Troubleshooting
Filament Troubleshooting: Symptom, Cause, Fix
Most print failures have three or four plausible causes, and the fastest way to fix one is to work from the symptom backwards rather than changing settings and hoping. This guide is built as a diagnostic table: find what you are seeing, read the likely cause, try the fixes in the order given. It also covers the one cause generic troubleshooting guides skip — moisture — and the settings each material actually wants.
Five-minute triage: filament or printer?
Before you touch a slicer setting, establish which half of the machine is at fault. This sequence answers it.
- Heat the nozzle and extrude by hand. Use the printer’s manual extrude or load function. Smooth, steady, shiny plastic means the hot end is healthy. Nothing, a trickle, or a curl that twists straight back up at the nozzle means you have a partial blockage or a feed problem.
- Listen and look at the nozzle while it extrudes. Popping, crackling or visible steam means the filament is wet. Stop here and go to the moisture section — nothing else you change will help.
- Check the extruder gear. Open the extruder and look at the filament where the drive gear grips it. Flattened, ground or chewed filament means the gear has been slipping because something downstream is resisting — a clog, too-high speed, or too-cold a nozzle.
- Feel the spool tension. Unclip the filament from the extruder and pull a metre off the spool by hand. It should come freely. If you feel a snag or a hard stop, you have a tangle or a strand tucked under a previous wrap.
- Swap the spool. Load a known-good spool of the same material and print a small test. If the problem disappears, it is the filament. If it persists, it is the printer.
That last step is the one people skip and the one that saves the most time. A spare spool of plain Core PLA is the cheapest diagnostic tool in the workshop.
Symptom, cause, fix
Fixes are listed in the order worth trying. The last column flags which filaments are most prone to each fault.
| What you see | Most likely cause | Fixes, in order | Worst on |
|---|---|---|---|
| Fine hairs and whiskers between features (stringing) | Material oozing during travel moves — too hot, too little retraction, or wet filament | 1. Dry the spool. 2. Drop nozzle temperature 5–10°C. 3. Increase retraction distance and speed. 4. Enable combing / avoid crossing perimeters. 5. Raise travel speed. | PETG, TPU |
| Blobs, zits and pimples on the surface | Pressure released at the wrong moment at layer changes and seams | 1. Enable coasting or pressure advance / linear advance. 2. Reduce retraction extra restart distance. 3. Randomise or align the seam. 4. Drop nozzle temperature slightly. | All |
| First layer will not stick | Nozzle too far from the bed, dirty bed, or bed too cool | 1. Clean the bed with isopropyl alcohol — skin oil is the usual culprit. 2. Re-level and lower the Z offset slightly. 3. Raise bed temperature 5–10°C. 4. Slow the first layer to 20 mm/s. 5. Add a brim. | ABS, ASA, composites |
| Corners lift off the bed mid-print (warping) | Uneven cooling shrinking the part away from the plate | 1. Enclose the printer or block draughts. 2. Raise bed temperature. 3. Reduce or disable part cooling for the first layers. 4. Add a brim or mouse ears. 5. Switch to a lower-shrinkage material. | ABS, ASA |
| A bulging, squashed bottom layer (elephant’s foot) | Nozzle too close to the bed, or bed too hot | 1. Raise Z offset a fraction. 2. Lower bed temperature 5°C. 3. Apply the slicer’s initial layer horizontal expansion / elephant foot compensation. | PLA, PETG |
| Thin, gappy walls and visible holes (under-extrusion) | Restricted flow — partial clog, too cold, too fast, or wet filament | 1. Dry the spool. 2. Raise nozzle temperature 10°C. 3. Slow print speed. 4. Cold-pull the nozzle to clear debris. 5. Check the extruder gear for grinding. 6. Calibrate flow rate. | All, especially composites |
| Bulging walls and rough over-filled surfaces (over-extrusion) | Flow rate too high, or filament diameter wrong in the slicer | 1. Set filament diameter to 1.75 mm. 2. Calibrate flow rate. 3. Check e-steps. 4. Lower nozzle temperature slightly. | All |
| Nozzle stops extruding part-way through a print (clog) | Debris, degraded plastic, or heat creep softening filament above the melt zone | 1. Cold pull. 2. Clear with a nozzle needle at temperature. 3. Replace the nozzle. 4. Check the hot-end fan is running. 5. Lower retraction distance if it is pulling melt up into the cold zone. | Composites, PETG |
| Layers shifted sideways part-way up | Belt slip, a motor losing steps, or the nozzle striking the part | 1. Tension the belts. 2. Reduce print speed and acceleration. 3. Check pulleys are tight on their shafts. 4. Enable Z hop to stop the nozzle clipping curled edges. | All |
| Part splits along a layer line under load (delamination) | Layers never bonded — too cold, too much cooling, or wet filament | 1. Dry the spool. 2. Raise nozzle temperature 10–15°C. 3. Reduce part cooling fan. 4. Enclose the printer for ABS and ASA. 5. Increase wall count rather than infill. | ABS, ASA, PLA |
