Tweak no more: Servos eliminate endless operator adjustments in machinery

Douglas Machine uses servos on its Invex case/tray packer to reduce assembly time and provide faster delivery. Source: Schneider Electric/Elau.

Automation of packaging machinery is nothing new, but the advantages enabled by automation can be surprising. Take reduction of downtime, for example. Packagers often focus their efforts on preventing large chunks of downtime. But short downtimes happen far more frequently and can have a greater overall impact on throughput, according to John Kowal, global marketing manager for Schneider Electric/Elau Packaging Solutions.When each operator on each shift makes small adjustments to the packaging machines they operate, says Kowal, their goal may be to make their machines run just a little bit faster. But the result can be an overly sped-up process that leads to jams, which then require a production stop to remove the stuck carton and manually adjust the machine…again.“An under-recognized benefit of automation is to create consistency by reducing manual intervention,” says Kowal. “By eliminating tweaking, automated changeovers reduce both changeover time and the root causes of stoppages.”

Kowal cites Douglas Machine, an automated packaging solutions provider that specializes in the design and manufacture of cartoners, sleevers, case-and-tray packers, and shrink-wrap systems. The company uses servo motors on its Invex case/tray packer, where 18 servo modules power the 17-cpm machine, reducing assembly time and providing faster delivery.When looking at a Douglas Machine product, users tend to be overwhelmed at first by all the servos, says Kowal. “But these servos translate into direct time savings because of the ability to mitigate manual adjustment. The servo-driven machine is more adaptable to a wider range of products and materials, not just format changes, because servo control is highly precise. The machine can handle wraparound and knockdown-style cases with no tool changeovers, for example. And adjustments within the machine’s size range are handled as an HMI entry, the interface allowing size changes in minutes.“When a machine can sense and adjust automatically to differences in the materials being used, those short, frequent downtimes can be prevented. That’s the biggest benefit to the packager, because typically the machine never gets back to full production speed, and that’s an often overlooked obstacle to increasing productivity,” Kowal says.According to Kowal, Douglas Machine chose to use an Elau automation architecture on its machines because of the smooth, responsive motion delivered by the controller. This motion is possible, he says, because the controllers perform all logic and motion in the same program on the same processor, and all motor control loops are closed inside the servo module (position loops are closed on the SERCOS network). This strategy eliminates latencies generated by multiple processors and hardware modules communicating over a backplane, he adds.Despite appearances, the 18 servo modules actually simplify the machine compared to a mechanical or conventional servo design. The servos require only two power supplies in the electrical cabinet, with two cables leading from the cabinet to machine-mounted modules.

A conventional servo arrangement would have required 18 cabinet-mounted drives with 36 cables snaking from machine to cabinet, or up to 54 cables for brake-equipped motors, he says.

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