Research On Processing Technics Of Magnetic Field Assisted WEDM Cutting Of Ferromagnetic Material

Wire Electrical Discharge Machining(WEDM)has the characteristics of high accuracy,no macroscopic cutting force,good surface quality and machinable complex surface parts.It can be used to process any conductive material and it is widely used in the field of precision parts processing.However,the machining efficiency of WEDM is low compared with the traditional machining.Magnetic field assist can effectively improve the efficiency and quality of Electric Discharge Machining(EDM).But previous researches about magnetic-assisted technique mainly focus on EDM for ferromagnetic or nonmagnetic material,and WEDM for nonmagnetic material.there is no research about magnetic assisted machining ferromagnetic material in WEDM.In this context,in order to improve the efficiency of processing of ferromagnetic materials by WEDM,the processing of ferromagnetic materials by magnetic field assisted WEDM is researched in this thesis.First,the mechanism of magnetic field assisted WEDM is analyzed.Theoretical study of the influence of additional magnetic field on discharge channel,dielectric and the wire tool are implemented.The influence of the uniform magnetic field on the magnetic field distribution of the ferromagnetic material and the influence on the movement trajectory of the charged debris are analyzed theoretically.The influence of the auxiliary magnetic field intensity on the molten pool and the crater during the single pulse discharge is studied by the magnetic field assisted single pulse discharge experiment.Through Taguchi experimental design,the influence of pulse-on time,pulse-off time,servo voltage,wire speed and auxiliary magnetic field intensity on material removal rate(MRR)and surface roughness(Ra)in magnetic-assisted finish cutting SKD11 are analyzed by signal-to-noise ratio analysis(SNR).The influence of the processing parameters on the material removal rate and the surface roughness is obtained.The results can provide reference for practical processing.Through the single factor experiment,the influence of the auxiliary magnetic field intensity on the deformation of WEDM machined acute angular thin-walled workpiece is studied.The mechanism of the auxiliary magnetic field to restraining the deformation and improving geometric accuracy of the process is analyzed.Taguchi experimental design and main effect analysis have been applied to get the effects of processing parameters on the tip deformation of acute angle.And a set of machining parameters with small deformation is obtained.On the basis of experimental research,the process parameters optimization of the material removal rate(MRR)and surface roughness(Ra)of magnetic-assisted finish cutting SKD11 in WEDM are carried out.The generalized regression models of MRR and Ra are established.The optimal Pareto frontier solution set is obtained by NSGA-II multi-objective optimization algorithm.The accuracy of the regression models and the effectiveness of the optimization algorithm are verified by experiments.