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Delamination: layers separate

Severity: HighAffects: Filament (FDM)Updated July 27, 2026

Symptom

The part opens along the layer lines: horizontal cracks appear, and under load it splits cleanly between two layers instead of breaking the material. It is most common on tall, thin parts.

Likely causes

In order: the most frequent cause comes first.

  1. 01Nozzle temperature too low: new material does not melt the previous layer enough
  2. 02Excessive cooling: the fan solidifies the bead before it welds
  3. 03Draughts or a cold room, especially with ABS and ASA
  4. 04Damp filament, which weakens the layer bond
  5. 05Under-extrusion: less material than needed to weld the layers

How to fix it

Apply one fix at a time and reprint the same test part. Changing three settings at once tells you nothing about which one worked.

  1. 01

    Raise the nozzle temperature in ten-degree steps

    Easy

    It is the most direct fix: more heat means more fusion between the new bead and the previous one. Raise within the range the filament maker publishes and test again. If you reach the top of the range and it still delaminates, the problem is cooling or moisture.

  2. 02

    Reduce part cooling

    Easy

    On PLA the fan runs at 100 % and rarely causes trouble, but on PETG it is worth dropping to 50 %, on ABS and ASA to 30 % or less, and on polycarbonate to 20 %. Prusa publishes exactly those figures for its technical materials.

  3. 03

    Close in the environment and eliminate draughts

    Hard

    With ABS, ASA and polycarbonate an enclosure is not a luxury: it keeps the ambient temperature high and stops the previous layer being too cold when the next arrives. Remember these materials also need ventilation because of their fumes, so the enclosure should have filtering or extraction.

  4. 04

    Dry the filament and add perimeters

    Medium

    If the filament was damp, layer bonding degrades even at the right temperature. Dry it per the manufacturer's table. And for parts that will work along the vertical axis, increase the perimeter count: inter-layer strength is always the weakest aspect of an FDM part.

How to prevent it

  • —Orient the part so the main load is not perpendicular to the layers
  • —Store ABS, ASA, nylon and polycarbonate in an airtight box with desiccant
  • —Use an enclosure with filtering or extraction for technical materials
  • —Calibrate temperature with a tower for every new spool

Sources

  1. [1]Layer separation and splitting (FDM) | Prusa Knowledge BasePrusa Research · Manufacturer · accessed July 27, 2026

Related problems

HighFDM

Warping: the part lifts and its corners curl up

The part's corners and edges separate from the bed mid-print and end up curled upward. The base stops being flat and, if the lifting continues, the head eventually knocks the part loose.

HighFDM

Under-extrusion: less material comes out than it should

Material lines are missing within layers: gaps appear between beads, walls look thin and translucent, and the part breaks easily. Prusa describes it as layers missing material and fragile parts that tend to fall apart.

MediumFDM

Overheating: the part deforms on small areas

In areas where each layer is very small — points, thin towers, fine detail — the material looks melted, with rounded edges and a shiny, irregular surface. The geometry is lost and sometimes the part topples.