Some insights on Combined Turning-Burnishing (CoTuB) process on workpiece surface integrity

Abstract

This paper deals with a combined manufacturing process called Combined Turning-Burnishing (CoTuB) that performs turning and ball-burnishing simultaneously on the same machine tool. This innovative process aimed to enhance surface quality and integrity by exploiting rough turning conditions. Consequently, this implies an increase in productivity when compared to conventional surface treatment processes. For this reason, a device was manufactured in order to hold both commercial cutting and burnishing tools to carry out the removal material and the surface mechanical treatment processes simultaneously and under the same operation. As the design of CoTuB device sets the cutting tool ahead of the ball, turning is followed by burnishing operation along the manufactured surface. It has been depicted experimentally that a considerable improvement in surface quality could be achieved using the new combined process under suitable process parameters. Burnishing force, Ball burnishing diameter and depth of cut are independent parameters. In order to carry out a parametric process study, several experiments based on Taguchi method were performed. The aim is to identify the optimal turning/burnishing parameters when treating AISI 4140 steel. This helps to get a compromise between the optimal arithmetic surface roughness (Ra), the compressive residual stress state and the micro-hardness (μH).