Don't Cut the Cord

Machine-mountable cordsets and remoteI/O connector

boxes let designers make theBest of previously unusable

machine surfaces, while reducing the material and labor costs

of running centralized I/O wiring. (Source: Phoenix Contact)

It also rings true for machine builders, who compete these days by selling the exact solution to those familiar end user dilemmas: machine productivity/uptime, ease-of-use, flexible and fast changeovers, and easy problem solving and diagnosis, as well as on price.

So, where do you go to find that competitive edge of supreme flexibility? One place to start is to look at the use of fabricated cordsets, connectors, fieldbus boxes, and sensor modules, etc., instead of traditional wiring schemes for both machines and process equipment. This approach can go a long way towards helping you reconfigure processes and machines quickly--and have you manufacturing product again with minimal delays.

Greg Osbelt is electrical design supervisor for Cambridge, Ontario-based ATS Automation Tooling Systems (www.atsautomation.com), a global leader in the manufacture of advanced factory automation systems, custom and standard automation equipment, and turn-key assembly machinery. His group has been using machine mountable I/O for about four or five years. "We now, almost exclusively, use field-mount, bus-style I/O for all our machine designs," says Osbelt. "We've moved totally away from the problems and cost of pulling all that wire and cabling harnesses, and the massive cabinets that are required."

Other areas most amenable to fast connect/disconnect wiring are those where machine modules are moved in and out of a process depending on the product being made at the time. "Assembly machines, automotive, material handling, machine tool, and printing are industries where I have seen a consistent move to 'connectorize' options on the machines," says Mark Gilliford, PlusCon marketing, Phoenix Contact (www.phoenixcon.com). "Products such as chip conveyors, bar feeders, parts unloaders and loaders, chillers, conveyors, vision cells, and gluing functions are examples. The industry leaders sell the base unit and let their customers add these options as needed. To make it easy to apply the options, they must be pluggable."

Gilliford is not alone in his enthusiasm for the approach, although in some cases, it's still a question of how you view costs. "Sales of our machine-mount IP-67 I/O products are increasing at three times the rate of our standard IP-20 product, for various reasons," says Graham Harris, president, Beckhoff USA (www.beckhoff.com). "Some machinery builders view wire and cable as general overhead, so they do not, or cannot allocate the cost of this material into their actual costs. So, these companies are not going to see the value of IP-67 or even IP-20 distributed I/O until they begin to allocate wiring to their machine costs.

Harris says there should be a call to action for this category of companies, since they are missing a key cost element. "In many studies the total cost of wiring sensors and actuators back to a central control cabinet averaged one dollar per foot," states Harris. "This includes the extra terminations involved in traditional systems plus labor plus material. So, a 100 I/O system with wires running 50 ft. will actually have a total cost around $5,000. This alone has been a major reason for using distributed I/O. Harris argues that many builders will deny this cost, until they do the study themselves. When they do it can be quite a revelation.

The quick connect/disconnect feature of on-machine IP-67 I/O products allow fast and reliable module replacement without tools, an asset when a machine has to be quickly back online.

Another value is that IP-67 I/O can be placed much closer to the sensor/actuator and that makes the associated wiring run as short as possible, which also can improve reliability and reduce signal transmission losses.

There are instances when a machine or process must be fully assembled, wired, and tested before shipment, then easily disconnected, shipped, and eventually reconnected at the installation site. "End users, working with system integrators and industrial OEMs have made it a requirement to build the equipment, test its functionality, then tear it down, ship anywhere in world, and reconfigure quickly using local labor, says Gilliford. He believes there are three factors that drive this concept:

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Some custom assembly builders have seen the value of on-machine IP-67 I/O. "Assembly machines/lines are often modular, so the I/O wiring becomes just a network cable, which is much easier to connect, break, and reconnect than conventional wiring," says Harris. "Assembly machines do not have much space for cabinets and on-machine I/O is easy to bolt onto a structural support." In addition, says Harris, assembly machines are normally customized for a specific customer, so I/O counts will vary from design to design and machine-mount IP-67 I/O provides design flexibility, "since no enclosure or cabinet is needed and wiring can be done on the floor with quick-connect cabling rather than cable harnesses, which need to be pre-designed and manufactured offline."

