Ultrasonic welding can handle most plastics assembly applications. Other friction-based processes, such as vibration welding and spin welding, can usually tackle the rest. However, that necessitates investing in three separate machines at considerable cost.

SOUTH BEND, IN—It’s 20 feet tall, weighs about 400,000 pounds and is now making its way from South Bend to Connecticut: It's the world's largest friction welding machine. Pratt & Whitney will use the machine, made by Manufacturing Technology Inc., to weld large-diameter jet engine components.

Established methods—like ultrasonic and resistance welding—increasingly face competition from advancing technologies like laser, friction and micro welding.