Welding Characteristics of 67 kHz Ultrasonic Plastic Welding System Using Fundamental and Higher-Resonance-Frequency Vibrations

Abstract

The welding characteristics of a 67 kHz ultrasonic plastic welding system using fundamental and higher-resonance-frequency vibrations were studied and compared with those of the 27 kHz and 40 kHz systems. At high frequency, welding characteristics were improved due to the larger vibration loss of plastic materials. The 67 kHz welding tip vibrates at a maximum velocity of more than 2.3 m/s (peak-to-zero value) at a fundamental resonance frequency and there are several higher resonance frequencies up to 94 kHz whose vibration velocities are more than one-fourth that of the fundamental frequency. The welding characteristics of lapped 1.0-mm-thick polypropylene sheets were measured for 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 when fundamental and higher resonance frequencies were driven simultaneously. The welding characteristics of the 67 kHz ultrasonic plastic welding system were improved significantly compared with those of 27 kHz and 40 kHz welding systems by driving fundamental and higher resonance frequencies simultaneously.