Quantitative Analysis of Surface Quality for Exterior Body Panels

One of the important considerations in SMC for automotive exterior body panels is the surface quality of molded parts. Various methods have been used to judge surface waviness, including profiling with electromechanical transducers and visual methods such as interference patterns and high and low angle reflections of grid patterns. Surface profiles can be quantified, but have not proven reliable and generally useful for evaluating surfaces. Host companies still rely on visual inspection and qualitative comparisons.

We have developed a quantitative method to evaluate surface waviness based on modelling low angle grid reflections. The method gives numerical evaluations of long-term waviness in molded parts which agree well with visual methods most widely used now. Line images are viewed with a video camera, digitized and analyzed with a computer, so the method is automated and routine.