a method for machine processing , in particular for machine welding processing of workpieces , in particular of plate - like workpieces , tubes and / or profiles , by means of a thermal processing beam , in particular by means of a processing beam is described , wherein the processing of the workpiece is carried out with a relative movement between the processing beam and the workpiece , wherein a process gas is fed to a processing zone in a settable quantity of process gas per unit of time . after a stored stabilization time , in which the processing of a workpiece is continued with a relative movement between the processing beam and the workpiece , a quantity of process gas per unit of time is automatically reduced . further a control apparatus of a setting device for process gas feed according to such a method is described .