Surface Finish of Stainless Mold Steel Using Vibration-Assisted Ball Polishing Process

An ultrasonic vibration-assisted ball polishing process has been developed on a 3-axis CNC machining center to improve the surface roughness of the stainless mold steel can and to reduce the volumetric wear of the polishing ball in this study. The Taguchi-based experiments has been designed and carried out to determine the suitable ball burnishing and ultrasonic vibration-assisted spherical polishing parameters, respectively. The effectiveness of the proposed combination of the ultrasonic polishing parameters has been justified by the verification experimental results. The optimal ultrasonic vibration-assisted polishing parameters were as follows: the amplitude of 10μm, the frequency of 23 KHz, the spindle speed of 5,000 rpm, the abrasive diameter of 0.3 μm, the feed rate of 60 mm/min, the stepover of 20 μm, the depth of penetration of 180 μm, the abrasive concentration of 1:10, based on the experimental results. The surface roughness of the polished test specimens could be improved from the burnished surface roughness Ra 0.122μm to Ra 0.022μm. The improvement of the volumetric wear of the polishing ball was about 62.5 % using the vibration-assisted polishing process compared with the non-vibrated polishing process.