Welding Depending on the application, we may call upon our expert welders to join components as part of the assembly process. Viking Plastics employs both ultrasonic and vibration welding techniques. Vibration welding is used for a wide range of assembly sizes. It can be used to weld small assemblies such as automotive armrests and glove boxes, and large assemblies like automotive instrument panels. Ultrasonic welding is limited to smaller welds. It is common to see multiple ultrasonic tools or stacks being used to weld several small components onto a larger part such as ports and brackets onto an engine manifold.