Design for TCO

By Dan Hebert, PE, Senior Technical Editor

The cost of owning and operating an industrial machine during its service life, called total cost of ownership (TCO), is an often-overlooked part of the decision-making process by machine purchasers.

TCO involves several factors besides the initial upfront costs such as the purchase price and the cost to integrate the robot, machine or process skid into the overall control system. There are long-term operating costs, including the amount of energy it takes to run the system, labor requirements and required maintenance. Other costs in the TCO equation include downtime and changeover expenses, off-spec product, floor space requirements, insurance, financing costs, training, security, safety, and a host of other expenses depending on the complexity of your cost accountant's TCO equation.

Features that reduce a machine user's TCO are welcome, but how can machine builders justify the extra hit to the purchase price for some of these longer-term cost reductions? How do they sell the potential savings to their customers?

Cutting Energy Costs

The cost of running a machine has a huge impact on TCO, so energy consumption is an obvious target. "Robot suppliers are decreasing their products' overall power consumption," says Michael Gurney, principal at system integrator Concept Systems (www.conceptsystemsinc.com). "Since the tsunami in Japan caused the cost of power to increase, Japanese robot suppliers are updating their systems to do just as much with a lot less power consumption. For example, the Nachi SRA robot uses something like 20% less power relative to the previous generation. We see falling power requirements as a trend throughout all product offerings, but more so from Japan in the next decade."

A machine builder can monitor energy consumption with simple modules, notes Robert Muehlfellner, director of automation technology at B&R Industrial Automation (www.br-automation.com). "For machines where the primary energy consumption is through servos, energy usage can be measured by the drive system directly," he explains. "With energy-consumption data available, every end user can take steps to optimize energy usage and reduce cost."

Another way that energy costs can be identified is with Profienergy, a function of Profinet. "One of the features of Profienergy is the ability to format data into useful information about energy demand," explains Carl Henning, deputy director of PI North America (www.us.profibus.com). "This information can be used to avoid demand peaks."

Components of Total Cost of Ownership

There are other benefits of monitoring. "Using devices with embedded intelligence to monitor motor currents, vibration and torque signatures allows machine builders to deliver machines with protective functions," notes Sandy Holden, market development manager of OEM business at Rockwell Automation (www.rockwellautomation.com). "These devices help guard against the damaging effects of electrical and other hazards, providing long-term equipment protection and, in turn, reduced cost of replacing equipment."

Hibernate If You Can

Some machine builders already offer a hibernation state. "Our machines only run when product is fed to the machine," says Derek Jones, marketing manager at Lantech (www.lantech.com), based in Louisville, Ky. "During downtime, the machine is not using much power at all. The cost to power down and power back up is greater than just leaving our machine in its automatic state."

Set the Bar High

Figure 1: This dual-infeed packaging machine accepts 350 granola bars per each of two sides. The bars are loaded into a single stream of top load cartons in different counts depending on retail requirements, and into bulk format cartons.

Propack Processing & Packaging Systems (www.propack.on.ca) in Beamsville, Ontario, builds robotic collators to feed topload, endload and multipack packaging machines (Figure 1). Propack's machines typically run three shifts per day, says Chris Follows, president. "If no product is available, we turn off all the conveyors that feed the machine," he says. "This also ensures cartons are not damaged due to conveyor friction."

This raises an interesting point about machines operating smartly, notes Howard Dittmer, vice president of engineering and technology at Arpac (www.arpac.com), maker of packaging equipment in Schiller Park, Ill. "For the machine to make these decisions, other parts of the manufacturing process and their human operators need to adapt," he explains. "Manufacturers today put significant effort into maximizing the utilization of their capital investments. Running machines at an energy cost optimized for time-of-day utility pricing means there will be significant parts of the day when the machine isn't running."

This means energy-saving hibernation tactics require some analysis, such as determining when to shut the systems down to save energy. Such an analysis can go all the way from the plant floor to an ERP system. "To ensure a hibernation scheme is compatible with workflow and other production realities, I/O can transfer data to an ERP or MES," says Charlie Norz, product manager at Wago (www.wago.us). "Integration with ERP will enable the entire organization to take a holistic approach to energy efficiency."

Adding a hibernate cycle can provide solid ROI, but monitoring motors is not the only way to save energy, agrees Darren Elliott, manager of global OEM technical resources at Rockwell Automation. "In an application that involves heating glue to seal a carton, a hibernate cycle can reduce the heat needed at different times of day, depending on production demands, saving tremendous amounts of energy and material," he explains.