step 4, Increase travel speed: Faster travel moves mean less time for filament to ooze. Most printers handle 150-250 mm/s travel speed safely. Faster is better for stringing reduction.

Step 5, Enable wipe and coasting: Wipe moves the nozzle along the last extrusion path before traveling, cleaning the nozzle tip. Coasting stops extrusion slightly before the end of a path, reducing nozzle pressure. Both are available in most slicers and make a measurable difference.

Problem 2: Poor First Layer Adhesion

What it looks like: The first layer does not stick to the bed, curls up at the edges, or detaches entirely during the first few layers. Sometimes the filament does not adhere at all and gets dragged around by the nozzle.

What causes it: Incorrect Z-offset (nozzle too far from bed), dirty or contaminated bed surface, incorrect bed temperature, or improper first-layer settings.

Systematic fix:

Step 1, Clean the bed: Wipe the build surface with isopropyl alcohol (90% or higher). Finger oils, dust, and residue from previous prints create a release layer that prevents adhesion. This single step fixes first-layer problems more often than any other adjustment.

Step 2, Adjust Z-offset: The nozzle needs to be close enough to the bed to slightly squish the first layer. Too far and the filament does not press into the bed surface. Too close and the filament is blocked from extruding. Adjust in 0.02 mm increments during a first-layer print until the lines are flat, slightly wider than the nozzle diameter, and show no gaps between adjacent lines. Our first layer guide has visual examples of correct vs. incorrect first-layer appearance.

Step 3, Verify bed temperature: PLA: 55-65°C. PETG: 70-85°C. ABS: 90-110°C. Incorrect bed temperature is a common cause of adhesion failure, especially for materials that need higher temperatures.

Step 4, Slow down the first layer: First-layer speed should be 50-75% of your normal print speed. Slower deposition gives the filament more time to bond to the surface. Most slicers have a dedicated first-layer speed setting.

Step 5, Use adhesion aids if needed: Glue stick (PVA) works well for PETG on smooth PEI. Hairspray works for ABS. Textured PEI sheets generally do not need adhesion aids for PLA. If nothing else works, a brim adds extra surface area that grips the bed and peels off after printing.

Problem 3: Warping

What it looks like: Corners and edges of the print lift off the bed, curling upward. Can range from minor edge lift to severe warping that detaches the entire print.

What causes it: Thermal contraction. As printed layers cool, the plastic shrinks. This creates internal stress that pulls the corners upward, away from the bed. Materials with high shrinkage (ABS, nylon, polycarbonate) warp more than low-shrinkage materials (PLA, PETG).

Systematic fix:

Step 1, Verify bed temperature: Higher bed temperature keeps the lower layers warm and reduces the temperature differential that causes contraction stress. Use the upper end of your material's recommended bed temperature range.

Step 2, Use an enclosure: For ABS, nylon, and other warp-prone materials, an enclosure maintains ambient temperature around the print and dramatically reduces warping. Even a simple cardboard box or plastic storage bin over the printer helps significantly. Our nylon filament guide covers enclosure strategies in detail.

Step 3, Add a brim: A brim extends the first layer outward from the print in a flat skirt, increasing the contact area with the bed. 5-10 mm brim width is usually sufficient. The brim peels off easily after printing.

Step 4, Reduce infill density and wall count on the first few layers: Less material in the lower layers means less thermal mass and less contraction force. Some slicers allow you to set different infill parameters for the bottom layers.

Step 5, Reorient the print: Long, thin parts with large footprints warp more than compact shapes. If possible, orient the part so the longest dimension is vertical, reducing the cross-section on the bed.

Problem 4: Under-Extrusion

What it looks like: Thin, weak walls with gaps between extrusion lines. Layers appear translucent or have visible holes. Infill lines are sparse with gaps. The overall print feels fragile and crumbly.

What causes it: The extruder is not pushing enough filament through the nozzle. This can be caused by a partial clog, incorrect extruder tension, wrong filament diameter setting, temperature too low for the print speed, or a worn nozzle.

Systematic fix:

Step 1, Check for a partial clog: Heat the nozzle to printing temperature and manually push filament through. It should extrude smoothly in a consistent stream that falls straight down. If it curls to one side, comes out inconsistently, or requires excessive force, the nozzle is partially clogged. Do a cold pull (heat nozzle to 230°C, push filament in, cool to 90°C, pull filament out, the filament will pull out gunk from inside the nozzle).

Step 2, Verify filament diameter: Measure your filament with calipers at several points. Standard filament is 1.75 mm. If your slicer is set to 1.75 mm but your filament is actually 1.68 mm, you are under-extruding by 8%. Update the filament diameter in your slicer profile or adjust flow rate to compensate.

