The 4-gang socket was manufactured from two Nylon housing mouldings.  The individual components were injection moulded, the wires and socket components assembled and, as the final stage of the assembly the two halves of the housing jointed by an ultrasonic weld.

The weld geometry consisted of a "tongue and groove" type joint, the tongue present on the lower half of the housing. To assist with focussing the ultrasound during welding and to produce a high stress a standard 30° energy director was moulded on the upper face of the "tongue".

Following initial batch approval, difficulties were encountered with inconsistent, low strength welds after products had been shipped to retailers.

Cause of Failure