ELEMENTS OF EFFECTIVENESS
Mechatronics can help boost a packaging system's OEE, but owners first need to know what they want and why it's important.
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Retrofitting packaging machines with new servomotors, like Yaskawa’s Sigma 5 family, makes it easier to achieve higher performance levels. |
Beauty, it’s been said, is in the eye of the beholder. For many packaging system owners, so too is the efficiency of their equipment.
To be sure, every production operation wants to maximize system productivity while also minimizing costs and waste. And with a measurement such as the overall equipment effectiveness (OEE) formula (Availability x Performance x Quality), it shouldn’t be difficult to determine what the packaging system equivalent of “beauty” looks like.
“What it represents is enormous,” says Andy Lovell, applications engineer at PIAB USA, Hingham, Mass. “Performance, throughput, cutting costs—all of the concepts that OEE embodies are very big on people’s minds.”
But like beauty, an OEE number by itself is only skin-deep. To fully understand its relevance, owners need to understand the metrics that comprise that calculation and the actions necessary to optimize them.
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The RPd 270 utilizes Schneider Electric/ELAU Packaging Solutions’ robotic, automation and servo module technologies with software that limits the robot arm’s acceleration while maintaining control of the product. |
Mel Bahr, owner of MGS Machine Corporation, Maple Grove, Minn., is among those who feel that OEE has too often been misapplied.
“Up until now, many end users have seen it as a ‘criteria,’ as in a factory acceptance test [FAT] specification,” he says. “In truth, OEE is a diagnostic tool for a line, something you use to identify and measure problems so that you can fix them.”
John Kowal, packaging market segment manager for Schneider Electric/ELAU Packaging Solutions, Schaumburg, Ill., adds that while more system owners recognize OEE as an important figure, not enough of them are asking for it.
“They just want to turn on the machine and run it,” he says.
Another OEE misconception is that the calculation is limited to what a machine actually does, not why the machine does it or the “ingredients” that go into its function—factors that typically comprise the availability metric. Potential losses may include material and product characteristics, cleaning and changeover, which itself is a highly volatile influence on many packaging operations.
“As manufacturing becomes more flexible and customized, minimizing downtime becomes more important,” says Bill Faber, senior manager for motion application engineering at Yaskawa Electric America, Oak Creek, Wis. “That means you have to account for both planned and unplanned downtime.”
It’s also important to keep the contributing metrics distinct from each other.
For example, Bahr believes that performance is strictly a function of those factors that affect the machine’s actual product output and run time. “This is where equipment jams should fall, though many users will include them in measuring both performance and availability,” he says.
Similarly, rejected products should be considered only as part of the quality metric, not performance, as many system owners tend to do. “When you don’t apply these metrics consistently, the calculation can become skewed,” Bahr says.
Those definitions may also vary if a packager applies OEE to a full line, rather than specific machines. But even then, the whole may not equal the sum of its optimized parts.
“If machines of different throughput capability are used on the same line it can result in an inefficient use of the machines,” says Andrew Stock, application engineer for Wittenstein, Bartlett, Ill. “That leads to higher initial and upkeep costs, both of which will directly impact the bottom line for the company.”
Packagers have all sorts of methods to gather data on these metrics, from human observation to control systems with built-in management and performance logging software. They can also work with consultants on metric definition, data collection and analysis.
But once they’ve accumulated all this data, there’s still the matter of doing something with it. “None of this is any good if you don’t follow through with the improvements,” Bahr says.
Retrofit Recipes
Because packaging systems and their associated metrics vary across and even within companies, no two OEE improvement strategies will be alike. The analysis of solutions will have to be as thorough as the analysis of the problems.
And because OEE’s Availability, Performance and Quality metrics have distinct contributors, an owner hoping for simple, “plug-and-play” kind of fixes will more likely than not be disappointed by the results.
Depending on the specific need, however, a potentially powerful improvement option is to retrofit or augment a packaging machine with mechatronics,
components that synergize mechanical and electronic hardware to enhance versatility and reliability, while also reducing overall energy requirements.
Stock says that advances in servomotor and actuation technology make OEE-driven retrofitting an option worth considering to ensure that the user is getting the most from a machine.
“A retrofit can range from the upgrade of a single axis to remove a production bottleneck, to a whole machine control upgrade keeping only the machine framework and mechanics the same,” he says.
Stock cites a customer that expressed interest in replacing a mechanical system (rotary to linear to rotary) with a simple actuator (rotary to rotary). By using servo technology to mimic more complex mechanical operations, “we were able to cut out a lot of additional moving parts, simplify the design, and, most importantly, increase acceleration from eight to 12g,” he says.
In another case, a customer’s process was limited by the indexes in between operations on a single-stage blow molding application. OEE was limited due to these index times as the operation time at each stage was fixed. “We replaced a hydraulic rotary actuator with a servo actuator and were able to cut the index times in half,” Stock says. “This resulted in 20 to 30 percent more machine throughput, and greatly increased the machine’s OEE.
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Wittenstein’s TPM+ actuator eliminates extra components, resulting in a size and mass approximately that of a standard motor and gearbox combination. |
Faber notes that a high-end servo with built-in advanced algorithms such as auto-tuning, vibration compensation and load modeling “will allow the machine to become more ‘forgiving,’ that is, better able to accommodate the changes in inertia that accompany different product and material loads during changeovers, leading to a more flexible machine.”
