Investigating effects of serration geometry on milling forces and chatter stability for their optimal selection

Serrated end mills are widely used in the milling processes due to several advantages they offer. Previous studies on serrated tools are limited to methods which predict mechanics and dynamics of milling process using these tools with a specific serration waveform and no comparative work has been reported for different serration geometries in selection, design or optimization of these tools. In this paper, different types of end mills with frequently used serration shapes, i.e. circular, sinusoidal and trapezoidal, are modeled parametrically. The mechanics of milling processes by using serrated end mills are modeled and experimentally verified. The effects of different waveforms on the mechanics of process are investigated where effects of phase shift direction and local cutting angles on milling forces are verified experimentally. Moreover, serration wave shapes are optimized using a Genetic algorithm for reduced milling forces where up to 30% reduction in cutting forces is achieved and the effects of cutting conditions on optimum serration wave shapes are discussed. Finally, the stability performance of the designed optimum serrated tools is compared with the standard ones, and results show that the chatter stability performance of the optimized tools is enhanced significantly.