There are, however, conditions where this approach is ill-suited for industrial applications, so the choice should always be a well considered one. There are still cases where single-function machines are built, installed, and rarely tinkered with. The up-front cost advantages of "When the machine is to be built on site and located where it will be used, the need for quick connectors might not be necessary," believes Gilliford. "If the plant has a skilled in-house service department, they can quickly diagnose a problem and fix it."

Quickly Reconfigurable

Assembly and re-assembly of machine modules is

simplified with rugged quick connectors, junction boxes,

and cordsets. (Source: Lumberg)

But if companies look only at the cost difference between IP-20 and IP-67 I/O, they probably won't go forward--the acquisition cost is higher for machine-mountable components. "Our IP-67 products are about 15-20% more expensive than IP-20," says Harris. "What they need to look at is the enclosure space needed to mount the I/O." Certainly, if the user has a large cabinet with available space, then the space could be considered free.

"However, if they can reduce their cabinet size by replacing the in-cabinet I/O with on-machine IP-67 I/O, then they need to add that savings to the cost equation," argues Harris. "This can account for a 5-10% savings depending upon the amount of change that is possible."

Osbelt agrees, and is convinced that the huge labor savings and reduced wiring costs make a compelling argument for machine-mountable I/O. "We don't have to push our customers to see the advantages," he says. "Besides, machine footprints in general are getting smaller, so being able to reduce the control cabinet size by making better use of distributed I/O makes sense to everyone."

Another cost that needs to be considered is the miscellaneous material needed to mount in-cabinet I/O such as DIN rails, mounting hardware, ground connections, terminal blocks, and cabinet-wall penetrations. This may add another 5-10% to the IP-20 I/O cost.

Design flexibility also means that changes are easier to make as custom designs often are modified during the build cycle. "Products such as our Fieldbus Box allow I/O expansions or changes to be easily made without adding more I/O nodes, because the master module has an expansion bus built-in," reminds Harris.

Osbelt sees the most activity in Profibus and DeviceNet for bus-style discrete I/O, much the same as preferences for standard IP-20 I/O. "At lot depends on the customer's PLC of choice," he says. "If they favor Siemens PLCs, then the I/O will probably be Profibus-based. We use a lot of Beckhoff hardware, too, since they offer PC-based solutions, as well as the major bus I/O configurations."

Another prime reason to consider quick disconnects and junction boxes becomes evident in rugged environments. "One of our customers in oil and gas exploration and production was using enclosures and terminal blocks for the electrical wiring of various motors, pumps and other process monitoring equipment on their offshore oil drilling platforms," says Mark Sweeney, vice president, sales and marketing at Remke Industries (www.remke.com). "All the equipment wiring was terminated inside the enclosure with terminal strips. However, the company was experiencing chronic problems with the traditional hardwiring of equipment particularly where enclosures were subjected to extreme conditions of seawater, rain, and wind. In these environments the air space within the enclosure can build-up condensation, which causes terminal strip corrosion and electrical shorting."

Dealing with these problems meant increased downtime spent on troubleshooting, repair of corroded terminal strips, replacing gaskets on enclosures, and rewiring equipment.

"This company had a unique set of physical and environmental conditions to overcome, so our design team decided a custom solution was needed," says Sweeney. "First, we redesigned the internal footprint of an eight-outlet mini-port distribution box to accommodate various pre-wired circuits and then tested it thoroughly to eliminate any circuit mis-wiring. Material of construction was changed to a polyester resin for enhanced corrosion-resistance and durability. The design of the distribution box was also changed to include stainless steel legend plates for easier circuit identification, and then completely sealed internally to eliminate air gaps and moisture/water ingress.

"The custom design all but eliminated downtime, as was the time and cost associated with troubleshooting and repair," says Sweeney. "In addition, it provided foolproof circuit identification, an enclosure completely sealed against corrosives and moisture, and, as a bonus, a smaller footprint: the company was pleased to have a smaller distribution box as available space is at a premium on an oil rig."