Humping Instant

When melt velocity significantly exceeds the welding speed, the weld groove cannot be filled instantly. This causes the melt stream to deflect upwards, initiating a hump.

Humping is primarily driven by fluid dynamics and thermal instabilities within the molten pool: humping

High scanning speeds create a swelling with a large contact angle due to the competition between flow inertia (driving metal backward) and surface tension (resisting deformation). When melt velocity significantly exceeds the welding speed,

Often explained by the Rayleigh instability model , the elongated melt pool behaves like an unstable cylindrical fluid jet, where surface tension causes it to collapse into individual droplets or "humps". humping