MODELLING AND ANALYSIS OF CHATTER MITIGATION STRATEGIES IN MILLING

Machining stability plays a major role in improving machine tool performance and product quality. Uncontrolled chatter phenomenon causes too many defects and problems in manufacturing industry such as increased surface roughness, tool wear and even machine breakdown. In this subject area, great effort has been focused on developing different mechanisms and techniques in an attempt to reduce and control the machining vibrations. Spindle speed variation is one of the common approaches that has received attention recently. Non-uniform tool geometry is an alternative method that could be used for regenerative chatter suppression. Basically these two methods focus on breaking up the regeneration of surface waves. A phenomenon known a process damping also has a vital effect on the stability improvement, particularly at low cutting speeds. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the arc surface. An alternative explanation for process damping is known with the short regenerative effect. This concept is based on the distribution of forces along the tool flank face. In the present research, a new approach based upon energy analysis is developed for more detailed interpretation of the stability of these different chatter mitigation mechanisms. Moreover, a comprehensive time domain model is developed to allow multiple effects such as variable spindle speed, process damping, loss of contact, variable helix tool and energy to be considered. Meanwhile performance of this milling model has been further benchmarked along with these effects to enable the numerical prediction to be computed more quickly with an acceptable numerical accuracy.