A study on geometrical features of electric discharge machined channels on AA6061-4%B₄C composites

Abstract

The aluminum alloy AA6061-4wt.% boron carbide (B4C) particulate metal matrix composites were fabricated by the stir casting method. The die-sinker electric discharge machining was performed to make the rectangular mini channels on these composites. The full factorial experimental design that consists of three input conditions, the current ( I), discharge duration ( T-on), and discharge idle time ( T-off) at three levels each (33 = 27 total runs), was used for experimentation. The volume, V, the taper, θ (along with the depth), the lateral overcut (along the width), and the difference in depth, Δ d (between total depth and depth up to the tapered profile) at entrance and exit cross-sectional profiles of the channel were considered as output responses. The θ, lateral overcut, and Δ d were calculated from the entrance and exit profiles which were obtained by extracting the data points of each channel with the help of an optical profile projector. The computer-aided geometric model was developed to estimate the volume. A set of optimum electric discharge machining parameter levels were identified for maximum V and a minimum of θ, lateral overcut, and Δ d. Analysis of variance was performed to identify the significant parameter and the contribution toward output responses. Results showed that the volume was found to be maximum at higher I (8 A) and lower T-On (25 µs) conditions. The taper was found to decrease with the increase in current but both lateral overcut and Δ d increased. Both I and T-On are found to be the significant parameters affecting both V and Δ d, whereas current is for θ and lateral overcut. In some cases, it was observed that there is a considerable difference in the θ and the lateral overcut values in the entrance and exit portions for the same channel. It is because of the randomly dispersed B4C particles which alter the material removal mechanism.

A comprehensive investigation on machining of composites by EDM for microfeatures and surface integrity

“…These profile curves were geometrically assembled to derive the model from which the Volume of the channel was computed. 37 The MRR (mm 3 min −1 ) is the volume of the machined channel produced for unit time.…”

“…Therefore, the full factorial experimental design was used to study the effect of EDM input parameters on various geometrical features of the machined channels. 37 But the other important output responses such as MRR, TWR, R a , and ARLT also need to be explored. Hence, MRR, Taper, TWR, R a , and ARLT are considered to be relatively important output responses in the present study.…”

“…The various MMCs were studied for machinability via several EDM invariants such as wire EDM, 22–2324252627282930 sinker EDM, 3132333435363738 ED grinding, 39 rotary EDM, 8 ultrasonic EDM, 40 powder-mixed EDM, 41, 42 magnetic field–assisted EDM, 25 hybrid EDM, 43 magnetorheological fluid–assisted EDM, 44 micro-EDM, 45 etc. It was observed that the crater size is proportional to the discharge energy with relatively less surface damage of Al-SiC composite in EDM as compared to laser machining and abrasive water-jet machining.…”