Several established monitoring approaches are suitable for laser-based manufacturing processes, including laser welding, laser cutting, and additive manufacturing. These methods are based on the detection of various physical signals, such as acoustic, optical or thermal, using specific sensors. In case of surface treatments using ns-pulses, a high temporal resolution online monitoring approach was already introduced, for an industrial laser-based surface pre-treatment process. In this case, the infrared (IR) spectrum recorded with a diode-based monitoring system was analyzed, that permitted to identify in real-time different issues related to the stability of the process. However, any cost-efficient method, such as commercial spectrometers, have been used to monitor the ultraviolet (UV) and visible (VIS) radiations emitted during the laser-based pre-treatment process in an industrial environment.
The objective of this work is to develop a monitoring approach for laser-based surface pre-treatment of aluminum parts using an IR nanosecond pulsed laser source in an industrial setting using a commercial spectrometer. A high-speed fiber optic spectrometer with a detectivity range of 200 nm to 1100 nm is implemented in the laser system and is utilized to detect the electromagnetic radiations, which are generated by the laser pre-treatment of aluminium surfaces. Next to process parameters such as laser power and repetition rate, geometric irregularities and different initial surface states of the sample material are implemented and considered. The detected signals are analyzed with regard to their correlation to the applied process and system parameters and the resulting surface conditions.