Temperature Rise and Welding Characteristics of Various-Frequency Ultrasonic Plastic Welding Systems

Abstract

Welding characteristics and temperature increases of ultrasonic plastic welding parts over a frequency range from 27 to 94 kHz are studied. Using 27, 40, 67, and 94 kHz ultrasonic plastic welding systems, temperature increases at welding surfaces of lapped 1.0-, 2.0-, and 3.0-mm-thick polypropylene plates and polymethyl methacrylate plates are measured using 0.1- and 0.2-mm-diameter thermocouples inserted between plates, and temperature distributions at cross sections of lapped plate specimens are measured using a thermotracer. The 94 kHz vibration system used for ultrasonic plastic welding consists of a bolt-clamped Langevin-type longitudinal vibration source using four 30-mm-diameter piezoelectric ceramic (PZT) rings, a stepped horn (vibration velocity transform ratio N=3.0) and a catenoidal horn (N=3.13) with an 8-mm-diameter welding tip. The other vibration systems have similar configurations. In the case of using a higher-frequency system, increases in temperature measured at the welding parts are larger. Temperature rises are larger for lapped plate specimens than that for a one-piece specimen owing to the vibration loss of welding surfaces.