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Near field ultrasonic welding Near Field Welding

Revised 03/07/2008 .



A second factor contributing to failure in this instance is again related to the microsctructure of the polymer used.  Semicrystalline polymers can be thought of as being relatively hard crystalline particles in a relatively soft, rubbery matrix.  This rubber matrix produces high attenuation of the ultrasound. 

For this reason semicrystalline polymers are most suited for use with “near field” ultrasonic welding techniques.  In essence this means that the ultrasonic horn (the energy source) should be no more than 6 mm away from the weld surface.  In this instance the distance was approximately 10 mm.  The implication being that the weld face would see a relatively low proportion of the applied energy.

The "far field" technique employed in the socket assembly in question is far more suited to amorphous thermoplastic materials.  Their glassy structure conducts ultrasound well with little attenuation.  For such materials the ultrasonic horn can be placed some distance (up to 200 mm) from the weld face.

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