FDM Troubleshooting · San Diego

Why Is My 3D Print
Failing?

Prints peeling off the bed, corners curling, hair-like strings everywhere, layers splitting apart. Almost every FDM failure traces back to a short list of causes — and most are a five-minute fix once you know what you're looking at. Here are the ten most common, diagnosed and solved.

10 problems · cause + fix · no jargon

10Failures, diagnosed

#1Cause: the first layer

5minMost fixes take

100k+Hrs repair experience

If you only remember one thing: most failed prints are decided in the first layer and by your temperatures. Get those two right and the majority of problems below simply never happen. Let's start by seeing what a good first layer even looks like.

The first layer, in cross-section. You want the middle one.

The 10 most common FDM failures

01 First layer won't stick

The print pops loose, corners lift, or the first layer looks like patchy, separated lines.

Cause Nozzle too far from the bed, a dirty bed, or a bed that isn't level/trammed.

Fix Re-level (or re-run auto bed leveling), wipe the bed with isopropyl alcohol, and lower the Z-offset a hair until the first layer looks squished and fused like the middle diagram. A thin coat of glue stick helps on glass and PEI.

02 Warping (corners curling up)

The base lifts off the bed mid-print, especially at corners, and the bottom ends up banana-shaped.

Cause Uneven cooling — the plastic shrinks as it cools and pulls the corners up. Worse with ABS/ASA and on cold, drafty benches.

Fix Use a heated bed at the material's recommended temp, add a brim or raft, kill drafts, and enclose the printer for higher-temp materials. For PLA, drop the part-cooling fan slightly on the first few layers.

03 Stringing and oozing

Fine hair-like strands stretched between separate parts of the print.

Cause Molten plastic leaking from the nozzle during travel moves — usually too-high temperature or too-little retraction. Wet filament makes it dramatically worse.

Fix Lower nozzle temp in 5°C steps, increase retraction distance/speed, raise travel speed, and dry the filament if it's been exposed to humidity (a big deal for PETG and nylon).

04 Under-extrusion (gaps and thin walls)

Missing material, gaps between lines, thin or skipped layers, weak walls.

Cause A partial clog, too-low temperature, a clicking/slipping extruder, or flow set too low.

Fix Raise the nozzle temp a little, check for a partial clog, confirm the extruder isn't skipping, and verify flow/extrusion-multiplier and filament diameter in your slicer.

05 Over-extrusion (blobs and rough walls)

Too much plastic — bulging walls, blobs, dimensional parts that come out oversized.

Cause Flow rate set too high, or temperature higher than needed.

Fix Reduce flow/extrusion multiplier in small steps, lower the temperature a touch, and run a flow-calibration test if your printer supports it.

06 Layer separation / cracking

Layers split apart or crack, often partway up a tall print, and the part feels weak along the layers.

Cause Poor layer bonding — usually printing too cold, too fast, or with too much cooling for the material.

Fix Raise nozzle temp, slow down, and reduce part cooling (PETG and ABS in particular hate aggressive fans). An enclosure helps tall ABS/ASA prints.

07 Clogged nozzle

Extrusion stops or sputters, the extruder clicks, and nothing comes out evenly.

Cause Debris or degraded filament in the nozzle, heat creep, or mixing materials with very different temperatures.

Fix Do a cold pull (atomic pull), clear the tip with a 0.4mm nozzle needle, and check the PTFE liner seats fully. Replace the nozzle if it's worn — especially after abrasive filaments like carbon-fiber blends.

08 Elephant's foot (squished bottom)

The first few layers bulge outward, leaving a flared base that ruins fit and flatness.

Cause First layer pressed too hard into the bed, or bed temperature a little too high.

Fix Raise the Z-offset slightly, lower bed temp a few degrees, and enable your slicer's elephant-foot compensation if it has one.

09 Layer shifting

The print suddenly steps sideways and every layer above is offset.

Cause The nozzle snagged the print, or belts/pulleys slipped — often from printing too fast or loose belts.

Fix Tension the belts, tighten pulley grub screws, reduce speed/acceleration, and make sure nothing is colliding with curled-up edges mid-print.

10 Ghosting / ringing

Faint echoes or ripples in the surface just past corners and sharp features.

Cause Vibration — usually speed/acceleration too high for the frame, or a wobbly surface under the printer.

