Determination of the optimal servo feed speed by thermal model during multi-pulse discharge process of WEDM

In wire electrical discharge machining (WEDM), the phenomena of wire electrode going back and hysteresis will appear when servo feed speed does not match the achievable material removal rate, and it is injurious to machining efficiency and accuracy in practical machining process. This study presents a thermal model for predicting the optimal servo feed speed during multi-pulse discharge process. Firstly, the effects of servo feed speed on the practical cutting speed and discharge state are analyzed to define the optimal servo feed speed. Additionally, based on previous thermal model and considering the latent heat of evaporation, a modified thermal model is established to obtain discharge crater size in single pulse discharge process, and this modified model is proved to be with higher precision than other thermal models in previous researches. Then, on the basis of single pulse discharge thermal model, a thermal model is developed to acquire achievable material removal rate in multi-pulse discharge process, and verified experiment data shows that the predicted achievable material removal rate agrees well with the optimal servo feed speed. Eventually, according to the results of cutting experiment under different servo feed speeds, it can be found that the optimal servo feed speed can simultaneously obtain the faster practical cutting speed and the narrower kerf width than those under the other servo feed speeds.