Product Code: ICAL06_1601

Optimisation of Production Rate in Diode Laser Hardening
Authors:
Barbara Previtali, Politecnico Di Milano; Milano Italy
Edoardo Capello, Politecnico di Milano; milan Italy
Moreno Castelnuovo, Politecnico di Milano; Milano Italy
Presented at ICALEO 2006

Thanks to the development of diode lasers, laser hardening of steels has become a stable, less expensive and reliable process if compared to CO2 laser hardening. Nevertheless, it is still characterized by a low production rate, and the time required for the hardening of a component is often not compatible with the limited cycle time imposed by the high investment costs of the laser technology. The present paper is a contribution to the definition of the optimal laser hardening conditions considering the production rate as the main goal. When the part to be treated is given, the optimization problem can be expressed in terms of minimal execution time subjected to two constraints: the depth of the treatment and the hardness of the transformed layer must be the desired ones. After the analytical expression of the objective function and of the constraints has been determined, the feasibility area was described and analyzed. Al last, an optimization algorithm was applied to identify the optimal solution as a function of the imposed constraints. Main results of the present work are: - The feasibility area of the treatment is quite narrow, process parameters must be carefully selected. - It was observed that the hardness specification constraint plays a minor role in the determination of the optimal treatment condition. On the other hand, the depth constraints is often involved in the determination of the optimal solution. - As the specification on the hardened layer is increased, also the focal height and the overlapping must be increases, while the travelling speed should be drastically reduced. - In many cases the optimal condition is in a cuspid of the feasibility area: even a small variation in the process parameters leads to a fault treatment. This implies that for achieving the maximum production rate it is better to apply a closed loop control to the process.