Natural fiber composites have attracted global attention due to their lightweight, low-carbon footprint characteristics as well as good mechanical properties. Due to these distinct advantages, the application spectrum of these composites has grown at an unprecedented rate. These composites are used for making a wide variety of sophisticated engineering products; therefore, certain degree of machining operations is necessary for assembly purposes. Drilling is an indispensable machining operation that is frequently performed for making of holes to facilitate assembly of several components into an intricate part. In the present research endeavor, the drilling behavior of unidirectional sisal-epoxy and sisal-polypropylene composite laminates has been experimentally investigated. Chip formation characteristics in the context of both thermoset and thermoplastic natural fiber composite laminates have been discussed. Further, the analysis of drilling force signals has been reported and the mapping of drilling forces has been proposed. Influence of drill geometry, feed, and spindle speed on drilling forces and a comparative analysis of damage characteristics of drilled hole have also been reported. From the current research work, it has been established that the tooling requirement for drilling of composite laminates under investigation is substantially different.

Electrochemical discharge machining (ECDM) has proven its usefulness for micro-machining of hard, brittle, and nonconductive materials. Pulse duration is one of the most important process parameters in ECDM. The present article investigates the effect of pulse duration on aspect ratio of glass material machined by ECDM. An effective range of pulse duration was identified experimentally to achieve better control on the quality characteristics. The quality characteristics measured were machining depth, surface damage, aspect ratio, and tool wear. Results reveal that a limited range of pulse duration affects the quality characteristics leading to high aspect ratio. Further, values of process parameters for high aspect ratio of holes were identified. Effect of applied voltage on tool wear was also investigated.

Electric discharge machining (EDM) is one of the unconventional machining methods used in machining difficult-to-cut materials. The EDM process uses hydrocarbons-based dielectrics during machining which produces hazardous gases and creates environmental as well as operator’s health and safety issues. Therefore, the present study explores the sustainable variant of EDM (Wet and near-dry EDM) along with the optimized process parameters (pulse-on-time and pulse-off-time) to achieve low gas emission concentration. Near-dry EDM was performed with two-phase dielectric medium (air and EDM oil) and only EDM oil used in wet EDM. The gas chromatography and mass spectrometry (GC-MS) were effectively employed for analyzing the components of gaseous emission. The investigation showed that near-dry EDM process has reduced 97% gaseous emission with higher MRR compare to wet EDM. This process may be termed as green machining process because of very less or negligible gas emission.