Research On Pulse Power Supply And High-Efficient Machining In HS-WEDM Based On FPGA

High-speed reciprocating wire-cut EDM(HS-WEDM),which is self-developed by China,has been widely applied in aerospace,military industry,mold machining and other areas,and has become an indispensable technique for mechanical manufacturing and processing.It has been a perpetual pursuit for HS-WEDM to improve its efficiency.After decades of research and development,the highest cutting efficiency of HS-WEDM now is about 300 mm2/min.However,the highest practical efficiency when the process can be stably maintained for a long time is merely 150 mm2/min,and it seems that the practical efficiency is stagnating for a very long time.The premise of high-efficient machining for HSWEDM is maintaining normal discharge condition between the gap without wire electrode breakage when high energy is applied.Theoretically,with the machining energy improved,the cutting efficiency can be improved as well.However,experiments show that the machined surface could be burned when the average current is over 6.5 A.Once the surface burn takes place,an increase in the input energy could aggravate surface burn and result in a very slow or no increase in the cutting efficiency,depraving the discharge condition and deteriorating the machining stability.Thus,to solve these problems,this thesis conducted systematic experimental research based on the design of pulse power supply,protection of wire electrode,micro-topography of machined surfaces and cooling,cleaning principle of the dielectric fluid at high energy.The main work is sorted as follows:(1)Design of pulse power supply for high-efficient HS-WEDM,which is designed based on FPGA and Lab VIEW with high energy capacity.The highest machining current of the designed power is up to 20 A,providing a good experimental platform for research.(2)Design and experimental research of pulse power supply with equal width of discharge current waveform and pulse power supply with discharge current waveform slope control.In this thesis,the effects of discharge waveform on machining efficiency,quality of machined surface and wear of the wire electrode were investigated.(3)Experimental study and research of the problems occurring in high-energy machining.These problems include surface burning,low efficiency improving rate and so on.This thesis investigated the cause of these problems according to the micro-structure of machined surfaces and discharge waveform.(4)Investigating the effects of dielectric fluid on high-efficient machining and analyzing the discharge principle of HS-WEDM at high energy.Based on the results and analyses,a new type of dielectric fluid specialized for HS-WEDM capable to obtain higher cutting efficiency was developed,and relative experiment was conducted.The result showed that the stable machining efficiency was more than 330 mm2/min when the average current is 15 A,which was a big breakthrough for improving the efficiency of HS-WEDM.