Analyse und Vorhersage der Prozessdynamik und Prozessstabilität beim Hochgeschwindigkeitsfräsen

(Analysis and Prediction of Process Dynamics and Process Stability in the High-Speed-Milling Process)

Kalveram, M.

Modern production processes like high speed milling enable a significant increase of cutting speed and feed rate whereby an increase in productivity can be reached. But often a machine tool’s usable range of performance is limited by the dynamic behaviour. An exact process design, optimised regarding process dynamics, is an essential condition to guarantee a stable, chatter free machining.

The theoretical stability prediction is a suitable and efficient method to determine stable parameter ranges prior to the actual machining. Recently developed alternative prediction methods enable to consider the instability of Flip-Bifurcation in addition to Hopf-Bifurcation, which occurs with the decrease of radial depth of cut.

In this research work the semi-discretisation-method is used for the first time, applied to the milling process and finally experimentally verified by using different milling strategies and radial immersion variations. Another focus of this work lies in the experimental determination of system parameters to aim at a high quality stability prediction. A method is developed which enables to determine semi-empirical the specific cutting force coefficients for different cutter geometries. The determination of modal parameters is based on experimentally determined transfer functions of the cutter – spindle – machine tool system both at zero and operating spindle speed.

This research work proves the semi-discretisation-method’s validity independently of radial depth of cut thus its universally valid character for the prediction of process stability in high-speed-milling processes. Furthermore, options are provided to modify the stability boundary with specific changes of system parameters in such a way that within a technologically or economically adequate process window a stable, chatter free cutting process can be guaranteed. The methods and results presented in this work show that the significance of process dynamics for the design of a machining process can be a decisive condition to use modern machines’ potential to full capacity.

Published as

Dissertation Universität Dortmund, Vulkan Verlag, Essen, 2005, ISBN 3-8027-8729-3, 978-3-8027-8729-4