Process control systems in laser materials processing

To obtain on-line information about the cutting and welding processes, optical sensors are integrated into the working head of a high-power CO2 laser machining system. In order to detect the dynamic light or plasma intensity fluctuation during cutting and welding, these sensors provide the real-time signal of the metal vapour and plasma flame intensity in the wavelength range 200–1100nm. Simultaneously, the real-time intensity of the laser power is measured with a pyroelectric sensor. The aim is to analyse the transfer function of each process. With the knowledge of the transformation characteristics of the specific process, a closed-loop control is set up. Distinguishing between CW and pulsed processes, different control algorithms have been developed and tested. A control system based on microcontroller hardware and its theoretical background for failure detection are described.