Closed-loop quality control system for laser chemical machining in metal micro-production

Abstract

Small geometrical features in the scale of 10 to 400 μm can be produced on metallic workpieces with the laser-induced chemical etching process at low costs. However, the interactions among the subsystems of the laser chemical etching process, the mechanical positioning unit, the etchant pump, the laser source, and among the removal paths hinder the precise determination of the required process parameters for producing the desired geometry. For this reason, a closed-loop quality control is designed to compensate the deviations of quality features of a single removal and also of a workpiece produced by a sequence of removals. The developed control approach is based on inverse process models, which are used for a feed-forward control. Finally, a closed-loop control is achieved by designing an adaptive controller for the non-linear multi-inputs-multi-outputs process. The closed-loop control is realized as a production-discrete control by using a post-production measurement, and applied for producing a micro forming tool in the shape of a rectangular die. As a result, the laser chemical etching process is stabilized and, thus, the desired geometrical quality features of the workpiece are obtained with a reduced shape deviation of 2.4 μm.