Experimental modeling and optimization of magnetic field assisted electrical discharge turning: Applicable for wind power turbine elements

Abstract

Electrical discharge turning (EDT) process is finding its application in machining of rotary elements that is usually difficult to be machined with conventional processes. In order to perform the process more efficient, in the present work a new modification through assistance of magnetic field with EDT process was adopted. Here, an experimental study was made to investigate effect of magnetic field assisted EDT parameters i.e. magnetic flux density, current, pulse time and spindle speed on performance measures i.e. material removal rate (MRR), overcut (OC), surface roughness (Ra), recast layer thickness (RLT) and hardness (H). Number of 30 experiments were carried out using face-centered central composite design taken into account three levels for each parameter. Empirical models were developed using regression analysis with 95% confidence level to correlate relationship between inputs and outputs. Analysis of variances was also carried out to check the adequacy of developed model and to identify which factor has greatest influence on performance measures. Finally, desirability approach function was utilized for multi-objective optimization of process taking into account maximum MRR and hardness as well minimum overcut, surface roughness and recast layer thickness. The research findings indicated that discharge current and pulse on time are most influential parameter on MRR and H; while, magnetic flux density has greatest effect on OC, Ra and RLT. Effectiveness of magnetic field assistance showed that this parameter results in 56% and 38% increase in MRR and H, respectively; also, it results in 31%, 43% and 47% reduction of overcut, surface roughness and recast layer thickness, respectively. Finally, the optimization results demonstrated that magnetic flux density of 0.4 T is an optimum value, however, upon the condition of roughing or finishing, the remaining parameter setting should can be changed.