Most industrial equipment contains extensive electrical wiring running between its components and subsystems. When the equipment is manufactured, the machine builder typically assembles and tests most of the systems at the plant prior to shipment. Then it is disassembled, much of the point-to-point wiring is disconnected, and everything shipped to the customer’s site. There it is reassembled and the wiring terminated.
It probably comes as no surprise that during installation, point-to-point (hard) wiring errors are common. This can cause equipment damage on startup or, at a minimum, delays due to troubleshooting time and repairs. Hard wiring also complicates maintenance when electrical problems crop up later on.
There’s a better way to do all of this. With what we call “connectorized” cables, equipment manufacturing, installation, and maintenance are all more efficient and cost effective.
Most engineers are familiar with the concept of a communications bus, with drops coming off a main trunk cable; it’s how Ethernet and other common networks are put together. What may be less familiar is that power for motors and control signals can be distributed the same way. Some connectors now use a bus structure to carry both power and data over a composite trunk cable containing several kinds of wires, with individual power and control drops to motors and other devices. The connectors can even carry compressed air for pneumatics.
A connectorized bus cable is designed and assembled at the factory along with the equipment on which it will be used. Technicians run the cable and plug in the drops as the machine is assembled. After factoryacceptance testing, connectors are unplugged for shipping and then reconnected at the customer’s site.
This method offers numerous benefits. It’s easier to design machines as a series of modules. Equipment can be shipped in smaller pieces, and planning for expansion is simpler. OEMs can prebuild standard components like control panels, motor assemblies, and power-distribution boxes which plug together at assembly time. All this leads to a better-looking, neater design with less panel clutter. And it makes troubleshooting easier.
During assembly, prewired and tested connectorized cable assemblies eliminate the need for conduit, reduce debugging and testing costs, and improve manufacturing efficiencies by permitting staged panel assembly. With the use of connectors, it’s no longer necessary to separately disconnect I/O, power, pneumatics, and signal cables.
Installation at the customer site also goes faster — the plug-and-play modules make rewiring, testing, and troubleshooting almost nonexistent.
With all the advantages, you’d think the technology would be readily accepted. Yet, overcoming the mindset that hard wiring is proven and less expensive is a constant battle, and some OEMs have been reluctant to change.
We’ve seen savings with connectorized cables ranging from hundreds to thousands of dollars on equipment like press brakes, conveyors, packaging machinery, and wind turbines. For instance, on a large material-handling crane, they cut installation time from several weeks to less than 4hours, saving the customer more than $13,000. Eliminating unwiring and rewiring for maintenance and repairs pushes savings even higher.
No doubt, when just looking at physical hardware, connectorized-cable assemblies cost more than simple wires and connectors. But one needs to factor in labor costs to get a more-complete picture. For example, a typical HARTING Han connector costs about $190 in labor and hardware, while a hard-wired assembly might cost $75 for an hour of labor, not counting the price of the parts. Assuming that major assemblies are shipped to the job site fully assembled, this means hard-wired cables must be disconnected in the field and then reconnected for installation. Experience shows there is about a 30% premium on field-wiring labor costs compared to the same work done in the plant, which raises hard-wiring costs to $195 on first installation. Any subsequent rewiring due to field-wiring errors and troubleshooting raises the cost to $253.50 for a second installation, and to $329.55 for a third.
All the while, the connectorized-assembly cost holds steady at $190 because simply plugging in subassemblies carries little cost. And this comparison does not consider additional savings from reduced downtime, no expenses for travel or contractors, and the opportunity costs from eliminating mistakes and start-up damage.
In general, when looking at a connectorized solution, one needs to consider the complete picture. How many cables and connections make it worthwhile? That depends on the application, but the engineers at a reputable connector manufacturer can quickly help you run the numbers. Long-standing practices like hard wiring are not always best. Embracing new concepts can open the door to substantial savings.
HARTING develops and manufactures electrical and electronic connectors, device terminations, backplanes, network components, and cable harnesses for networks, machinery, and power and data applications.