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The click that revolutionises heavy-duty connectors

07 May 2019

The demand for heavy-duty multipole industrial connectors has never been greater, but wiring these connectors is often a tedious and time-consuming task. Now, however, as Ivor Hunt of Weidmüller UK explains, there is a revolutionary new technology solves these problems and is, therefore, certain to click with connector users.

Downtime is costly and disruptive. In fact, in today’s fast-paced and fiercely competitive industrial sector, it’s close to unaffordable. These considerations have had a sizeable impact on the design of automation systems, with one of the most significant trends being the rapid growth of modularised solutions. The concept is simple: if an automation system is made up of modules that can be quickly replaced in the event of a failure, downtime can be minimised. This is a very effective approach but, for it to work, it’s essential that the electrical connections to the modules are made with plug-in connectors, as conventional terminals simply slow things down far too much. 

The result is that heavy-duty plug-in industrial connectors are being used more widely than ever before, and the growth in their usage is set to continue. And there’s no doubt that, once they’re wired and installed, good quality industrial connectors are dependable and convenient. Equally, however, there’s also no doubt that wiring the connectors – that is, connecting the cables to them during the build phase of the automation equipment – can take up a lot of time. 

This matters more than might at first be apparent because the essential feature of modularisation is that equipment is split into multiple modules, so there are far more interconnections than would be found in similar equipment featuring a non-modular design. And, with more connections to make, the time taken to make each individual connection can have a surprisingly big impact on the overall cost of the equipment.

With this in mind, let’s take a look at the technologies that are available for making connections between cables and the individual connector pins – in other words, for wiring the connector. One of the oldest technologies is soldering and, decades ago, this was the dominant technology for wiring multipole connectors of all types. Its shortcomings are that a high level of skill is needed to make consistently good solder connections quickly and there is a risk of heat damage to the insulation of the cable and the connector. For these reasons, soldered connections are now rarely used in automation applications.

Crimp connections, where the wires are crimped directly into the connector pins, are in many ways a better option. No heat is needed and, provided the correct crimp tool is used, it’s relatively easy to make good, reliable connections. However, the connector pins have to be crimped before they’re inserted into the connector housing and this takes time. Crimp connections are, therefore, by no means the fastest solution. And they have another potential disadvantage. If it becomes necessary to break and remake a connection – possibly on site to incorporate a modification – the wire ends up shorter, a new connector pin is needed, and the right crimping tool must be available. 

Screw-clamp connections are another option. They remain popular, but they’re slow to use simply because of the time it takes to tighten the screw. Remember that if it’s 24 pole connector, that’s 48 screws to tighten – 24 in the female half and 24 in the male half. Even at just a few seconds a screw, the time quickly mounts up. Also, if the connector is to function dependably, the screws must be tightened to a specific torque value. Finally, screw-clamp connections, unless the connector is very well designed, are likely to be adversely affected by high levels of vibration and shock, which means that connectors with screw-clamp terminals are usually not the best choice for use in machine-mounted equipment.

The next option is tension-clamp connections, where a screwdriver is inserted into the connector to open a sprung clamp so that the stripped wire end can be inserted. When the screwdriver is removed, the clamp closes and grips the wire. Connectors of this type are faster to use than the screw-clamp alternatives and, like screw-clamp connectors, they need no wire-end ferrules. However, it is still necessary to open the clamp with a screwdriver and, if this isn’t done correctly, there’s a risk with flexible cables that not all of the strands will be clamped, which degrades the quality – and reduces the current-carrying capacity – of the connection.

In recent years, one of the most popular options has been the use of so-called push-in connectors. These are similar to spring-clamp connectors, but they don’t have to be opened with a screwdriver to insert the stripped cable end. The trade-off, however, is that a wire-end ferrule must be fitted to the cable end. These connectors are an excellent solution in many ways – they’re fast and easy to use, no tools are needed, they provide reliable connections that are unaffected by vibration and shock, and the connections can be broken and remade without damage to the wire or the connector. The sole drawback is the need for the wire-end ferrule, the fitting of which adds significantly to the connector wiring time.

With this in mind, a little thought will suggest that the ideal solution would be something similar to the push-in connector, but without the need for the wire-end ferrules. At first, this may seem impossible, at least for flexible cables, as a stripped cable end without a ferrule would simply distort if an attempt were made to force it into a push-in connector. But what if the clamp were initially wide open, and then sprang shut when the wire end was fully inserted, rather like a mousetrap, with a readily audible confirmatory click? 

Designing such a connector and producing it in huge volumes are, of course, challenging tasks but that challenge has now been overcome. The result is SNAP IN connection technology for use in heavy-duty industrial connectors. And the new modules really are fast and easy to use. No tools are needed to make the connection itself. The wire end is simply stripped to the specified length and inserted into the connector. When the wire end reaches the correct depth, the connector springs shut clamping it firmly and the audible click confirms that the connection has been properly made.

The whole operation takes just fractions of a second; the resulting connection is totally dependable and is completely unaffected by vibration, shock or temperature cycling. Should it be necessary to break and remake the connection, this can be done quickly and easily using nothing more than an ordinary flat-blade screwdriver to “reset” the clamp.

Efficiency in every step
The time savings provided by this novel connector technology are substantial and there is, of course, a modest but useful cost saving compared with connectors that use push-in technology as there’s no need to purchase wire-end ferrules.

At present, SNAP IN modules for heavy-duty industrial connectors are available in 6, 10, 16 and 24 pole versions with each pole rated 16 A at up to 500 V. The modules are compatible with wire sizes from 0.5 mm2 to 2.5 mm2. An added bonus is that each pole has an individual test point associated with it, which can accommodate a standard 2 mm test plug, therefore not only do the modules speed and facilitate the manufacture of the equipment in which they are used, they also make maintenance and fault finding faster and easier.

Multipole connectors are fast becoming ubiquitous in today’s automation systems, so when a new technology emerges that will provide unimpeachable performance, reliability and convenience while also significantly reducing wiring time for these connectors, what possible reason can there be for failing to evaluate it? To find out more, and to receive a free evaluation kit, simply contact Weidmüller.

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