Integrated Dexels Geometric Model and Predictive Force Model for Feedrate Optimization in 03 Axis Milling Machine

Machining of sculptured surfaces engender abrupt variations in cutting forces, excessive tool deflections and undesirable vibrations and therefore poor surface finish. To reduce these problems and to have a stable machining it is more indispensable to select the appropriate cutting conditions. The aim of this paper is to propose an approach for determining the optimum feedrates along tool path during finishing of sculptured surfaces with ball end tools on 03-axis CNC milling machines using a predictive mechanistic model of cutting forces. Its steps are :1) approximation of the workpiece geometric model by dexels, 2) localization of the contact zones between tools and workpiece using machining simulation, 3) prediction of the cutting forces, 4) optimization of the feedrates and 5) updating of the machining program « G-Code ».

Impact of Coupled Whirling and Tool Geometry on Machining Dynamics

Turning dynamics is investigated using a 3D model that allows for simultaneous workpiece-tool deflections in response to the exertion of nonlinear regenerative force. The workpiece is modeled as a system of three rotors, namely, unmachined, being machined and machined, connected by a flexible shaft. Such a configuration enables the workpiece motion relative to the tool and tool motion relative to the machining surface to be three-dimensionally established as functions of spindle speed, instantaneous depth-of-cut, material removal rate and whirling. The equations of motion for the model are coupled through the nonlinear cutting force. The model is explored by considering the tool geometry. Different stages of stability for the workpiece and the tool subject to the same cutting conditions are studied.