Abstract
In this paper we describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by controlling the laser power. Our novel approach is to analyze the optical emission from the laser generated plasma plume above the keyhole, to calculate its electron temperature as a process-monitoring signal. Laser power has been controlled by using a quantitative relationship between the penetration depth and the plasma electron temperature. The sensor is able to correlate in real time the difference between the measured electron temperature and its reference value for the requested penetration depth. Accordingly the closed loop system adjusts the power, thus maintaining the penetration depth.
Highlights
Laser beam welding is a well established joining technique for several applications in both the aerospace [1,2] and automotive industries [3,4,5], by using different traditional sources, such as CO2 orNd:YAG lasers
We describe a novel spectroscopic closed loop control system capable of stabilizing the penetration depth during laser welding processes by using the laser power as the control variable
In particular we have investigated how rapidly any perturbation of the incident laser power induces an appreciable change of both the penetration depth and the plasma electron temperature and, correspondingly, how fast is the response of the designed control system
Summary
Laser beam welding is a well established joining technique for several applications in both the aerospace [1,2] and automotive industries [3,4,5], by using different traditional sources, such as CO2 orNd:YAG lasers. The influence of the process parameters, including laser power, welding speed, focal point position, nozzle configuration and protection gas flow on the weld quality has been explored in recent papers by using, for example, post-process analysis of local deformation during tensile tests [8]. A lot of studies have been focused on monitoring of quality of the welded joints Most of these methods rely on photodiode-based systems that acquire and analyze the electromagnetic emissions generated during the interaction of the laser beam with the materials [12,13]. Optical sensors based on fast spectrometers have the further advantage of providing a detailed analysis of the emission spectrum over a wide wavelength range
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
