Estimation of scallop height in freeform surface CNC Machining

Abstract

Scallop height is primarily used to assess the quality of complex freeform surface parts manufactured on multi-axis computer numerical control (CNC) machines. Currently, the inspection methods used in practice are slow and expensive as they need sophisticated equipment and skilled personnel. No simulation technique seems to exist to estimate the part quality a priori. This paper reports the development of a software system to estimate the scallop heights for freeform surface machining from the CNC part programs. Two approaches have been proposed. The first one processes the CAD model of the machined component obtained from the simulation software while the second approach directly processes the CNC toolpath to generate scallop points on the surface. The scallop points generated from both approaches are analyzed to estimate scallop heights at various regions on the surface using numerical curve fitting techniques. The developed system was extensively tested for different surface types, toolpath strategies and the results from the machining trials. The system was found to be robust and accurate to estimate the part quality a priori.