Investigation on the melt ejection and burr formation during laser fusion cutting of stainless steel

When the melt is ejected from the cut kerf by an assist gas during laser fusion cutting, a fraction of it may adhere to the lower cut edge and form a burr. Adjusting the process parameters to minimize burr formation is a challenging task that becomes more and more difficult as sheet thickness increases. The burr length has significant relevance when the quality of a cut is evaluated, but the underlying mechanisms that control its formation are still not fully understood. In this paper, new results of an experimental investigation focused on identifying characteristic melt ejection regimes are presented. The experiments were conducted on 6 mm thick stainless steel sheets using a disk laser at a power of up to 10 kW. The melt flow exiting the kerf channel and the temporal formation of burr were analyzed using two high-speed cameras. The dependency of melt ejection regimes from process parameters as well as their influence on burr formation is discussed. Furthermore, the authors demonstrate that melt ejection forming a compact and stable threefold outflow is a characteristic property of a burr free cut.