The part peels apart along layer lines under stress. Sometimes it separates during printing itself; sometimes the failure only appears when you try to use the part.
Distinguish From Other Problems
Poor adhesion looks different from delamination cracking. Run your thumbnail along the layer lines: if you feel distinct ridges with gaps between them, it’s adhesion failure. If the surface looks normal but the part splits easily, it’s also adhesion — but the visual test isn’t enough; snap a test piece and look at the fracture surface. A good fracture pulls material across layer lines (rough break). A bad fracture is a clean horizontal plane (layers peeling, not breaking).
Layer separation (visible horizontal gaps mid-print) is a different symptom — see the layer-separation guide.
Primary Cause: Temperature
Layer adhesion is primarily a thermal problem. Each new layer needs to briefly remelt the surface of the layer below it. If the material cools too fast — from too-aggressive fan cooling, low nozzle temp, high speed, or cold ambient — the bond is weak.
Fix sequence:
-
Raise nozzle temperature 10°C. This has the largest impact. For ABS printing at 240°C, try 250°C. For PLA at 200°C, try 210°C. Don’t exceed material limits, but most published “maximums” are conservative.
-
Reduce fan speed. For ABS/ASA: fan off completely, or 15% maximum. For PLA: 50–60% instead of 100%. Fan is the enemy of layer bonding — use only enough to prevent overhangs sagging.
-
Reduce print speed by 25%. Slower movement means the nozzle spends more time over each point, delivering more heat. Speed reduction helps even when temperature is already at the upper limit.
-
Add an enclosure. At 18°C ambient (winter room), ABS delaminates because the chamber never heats up. An enclosure holding 40°C ambient makes a larger difference than any slicer setting.
Layer Height vs. Nozzle Diameter
Layer height above 75% of nozzle diameter creates weak bonds because the bead isn’t being compressed into the layer below. At 0.4mm nozzle: maximum effective layer height is 0.3mm. At 0.6mm nozzle: 0.45mm max. Beyond these limits, layer adhesion drops sharply regardless of temperature.
Wet Filament
Moisture in the filament creates steam bubbles at the layer interface, leaving micro-voids that prevent bonding. Signs: popping or crackling sounds during printing, rough surface texture, inconsistent width of extrusion. Dry the filament (PLA 45°C/4h, PETG 65°C/6h, Nylon 80°C/12h) and test immediately.
When Temperature Fixes Don’t Work
If raising temperature past 15°C above normal doesn’t improve adhesion, the problem is mechanical — likely under-extrusion. Not enough material is being deposited per layer to create adequate contact area. Fix under-extrusion first.