On-line monitoring and process control in selective laser melting and laser cutting

Real-time or on-line process monitoring and control is almost a ‘conditio sine qua non’ for many physical or chemical machining processes or so-called non-traditional or nonconventional machining. The augmented need for real-time monitoring and control in those processes, as compared to conventional (i.e. mechanical) machining, is due to the large number of process variables and disturbance factors characterizing physical and chemical processes, and to the physical or chemical nature of the process itself that is less deterministic or more variable than mechanical processes. This is why on-line monitoring and control has been developed in the past for several laser processes like laser welding and cladding. The present paper focuses on two other laser machining processes: i.e. the laser cutting and Selective Laser Melting. The paper discusses typical hardware (mainly optics) used for monitoring laser processes and gives some monitoring application examples. It also shows how such monitoring systems can be applied for adaptive feed-back control and demonstrates the performance of such control systems in improving the laser process robustness and productivity, as well as the resulting part quality.