Machining of microholes in Ti-6Al-4V by hybrid electro-discharge machining process

In this work, efforts are made to optimize the machining of micro-holes using EDM and explore the mitigation of debris accumulation in the sparking region. The work tries to implement a hybrid process involving a sequence of two methods; the first uses a low-frequency vibration platform with added dielectric particles and the second with a flushing technique using a convergent nozzle. The experimental design is formed using an L9 orthogonal array with three input parameters namely input current (I-p), pulse on time (T-on), and pulse off time (T-off). The output responses are material removal rate (MRR), tool wear rate (TWR), diametrical accuracy (DA), and surface roughness (SR). The multi response optimization GRA is used to find the optimum machining parameters. Thus obtained optimum parameters of I-p = 4A, T-on = 5.2 mu s, and T-off = 14.4 mu s is used for experimentation in low-frequency vibratory set-up. The results showed 127% improvement in MRR and 45.3% reduction in surface roughness. On analyzing further, it is found that 41.7% of carbonaceous and 6.28% of Ti particles are deposited over the machined electrodes, which resulted concomitant increase in electrode weight and it further hindered predicting the TWR. In the second method, the pressure drops inside the hole and its significance in removing the debris particles is mathematically modeled and validated using the fluid flow simulations. The simulations are modeled by causing a fluid flow at a velocity 10 m/s and 15 m/s through a convergent nozzle stationed near and far from the hole region. Simulation for nozzle with fluid flow velocity of 10 m/s and located far from the hole showed pressure variation ranging from 1.3 x 10(3) to - 5.4 x 10(3) pa in the hole region. This result validates the proposed analytical model and confirms the generation of suction pressure, P-s in the hole which can enhance flushing effect.