Step 3, Check extruder tension: The extruder gear needs proper tension against the filament to grip and push it. Too loose and it slips. Too tight and it deforms or grinds the filament. Adjust the tension screw until the drive gear leaves a slight tooth mark on the filament without grinding flat spots.

Step 4, Increase temperature: If you are printing at the lower end of your filament's temperature range, the material may be too viscous to flow through the nozzle at your print speed. Increase by 5°C and test. Higher print speeds require higher temperatures because the filament has less time to melt.

Step 5, Calibrate e-steps: Your extruder motor may not be pushing the exact amount of filament the slicer expects. Mark 100 mm on your filament above the extruder, command 100 mm of extrusion, and measure how much actually moved. Adjust the e-steps in firmware accordingly.

Problem 5: Over-Extrusion

What it looks like: Blobs and bulges on the surface, rough texture, filament squeezing out at corners, and a generally messy appearance. The print may also have dimensional inaccuracy (too thick).

What causes it: Too much filament being pushed through the nozzle. Common causes are flow rate set too high, incorrect filament diameter (actual filament thicker than slicer setting), or incorrect e-step calibration.

Systematic fix: Reduce flow rate by 2-5% in the slicer and test. Verify filament diameter with calipers. Calibrate e-steps as described above. Over-extrusion is less common than under-extrusion but equally harmful to print quality.

Problem 6: Layer Shifts

What it looks like: Mid-print, layers suddenly offset horizontally. The upper portion of the print is shifted to one side relative to the lower portion. Looks like someone bumped the printer during the print.

What causes it: The printhead or bed lost position during a move. Usually caused by the nozzle colliding with a curled-up part of the print, loose belts, stepper motor overheating, or excessive print speed causing missed steps.

Systematic fix:

Step 1, Check belt tension: Loose belts are the most common cause. Pluck each belt like a guitar string, it should have a medium-low pitch, taut but not guitar-string tight. Adjust belt tensioners until there is no visible slack.

Step 2, Reduce print speed: If you are pushing speed limits, the stepper motors may be skipping steps. Reduce speed by 20% and test. This is especially relevant for the heavy direct-drive printhead setups where inertia at high speeds can cause missed steps.

Step 3, Check for mechanical obstructions: Make sure cables are not catching on the frame, the bed moves freely along its axis, and nothing is physically preventing smooth motion. Also check that the print itself is not lifting and colliding with the nozzle (see warping fixes above).

Problem 7: Z-Banding (Visible Lines on Walls)

What it looks like: Consistent horizontal lines visible on the vertical surfaces of your print. The surface has a ribbed or banded texture instead of being smooth.

What causes it: Inconsistent Z-axis movement. On printers with lead screws, this is often caused by a bent lead screw, inconsistent lead screw lubrication, or the lead screw binding at certain heights. On belt-driven Z-axis printers, it can be belt tension inconsistency.

Systematic fix: Lubricate the Z lead screw with white lithium grease. Check that the lead screw is straight (roll it on a flat surface). Verify that the anti-backlash nut is properly tensioned. If the banding correlates with consistent intervals, it may be a mechanical resonance, adjust print speed or enable input shaping if your firmware supports it.

Problem 8: Elephant's Foot

What it looks like: The bottom one to three layers of the print are wider than they should be, creating a bulge at the base. The print does not sit flat on a surface because the bottom flares outward.

What causes it: Nozzle too close to the bed (squishing the first layer too much), bed temperature too high (softening the lower layers so the weight above squishes them), or insufficient cooling on the lower layers.

Systematic fix: Increase Z-offset slightly (move nozzle away from bed by 0.02-0.04 mm). Reduce bed temperature by 5°C. Enable "elephant's foot compensation" in your slicer, which automatically insets the first layer to compensate for the expected expansion.

Problem 9: Ghosting/Ringing

What it looks like: Ripple patterns on flat surfaces, usually visible as repeating echoes after sharp corners or edges. The surface looks like it has waves radiating from features.

What causes it: Mechanical vibration. When the printhead changes direction sharply (at corners), the inertia causes the frame to vibrate. These vibrations transfer to the nozzle and create visible artifacts on the print surface.

Systematic fix: Reduce print speed (especially jerk/acceleration settings). Enable input shaping if your printer firmware supports it (Klipper and newer Bambu Lab/Prusa firmwares have this). Tighten all frame bolts and ensure the printer is on a stable, non-resonant surface (not a wobbly table). Add mass to the printer frame if it is lightweight.

Problem 10: Clogged Nozzle (Complete)

What it looks like: No filament comes out at all, or extrusion starts and stops randomly. The extruder gear may click as it tries to push filament through a blocked nozzle.

What causes it: Carbonized filament buildup inside the nozzle, foreign particles, or heat creep (filament softening too far above the melt zone, creating a plug in the cold zone).

