Influence Of The Planetary Movement Of Tool On The Aspect Ratio And The Performance Of Micro Holes Machined By Micro-USM

The times are improving and technology is developing.With the continuous development of mechanical miniaturization,the demand for micro parts in the medical,aviation,precision instruments and other industries is increasing day by day.As a result,a variety of micro processing methods such as micro-electrical discharge machining(micro-EDM),micro-electrochemical machining,lithography machining,laser processing and micro-ultrasonic machining(micro-USM)emerge to meet the needs of production.Micro-USM is of particular interest for the cutting of brittle workpiece materials such as quartz crystals and engineering ceramics.Mechanical abrasion by direct hammering of the abrasive particles against the workpiece surface of brittle-hard materials mainly achieves the purpose of removing material in Micro-USM.Micro-USM doesn't rely on the fact that the workpiece material is conductive materials and is not affected by the thermal conductivity of materials.It can also machining high aspect ratios and complex three-dimensionality cavity.As the depth of tool feed increases,the processing force increases with the tool feed,and even the tool breaks,resulting in the inability to continue processing of micro hole machining with micro-USM.This phenomenon exists in both constant force and constant speed machining.The reason for this phenomenon is that when the machining depth increases to a certain extent,there is no entry of abrasive particles at the bottom of the hole,and the abrasive particles cannot be exchanged,so that the tool directly hits the workpiece and causes the processing force to increase,eventually causing the tool to bend or even break.In order to solve the above problems,this paper proposes a new method that is applying the planetary movement of tool to micro hole drilling in micro USM.The planetary movement of tool was first proposed in EDM.It is a machining method in which a regular and periodic interpolation movement of motion axes except the main servo machining axis is coordinated with the spindle servo feed motion.In this paper,the circular movement trajectory is achieved through the two-axis linkage of the XY motion platform,that is,while the tool rotating feeds,the workpiece moves in circular trajectory movement relative to the tool relative to the tool.In micro-USM with planetary movement,the movement increases the activity space of the debris and the abrasive particles,facilitating the discharge of the debris and promoting the renewal of the abrasive particles in the machining area,which allows the tool to reach a greater depth of feed without appearing bending or breaking halfway.In this paper,the feasibility experiment was designed.The experimental results preliminarily proved that the ultrasonic machining microporous with planetary movement of tool can make the tool reach a greater depth of feed,which can improve the aspect ratio of the micro hole,and the processing efficiency has been greatly improved.After that,several groups of experiments in this paper to study the effect of planetary movement of tool on ultrasonic machining of micro holes.The experimental results show that the planetary movement of tool has the following effects on the ultrasonic micro-hole machining compared to that without planetary movement of tool: the movement can increase the aspect ratio of the micro-holes via promoting the discharge of the debris and the renewal of the abrasive particles at the bottom of the hole.The machining efficiency of machining with the movement has been greatly improved.When studying the influence of planetary movement parameters on machining efficiency,it was found that the material removal rate will increase with the increase of planetary movement speed,and sometimes it will decrease when it increases to a certain extent.The tool movement promotes the renewal of the bottom of the hole which accelerates the removal of the workpiece and tool material at the same time,thereby increasing the wear of the tool.The planetary movement has little effect on the machining gap in micro-hole machining.