ENHANCING THE MACHINING PERFORMANCE OF HSS DRILL IN THE DRILLING OF GFRP COMPOSITE BY REDUCING TOOL WEAR THROUGH WEAR MECHANISM MAPPING

The wear characteristics of cutting tools is affected by the machining factors such as the magnitude of the cutting speed, extent of the cutting tool movements in the feed direction, the geometry of the cutting tool etc. This research paper presents some original research into the wear types, as well as the phenomena that occurs in the cutting tool/work material interface zone and their relationships to cause different wear mechanisms (adhesion, abrasion and diffusion) in hole machining process. A wear mechanism map involving the tool wear characteristics of uncoated High Speed Steel (HSS) drill of 6mm diameter is constructed for the drilling of Glass Fiber Reinforced Polyester (GFRP) composite laminates. Different wear modes observed and identified by the surface micrograph image of land / flank of uncoated HSS drillsto describe a number of wear mechanisms. The dominant wear mechanisms include adhesive wear, adhesive and abrasive wear, abrasive wear and fatigue / thermal wear. In the wear mechanism map, a wear region was identified, which is called “safety cutting zone” or “mild wear zone”, where the minimum flank wear of the HSS drill tool occurs. In order to carry out the drilling operation on the GFRP composite in the “safety cutting zone” or “mild wear zone”, it was found that the spindle speed should be set in the range of 1200-1590 rpm and feed rate must be set to 0.10 ? 0.16 mm/rev. Thus, the wear mechanism map constructed here can be used as a reference for selecting suitable drilling parameters of uncoated HSS drill tools for GFRP composites.