ENHANCEMENT OF SURFACE QUALITY AND STUDY ON MATERIAL REMOVAL MECHANISM IN MICRO ULTRASONIC MACHINING

摘要

Surface integrity, mechanical deformation, and thermal deformation are among the crucial error generation factors in tool-based micromachining the influence of which should be minimized. As a micromachining process, micro ultrasonic machining (micro-USM) must satisfy the above considerations. In micro-USM, material is removed by fine and free abrasive particles inside a fluid; hence, there is no direct contact between micro-tool and the workpiece. Furthermore, no thermal damage is induced into the machined surface. Therefore, this process can satisfy the requirements of minimum mechanical and thermal deformation as a tool-based micromachining process. However, usually a rather course surface with subsurface microcracks is generated by USM processes. As such, study on surface characteristics and improvement of surface quality in micro-USM is considered necessary in order to introduce this process as a mature micromachining process. In this paper, the effect of various process parameters on surface quality in micro-USM is studied. The parameters include static load, vibration amplitude, abrasive particle size, and slurry concentration. Machining experiments were conducted using a self-developed micro-USM system with the method of workpiece vibration and using a precision static load measurement system with high sampling rate. An average surface roughness as small as 24 nm was achieved through the investigations on machined surface quality which has not been reported in micro-USM process using the workpiece vibration method. Moreover, the effect of process parameters on dominant removal mechanisms is investigated.