Experimental investigation and process optimization of thermal drilling of galvanized steel

Abstract

Thermal drilling is a novel technique of sheet metal drilling process in which the frictional heat is generated in between the rotating conical drill and workpiece This heat is used to create a hole by the penetration of drill into the metal plate without any metal material loss During this process the ductility of workpiece material has enhanced with frictional heat which causes the softened workpiece material to extrude on the top and bottom sides of the drilled hole Subsequently it creates the washer like shape and a bush respectively in the drilled workpiece thus it offers the required portion for making threads Therefore the bushing formation is significant in the thermal drilling process and the present study is more focused on it The workpiece material used for this research work is galvanized steel which is commercially available sheet material Generally galvanized steel has been manufactured by applying zinc coating over the surface of steel through hot dipping technique which acts as a shielding to corrosion environment The demand for galvanized steel is increased in many remarkable applications which include metal roofing boat construction structural beams water transporting pipes and domestic appliances owing to their corrosion resistant property In all these significant applications the fastening strength of the sheet metal structure is very important In the present work a cost-effective thermal drilling machine has been developed In the present work a cost-effective thermal drilling machine has been developed for drilling of galvanized steel sheet metal This moderate automated machine is simple strong and easily operated Also three thermal drilling tools were developed out of M2 tool steel with three different tool angles such as30o 37.5o and 45o The three different thickness of galvanized steel such as 1 mm 1.5 mm and 2 mm are selected for performing the thermal drilling process The thermal drilling of galvanized steel was carried out effectively in the developed thermal drilling machine