Prediction of Machined Surface Geometry Based on Analytical Modelling of Ball-end Milling

This article presents a surface reconstruction model based on a methodology developed for the prediction of cutting forces in free-form milling. From global and local geometry of the tool, initial surface and tool path, this approach allows us to predict cutting forces and now surface form and roughness directly from CAM data. Good results were observed even for complex ball-end milling operations and the idea is to make benefit from the fine geometrical description developed for tool-workpiece engagement calculation to deduce the resultant cut surface. The principle is firstly to store the calculation points coming from the discretization of the cutting tool and identified as engaged in the workpiece material. The second step is to consider a regular grid in plane (X,Y) and to keep the lower points in each created column in order to obtain a Z-Map surface. The procedure of point's determination, recording and filtering is presented. Moreover, some results are discussed and compared to metrological data.The conducted milling tests concern a wavelike form with or without transverse inclination produced with a tungsten carbide ball end mill. The experimental device was mainly composed of classical 3-axes milling machine, a 4 components dynamometer and a dedicated clamping plate. The dynamometer is useful to validate the cutting forces calculation, but in this work, the main interest is to check the stability of the test by observation of forces and frequency responses. The measurements of surface form and roughness were made on a 3D profilometer. This system acquires patches of local micro-topography and allows reconstructing and analyzing several successive tool tracks.