Effect of tool design parameters study in micro rotary ultrasonic machining process

Abstract

Selection of tooling to perform specific operations like drilling and milling on ceramic materials using rotary ultrasonic machining process is an important aspect to meet stringent dimensions on workpiece as well as intended performance of tool. This phenomenon is more critical for micro rotary ultrasonic machining. In the present study, an effort was made to do micro drilling operation of O0.3 mm tool with varying geometry, having different wall thicknesses and abrasive grain sizes using design of experiments. The effect of tool-based parameters like grain size and wall thickness has been studied on axial cutting force, radial cutting force, tool wear, edge chipping area and taper. After examining axial and radial cutting forces, it has been concluded that lower wall thickness (80 μm) tool is good for drilling operation; and higher wall thickness (100 μm) tool is good for milling operation under same material removal rate conditions. It has been also investigated that lower wall thickness (80 μm) tool has less edge chipping area and less taper and can impart high drilling depth as compared to higher wall thickness (100 and 150 μm) tool. It is also concluded that lesser grain size (15 μm) tools are advantageous in terms of edge chipping area and cutting force for drilling and milling operations as compared to higher grain size (30, 35 and 45 μm) tool at constant material removal rate. Higher grain size tools have been broken at 1.13 mm3/h material removal rate conditions due to bad profile accuracy. But higher grain size tools have worked fairly well at less material removal rate condition. Higher grain size tools produced less wear. Tool wear was found minimum in higher wall thickness (100 μm) tool having higher abrasive grain size (30 μm). Using inferred results, O0.3 mm drilling experiments have been carried out on six aerospace ceramic materials. Also, groove of 0.5 mm size using O0.3 mm optimised tool has been successfully carried out in sintered SiC.