Research On Electrical Discharge Milling (ED Milling) Process Of Tungsten Carbide For Micro Lens Molds

The process of micro molds made of ultra-hard material tungsten carbide is a big challenge in the field of mechanical machining.Electrical discharge machining is characterized with materials processing of unlimited hardness,non-contacting machining and without macroscopic force.It has a greater advantage in optical mold manufacturing,especially when it comes to micro lens molds of difficult-to-cut materials.Therefore,EDM has become a promising way to fabricate micro lens molds of ultra-hard materials.However,there are some limitations in EDM technology,such as high surface roughness and low machining efficiency.This paper aims to analyze ED milling technology to machine micro lens molds of tungsten carbide.Firstly,the basic processing technology of ED milling is studied for tungsten carbide,and the machining parameters are optimized,which provides a selective criteria for machining lens molds.Then,the tilt ED milling method is established based on electromagnetic effect to process lens molds.Meanwhile,the surface defect of the mold is analyzed.The micro convexity elimination method is built on the basis of boundary layer theory,and the fluid state of discharge gap is simulated in the model of ED milling by spherical electrode.1.The influences of the parameters such as electrical parameters(gap voltage,peak current,pulse width),nonelectrical parameters(spindle speed)and electrode shape(ball endmill,spherical and hemispherical electrodes)on the material removal rate,surface roughness and the electrode wear rate were analyzed through the ED milling experiment for tungsten carbide by using copper tungsten electrode.It should be used with small discharge enery in micro scale machining,which means a smaller gap voltage,peak current and pulse width,and the electrode spindle speed is selected in a certain range.Utilizing spherical electrode to machine lens mold to ensure the machining accuracy of the mold.2.Through theoretical analysis of ED milling model,the processing mechanism by spherical electrode is studied.At the same time,the surface defects of the lens mold after machining are analyzed,and the forming mechanism is established according to minimum energy principle.The micro convexity elimination method is built on the basis of boundary layer theory,and the fluid state of discharge gap is simulated in the model of ED milling by spherical electrode.3.According to the tilt ED milling experiments,the tilt ED milling method is established based on electromagnetic effect to process lens molds.The experiment of tilt angles was conducted to investigate the influence on the workpiece surface roughness and material removal rate.Tilt ED milling quality optimization method was built considering the two indicators such as the surface roughness and machining efficiency.