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Unformatted text preview: Ultrasonic welding Ultrasonic welding is one of the most common methods of assembling two thermoplastic parts. Ultrasonics provides strong, reliable bonds at very fast cycle times. A single ultrasonic welder can be used to join parts up to approximately 8” in diameter, but several welders can be combined or “ganged together” to weld larger parts. Output frequency (20,00 Hertz) Converter Booster Horn Mechanical vibratory energy output (20,000 Hertz) Electrical energy input (50 to 60 Hertz) An ultrasonic welding system generally consists of two major components. The fi rst is the power supply, which converts 60 cycle electric power to high frequency (generally 20,000 cycle) electrical energy. This unit may also contain process controls for the welder. The second unit houses the elements that convert the electrical energy to mechanical motion and apply it to the part in the proper form. The converter contains the driver and the piezoelectric elements that provide this vibrating mechanical energy. A booster unit connected to the converter increases, decreases, or just couples the vibrational amplitude from the converter to the horn. Boosters that supply from 0.5 to 2.5 times the converter output amplitude are commonly available. The mechanical motion then is transmitted via a horn to the part. The horn is designed specifi cally for the parts to be assembled—delivering the proper amplitude directly to the joint area. Only one of the mating plastic parts comes in contact with the horn. The part transmits the ultrasonic energy to the bonding area, producing a rapid, consistent weld. Both mating halves remain cool, except at the weld interface, where the energy is quickly converted to heat and plastic melt. Optimum energy transmission and control occur when the horn is close to the bond. “Near fi eld” welding describes the process when the horn is within 0.25” of the weld(see Figure 1). “Far fi eld” welding, with distances greater than 0.25”, is less effective. Figure 1 Near and far fi eld welding Near fi eld Far fi eld Horn Horn < 0.25” > 0.25” 2 SABIC Innovative Plastics The key elements for successful ultrasonic welding include joint design, part design, horn confi guration and fi...
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- Spring '12