Research On EDM Trimming Technology Of The Edges Of Aeroengine Blade

As one of the core components of aeroengine,the blades are made of nickel-based superalloy and titanium alloy with high strength,high temperature resistance and corrosion resistance.For this kind of hard to machine metal,the common machining methods are precision forging,precision casting,CNC milling and electrochemical machining(ECM).In these methods,however,the leading and trailing edges of blade cannot reach the design accuracy.Nowadays,ECM is widely used in blade machining at home and abroad.However,the flow field and electric field in the gap of ECM are very complex,which results in dimensional and shape errors of leading and trailing edges of blade.Therefore,it must be precisely trimmed to meet the design requirements.Electrical discharge machining(EDM)relies on the high temperature generated in the discharge channel to melt the material,which is independent of the hardness and strength of the material.In this paper,vibration-assisted EDM is used to correct those errors.First of all,according to the experimental requirements,this paper participated in the transformation of vertical EDM machine tools,and built auxiliary equipment such as piezoelectric ceramic actuator clamping module,electrode clamp,workpiece clamp,flushing module and developed the relevant technological process based on the built experimental platform.The control program is improved based on LabVIEW.For the selection of EDM parameters of hard to machine metals such as nickel-based superalloy,firstly,the machining area and polarity are selected,and the machining is divided into two steps:rough and finish.In rough machining,the processing parameters of GH4169 and GH3600 nickel-based superalloys were compared by orthogonal experiment,and the parameters were optimized by material removal rate.It is found that the pulse width plays a significant role in material removal rate and tool electrode wear rate when the nickel base superalloy GH3600 is processed by graphite electrode.The material removal rate of the optimal parameters can reach 12.99mm~3/min.For the nickel-based superalloy GH4169 used in aeroengine,the effect of peak current and pulse width on the material removal rate is significant.The material removal rate achieved by the optimal parameters is 10.01mm~3/min,and the electrical machining performance of GH4169 is lower than that of GH3600.In order to improve the processing performance of GH4169,brass electrode is used.The experimental results show that the material removal rate is increased by 1-2mm~3/min,which has achieved remarkable results.In finish machining,the influence of peak current,pulse width and open circuit voltage on surface roughness are mainly considered,and the method to remove the residual accurately is proposed.By comparing the coordinates of three points before and after machining,we can judge the amount of residual removed.According to the roughing machining scheme,the feeding distance of finishing is 15μm.The experimental results show that with the decrease of peak current,the surface roughness of the workpiece decreases,but when it decreases to 5A,the machining fails.With the decrease of pulse width,the surface roughness also decreases.When the open circuit voltage of 120V is used,the surface roughness is smaller.The minimum surface roughness is 1.1μm.