EXPERIMENTAL INVESTIGATION OF SURFACE ROUGHNESS IN CYLINDRICAL WIRE ELECTRO DISCHARGE MACHINING (CWEDM)

摘要

In this paper the effects of machining parameters on the surface roughness (Ra) in cylindrical wire electro discharge machining (CWEDM) are investigated. CWEDM is a new technology in which a rotary axis is added to a usual Wire EDM machine. In this process, a new machining parameter, such as rotational speed, is introduced, which changes the normal machining conditions in conventional wire electrical discharge machining (WEDM). Current paper investigates the effects of main parameters of CWEDM including power, voltage, pulse-off time, rotation speed of rotary axis and form factor (cone angle) on the surface roughness in CWEDM. This has been done by means of the technique of design of experiments (DOE); the three levels fractional factorial method (3~(k-p)) was used for studying the selected factors which allows us to carry out the above-mentioned analysis performing a relatively small number of experiments. Analysis of Variance (ANOVA) has been used to determine significant factors; also an equation based on data regression has been presented. Results from ANOVA show that power is a significant variable to surface roughness of cylindrical wire-EDMed AISI D3 cold worked steel parts. The surface roughness of test specimen increased as power and voltage increased and pulse off time and rotation speed decreased. Surfaces of the cylindrical WEDM parts were examined using Scanning Electron Microscopy (SEM) to identify the macro-ridges and craters on the surface. Cross-sections of the EDM parts are examined using the SEM to quantify the sub-surface recast layers and heat-affected zones under various process parameters and to determine their relation with surface roughness of parts.