This research is to study the performance of mechanical arm for welding cover gas. Types of welding aws a5.18 er 70s-6 that affect ss400 grade steel and steel s45c purpose was to study the effects of using different types of welding electrical potential difference. And the movement of the welding head Which is a factor in the trialPlate size 15 x 10 cm, 6 mm thick, is connected by the weld head is perpendicular to the plate.