Layer adhesion is how strongly each printed layer bonds to the one below it. It is usually the weakest point of an FDM part: prints break along layer lines because layers are bonded, not fused.
What improves layer adhesion
- Temperature: hotter nozzle = better melt bonding (within the material's range)
- Less cooling: high fan speeds weaken bonds (PETG/ABS need low fan)
- Dry filament: moisture causes steam bubbles that break bonds
- Wider extrusion: larger layer width increases contact area
- Orientation: Z-direction parts are weakest — design to load X/Y
How to test it
The snap test: print a thin coupon and bend it — brittle snap along layer lines means weak adhesion (often wet filament or too much cooling). VOXFIL publishes layer-bond-relevant data (drying, cooling) on every material page.