| Blade is one of the key parts of aeroengine,made of titanium alloy,nickel-based superalloy and other high strength,high hardness materials.Electrochemical Machining(ECM)is often used in blade machining,but due to the existence of clearance in ECM,the flow field and electric field of blade edge machining by ECM are very complex and difficult to control,resulting in the shape and dimensional error of the machined edge,which seriously affect the aeroengine performance.Electrical Discharge Machining(EDM)is suitable for the processing of difficult cutting materials and complex shape parts.This paper adopts EDM to trim the blade edge.The machining process can be divided into two stages: rough and finishing machining.In this paper,the process parameters of rough and finish machining are optimized and the motion control system of EDM is designed.In the rough machining stage,the blade edge was removed a large amount of material.The vertical vibration assisted EDM machine was used in the experiment.Graphite as electrode material and TC4 titanium alloy and GH4169 nickel-based superalloy sheet with a size of(29×29×0.5)mm3 as workpiece material were used.A series of cutting experiments with a edge of 2mm were carried out.Based on primary experimental results,orthogonal experimental design was used to study the effects of peak current,pulse width,amplitude and frequency of vibration on material removal rate(MRR).Based on range analysis and verification experiments,the optimum processing parameters of TC4 titanium alloy are peak current of 30 A,pulse on-time of 4?s,vibration amplitude of 1.8?m,vibration frequency of 700 Hz,and MRR is up to 11.18mm3/min,The optimum processing parameters of GH4169 nickel base alloy are pulse on-time of 4?s,peak current of 30 A,vibration amplitude of 1.2?m,vibration frequency of 1200 Hz,and MRR is up to 10.86mm3/min.Compared with the previous experiment,it is found that the MRR of different materials is obviously different under their optimal electromachining parameters.In order to compare the influence of different materials on the experimental results,the investigation is carried out under the same processing parameters,and the reasons for the differences were analyzed.After rough cutting,the finishing parameter optimization experiment was carried out.Using the control variable method,the optimal machining parameters of TC4 titanium alloy were obtained as pulse on-time of 0.5 ?s,peak current of 5A,open circuit voltage of 90 V,and average surface roughness 1.356?m.The optimal machining parameters of GH4169 nickelbased superalloy are pulse on-time of 0.5?s,peak current of 10 A,open-circuit voltage of 120 V,and average surface roughness 1.43?m.A set of six-axis EDM machine was designed and developed to trim complex blade edge shape.The structure of EDM motion control system was designed and the related hardware equipment was selected.Based on Lab VIEW,the rapid positioning module,single step moving module,rough machining cutting module and forming finishing module of machine tool motion control program were programmed.After debugging on the machine,the control program of the machine tool can run accurately and stably,and realize various functions needed for machining.A post-processing program was written based on the generated tool path source file,and based on planar two-axis interpolation,a six-axis EDM interpolation program was constructed with the idea of compound interpolation based on Lab VIEW.Finally,the control system is optimized by PID adjustment. |
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