Medium Frequency DC Spot Welding Machine The medium frequency DC spot welding machine uses advanced inverter technology to produce firm and consistent weld nuggets with up to 30% lower energy consumption. It is an ideal choice for door panel and sheet metal welding with high quality requirements. Key Features - Firm Welding & Labor Cost Reduction Medium frequency DC inverter produces firm and uniform weld nuggets Up to 30% energy saving compared with traditional AC welders