Development Of Edm Pulse Power For Machining ZrB₂-SiC Ceramic And Experimental Research

In recent years,ceramic ZrB₂-SiC has the bright future to be used to fabricate hot end components for hypersonic weapons and aircraft engine,due to its high melting point,low density,and excellent capability of resisting to thermal shock.Generally these components are fabricated using an approach of powder-sintering.Subsequent processes need to be introduced for further i mproving its geometric precision.However,ZrB₂-SiC has characters of high toughness and brittleness,which poses a huge challenge for traditional machining methods.Comparing to the untraditional machining methods,Electrical discharged machining（EDM）has prominent advantages high geometrical precision,because this method can achieve non-contact machining and has no limitation on the toughness and brittleness.Pulse power supply is a key factor for the perfo rmance.the objective of this work is to develop a pulse power supply,and carry out fundamental experimental investigation,based on this device.The specific details are as follows:A pulse power supply was developed,based on FPGA and VHDL.This power supply consists of FPGA main circuit,MOSFET main circuit,and inspection circuit for gap discharge.Series received code,parameter selection code,and pulse generation code was programmed based on VHDL.Combing hardware circuit and software programs,this pulse power can achieve four pulse waveforms those are identical voltage pulse,identical current pulse,comb ining pulse and plus and negative pulse waveforms,respectively.Secondly,a method of combining compative,threthold and the delay after break down was proposed to distinguish the open circuit,discharging,stable arc,and short circuit.To improve the discharging status and performance of EDM,a method of combining clean pulse and the cut off of short circuit was also proposed to avoid arc and short circuit.Furthermore,comparison tests were conducted to verify the feasability and validity of this pulse power.The results were shown as follows: the combination between clean pulse and the cut off for short circuit can effectively improve the performance for EDM of ZrB₂-SiC.Furthermore,the identical current pulse can achieve a best productivity,and desirable surface roughness and the lateral gap of hole.Finally,a fundamental experimental investigation was carried out to explore the performance for EDM of ZrB₂-SiC using the pulse power.In this investigation,signal-factor experiment was designed.The polarity of electrode,peak current,pulse duration,pulse interval,servo voltage,and the diameter of el ectrode were selected as experimental factors.The machining speed,lateral discharge gap,and surface toughness of hole were determined as responses.