| Gaps and pinholes in the top surface (pillowing) | Top layers bridging too little infill with too little cooling | 1. Add top layers until they total at least 0.8 mm. 2. Raise infill density to 15–20%. 3. Increase part cooling on top surfaces. 4. Slow the top solid infill. | PLA, PETG |
| Drooping, curling overhangs | Unsupported material not cooling fast enough | 1. Maximise part cooling. 2. Slow overhang perimeters. 3. Reduce layer height. 4. Reorient the part or add supports. | PETG, ABS, ASA |
| Regular horizontal banding up the part (Z banding) | Lead-screw wobble, binding, or inconsistent extrusion | 1. Check the Z lead screw is clean, lubricated and not over-constrained. 2. Confirm the coupler is not bent. 3. Calibrate extrusion. 4. Rule out wet filament. | All |
| Spaghetti: the print detaches and keeps extruding | First-layer adhesion failed, or a tall thin part was knocked over | 1. Fix adhesion as above. 2. Add a brim. 3. Reorient or add supports for tall narrow geometry. 4. Slow the print. | All |
| Filament ground flat at the extruder gear | The gear has been slipping against resistance | 1. Clear the blockage first — the grinding is a symptom. 2. Raise nozzle temperature. 3. Slow the print. 4. Cut off the ground section before reloading. 5. Clean filament dust out of the gear teeth. | All |
| Rough, furry, matte surfaces plus popping from the nozzle | Wet filament. Not a settings problem. | Dry the spool — see below. | TPU, PETG, composites |
Wet filament: the cause most guides bury
Moisture deserves to be checked first, not listed sixth, because it mimics half the faults above and none of the usual fixes touch it. Filament absorbs water vapour from the air; at printing temperature that water turns to steam inside the nozzle and blows holes through the extrusion on its way out.
The tells are distinctive once you know them:
- Audible popping, crackling or hissing at the nozzle — the most reliable single sign
- Visible steam or wisps at the nozzle tip
- A surface that has gone furry or matte on a filament that used to print glossy
- Stringing that was not there when the spool was new
- Under-extrusion with no blockage
- Filament that snaps dryly when bent off the spool
- Parts that split along layer lines under mild load
The decisive question is simple: did this spool print well when it was new? If yes, and nothing else changed, it is moisture.
| Material | Drying temperature | Time |
|---|---|---|
| PLA, PLA+ and PLA variants | 45–55°C | 4–6 hours |
| PETG | 60–65°C | 4–8 hours |
| TPU 95A | 50–55°C | 6–12 hours |
| ABS, ASA | 70–80°C | 4–6 hours |
| Carbon- and glass-filled | As the base polymer, upper end | 6–12 hours |
These are typical ranges — check the spool label, which reflects the exact formulation. A filament dryer or a food dehydrator holds temperature more honestly than a domestic oven, and PLA in particular needs care because it begins to soften around 55–60°C, barely above its drying temperature.
Australian conditions make this a routine problem rather than an occasional one. Summers on the east coast and in the tropical north are humid, and a garage or unairconditioned spare room tracks the outside air. A PETG or TPU spool left open across a humid weekend can be noticeably wet. The full treatment — storage containers, desiccant, recharging silica gel, dry boxes — is in our filament storage guide.
Starting settings by material
Many printer problems are really a PLA profile being used on a material that wanted something else. These are sensible starting points, not gospel — the label on the spool is authoritative for the product in your hands.
| Material | Nozzle | Bed | Fan | Enclosure | Nozzle type | Watch out for |
|---|---|---|---|---|---|---|
| PLA | 190–220°C | 50–60°C | High | No | Brass | Brittleness; softens ~55–60°C |
| PLA+ | 205–230°C | 55–65°C | High | No | Brass | Run hot enough to get the toughness |
| PETG | 230–250°C | 70–85°C | Low to medium | No | Brass | Stringing; sticks hard to smooth PEI |
| TPU 95A | 210–230°C | 30–50°C | Low | No | Brass | Needs slow speeds, minimal retraction, direct drive |
| ABS | 230–260°C | 90–110°C | Off or minimal | Yes | Brass | Warping, cracking, styrene odour — ventilate |
| ASA | 240–260°C | 90–110°C | Off or minimal | Yes | Brass | As ABS, but UV stable outdoors |
| PLA-CF | 200–230°C | 50–60°C | High | No | Hardened | Abrasive; more brittle than plain PLA |
| PETG-CF / PETG-GF | 240–260°C | 70–85°C | Low to medium | Helpful | Hardened, 0.6 mm+ | Abrasive, thirsty, clogs small nozzles |
| ABS-CF | 240–265°C | 90–110°C | Off or minimal | Yes | Hardened, 0.6 mm+ | All of ABS, plus abrasion |
Three hardware rules cover the whole range: ABS and ASA want an enclosure and ventilation, TPU strongly prefers a direct-drive extruder, and every carbon- or glass-filled composite requires a hardened nozzle. Everything else runs on a stock modern printer.
