63” x 24” hydraulic lift table, 170-260 Hz, 90 Kg upper tool, 65 KW vibration drive, Siemens S7-300 PLC, 2006
Linear vibration welders use motion and pressure to friction weld thermoplastic part halves. Lower parts seat in tooling attached to a lift table (hydraulic or motorized) which brings them into contact with the upper parts. Upper tooling hangs from springs, which vibrate controllably between magnets rigidly attached to the machine frame via a supporting bridge. The frequency at which upper tools vibrate is determined by their weight and mass. Each tool needs to be tuned. A DC power supply (inverter) controls the frequency and amplitude (distance) at which the springs vibrate. Once part halves melt at the contact area, clamping pressure forces them together, creating strong welds, once joints cool and re-solidify. Small and medium sized parts (6″ – 48″ long) are rubbed quickly, using high frequencies (180 – 240 Hz). Large parts (60 – 120″ long) are rubbed more slowly using low frequencies (80 – 120 Hz). Internal walls can be welded as well as the perimeter of parts. Vibration welding is relatively fast (5 – 30 second cycles), making it suitable for production. Properly maintained machines can make millions of parts over decades of use.