... Convenient and save labour YP-D21 20Khz Ultrasonic Metal Welding Machine By using the ultrasonic high frequeccy vibration principle, the ... various hardware and tolls, automobile and motorcycle, machine tools, hardware parts and machine parts, hardware mold, etc.4.Welding/Brazing ... protection, conservation of energy and safety operation, which is free of any noise, exhaust gas and dust.12. Elimination ...