To servo or not? That is the perpetual question for packaging equipment engineers.
Few would dispute that servo drives have long held potential for machines with greater accuracy and control, higher speeds, and improved flexibility. But in packaging, the high cost of servos has until now inhibited broad use of the technology. And despite continuing servo price declines, many packaging machine builders believe the technology is still too expensive.
Now, however, there are growing signs that servo technology may be primed for wider use in the packaging industry. Driven by end-user demands for improved machine performance, more packaging equipment vendors are rolling out a new style of machine known as "Generation 3."
The distinguishing characteristic of Gen 3 machines: they're designed from the ground up to exploit the advantages of closed-loop servo control technology. The result: Machines that are cost-effective and offer performance improvements over mechanical and hybrid servo/mechanical designs.
"Today, only about 15% of packaging machines are making use of servos in a big way," estimates Rick Lidington, executive vice president at machine builder R.A. Jones & Co. Inc. (www.rajones.com). But Lidington says the servo trend is definitely upward-around 90% of the machines that Jones is currently building are servo-based.
High Cost Hurdles
Still, the relatively high cost of using servos remains an issue. "The installed cost of our servos has gone down by 5 to 10% annually for 10 years," points out John Downie, packaging industry manager for vendor Yaskawa Electric America, Inc. (www.yaskawa.com). But most also agree that servos are still significantly more costly to deploy-at perhaps $3,000 per axis on average.
"There's still a substantial part of the market, maybe 50%, that has not yet appreciably adopted servos," observes Cosmo Mirra, director of product planning and market development for the General Purpose Systems Group of Danaher Motion (www.danaher.com).
Besides the cost of the technology itself, says Mirra, another major hurdle is a "knowledge void" at many machine builder shops. "The packaging industry is still dominated by small to medium-sized companies, and they are less likely to have someone on staff to convert their machines from mechanical or hydraulic to servo," Mirra explains.
In addition, not all packaging applications necessarily need the benefits of multi-axis servo technology. Cartoners made for the candy and confectionery industry, for example, which changes packages sizes frequently, could likely benefit from the faster changeovers possible, notes Maria Ferrante, director of technical services for the Packaging Machinery Manufacturers Institute. On the other hand, a bottling operation running the same product at high speeds for long periods might not need a servo-based machine.
However, machine builders may want to keep a close eye on the trend toward servo-based, third-generation equipment. "The big-name players in the packaging business today are specifying and using servo technology, and they're continuing to push the envelope," says Sal Spada, research director who follows the automation market for ARC Advisory Group (www.arcweb.com).
Strong Industry Support
Indeed, some of the world's largest packagers-including Hershey, Nestle, and Unilever-are among the strongest proponents of Gen 3. All are members of a group known as the OMAC (for Open, Modular Architecture Controls) Packaging Workgroup, whose mission promotes use of digital motion control and open architectures. Major machine builders and motion controls vendors are also part of the group, whose so-called "Plug-and-Pack" interoperability initiatives depend heavily on servo technology.
Servo motors used in previous generations of packaging machines were typically added as retrofits. But Gen 3 designs start from a clean sheet of paper, eliminating many of the traditional mechanical components, such as mechanical line shafts, chains, and cams. In their place: an electronic line shafting design that relies upon individual servo drives on each of multiple axes, some with up to 80 servo motors.
This approach significantly reduces parts count and mechanical complexity, creating smaller, more streamlined machines that are modular and more flexible for faster changeovers. Third-generation machines are also easier to sanitize and maintain, their developers say. The high precision afforded by closed-loop servo control-with continuous positional accuracy to about 0.00005 of a shaft revolution-often also lets the machines run at higher line speeds, by eliminating mechanical backlash and creep.
And fewer parts and faster assembly times are sometimes enough to offset the higher costs of adding servos to a design, some machine builders contend. This means that Gen 3 machines can be priced at no more-and sometimes less-than their mechanical predecessors.
To be sure, some Gen 3 machines will cost more. ARC Advisory Group's Spada notes that heavy use of servo technology can add up to 30% to the price of a packaging machine. But that can be quickly offset by operational advantages, he says. "A lot of end users I talk to don't even think about the extra cost because they can very quickly cost-justify servo."