Development of high-power ultrasonic generator based on LCC matching network for ultrasonic metal spot welder

Ultrasonic metal spot welding has minimal requirements for the welded components’ outer surface, and the welded products’ resistivity is exceptionally low. Its advantages include high fusion strength, high welding efficiency, and a clean and environmentally friendly welding process. This paper examines the action mechanism of the spot welder on the welded piece. It investigates the characteristics of the impedance and phase angle of the ultrasonic component with frequency based on the equivalent circuit model. The change in the impedance characteristics of the ultrasonic component under radial pressure load conditions is explored. Based on the analysis of impedance characteristics, the method for matching the parallel inductance of the ultrasonic component is determined, and the tuning matching circuit is designed. The ultrasonic generator and control program are designed to ensure stable amplitude output of the ultrasonic component. The performance test of the ultrasonic metal spot welder is conducted to assess the output characteristics of the ultrasonic generator. This test also establishes an appropriate variable load environment to evaluate the effectiveness of constant amplitude control. Underwater load conditions, the amplitude fluctuation of the ultrasonic component is kept within ±1 µm. Spot welding experiments are conducted to verify the capabilities of the spot welder by welding sheets of copper and pure aluminum. The ultrasonic generator welds 1.0 mm thick copper sheets and 2.0 mm thick pure aluminum sheets, with the resulting samples able to withstand at least 400 N of shear force.