I regularly get an email from someone who has run into a problem with a 3D print. The print comes loose from the bed, thin strings appear between the parts, or suddenly hardly any filament comes out of the nozzle. Good news: in almost every case a few targeted adjustments will fix it. And it is rarely the filament itself; much more often it is a greasy bed, damp filament or a setting that is not quite right.

3D printers have become a lot smarter in recent years. A Bambu Lab, Prusa MK4 or Creality K1 levels its own bed and calibrates many settings automatically. Yet the same problems still come up. In this article I list the most common ones, with the cause and what you can do about it.

Quick overview: which problem do you have?

ProblemMost likely causeTry first
First layer won't stick, print comes looseGrease on the bed or nozzle too highClean the bed with isopropanol, lower the Z offset
Print sticks too wellPETG on a smooth PEI plateRelease layer of glue stick or adhesive spray
Corners lift (warping)Material shrinks as it coolsBrim, no draughts, enclosure for ABS and ASA
Thin strings (stringing)Damp filament or temperature too highDry the filament, print 5 °C cooler
Gaps or thin wallsToo little filament (under-extrusion)Check the nozzle, print slower
Nothing comes out of the nozzleClogged nozzle or heat creepCold pull, check the hotend fan
Shifted layersBelt, obstacle or speed too highCheck belts and axes
Bottom layers bulge out (elephant's foot)First layer squashed too muchSlightly higher Z offset, slightly cooler bed
Messy overhangsToo little cooling or supportMore cooling, support or a different orientation
Crackling, bubbles, rough surfaceDamp filamentDry the filament and store it dry

The basics first: three things that prevent most problems

1. A clean, grease-free print bed

I cannot say it often enough: filament does not stick to grease. A single fingerprint is enough to ruin a first layer. So hold the build plate by its edges and wipe it before printing with a lint-free cloth and isopropanol (IPA). Every now and then you can also wash a textured PEI plate with warm water and a drop of washing-up liquid. Rinse it well and dry it before putting it back.

2. Dry filament

PLA, PETG, PCTG and especially nylon and TPU absorb moisture from the air. Damp filament crackles while printing, strings more and gives a rough or weak result. So store spools you are not using sealed, with silica gel beads. If a spool has been left open for a long time, dry it in a filament dryer or oven at the temperature the manufacturer recommends.

3. The right settings for your filament

In your slicer, such as Bambu Studio, OrcaSlicer, PrusaSlicer or Cura, use a filament profile that matches the material. Use the temperatures on the spool as a starting point. If your printer has a flow or pressure advance calibration, run it once for each new type of filament. It saves a lot of guesswork.

The first layer won't stick, or the print comes loose from the bed

This is the problem I get the most questions about, and the first layer is also the most important part of every print. The cause is almost always one of these:

  • Grease or dust on the bed. Clean the bed as described above.
  • The nozzle is too high. The filament is then laid down as a loose round strand instead of being pressed on lightly. Lower the Z offset in small steps (0.02 mm). On many printers you can even do this while the first layer is printing.
  • The bed is too cold. Check the recommended bed temperature on the spool. For PLA it is usually between 50 and 60 °C; for PETG and PCTG it is quite a bit higher.
  • Too little contact area. Small or tall, narrow parts have little grip. Turn on a brim in your slicer: a thin rim around the print that you remove afterwards.
  • Too fast. Print the first layer slowly; most slicers already do this by default.

Still not sticking well? A thin layer of 3DLAC adhesive spray or Magigoo glue stick helps. Your part sticks extra well while printing, and comes off easily again once the bed has cooled.

Do you have an older printer without automatic bed levelling? Then level the bed with a sheet of printer paper: the nozzle should just touch the paper, so you can still move it with a little resistance. Go round all corners a few times with small adjustments. Stiffer yellow bed springs help the bed hold its setting for longer.

The print sticks too well

The opposite also happens, especially with PETG and PCTG on a smooth PEI plate. They can stick so well that they tear a piece out of the plate when you remove them. So use a release layer of glue stick or adhesive spray, and let the bed cool down completely before removing the print. With a flexible plate you can then simply bend the print off. Preferably avoid sharp scrapers: you will see every scratch again in your next first layer.

