The electromagnetic welding equipment consists of a radio frequency generator,
water cooled coils and fixtures to contain and align the parts to be joined.
The generator creates a high frequency current in the coils, producing an
oscillating magnetic field in the joint area. The parts to be joined must be
transparent to the magnetic fields. The high frequency magnetic field
generates eddy currents in the bonding material through induction and the
hysteresis loss in this process is responsible for the heat generation. The
bonding material melts and the parts are joined under low pressure. The
plastic solidifies again as soon as the magnetic field is switched off.
The bonding material can be supplied as extruded tape, strand or other
profile, or as a molded gasket for complex geometries or for ease of handling.
The bonding material is normally produced from the same polymer as the parts
or from a compatible polymer, and is filled with finely dispersed micro
particles of ferromagnetic material, such as iron, iron oxide or stainless
steel. The loading of the ferromagnetic powder is generally less than 15% by
volume.
Hygroscopic thermoplastics, such as
Stanyl and Akulon, may need to be dried to
eliminate moisture related welding problems.
Process parameters
Complex 3D-contours can be welded. The electromagnetic field typically has a
frequency between 2 and 8 MHz. The cycle time can vary from 3-10 seconds, for
small parts, to 30 seconds for large assemblies.
Materials
Stanyl,
Arnitel, Akulon, Arnite, and
Xantar can all be electromagnetically welded. The process is specially
suited to welding soft plastics, such as Arnitel TPE.
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