Research On Mechanical Technology Of Micro-parts By Micro Wedm-wecm Combined Processing

As an important technology in micro-machining,micro wire electrical discharge machining(micro-WEDM)has the advantages of high machining precision,simple tool electrode and strong application characteristics.It shows great advantages in the machining of micro-gear,micro-cutter and micro mould etc.But the WEDMed surface has the recast layer,restricting the processing surface wear resistance,corrosion resistance and service life.Micro wire electrical chemical machining(micro-WECM)has the advantages of high processing surface quality,no recast layer,but its processing precision is poor.In this paper,considering the characteristics of the above two machining processes,a method combining micro-WEDM and micro-WECM is proposed.The combined machining platform is developed to meet the in-situ fabrication of miniature parts by micro WEDM and WECM.The small reciprocating wire device is amended to solve the vibration of the electrode wire vibration problems and improve the processing accuracy and stability of the device.After replacing the relevant parts and the key institutions for anti-corrosion treatment,it can adapt to the combined processing.The 304 stainless steel with 500?m thickness is selected as workpiece.In order to explore the mechanism of WEDM,the simulation model of micro-WEDM temperature field is established.The energy distribution,heat source form and discharge channel radius in micro-WEDM process are analyzed.The temperature field distribution of discharge process is obtained by ANSYS software.Then,the effect of the pulse width and peak current on discharge pits size is analyzed.The mobile heat source is used to simulate micro-WEDM process.Considering the simulation results of the thickness of the reclaimed layer,the error of the simulation model is controlled within 10%,which indicates that the simulation is of significance for the selection of actual processing parameters.Based on the simulation results of temperature field,the micro-WEDM process and the surface microtopography are researched,and the properties of recast layer on microstructures are analyzed.The effects of open voltage,capacitance and pulse width on kerf width,recast layer thickness and material removal rate are investigated by the single factor experimental method.Based on the above results,the central composite experiment is used to optimize processing parameters with the minimum recast layer and kerf width.Compared with the matrix material,there are microcracks and stomata appearing on the recast layer,but its hardness is higher.Besides,the content of C and W on the machined surface increases obviously.The influence of different parameters on kerf width and surface quality is studied.The single factor experiment results show that the low voltage,large pulse,high feed rate and low electrolyte concentration can effectively control the spurious corrosion,and improve processing accuracy.The basic machining results show that the surface roughness after combined machining is reduced by 56.8% compared to that after micro-WEDM,and the combined machining precision is 38.2% higher than that of the electrolytic wire cutting.Finally with the combination of processing micro-array sharp corners and small splines,processing error is kept within 4?m,which verifies that the method of combining micro-WEDM and micro-WECM can achieve the fabrication of miniature part with high precision and high surface quality.