Systematic fix:

Step 1, Cold pull: Heat nozzle to 230°C, insert nylon or cleaning filament, cool to 90°C, pull sharply. The filament will bring debris with it. Repeat until the pulled filament comes out clean. This resolves about 70% of clogs.

Step 2, Acupuncture needle: Heat the nozzle and carefully insert a 0.3 mm or 0.35 mm acupuncture needle (for a 0.4 mm nozzle) from below. Gently poke through the clog. This works for partial blockages that cold pulls do not fully clear.

Step 3, Replace the nozzle: If cold pulls and needles do not work, the nozzle is damaged or has irrecoverable buildup. Brass nozzles cost $1-3 each and should be considered consumables. Replace every 500-1000 print hours for brass, longer for hardened steel. Keeping spare nozzles on hand is essential, and connects to the workshop supplies we discuss in our workshop tools article.

Problem 11: Blobs and Zits on Surface

What it looks like: Small bumps or pimples on the print surface, usually appearing at the same X-Y position on each layer (the Z-seam) or randomly scattered across surfaces.

What causes it: Z-seam artifacts (where the printer starts and ends each layer perimeter), pressure fluctuations in the nozzle during travel moves, or moisture in the filament causing steam bubbles.

Systematic fix: In the slicer, set Z-seam position to "sharpest corner" to hide seam artifacts in corners rather than on flat surfaces. Enable linear advance or pressure advance in firmware to equalize nozzle pressure during speed changes. If blobs are random, dry your filament (moisture is the likely cause). Our nylon guide covers filament drying techniques that apply to all hygroscopic materials.

Problem 12: Spaghetti (Print Detaches and Creates a Mess)

What it looks like: A tangled mess of filament on and around the build plate. The print detached from the bed at some point and the printer kept extruding into empty space.

What causes it: First-layer adhesion failure (see Problem 2), support structure failure for overhanging features, or a part of the print curling up and getting knocked off by the nozzle.

Systematic fix: Improve first-layer adhesion. Add more support material for overhanging features. Use a brim for parts with small bed contact area. Consider using OctoPrint or Obico with a camera for remote monitoring that can automatically pause the print when spaghetti is detected. Our OctoPrint remote monitoring guide covers AI-powered failure detection that catches these issues within seconds.

Problem 13: Gaps Between Infill and Walls

What it looks like: Visible gaps where the internal infill pattern meets the outer wall perimeters. The surface may show depressions or slight transparency where infill lines do not quite reach the wall.

What causes it: Infill lines are not overlapping with wall perimeters sufficiently. Common when infill and wall speeds differ significantly, or when the infill overlap setting is too low.

Systematic fix: Increase infill-wall overlap percentage in slicer (default is usually 10-15%, try 20-25%). Reduce the speed difference between infill and wall printing. Ensure you do not have under-extrusion (see Problem 4), which makes the gap more visible.

Problem 14: Rough Overhangs

What it looks like: The underside of overhanging features is rough, droopy, and messy compared to supported or upward-facing surfaces.

What causes it: Printing layers that extend beyond the layer below without adequate support. Each layer needs at least partial support from the layer below it. Beyond 45 degrees of overhang, quality degrades rapidly without support structures.

Systematic fix: Add support structures for overhangs steeper than 45 degrees. Increase cooling fan speed to 100% for overhangs. Reduce print speed for overhang areas (some slicers have dedicated overhang speed settings). Reduce layer height, which improves overhang quality by decreasing the step distance between layers. Reorient the part if possible to minimize overhang angles.

Problem 15: Inconsistent Extrusion (Periodic Under/Over)

What it looks like: Alternating sections of thin (under-extruded) and thick (over-extruded) lines. The pattern may be regular (repeating at consistent intervals) or irregular.

What causes it: Regular patterns usually indicate a mechanical issue with the extruder gear: a flat spot on the gear, inconsistent tension, or a slipping coupler. Irregular patterns suggest filament diameter variations, moisture, or intermittent clogs.

Systematic fix: Check the extruder drive gear for wear or flat spots. Verify the gear set screw is tight. Measure filament diameter at multiple points to check for consistency. Dry the filament if moisture is suspected. Replace the PTFE tube if it shows signs of degradation or internal buildup.

Building Your Troubleshooting Reference

I strongly recommend starting your own failure photo collection. When a print fails, take a photo before discarding it. Note the material, settings, and your diagnosis. Within a few months, you will have a personal reference that lets you instantly recognize problems and apply proven fixes. It is the fastest path from frustrated beginner to confident operator.

Every problem on this list has a solution. Most have multiple solutions that depend on your specific printer, material, and conditions. The key is approaching each failure as a data point, not a frustration. Each failed print teaches you something, and each fix adds to your toolkit. Print by print, you will encounter these problems less often and fix them faster when they appear.

Happy troubleshooting, Alex