Research On Micro-wedm Machining Complex Rotary Structures

Micro wire electro discharge machining (Micro-WEDM) is a micro machiningtechnique, featuring high efficiency, high precision and flexibility. Because of itsphysical non-contact between the workpiece and the tool, this technique is unrestrictedto the physical characteristics of the workpiece and can process many kinds of materials.Micro-WEDM has brilliantly developable prospects on machining Micro/Meso metalcomponents, micro tools and micro dies with partial micro structures. This project willexpand the category of traditional narrow slot and narrow groove manufacturing,explore micro-WEDM machining micro rotary workpieces and examine problems aboutaccuracy and stability induced by miniaturization of the wire electrode and the rotationof the workpiece. The final goal is to realize controllable manufacturing complex rotarymicro structures with low cost and high precision.The author set up a hardware system for rotary structure manufacturing on thebasis of analyzing the process of machining rotary structures by micro-WEDM, whichcan accomplish block electro discharge grinding (BEDG) and machining rotaryworkpieces by micro-WEDM on the same machine tool. Based on this system,fundamental experiments of machining rotary grooves and columns are conducted. Theinfluences of electrical parameters, the tension of the wire, feed rate and rotationalspeed of the workpiece on the width of the rotary grooves are discussed. Moreover, theinfluences of feed rate and rotational speed on the material removal rate (MRR) andsurface quality of the columns machined by micro-WEDM are also investigated.This paper introduces multiplicity cutting into rotary structure machining andvalidate that this technique can manufacture simple columns and complex rotary surface.In addition, this paper focuses on the final finishing process in multiplicity cutting andcarry out the research about machining rotary structures at low voltage and machiningwith reversed polarity. With the help of scanning electron microscopy (SEM) and laserscanning confocal microscope (LSCM), the machined surface topography and surfaceroughness are characterised and measured. Also, MRR of different finishing processesare compared. Simultaneously, the phenomenon that current servo and inspectingsystem and wire stability restrict machining at the low voltage is also analyzed.Based on the previous fundamental studies, two typical rotary structures, microball-ended probe and rotary sharp corner, are fabricated with high controllability, onlyusing two steps, roughing and finishing. Different flushing strategies and the effect ofthe wire feed rate on the machined surface quality of ball-ended probe are discussedrespectively. Finally, a ball head with97.6μm in diameter is manufactured and thesurface is almost free from flaw. In addition, through the experiments, a properrotational speed of5000r/min and a offset distance of the wire7μm for roughing of the rotary sharp corner are obtained. When the tension of the wire is set to2N duringfinishing,1μm in radius of rounded corner can be got. Moreover, a rotary structure withcomplicated curved surface and a1.9-millimetre corrugatedpipe core mold with largeratio of length to diameter are fabricated, which reveals this technique has a wideapplicability.