Carbon- and glass-filled filament faults
Filled filaments fail in ways that generic guides do not cover, because the abrasive filler changes the problem set.
Nozzle wear reads as under-extrusion. Carbon and especially glass fibre grinds a brass nozzle wider over time. A worn nozzle over-extrudes thin walls and loses fine detail, and the effect creeps in gradually so it looks like a slicer problem. If you have printed composites through a brass nozzle, suspect wear before anything else. Use hardened steel.
Small nozzles clog. Chopped fibres bridge across a 0.4 mm orifice. Run 0.6 mm or larger for glass-filled materials, and expect 0.4 mm to be marginal even with carbon.
Filled does not mean tougher. This is the most common misunderstanding. Carbon and glass fibre add stiffness and dimensional stability; they generally make the part more brittle, not less. If you want a part that survives being dropped, you want PLA+ or PETG, not PLA-CF.
They are thirsty. Composites absorb moisture faster than their base polymers and show it more obviously. Print them from a dry box if you can.
When it really is the spool
Most of the time the printer is at fault. Occasionally it is not, and these are the genuine filament defects worth knowing.
- Tangles and crossed wraps. A strand tucked under an earlier wrap will feed fine for hours and then stop the print dead. Usually caused by letting the free end go during storage rather than by winding.
- Diameter variation. Filament should be close to 1.75 mm and round. Measure with callipers at several points and across two axes. Consistent ovality or swings of more than about 0.05 mm will show as alternating over- and under-extrusion.
- Brittle on arrival. Filament that snaps straight off a newly opened spool has been stored or freighted badly — typically weeks in a hot, humid container. Try a full dry cycle; if it still snaps, the polymer has degraded.
- Winding tension. Over-tight winding can dig lower wraps into the spool wall and bind. You will feel it pulling filament off by hand.
If a spool shows any of these, that is a product fault, not a settings problem. Email support@3dma.au with your order number and photos and we will sort it — see Shipping & Returns.
Frequently asked questions
What are some common 3D print problems?
In rough order of how often they come up: poor first-layer adhesion, stringing, warping, under-extrusion, clogged nozzles, layer shifting, delamination under load, and gaps in top surfaces. Wet filament sits behind a surprising share of the stringing, under-extrusion and delamination cases, which is why it is worth ruling out first. The table above gives the fix order for each.
My 3D printer is not printing filament. What could be the problem?
Work through it in this order: is the nozzle actually at temperature; does it extrude when you command it by hand; is the extruder gear gripping or grinding; does filament pull freely off the spool; is there a clog. A nozzle that extrudes nothing at temperature with an audible click from the extruder is a blockage. A nozzle that extrudes fine by hand but fails mid-print is usually heat creep or a spool snag.
How do you tell if a 3D printer nozzle is clogged?
Heat the hot end to printing temperature and extrude manually. Healthy flow is smooth, steady and comes straight down. A partial clog gives you a thin, slow or inconsistent stream, or filament that curls sharply back up the side of the nozzle. A full clog gives you nothing at all, usually with the extruder gear clicking or grinding as it fails to push. A cold pull — heat, push filament through, cool to about 90°C for PLA, then pull the plug out sharply — clears most of them and brings the debris out with it.
How do you tell if filament is stuck in the feeder or the extruder?
Release the extruder idler and pull the filament back out by hand. If it comes out easily and the spool turns freely, the problem is downstream in the hot end. If it will not move, look at where the drive gear grips it: flattened or ground filament means the gear has been slipping against a blockage further down. If the filament is free at the extruder but will not pull off the spool, you have a tangle, not a machine fault.
Can wet filament damage the printer?
It will not usually break anything, but it makes clogs more likely because steam pockets disrupt flow and leave partially degraded plastic behind in the nozzle. Drying the spool is quicker than clearing the clog it eventually causes.
Why did a spool that printed perfectly start printing badly?
Moisture, nine times out of ten — especially PETG, TPU or a composite that has been sitting open. The next most likely cause is nozzle wear if you have been printing filled materials, then a partial clog building up. A spool does not change on its own; its water content does.
Still stuck?
Email support@3dma.au with your printer model, the material, and a photo of the failure. Real answers from people who print — or browse the Materials Guide if you suspect the material is wrong for the job.