Practical application of ultrasonic welding for rigid plastics was completed in the 1960s. At this point only hard plastics could be welded. The patent for the ultrasonic method for welding rigid thermoplastic parts was awarded to Robert Soloff and Seymour Linsley in 1965.[1] Soloff, the founder of Sonics & Materials Inc., was a lab manager at Branson Instruments where thin plastic films were welded into bags and tubes using ultrasonic probes. He unintentionally moved the probe close to a plastic tape dispenser and the halves of the dispenser welded together. He realized that the probe did not need to be manually moved around the part but that the ultrasonic energy could travel through and around rigid plastics and weld an entire joint.[1] He went on to develop the first ultrasonic press. The first application of this new technology was in the toy industry.[2]
The first car made entirely out of plastic was assembled using ultrasonic welding in 1969.[2] Even though plastic cars did not catch on, ultrasonic welding did. The automotive industry has used it regularly since the 1980s.[2] It is now used for a multitude of applications.