High-speed imaging in plasma arc cutting: a review and new developments

The aim of this paper is twofold: (i) to review all the achievements in our understanding of the phenomena related to plasma arc cutting (PAC) technology by means of high-speed camera (HSC) imaging and flow visualization techniques and (ii) to report on new studies that make use of recent and advanced instrumentation for HSC diagnostics, also highlighting some previously uncovered research subjects. In the last decade HSC imaging and flow visualization techniques have progressed considerably as a powerful qualitative diagnostic technique for investigating some of the fundamental phenomena typically occurring in PAC technology. More recently, HSC imaging has also been used to investigate pre-cut phases in PAC analysis, such as pilot arcing and piercing of mild steel and stainless steel plates with dual gas torches in various operating conditions, providing new insight into the process and highlighting some interesting plasma behaviour. HSC imaging of pilot arcing has been used to investigate the influence of the arc current, plasma pressure and swirl strength on the shape of the arc, on the type of the rotational motion of its attachment on the nozzle tip and to track trajectories and velocities of hafnium particles emitted from the electrode insert during that phase. HSC imaging can also highlight the behaviour of the arc during piercing phases and the possible presence of short non-destructive double arcing, otherwise impossible to recognize.