Monitoring of plasma arc cutting process by cutting sound

Plasma arc cutting sound containing useful information about the cutting process has close relation with cut quality. The present paper investigates quality diagnosis method of plasma arc cutting by the cutting sound. In the present study the cut quality is divided into three types based on bottom kerf width and dross attached state. There are attached dross state (type 1), free dross state (type 2) and uncut through state (type 3). It is shown that a peak about 20 Hz appears obviously at cut quality type 2 and as cut quality becomes the type 3 the value of ∼40 kHz decreases remarkably. And influence of the emitted area of molten metal from plasma arc cutting on the cutting sound also has been revealed. At last corresponding relationship between the cutting sound and the cut quality has been discussed as cutting condition such as arc current and torch standoff height varied suddenly during the cutting process. Experimental results also suggest the possibility to make an acoustic based monitoring system for plasma arc cutting process by the cutting sound.