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.
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".
initial batch approval, difficulties were encountered with inconsistent, low
strength welds after products had been shipped to retailers.
Cause of Failure
The joint design is unsuitable for the
choice of material
The ultrasonic welding technique adopted
is inappropriate for the material used.
Nylon is a hygroscopic material.