Machining forces in ultrasonic-vibration assisted end milling

Ultrasonic assisted milling (UAM) is one of the advancements in the area of conventional milling process. Literature suggests that superpositioning of ultrasonic vibration with milling process improves its efficacy by reducing forces and improving surface finish. In the present study experimental investigations were carried out to evaluate the effect of process parameters (power of ultrasonic vibration (UP), rotational speed, axial depth of cut (DOC) and feed rate) on the cutting responses (average cutting force and the standard deviation in cutting forces). An experimental setup was designed and developed to perform UAM process with axial vibrations. The end mill used in this setup was designed by performing harmonic analysis on ANSYS workbench. UAM experiments based on central composite design (CCD) technique were performed on Al6063 aluminum alloy. Analysis of variance (ANOVA) was performed and regression equations were obtained. Further, the obtained results were analyzed to study the effect of machining parameters on the responses. The developed models were then validated by performing experiments on random and optimized set of process parameters. The ANOVA results suggested that the most effective parameter for cutting forces was feed rate, however its standard deviation was affected by rotational speed. Also the assistance of axial vibration reduced the average cutting force and increased its standard deviation. In order to evaluate the effect of axial ultrasonic vibrations, simulations were performed to study the cutting kinematics in UAM process. The simulations showed that the presence of torsional vibration at the cutting tip, caused intermittent cutting during UAM.