Near-process indirect surface characterization of laser-chemically produced removal contours

Abstract

The manufacturing rate of laser chemical machining (LCM) is currently restricted to avoid disruptive boiling bubbles in the process fluid. An increase necessitates adjustments to the laser beam or fluid properties. However, the current understanding of the surface removal mechanisms is insufficient to achieve a consistent removal quality under these conditions. For an improved process modeling, in-process measurements of the surface geometry, the surface temperature and the boiling bubbles are required. Due to the complex process environment, no suitable in-process measurement technique for the geometry or surface temperature exists. This contribution presents an indirect geometry measurement approach based on confocal fluorescence microscopy that offers the potential for near-process application in the LCM process environment. As a result, the micro-geometry of different surfaces is shown to be indirectly measurable under LCM-equivalent process conditions such as thick fluid layers or gas bubbles in the beam path. Furthermore, a combined fluorescence-based measurement of geometry and temperature is proposed.