The corners lift (warping)

Plastic shrinks as it cools. If the bottom layers cool faster than the rest, the corners are pulled up. This rarely happens with PLA, but often with ABS, ASA and nylon. This is how to prevent it:

  • Print ABS and ASA in an enclosed printer or enclosure, and keep the lid closed.
  • Avoid draughts: no open window, fan or air conditioning near the printer.
  • Use a brim, and for large flat parts possibly a raft.
  • Turn the part cooling fan down or off for ABS and ASA.

Thin strings between parts (stringing)

Stringing happens when filament leaks from the nozzle while the print head travels from one part to another. Check in this order:

  1. Is the filament dry? Moisture is by far the most common cause, especially with PETG.
  2. Is the temperature too high? Lower the nozzle temperature in steps of 5 °C.
  3. Is the retraction right? Print a retraction test from your slicer and choose the setting with the fewest strings.

A few loose hairs are quickly removed afterwards with a hair dryer or heat gun: a quick pass is enough. Want as little trouble as possible? Fiberlogy Easy PETG was developed specifically to string less.

Gaps, thin walls or a weak print (under-extrusion)

If less filament comes out of the nozzle than the slicer expects, you see gaps in the top layer, thin walls or layers that bond poorly. Possible causes:

  • A partly clogged nozzle. See the next section.
  • Printing too fast for your hotend. Fast printers can move faster than the hotend can melt filament. Lower the print speed or the maximum volumetric speed in your filament profile.
  • Incorrect flow. Run your printer's or slicer's flow calibration.
  • Resistance in the filament path. Check that the spool turns freely, that the filament does not kink anywhere and that the PTFE tube is intact. Also look for filament dust on the extruder gear.

Older printer? Then also check your extruder's e-steps: feed 100 mm of filament and measure whether 100 mm has really been used.

Nothing comes out of the nozzle (clog)

Does the extruder click, or does nothing come out any more? Then the nozzle or hotend is probably (partly) clogged. Here is what you can do:

  • A cold pull. Heat the nozzle to your filament's print temperature and push some filament through by hand. Then let the temperature drop to about 90 °C (for PLA) and pull the filament out with a firm tug. You will see the dirt that came out on the tip. Repeat until the tip is clean.
  • Clean from the outside. A copper brush removes baked-on filament from the warm nozzle. A stainless steel needle helps with a particle stuck in the opening.
  • Prevent heat creep. If filament softens before it reaches the nozzle, the hotend jams. Check that the hotend fan is free of dust and running properly. If you print PLA in an enclosed printer, open the lid or door; PLA does not like a warm environment.
  • Replace the nozzle. A nozzle wears, especially with abrasive filaments. If it is worn or keeps clogging, replace it. Check your printer's manual for the type it uses: for example an MK7/MK8 nozzle, an E3D V6 nozzle (M6) or the manufacturer's own hotend.

Note: filaments with fibres or other particles, such as carbon (CF), glass fibre (GF), wood filament and glow in the dark, are abrasive. Print them with a hardened nozzle, and for wood preferably with a 0.5 or 0.6 mm diameter.

Layers have shifted (layer shift)

If part of your print is suddenly offset to one side, the print head has skipped steps. Check that the belts are properly tensioned, that nothing was in the way (a cable, or a curled-up corner of the print itself that the nozzle hit) and that the axes move smoothly. If it happens more often at high speeds, lower the speed or acceleration.

The bottom layers bulge out (elephant's foot)

If the bottom millimetres of your print stick out a little, the first layer is being pressed down too hard or stays soft for too long. Raise the Z offset slightly and lower the bed temperature by 5 °C. Many slicers also have an elephant's foot compensation setting.

Messy overhangs and bridges

When you print high up in the air, you run into a small nuisance called gravity: the filament needs something to rest on. Let your slicer add support where needed, or rotate the model so there is less overhang. For PLA, turn the cooling up so the filament solidifies quickly. With PETG, printing a few degrees cooler helps.

Maintenance: keep your printer in top shape

Even a modern printer needs a service now and then. Wipe dust and print residue off the axes and guides and lubricate them as described in the manual. Check the belt tension, clear the fans of dust and check that the PTFE tube and nozzle still look good. And treat your build plate with care: a clean, undamaged plate is half the work.

Still stuck?

These are the tips I give most often by email or phone, and usually I hear back afterwards that it worked. Still can't figure it out? Feel free to contact us; we are happy to help. And would you rather not print a part yourself? You can also have it printed through our 3D printing service.