Resin has ideal properties for connector maker

Edited by the Engineeringtalk editorial team Apr 2, 2004

For its new colour-coded Aqualok connectors, ITT Cannon uses DuPont Crastin polybutylene terephthalate PBT resin.

For its new colour-coded Aqualok connectors, ITT Cannon uses DuPont Crastin polybutylene terephthalate PBT resin, chosen for its chemical resistance, good mouldability and electrical properties, and its dimensional stability.

These single, twin and 51-pin connectors are the latest addition to ITT Cannon's APD range of circular connector system, intended mainly for tractors, construction machinery and heavy-duty industrial applications.

Tractors made by the Case New Holland (CNH) group are among the first users of Aqualok connectors.

For this application, the connectors are held on a custom-designed mounting base, made of glass-reinforced DuPont Zytel nylon, allowing rapid yet foolproof assembly.

The colour-coding system helps to differentiate the electrical circuits in field use and makes maintenance work easier.

Matthias Raithel from ITT Cannon's Aqualok Project Management group says: "The single and twin-pin connectors of the Aqualok connector system, which we developed in our works here at Weinstadt, are for transmitting high-ampere current, which agricultural machinery needs for starting up".

"The 51-pin connectors carry signal current, to operate headlights, horn, direction indicators and other ancillary functions".

"These 51-pin connectors have multiple poles in a limited space, so we need a resin with good mould-flow characteristics and outstanding dimensional stability, and it must be capable of accepting a permanent four-colour-coding system in clear, luminous colours".

Together with DuPont, ITT Cannon chose Crastin LW9030 for making the Aqualok connector.

This glass-reinforced PBT has very low warpage, so that the matching male and female halves can always be easily connected and separated, whatever the outside temperature, without risk of damage to the contact pins.

Crastin also has good electrical properties, so that there are no tracking currents, even at high current flow rates.

The mounting base is made to CNH specifications.

For this part ITT Cannon uses Zytel 70G20HSL nylon, a heat-stabilised, glass-reinforced type designed mainly for automotive applications, both external and under the bonnet.

This resin combines high flexibility with high rigidity.

This combination allows the connectors to be pushed through the holes in the base without damage; snap-fit hooks are integrally moulded into the periphery of the holes, so that the connectors are firmly held.

"We optimised the geometry of the hooks with comprehensive FEM calculations", Raithel continues.

"Weld-lines are unavoidable around the holes in the base".

"However, using Moldflow studies at an early stage of the development, we positioned the weld-lines in such a way that they did not weaken the critical regions of the moulded parts".

All the connector sizes are waterproof to IP67 standard, withstand continuous temperatures up to 125C, and are designed to maintain good electrical contact despite the extreme vibrations in a typical motor compartment.

Thanks to the two DuPont resins, the whole connector unit withstands fuels, brake fluids, motor and gear oils, greases and other automotive fluids.