 Metal inserts may be secured in plastic and dissimilar materials can often be bonded with proper tooling design.Ultrasonic horns come in a variety of shapes and designs, but all must be tuned to a specific operating frequency; the most common being 15 kHz, 20 kHz, and 40 kHz.Ultrasonic welding utilizes high frequency, vertical motion to produce heat and the flow of thermoplastic material at the interface of mated parts.