µ-WEDM, Nitinol, WLT, MRR, KERF, Surface roughness, hardness, RSM, PSO.

Recently, the use of nitinol as a shape memory alloy (SMA) has become significant in vital industries, such as the medical and aerospace industries, due to its distinctive characteristics of pseudoelasticity and shape memory effect. Due to its high hardness, high fracture toughness, strain hardening and issued such as rapid tool wear the use of conventional machining processes has become difficult when producing complex shapes from nitinol. Therefore, nontraditional machining processes, especially wire electro-discharge machining (WEDM) has become the dominant method of machining nitinol alloy. However, WEWD faces some challenges, especially in terms of surface integrity of the workpiece which requires an in-depth investigation. In this study, the effect of µ-WEDM process on nitinol alloy was studied. 100 µm diameter brass wire was used for the cutting in addition to a set of µ-WEDM adjustable input cutting parameters, such as peak current (Ip), servo voltage (Sv), pulse on time (Ton), and pulse off time (Toff) are selected. The experiments were designed based on L27 Taguchi orthogonal array to reduce the number of experiments. Multi-regression analysis was applied based on the surface response methodology (RSM) to determine the effect of µ-WEDM process parameters on the surface integrity of the nitinol alloy. The aim of surface integrity studies was to minimizing Kerf width variation, minimizing white layer thickness (WLT), maximizing metal removal rate (MRR), minimizing surface roughness (Ra), and minimizing µ-hardness. Optimization studies were performed using two algorithms, the gradient algorithm (GA) and the particle swarm optimization algorithm (PSO) to determine the best µ-WEDM cutting parameters set for each output parameter individually according to the target that was specified. Moreover, a combined multi-response optimization analysis was performed to find the best set of µ-WEDM process parameters to achieve the best surface integrity of the nitinol alloy sample that satisfies the goal of all output responses’ simultaneously.