Assembly Considerations

Induction/electromagnetic welding uses inductive energy to achieve fusion temperatures at the welding interface. A magnetically active preform (typically in the form of a gasket), usually made of the base thermoplastic material with finely dispersed micron-sized particles of a ferromagnetic material, is placed between the welding surfaces. Work coils carrying high frequency (2 to 8 MHz) oscillating current are positioned close to the joint area. Strong electromagnetic field from the coils excites the ferromagnetic particles producing heat and melting the polymer in the preform. Fusion time is very short (typically from 1 - 10 seconds). Larger assemblies may require longer times. Assemblies with bond lines as much as 20 feet have been bonded with induction welding. The figure below shows a schematic of the Induction Welding Process.

Some of the positive attributes of hot Induction welding are:

Fast weld times with high joint strength
Allows for the components to be welded in the same orientation as the final, assembled position
Allows capture of additional parts between the welded components as long as they do not respond to the electromagnetic field
Disassembly is possible for recovering captured parts
Can be used to weld dissimilar materials in most cases
Can create excellent fluid-tight seals even with components having uneven surfaces
Can be used for large parts

And the negative attributes are:

More expensive than most other welding processes and requires special preforms
Technique limited to certain component geometries that allow close proximity to the coil
High equipment and work coil cost. Due to close proximity requirements, coils have to be specially configured
Additional assembly step required for placing the preform in position
Metal inserts within the range of the electromagnetic field will also become hot
Exposure of the operator to the electromagnetic field could pose a health hazard

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