Quality optimisation for laser machining under transient conditions

Quality improvements in laser machining have been achieved by a newly developed model-based optimisation strategy. The speci®c aims of such efforts are to assure machining quality right up to boundaries or pre-machined sections, which are inherent in intricate part geometry. Such boundaries frustrate heat-transfer and result in bulk heating of the workpiece. This in turn leads to a degradation of the machining quality. In order to achieve such optimisation, transient heat-transfer is modeled. Close inspection of the laser±workpiece interaction zone reveals that the machining front exhibits dynamic behaviour, and such mobility plays a signi®cant role in temperature determination. Non-linear parameter adaption pro®les are generated via the optimisation strategy in order to stabilise the machining front temperatures. Currently, trial-and-error based experimentation is needed in order to improve machining quality in such regions. Thus model-based optimisation has the added bene®t of reducing this step whilst leading to an optimal solution. Experimental results are presented and it is demonstrated that such process manipulation can lead to signi®cant quality improvements. # 2000 Elsevier Science S.A. All rights reserved.