Assist gas strategy has become a margin decision, not a process detail

For most of the fiber laser era, assist gas was a process parameter chosen from a table and rarely revisited. At current power levels it has become one of the largest controllable costs in a cutting cell, and shops are treating it accordingly.

Why consumption outruns speed

High-pressure nitrogen cutting produces an oxide-free edge by blowing molten material out of the kerf with inert gas. As power rises, the nozzle diameter and pressure needed to clear the kerf rise too, and gas flow scales with the square of nozzle diameter. Cutting speed, meanwhile, scales far more gently. The result is that a machine cutting twice as fast can easily consume more than twice the gas per hour, and the cost per part moves in the wrong direction.

Three responses

Air cutting. Compressed and filtered shop air, dried and delivered at pressure, produces a slightly oxidised edge on mild steel and a darker edge on stainless. For parts that will be painted, powder coated or hidden inside an assembly, that is often acceptable, and the gas cost falls to the price of electricity for the compressor.

On-site generation. Membrane or PSA nitrogen plants convert a volatile commodity price into a capital cost plus power. The economics depend on purity: cutting stainless to a bright edge needs high purity, and purity is expensive, while mild steel tolerates lower grades.