# Optimization of Machining Parameters for Corner Accuracy Improvement for WEDM Processing
## 1 Introduction  
Nowadays, with the rapid development of the mechanical processing industry, the requirements for processing materials and the manufacturing industry have been continuously improved, and the demand for materials with high hardness and high strength has also increased, especially for molds and dies. For such special hard materials, the use of traditional machining methods will speed up the reduction of tool life due to its hardness and strength [1]. Special alloy tools must be used to process them; however, it will result in high machining costs. The nontraditional machining method is an alternative to process hard materials. Wire electrical discharge machining (WEDM) is one nontraditional machining method that is suitable for processing material with high hardness and high strength. WEDM is a thermoelectric process to remove material from the workpiece by using electrical discharges (sparks) to obtain complex shapes with fine accuracy and dimensions. Corner accuracy, surface roughness, and machining speed for complex cutting are the main concerns in the WEDM machining process. The machining speed is usually expressed by the material removal rate and the surface machining speed. The main factors that affect the machining speed are workpiece material, workpiece thickness, dielectric fluid, and machining parameters. The electrical conductivity and thermal conductivity of the workpiece material will also affect the machining speed of WEDM. The larger the thickness of the workpiece, the larger the machining area, which increases the surface machining speed. However, as the distance between the upper and lower guides increases, the vibration of the wire also increases, which makes the straightness of the workpieceworse. Deionized water is used as dielectric fluid which acts not only as a flushing agent to wash away the debris created during cutting but also as a semiconductor between the workpiece and wire. In addition, it will maintain the stable condition to achieve machining accuracy and cutting speed. The machining accuracy of WEDM is generally divided into shape accuracy and positioning accuracy. The shape accuracy mainly includes the corner machining accuracy and the straightness of the workpiece surface. The factors that affect these accuracies are wire vibration, machining speed, machining parameter setting, the resistance value of the dielectric fluid, etc. The straightness of the workpiece surface is mainly due to the deflection of the wire during processing, which leads to the occurrence of drum-shaped inaccuracy phenomenon, and when machining the corner part, it will also cause an overcutting phenomenon. During corner machining, the overcutting will occur at the tip of the corner if the discharge energy is too large. The positioning accuracy is the accuracy of the mechanical movement and the accuracy of the origin positioning. [PERSON] et al. [2] investigated the corner geometry error generated by roughing and finishing cuts. The errors at different corner zones were identified and related to the material removal rate (MRR) for each cut. It was concluded that a corner accuracy optimization must consider the error generated by previous cuts. [PERSON] et al. [3] used an experimental approach to investigate die corner accuracy. Various machining parameters such as pulse-on time, pulse frequency, peak current, servo voltage, and wire tension were chosen for the experiment. The results showed that the cutting parameter modification strategy gave poor results in improving corner accuracy during the presence of wire lag. In a similar experiment carried out by [PERSON] et al. [4], machine control parameters such as input voltage, wire feed, current, wire diameter, wire tension, and pulse-on/off time were taken to maximize MRR and minimize surface roughness regarding the corner cutting process. [PERSON] et al.