Machine mount — the placing of everything from I/O to PCs directly on factory floor equipment instead of in a cabinet — is increasingly being used. The benefits are less cabinet space and wiring, as well as reduced commissioning time and expense. Other advantages are easier maintenance, greater modularity and more flexibility.
However, compared to cabinet-enclosed equivalents, machine-mount components are more expensive because they must be rugged enough to survive and work on the plant floor. Consequently, machine mount may not make sense for simple machines with few I/O points or in cases where cabinet space cannot be eliminated and is not at a premium.
Spend to Save
For an example where machine mount saves even though the components cost more, consider the experience of Durrer Spezialmaschinen. Based in Kussnacht am Rigi, Switzerland, Durrer makes a variety of specialized machines. The company’s REGA 3 counts different paper types and cuts step indexes into books, catalogs and other printed material. This involves complex movement along 21 axes in a system measuring 2.8 by 1.8 by 2.0 m (9.2 by 5.9 by 6.6 ft).
Patrick Suter, Durrer’s head of development, says the I/O is handled by machine-mount modules that are IP67-rated, a standard protection category for direct installation on a machine (Figure 1). Being dust-tight and water-immersion-resistant, these cost more than functionally similar components in a cabinet but are worth it.
"Because most I/O signals are recorded in the machine by the IP67 modules, we have just a few signals in the electrical cabinet," says Suter. "So, then we could reduce the I/O space inside of the electrical cabinet by approximately 80%. On the wiring, we saved approximately 50% of the installation time."
One of the reasons for the wiring decrease is that now only two wires are used, one for power and another for an EtherCAT connection. In the past, there would have been several multi-wired cables to configure with plugs, Suter says.
The machine-mount I/O modules are supplied by Beckhoff Automation, all with an EPxxxx (industrial housing) part number. They consist of a total of 56 digital inputs, 24 digital outputs and 16 safety inputs, in an array of 16- or 8- channel digital input or output boxes.
Machine-mount use is expanding because the environments in which machine-mount devices can function are growing, according to Kurt Wadowick, I/O and safety specialist at Beckhoff Automation. For example, devices can now withstand pressure washdown, common in food, beverage and pharmaceutical processing. They also can work over an extended operating temperature range of -25 to +60 oC.
"The robust nature of these machine-mount solutions makes them well-suited for many specific application types, and they remove the need for a control enclosure," says Wadowick.
He adds that these I/O modules are accessible without even having to touch a cabinet door. This allows operators to quickly and easily determine the status of the I/O and, if need be, replace faulty sensors. It also streamlines the machine’s cabling, improving safety, appearance and cleanliness, says Wadowick.
Less Cabinet Space and Wiring
Another example of machine mount savings can be found in baggage handling (Figure 2). In solving this material-handling problem at Halifax Stanfield International Airport in Nova Scotia, Canada, Cofely Services, a worldwide technical services company, went with machine-mount IP67-rated modules and M12 connectors (Figure 3 on next page). The choice paid off in various ways.
"We estimated that for this project we decreased probably 30% of electrical cables and electrician time," says Yan Le Meur, automation technology expert with Cofely Services.
Other cost savings were in panels, with more than two-thirds eliminated. A final savings came in commissioning. Earlier projects were plagued with short circuits, inverted polarities and other electrical problems. In contrast, none of these appeared during commissioning of the Halifax project, Le Meur reports.