Welding Characteristics of 40 kHz Ultrasonic Plastic Welding System Using Fundamental and Higher-Resonance-Frequency Vibrations

Abstract

The welding characteristics of 40 kHz ultrasonic plastic welding system using fundamental and higher-resonance-frequency vibrations were studied. At high frequency, welding characteristics can be improved due to the larger vibration loss of plastic materials. The 40 kHz welding tip vibrates at a maximum velocity of more than 3.0 m/s (peak-to-zero value) at a fundamental resonance frequency and there are several higher resonance frequencies up to 107 kHz whose vibration velocities are more than one-fourth that of the fundamental frequency. The welding characteristics of lapped 0.5-mm-thick polyvinyl chloride and 1.0-mm-thick polypropylene sheets were measured in the cases where the vibration system was driven using combined driving voltages of both fundamental and higher resonance frequencies. The welded area and weld strength increased as fundamental and higher resonance frequencies were driven simultaneously. The welding characteristics of ultrasonic plastic welding were improved significantly by driving fundamental and higher resonance frequencies simultaneously.