MAIL-multisensor assisted intelligent laser processing

Laser spot welding is widely used in production with currently over 200000 laser welding cells in use. This number is increasing by 10-20% per year. A typical application area for micro-spot welding is the assembly of micro-mechanical components and semiconductors. There are a number of advantages from using this technology as opposed to, for example, resistance, ultrasonic or friction welding: no special tools are needed; the heat applied is strictly local; it is suitable for miniature welds; and processing speed is very fast. The basic problem associated with this technology is how to attain the part per million defect level needed for the industrial application of laser spot welding in micro-mechanics and electronics. This project addresses the two most important defect sources, namely those due to position tolerances of the products and those resulting from variations in the surface conditions. MAIL project was started to improve the reliability of micro-spot laser welding through the development of a self-learning, real time feedback control system. The basic innovations in the project include: (i) an “aim and shoot” system which addresses the problem of position tolerances by recognising the joint positions and adjusting the actual laser spot position accordingly; (ii) a generic multi-sensor real time monitoring system takes care of the defects which result from the surface variations (this system contains modules for advanced pattern recognition, adaptive control based on process modelling and a self-learning neural network and real time closed loop control of the beam energy)