Known as PackML, the state model provides a common set of definitions for servo-driven packaging machinery states, such as Ready, Running, Holding and Aborted. It is patterned after the S88 state model for batch processing and provides the basis for a common language for supervisory control systems and other plant-floor integration efforts, according to Fred Putnam, chairman of the PackML team of OMAC (Open Modular Architecture Controls).
The state model is a roadmap for machine functions and the paths they follow. Manufacturers are free to omit various states—a printer could go directly from Off to Running, for example, skipping the Stopped, Starting and Ready states defined in the model—but the model clearly defines the various states, giving machines for multiple suppliers a common language.
“People aren’t even using the same names for the states currently,” says Putnam, a consultant to Markem Corp., a Keene, N.H., maker of marking and coding equipment for food packagers and others. “If people apply the same terms to the equipment’s states, it is much easier to integrate machines into a supervisory control.”
Markem became the first supplier to adopt the state model when it introduced last spring several products networked with the common user interface. “We’re committed to a common definition of machine states, and it has direct benefits because we sell to OEMs,” explains Putnam. “This makes it easier for them to integrate our units into their equipment.”
The state model got another boost during PACK EXPO with the announcement Pharmacia Corp. specified it in an order for tube filling equipment. Machines making use of the standard could be found at various booths on the trade floor, including three units from Campbell Wrapper Corp. and a horizontal flow wrapper from Food Machinery Sales Inc. (FMS).
FMS’s Mach III also was notable for its use of the Allen-Bradley Kinetix 6000 servo drive and a ControlLogix controller, features that greatly simplify wiring and programming, according to Jeffrey Wilkins, FMS controls engineer. “You accomplish a lot with just a few motion commands, and that simplifies diagnostics.” Setup time and functional expansion is a relative snap: Wilkins says a fourth servo axis was added to the machine in minutes, not hours.
The state model’s most ambitious application to date involves a retrofitted packaging line at Hershey Foods. The line includes obsolete wrappers with mechanical drives that were replaced with A-B motion control technology and mechatronics design. By implementing the state model, engineers were able to effect modular integration. “Each state represents a different metric for reporting,” which will help pinpoint problems and permit standardized servicing, according to project engineer Kevin Feidenzer.