Design and Fabrication of Portable Automatic Spot-Welding Machine

Resistance spot welding is getting significant importance in car, bus and railway bodies etc due to automatic and fast process. There are many spot-welding machines available in the market, most of them are for industrial purposes and are costly. There is a need to develop low-cost spot-welding machine for students in higher institutions. The major factors controlling this process are current, time, electrode force, contact resistance, property of electrode material, sheet materials, surface condition etc. the quality is best judged by nugget size and joint strength. This study presents a systematic approach to determine effect of process parameters like electrode force, weld time and current. In this project, the effect of welding time on the tensile-shear strength and tensile-peel strength of the welding joints in electrical resistance spot welding of mild steel plates having 1.0 mm thicknesses were investigated. The plates are welded by electrical resistance spot welding by fixing electrode form, materials type and electrode force while changing welding current and time (second). The welding current was fixed at 4 kA. The electrode pressure was fixed at 6 kN while the welding time were changing at 2, 4, 6, 8, and 10 sec. The welding joints were exposed to tensile-shear and tensile-peel test and the effect of the welding time on tensile test were being investigated using related period diagram. The optimum welding times for tensile-shear test obtained at 4 sec and for the tensile-peel test also obtained at 4 sec.