Wire-EDMing Parameters Investigation and Machining Cost Analysis

1. Introduction

Wire-EDMing technology has been introduced as a very popular method regarding its ability to cut hard materials into highly accurate shape with a good surface result. The cutting process is done by sparking a wire electrode to a workpiece surface under the flooding flow of dielectric fluid. Using this non-traditional machining process can cut any electrically conductive materials precisely and accurately (El-Hofy, 2005), making it viable for various sectors of manufacturing such as aerospace, automobile, and medical applications (Petel et al., 2015).

In cutting operation, the wire electrode is moved independently along the controlled path with the aid of a computer numerical control (CNC). The sizes of wire are varied from 0.3 mm diameter down to 0.1 mm for high-precision work, and it can cut the material with the tolerance of +/-0.002 mm (Petel et al., 2015). The rapid spark happens in microseconds and it is generated between the wire electrode and workpiece. The electrical spark is in turn converted into the thermal energy causing a rapid raise of temperature of 8,000-12,000 ^oC in the sparked region. With this temperature level, most material elements are quickly vaporized to form a cut in workpiece regardless the strength of material being processed (Abulais, 2014). Wire-EDMing is also equipped with the dielectric fluid. The fluid is used for focusing the sparks into the assigned contour path (Maher et al., 2015). The reduction of workpiece temperature and flooding of cut debris are effectively attained by supplying a proper dielectric fluid during the process (Figure 1).

There are several factors affecting the performance of wire-EDM, such as wire electrode, electrical power, and dielectric fluid. Copper, brass, molybdenum and tungsten are normally utilized as the wire electrode with 0.02 mm to 0.30 mm diameter (Kapoor, et al., 2010). Kapoor et al. (2010) noted that the mechanical properties of wire electrode have the direct influences on the feasibility of the wire to be used in certain tension and vibration. This importantly affects the machining accuracy and process stability to some extent.

Figure 1.

Wire-EDM cutting process

According to Stephenson (2007a), the electrical pulse with a magnitude of 20-120 V and frequency on 5 kHz was occurred during the sparking process between the wire and work material, with 0.01 mm up to 0.15 mm gap. The system controlled the pulse through the adjustment of the on-time, off-time and amperage supplied into the wire during the cutting process. One cycle consisted of one on-time and one off-time. Moreover, the cycle time was measured in microseconds. In order to obtain the optimum performance of the wire-EDMing operation, several experiments were reported by using various methods (Table 1).