Capitalizing on Motion Control Innovation

Single-serve stick packs are one of the hottest trends in consumer packaging, and Ropak Manufacturing Co., Decatur, Ala., is poised to service that growing market with an innovative machine it calls Stik Pak.

It’s a multiple-lane, continuous motion vertical form/fill/seal machine that employs 14 iSH integrated servo motor and drive modules from Elau Inc., Schaumburg, Ill.—10 to control dosing heads and four to control sealing jaws and cut-off knives, with a virtual (i.e., software) axis for controlling the phasing of the system. In operation, dancer-controlled infeed to 10 in-line slitters is transferred by adjustable turning bars reminiscent of newspaper presses to the modular forming, filling and sealing station, which can produce 600 to 1,000 stick packs per minute, depending on product flow characteristics, packaging materials and fill temperatures.

The dosers can be run individually, not just for jogging or set-up, but also to adjust production rates and allow operation even if some dosers were to be disabled. Finished packs can be automatically collated onto optional lug conveyors for secondary packaging.

According to Ropak Technical Services Manager Richard Matthews, the use of Elau’s integrated servo modules has helped reduce Stik Pak’s component count, cabling and electrical cabinet space requirements, and Elau’s PacDrive automation platform’s software modularity supports Ropak’s recipe-based approach to operator interface. Recipes can be stored in the PacDrive controller’s flash memory and accessed from the operator’s touch panel.

The high-speed machine is also exceptionally flexible, thanks in part to its use of the integrated servo modules. While some competitive machines require a factory technician on site for days and $70,000 to $80,000 in assemblies for each format change, the Stik Pak can be changed over in a few hours by plant personnel, with minimal part change.

Streamlined assembly

The Stik Pak is the first of Ropak’s vertical form, fill and seal machines to use Elau's iSH units, and Ropak President Andrew Fenton is pleased with the results this integrated servo module approach has yielded, particularly in terms of wiring. “The connection system so simplified the machine's set-up, that I would say conservatively that we saved 15 percent of the construction time involved with the more usual system. As we streamline our assembly process on these machines, it is not out of the realm of the possible to expect construction time savings of 20 percent to 25 percent.”

As mentioned above, the use of integrated servo modules has helped Ropak address the issue of cabinet size, and, as Fenton observes, “I think anyone who builds multi-axis machines has to grapple with this problem.

“The primary size consumption in such cases,” he continues, “usually comes from the rack or racks of servo drives. Apart from miniaturization, which apparently has been naturally happening for many years, we have seen two approaches to solving this problem. One is to shave off servo drive width and exchange it for added drive height and depth. Sometimes this trade works out, but in some cases, it just changes the dimensions of the problem. The second approach is to incorporate the drive with the servo motor itself.” It’s this second approach that has worked for Ropak’s Stik Pak.

What’s the optimum amount of intelligence to distribute to the servo/drive level? That question is always at least potentially present today when servos are employed, and Stik Pak is no exception. “To me, the importance of distributed servo or drive intelligence really depends on the nature of the application,” says Fenton. With Stik Pak, “because the various axes are timed together, a central controller makes the most sense.

“On the other hand, my company has also made use of an intelligent drive where we required only a single axis performing its intended task. The drive included its own logic processor for dealing with the sensors and the HMI (human-machine interface) on the unit, as well as the unit's motion control. The unit was incorporated as part of an assembly line.

Do your thing

“Where I see this becoming really powerful,” Fenton continues, “is in process control where designers want to simplify the process by localizing the complexity where necessary. In other words, drives with distributed intelligence become specific process modules. The process controller need not possess the details of how the process module performs its task. It merely needs to be able to tell each process module, ‘Do your thing now,’ and watch the feedback.”

Fenton feels this modular approach has significant advantages for users. “Each specific process module is oriented toward a single primary task. It follows that the program in each will be easier to read and understand than a central controller program designed to manage multiple devices. For the same reason, troubleshooting and diagnostics should also be simpler.”

The future of motion control technology is a subject to which Fenton has given some thought, and he sees a number of factors driving innovation in this area. “One that comes to mind where packaging is involved is waste and sustainability concerns. Companies involved in packaging often pay more for the packaging material than for the product inside. Furthermore, as consumer consciousness over reducing waste increases, producers catering to these sensibilities will seek ever more innovative packaging solutions.”

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