Topography simulation of free-form surface ball-end milling through partial discretization of linearised toolpaths

Abstract

Free-form surfaces are commonly present in several engineering components, from molds to more sophisticated components of aeronautical engines. These parts are usually finished by machining, more specifically, ball-end milling. In this process, the contact between the tool and the part constantly changes along the toolpath, resulting in several manufacturing problems that damage the surface and compromise the performance of the part. Besides the ordinary cutting parameters, these machined surfaces are deeply influenced by the tool tip center and the elastoplastic deformation of the material through the shearing and plowing pair. Knowing the exact orientation of the tool in relation to the surface determines all aspects of the milling process and is necessary for process modeling. The current CAD/CAM software platforms is not able to predict such surface topography. In this direction, the current work presents a software routine developed and implemented on an open interface CAD/CAM software (Siemens® NX). The normal vectors of the surface to be machined, the cutter contact (CC), and cutting location (CL) data from the toolpath calculated by the CAD/CAM were used to obtain a complete discretization of the cutter-workpiece position along the toolpath. This information was used to predict the surface topography and identify the cutting-edge elements. Then, the developed model was used to evaluate the free-form surface of a blade milled on 5-axis together with confocal imaging analysis. The results show that the methodology developed can predict the topography aspects of a free-form machined surface and support the analysis of milling problems such as run-out.