The part breaks cleanly between layers, or visible cracks open on tall walls mid-print.
delaminationcrackingparts snap along layer lines
Ordered by how often each is actually responsible, not by how interesting it is. Work down the list.
Run a temperature tower and choose for LAYER ADHESION, not looks. The prettiest band is frequently the weakest.
Reduce the fan. On ABS/ASA turn it off entirely — cooling is the direct cause of splitting on those materials.
A cold draught across a tall ABS part splits it every time. Enclose it.
Layers cannot fuse with insufficient material. Fix flow first, then re-assess.
Calibration step: Calibrate flow ratio / extrusion multiplier →
Steam bubbles at the nozzle interrupt the bead and weaken the bond. Dry the spool.