Penetration Detection And Experiments Of EDM & ECM Hybrid Machining For Micro-hole

EDM & ECM hybrid machining for micro-holes combines two processes of EDM and ECM in a single hole’s machining and is a kind of innovative nontraditional machining method with high efficiency,good machining accuracy and almost without recast layer. It is expected to be used in manufacturing of film cooling hole of turbine blades in the future. Turbine blade is a kind of hollow parts with cold runner structure inside, which are only a few millimeters thick. Mistaken machining of structures in turbine blades will be performed when penetration length of tool electrode out of the workpiece is too long, resulting in scrap of workpiece. As a result, it is necessary to do a research on penetration detection of EDM & ECM hybrid machining.The theory of judgement for penetration detection of EDM & ECM hybrid machining has been researched in this paper and criteria of penetration based on voltage and current has been obtained. A platform for penetration detection of hybrid machining has been established with a DAQ card, PC and software of LabVIEW. Experiments of penetration detection on the platform have been conducted, which lead to a result of good consistency. The effect of parameters of the platform to machining quality of micro-holes has been evaluated. The detail tasks are as follows:(1)Theory of penetration detection of EDM & ECM hybrid machining has been analyzed. Flow field simulation with three kinds has been carried out by using flow field software of finite element method which showed the interior flushing is the best for EDM & ECM hybrid machining. Then experiments for wave shape evaluation of EDM & ECM hybrid machining have been conducted where the different performances of EDM effect and ECM effect were showed. Different performances of EDM effect and ECM effect have been analyzed during penetration under two kinds of hybrid machining(with and without insulating substrate on the back of the workpiece). The theory of judgement for penetration detection of EDM & ECM hybrid machining was proposed at the end.(2) Platform for penetration detection of EDM & ECM hybrid machining has been established. Platform for penetration detection of EDM & ECM hybrid machining has been established with DAQ card and PC as hardware and with LabVIEW as software. Data of voltage and current while machining can be acquired on the platform. Also, the platform can do analysis and criteria of status of penetration and output the signal of penetration to stop spindle from feeding based on program written with LabVIEW. The platform was designed to ensure the function of realization of penetration detection.(3)Experiments of penetration detection for EDM & ECM hybrid machining have been done on the platform. With two kinds of hybrid machining, with and without insulating substrate on the back of the workpiece, experiments of penetration detection of hybrid machining have been conducted and good detection consistency has been received. Influences of penetration delay and pause after feed have been analyzed to evaluate the length of penetration, tapper of micro-hole, pattern of orifice and residue of recast layer. Also, machining effect has been analyzed both with and without penetration detection. The results showed the positive effects of penetration detection for EDM & ECM hybrid machining, such as increased stability and quality of this hybrid machining.