Fix Lower acceleration and jerk, put the printer on a solid surface, tighten the frame, and use input shaping if your firmware supports it.

Change one variable at a time. The fastest way to never solve a print problem is to change five things at once.

Quick diagnostic reference

See the symptom, start with the first fix. Work down only if it doesn't resolve.

Symptom	Most likely cause	First thing to try
Won't stick to bed	Z-offset / dirty bed	Re-level, clean with IPA, lower Z-offset
Corners lifting	Uneven cooling	Heated bed + brim, kill drafts
Hairy strings	Temp high / wet filament	Lower temp, more retraction, dry filament
Gaps / thin walls	Under-extrusion	Raise temp, check for partial clog
Blobs / oversized	Over-extrusion	Reduce flow rate
Layers splitting	Weak layer bonding	Raise temp, slow down, less cooling
Nothing extruding	Clog	Cold pull, clear nozzle, check liner
Flared base	Elephant's foot	Raise Z-offset, lower bed temp
Sudden sideways step	Layer shift	Tension belts, slow down
Ripples past corners	Ghosting	Lower acceleration, steady the surface

Safety first

Don't leave a failing or sputtering print running unattended — a clog or thermal fault can damage the hotend or worse. If your printer overheats, smells of burning, or throws a thermal-runaway error, power it down and stop until it's diagnosed.

When to stop tinkering

If you've worked the table and it still fails, the issue is often mechanical — a worn nozzle, a failing heater cartridge or thermistor, a clogged heatbreak, or a frame out of square. That's where a hands-on look saves hours. We service every major brand across San Diego County, and a lot of issues we can solve over email for free.

Stuck? We'll get it printing again.

Mobile 3D printer repair across San Diego — we come to you. Send a photo of the failure and a few details, and in many cases we'll point you to the fix for free before anything else.

Don't want to chase settings at all?

Plenty of people just want the part, not the hobby. Send us the file and we'll print it dialed-in on calibrated machines — FDM or resin — and ship it anywhere, or you can pick up locally in San Diego. No leveling, no clogs, no late-night recalibrating.

Frequently asked questions

Why won't my first layer stick to the bed?

Almost always the nozzle is too far from the bed or the bed is dirty. Re-level (or re-run auto leveling), wipe the surface with isopropyl alcohol, and lower the Z-offset until the first layer looks squished and fused rather than round and separated. A light glue-stick coat helps on glass and PEI.

What causes warping and how do I stop it?

Warping is uneven cooling pulling the corners up as the plastic shrinks. Use a heated bed at the right temperature, add a brim or raft, eliminate drafts, and enclose the printer for higher-temp materials like ABS and ASA.

How do I get rid of stringing?

Lower the nozzle temperature in small steps, increase retraction distance and speed, raise travel speed, and dry your filament — moisture is a leading cause, especially with PETG and nylon.

My layers are separating or cracking — what's wrong?

That's weak layer bonding, usually from printing too cold, too fast, or with too much part cooling for the material. Raise the nozzle temperature, slow down, and reduce the fan. Tall ABS/ASA prints also benefit from an enclosure.

Why does my nozzle keep clogging?

Common causes are debris or degraded filament in the nozzle, heat creep, and abrasive materials wearing the tip. Try a cold pull, clear the nozzle with a fine needle, confirm the PTFE liner is seated, and replace worn nozzles — especially after carbon-fiber blends.

What is elephant's foot and how do I fix it?

It's a flared, bulging base from the first layers being pressed too hard into the bed. Raise the Z-offset slightly, lower the bed temperature a few degrees, and enable elephant-foot compensation in your slicer if available.

I've tried everything and it still fails. Can you help?

Yes. Persistent failures are often mechanical — a worn nozzle, failing thermistor or heater, clogged heatbreak, or a frame out of square. We offer mobile repair across San Diego County and free email troubleshooting for many issues. Call or text 858-342-6984.

Printer fighting you? Let's fix it.

On-site repair, setup, and calibration across San Diego — or send us the file and let us print it for you. Either way, you get back to making things.

📞 858-342-6984
✉ dreaming3dprinting@gmail.com
📷 @dreaming3dprinting
📍 3880 Valley Centre Dr, San Diego

Why Is My 3D Print Failing?