Nylon

Nylon (PA) prints into tough, wear-resistant parts, but it punishes sloppy moisture control and uneven cooling. If you keep it dry (drying + sealed storage/print-from-drybox) and print warm and draft-free (often with an enclosure), you’ll avoid the two big nylon failure modes: steam-caused porosity/stringing and shrink-stress warping/layer splits.

TL;DR

Nylon rewards two habits: keep it dry and cool it evenly. Dry the spool, store it sealed (best case: print from a dry box), and print warm and draft-free (often with an enclosure). If you hear popping/sizzling or see lifted corners or mid-print cracks, stop and fix moisture or cooling before wasting a long job.

What nylon is good for (and when to skip it)

Nylon (PA) is a tough, wear-resistant engineering plastic for functional parts like gears, bushings, hinges, clips, cable guides, and shop fixtures. It handles impacts and repeated flexing better than many common filaments. The downsides are practical: nylon soaks up moisture from the air and it shrinks as it cools, so it needs more prep than PLA/PETG and it’s often not the best choice when you need tight dimensions or maximum stiffness.

Common nylon filament variants (what changes)

PA6 / PA66 harder
  • Very tough and wear-resistant parts
  • High ductility when the filament is truly dry
  • Soaks up moisture quickly; prints degrade fast when exposed
  • Higher shrink/warp risk, especially on larger parts
PA12 medium
  • Often warps less than PA6/66
  • Often holds dimensions better than PA6/66
  • Still needs drying and sealed storage
  • Often costs more
Filled nylon (CF/GF) harder
  • Stiffer prints than unfilled nylon
  • Often warps less than unfilled nylon
  • Strong option for rigid fixtures and structural brackets
  • Abrasive; use a wear-resistant nozzle
  • Can be more brittle than unfilled nylon
  • Drying is still required

Material decision points (nylon)

Moisture control
Plan to dry it. Store sealed with desiccant, and for repeatable prints, feed it from a dry box.
Temperature capability
Make sure your hotend and bed can reach the filament’s recommended range; nylon usually needs higher temps than PLA/PETG.
Enclosure / drafts
Assume drafts will hurt you. An enclosure often makes the difference between flat parts and warping/layer splits.
Bed adhesion plan
Decide on a surface and adhesive approach before you start; once nylon starts shrinking, small first-layer issues become big failures.
Wear and friction needs
Use nylon for toughness and sliding wear. Avoid it when stiffness and tight dimensional stability matter most.
Proof test
Run a small functional coupon first (fit test, snap arm, gear segment) to confirm dryness and settings before a long print.

Moisture: what’s happening inside the hotend

Nylon pulls water into the filament itself, not just on the surface. In the hotend, that water flashes into steam and expands, disturbing the flow of plastic. You may hear popping/sizzling and see rough, pitted, or foamy extrusion. The tiny voids left behind weaken layer bonding, so parts can snap along layer lines even if the outside looks acceptable.

Moisture signs to check in the first few minutes

  • Popping or sizzling sounds at the nozzle
  • Stringing that stays bad even after sane retraction settings
  • Rough, pitted, or slightly foamy surfaces
  • Micro-surging extrusion with otherwise stable temperatures

Drying and storage habits that make nylon printable

  • Dry the spool using the filament maker’s temperature/time guidance; don’t “just crank heat” (spools can deform).
  • After drying, seal it immediately with desiccant; don’t leave nylon sitting on the printer between sessions.
  • If prints degrade over a day or two, switch to printing from a dry box or re-dry before the next job.
  • Treat “new in box” nylon as possibly wet; confirm with a quick test print or by listening for nozzle popping.

Shrink stress: why nylon warps and splits

Nylon shrinks as it cools. If some areas cool faster than others, the part builds internal stress. On the bed, that stress pulls corners up (warping) and can pry the first layer loose. Higher up, the same stress can open cracks between layers (layer splitting), especially on tall parts, thin walls, or long straight sections that cool between passes. An enclosure helps by cutting drafts and keeping the whole print warmer so it cools more evenly.

Nylon troubleshooting: symptom → likely cause → first fix

Stringing, bubbles, popping at nozzle, rough/foamy surface

Likely cause: Wet filament; moisture flashing to steam in the hotend

Fix: Dry the filament; then keep it sealed or print from a dry box.

Corners lifting, warped base, poor bed hold

Likely cause: Shrink stress plus weak adhesion and/or drafts

Fix: Use an enclosure, improve bed adhesion method, and reduce aggressive cooling.

Cracks forming mid-print (layer splitting)

Likely cause: Cooling too fast; large temperature gradients through the part

Fix: Enclose the printer and keep the chamber warmer if possible; reduce fan.

Weak layers even though the surface looks decent

Likely cause: Moisture and/or nozzle temperature too low and/or too much fan

Fix: Re-dry; then raise nozzle temp within spec and reduce cooling.

Inconsistent extrusion or jams

Likely cause: Nozzle temperature too low, heat creep, or steam expansion from wet filament

Fix: Increase nozzle temp within spec; verify hotend fan is working; dry filament.

Nozzle wear, widening lines over time (filled nylons)

Likely cause: Abrasive carbon/glass fibers eroding the nozzle

Fix: Switch to a hardened nozzle and re-check flow/extrusion calibration after the change.