Abstract
Chatter is a harmful machining vibration that occurs between the workpiece and the cutting tool, usually resulting in irregular flaw streaks on the finished surface and severe tool wear. Stability lobe diagrams could predict chatter by providing graphical representations of the stable combinations of the axial depth of the cut and spindle speed. In this article, the analytical model of a spindle system is constructed, including a Timoshenko beam rotating shaft model and double sets of angular contact ball bearings with 5 degrees of freedom. Then, the stability lobe diagram of the model is developed according to its dynamic properties. The Monte Carlo method is applied to analyse the bearing preload influence on the system stability with uncertainty taken into account.
Highlights
The dynamics of spindle system plays a crucial role in machining processes
The vibrations are usually classified into two types according to their sources: forced vibrations induced by periodic varying cutting loads and self-excited chatter vibrations caused by the variation in chips thickness, which is the result of dynamic cutting forces and in turn modulates the cutting force.[1]
The estimation of the true values of these key parameters of the system is challenging, because approximation or uncertainty errors always exist in studies of dynamic engineering systems
Summary
The dynamics of spindle system plays a crucial role in machining processes. Vibrations between the workpiece and the cutting tool may cause degradations of machining accuracy and surface processing quality. The vibrations are usually classified into two types according to their sources: forced vibrations induced by periodic varying cutting loads and self-excited chatter vibrations caused by the variation in chips thickness, which is the result of dynamic cutting forces and in turn modulates the cutting force.[1]. Combined with the effects of these vibrations, if the spindle-tool-workpiece system works in unstable state, the cutting force may grow very large until the tool cracks. It is well known that the onset of chatter is bound up with the process parameters, such as spindle speed, depth of cut;[2,3] by keeping these parameters below certain limits, unstable cutting vibrations can be avoided
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