Fabrication of microchannels using rotary tool micro-USM: An experimental investigation on tool wear reduction and form accuracy improvement

Tool wear is an inevitable phenomenon and hence a prime challenge in micro-ultrasonic machining (micro-USM) process. Therefore, quantification and reduction of tool wear is essential to enhance the quality characteristics of machined microchannels. The present investigation establishes the quantitative relationships among the tool wear, form accuracy and material removal rate (MRR). This relationship is reported for the first time for rotary tool micro-USM (RTMUSM) process. An attempt has been made to understand the different types of tool wear in RTMUSM process. Later, a 2D geometrical model for the quantification of tool wear in RTMUSM process was developed. Further, the contribution of the different types of tool wear on the dimensional as well as form accuracies were evaluated. The experimental results revealed that the RTMUSM process is affected mainly by two types of tool wear (i.e. longitudinal wear and edge rounding wear). The lateral wear was revealed as negligible. It is suggested that the desired depth of channel (DOC) with best possible form accuracy of microchannels can be achieved by providing longitudinal wear compensation to the tool. The effect of process parameters such as tool rotation speed, work feed rate, power rating, slurry concentration and abrasive particle mesh size on total volumetric wear (TVW) of tool, MRR, dimensional and form accuracy of microchannels were also investigated. Additionally, the desirability approach was applied for optimization the RTMUSM process parameters for maximum MRR, DOC, form accuracy and minimum TVW and width of channel.