That improved accuracy can yield major benefits. In one retrofit, a Yaskawa advancing cam, servo-driven rotary placer enabled a machine’s throughput to increase from 125 to 400 parts per minute—a 320 percent increase—while also reducing the occurrence of scrap items from 10 to one percent.
Boosting System Brainpower
Choosing the right control system architecture for a mechatronics system is as important as selecting controller and servo components. A system designed with deterministic backplanes allows PLC, motion, network, I/O and specialized functional modules to be more seamlessly integrated and synchronized with the application program.
“This can be the difference between achieving or exceeding machine throughput or uptime requirements,” Faber says.
For example, if an operator has to stop the line in an emergency, a properly designed control system will allow e-stop recovery to re-engage electronic cams without having to unload manufactured product or re-home the servo axis. “This saves restart time and reduces scrap, positively impacting OEE,” Faber adds.
An updated control system, particularly one that uses PackML state models and tag naming definitions for standardized data acquisition, also provides packagers with consistent, comparable performance data that helps benchmark and evaluate their operations—the very foundation of OEE.
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Banner Engineering laser diode sensors combine the alignment advantages of a visible sensing beam with the increased sensing range of a laser to perform multiple functions as opposed to single point sensors. |
Kowal notes that owners may be surprised by what they learn once they begin accessing performance data across packaging lines and shifts. “Everyone looks at major downtime incidents, for example, but more often, it’s the shorter, frequent stoppages such as jams that take the highest toll because the line may never ramp back to full speed before the next occurrence,” he explains.
Even changes in smaller components such as sensors—the “eyes and ears” of mechatronics—can make a difference in OEE metrics. “You get the latest technology that will perform more tasks and last longer because of component housing,” says Scott Logan, packaging business development manager for Banner Engineering Corp., Minneapolis, Minn.
Sensor upgrades are particularly attractive, given their ability to expand the machine’s capabilities without requiring additional space. “The right sensors can make a machine with 20-year-old technology much more efficient than before,” says Logan.
The same holds true for hydraulics and pneumatics. David Brittain, director of engineering and marketing for Becker Pumps Corp., Cuyahoga Falls, Ohio, cites how a manufacturer saved more than $100,000 in energy costs and cut water use “simply by changing to a newer type of pump they hadn’t tried before, and getting us involved with the project early.”
Lovell adds that a custom-designed suction cup can increase efficiency just by being able to grip and move more consistently within a specified safety margin as opposed to trying to get by with a generic design. “The machine won’t be dropping or damaging products, which should increase throughput,” he says.
While these and other mechatronic retrofit examples may sound appealing, it’s important to remember that they are rarely as simple as swapping out a few parts. Upgrading or changing one component often has a domino effect across the system, ranging from the need to switch from chain drives to timing belts to handle higher throughputs, to a full-scale overhaul. And the more parts, labor and downtime required, the higher the cost to implement them—one that may well offset any expected productivity and efficiency gains.
“Replacing all mechanical components to go to mechatronics costs a lot in time and money—as much as 80 percent of a new machine in some cases,” Kowal says. “That may not be significant enough to make it worthwhile, compared with spending a little more on a new machine.”
Or as Stock puts it, “Just because you can upgrade, it doesn’t mean you should upgrade.”
New Ways of Thinking
As noted earlier, packagers who are in the market for new equipment should not look at a machine’s OEE as its only criteria or selling point. However, there are attributes of new systems that can provide them with a head start on optimizing their OEE metrics.
A good start is a flexible, robust design that can compensate for variations in the user’s existing and long-term processes, “not something that will be marginal or ‘good enough’ for the short-term,” Lovell says.
Another plus are machines that are “upgrade-ready” with features such as room in cable tracks, available space in control cabinets and a flexible layout to allow for future changes or additions.
And whether the strategy calls for a retrofit or starting from the ground up, drawing on the widest range of expertise—machine-builders, mechatronic manufacturers and suppliers—from the outset is critical to making a sound investment in equipment.
“You really want to see what technology is out there that can make the machine the best it can be,” Logan says. “For example, once-expensive devices, such as laser sensors and diodes, are now widely available. That means users can now get a higher level precision across their machines for less cost.”
Logan says even a seemingly simple change requires a manufacturer’s expertise. “Going from a mechanical relay output to solid state may require changes to the PLC,” he says. “There are sensors that will work with the few machines that use AC power, but switching to DC power may be more practical from an economical or operational standpoint.”
At the same time, it’s also essential to identify potential machine and mechatronic partners that know these components the best and have the technical smarts to tackle all kinds of applications issues.
“Choose companies that have a proven track record, and give the support you need all the way down the line,” Lovell says.
Brittain agrees, adding, that not all suppliers are familiar with the physics involved with system upgrades. “While a vacuum system may help performance, for example, they also require more compressed air, which really doesn’t help efficiency,” he says.
Whatever course a packaging system owner chooses in the pursuit of improved OEE, Bahr urges them to make sure they fully know what they’re doing and why.
“Spend a little time and understand what OEE is and set definitions that fit your company,” he says. “Success requires a commitment to improvement, which includes considering all aspects of your operation—including those that may not be related to the machines—and following through on them.”
Stressing that many OEE improvement opportunities don’t directly involve the machinery itself, Bahr adds, “They’re your tools, and they’re only as good as the way that they’re used.”
Jim Parsons has written about business and technology issues for more than 14 years.
