Though it's not a new development for the large variety of packaging machines that produce myriad packaged products, automation now offers a whole new level of packaging productivity. Much of prior automation was limited to an architecture where a large mechanical line shaft, driven by a main motor, powered devices and actuators to accomplish various packaging functions. These so-called Generation 1 machines offered very little, if any, variable-speed operation. Thus the term "islands of automation" applied equally well to packaging lines.

Much of that has changed. Today's Gen 3 machines are all electric, with servo-control to tightly synchronize multi-axis movements through advanced features such as electronic gearing and camming. This evolution had at least one intervening phase—Gen 2 hybrid machines, which employ largely mechanical automation but add servo control for certain critical motions. Generation 2 machines have a large installed base and remain dominant in many applications.

Any packaging line automation project must begin with thorough planning. Dan Throne, Food and Packaging industry manager, Electric Drives and Controls business unit, Bosch Rexroth Corp., suggests a three-step plan that focuses on determining project needs, selecting the right automation partner, and evaluating long-term goals and costs.

Servo motion controls from Bosch Rexroth Electri Drives and Contorls division, use electronic gearing and camming to synchronize machine footprint and maximun product flow.

Throne lists throughput, accuracy, and changeover time as prime parameters for measuring the level of automation needed, including the overall layout of packaging lines and the number of lines needed to handle a given set of products. Both an OEM and automation partner will be needed. He recommends choosing the automation partner beforethe OEM to ensure continual contact with expertise in the latest technologies and control architectures. For a detailed version of Throne's "Three steps to effectively automate a packaging line," visit this article online at www.controleng.com/issues.

Forte Industries (Mason, OH), a nationally known specialist firm for supply-chain distribution operations improvement, likewise stresses thorough planning and a multi-step approach for automation success. "Look at key business requirements. Understand your processes, product volumes and mixes. Control complexity goes with process complexity," says David Gealy, systems consultant at Forte.

Bill Tyng, another Forte consultant, suggests checking product variability and process bottlenecks. These preliminaries help estimate the number of packaging lines, footprint requirements, etc. An automation project moves along typical steps of conceptual design, detailed design—where vendors are identified and bid packages issued for quotes—followed by implementation by selected vendors.

In a similar vein, David Grimmett, sensor marketing manager at Omron Electronics, states, "Automation of packaging lines has to address the business needs of the company as well as purely technical issues." He suggests that automation costs be justified over a five- to 10-year cycle time. "Objectives of automation are quicker commissioning and rapid product changeover for short production runs."

It's not unusual for an automation system integrator to set up the prototype line for a demonstration in a central facility before shipment to the customer.

PLCs still dominate the overall control architecture of packaging lines, however software-based and PC-based control are on the rise. Omron's Grimmett sees an approximate 80-20 proportion in favor of PLCs versus PCs. Bosch Rexroth has a similar view. With the large installed base of pre-Gen 3 machines, it estimates PLC-based architecture still holds an approximate 70-30 edge over motion-control-type architecture.

Type of control architecture depends on who will support the system, according to Forte Industries' Tyng. Certain customers have specific PLC preferences. "It also depends on the level of control sophistication. If there is no expertise to support the PLC, then perhaps PC control is the way to go," he adds.

PLC architecture and HMI features were prominent in packaging machines until recently. "Now with all-electric machines, servo-control content is so high that users focus on such issues as, 'Which motion controller do I use?' or 'What interfaces does the controller require?' " says Bosch Rexroth's Throne. PLCs have become an extra option on these machines, relegated to doing relatively minor control tasks. "PLCs are still on the machine to satisfy customers' specifications and requirements," he adds.

Elau Inc.—an automation technology specialist in Gen 3 machine control solutions—notes that focus of packaging automation in the past five years has been to increase throughput of individual machines. Success has come from using servos, integration of IEC 61131-3 motion and logic controls on the same processor, and various initiatives now part of OMAC (Open Modular Architecture Controls) Plug-and-Pack Guidelines.

In Bosch Rexroth's experience, 30-40% of packaging machines sold today have servo drives and motion-control content. Surprisingly, the differential cost between Gen 3 and Gen 1 machines can be quite small, based on a total system, according to Throne. In part, it's due to as much as 80% reduction of mechanical parts, which incur wear and maintenance costs. Omron's Grimmett estimates an even higher percentage of servo-motor control going into new packaging equipment.

Older packaging "automation" typically employed one main motor with gearboxes, chains, pulleys, etc., to transmit power and torque where needed. This also meant hours spent in changeovers, for example, to change box sizes on a cartoner. "Now encoder feedback [to a servo motor] is used to quickly adjust guide rails or other packaging machinery functions," explains Grimmett.

Motion control enhancements have few limits other than engineering imagination. At the sophisticated end, there is automatic web splicing of one roll of packaging material onto the next, eliminating the need to stop the machine for an operator to load a new roll. Servo control can also help at the back-end of the line to orient packages or bottles for inspection, labeling, etc.

Packaging line automation increasingly makes use of machine vision for product inspection. This can be to check a certain feature of the item or to detect the presence and/or correct position of labels. Driving the trend are lower costs and greater user awareness of vision systems.

Criticality of the application is another factor. Pharmaceutical packaging has the highest demands, including the need to provide 100% process validation. "By incorporating a vision system right in the process, one bad item in a batch can be detected and eliminated. It's like closing the loop on the process," states Omron's Grimmett.

Ability to sense clear materials (storage bags, bottles, etc.) has a growing demand in some packaging applications. One product example is Omron's E3Z-B retro-reflective sensor, capable of detecting very small light-level changes, explains Grimmett. Custom optics and electronics make sensors with this level of sophistication possible. Typical application is in PET plastic bottle lines, checking position of caps and labels. [Just in case you're asking, PET is short for polyethylene terephthalate—a common plastic resin used in manufacturing bottles.]

Touchscreens, operator displays with online diagnostics, weigh scales, and similar devices represent yet another branch of automation. For operator interfaces and displays, the key is to filter the vast amount of data available and present the most meaningful information to the user, explains Forte's Gealy. Graphics and data critical to the operator must be identified in the automation process.

Perhaps the greatest advance with Gen 3 packaging technology is ability to distribute motion control to each individual machine or line section. Individual servo drives and servo motors handling specific packaging stations can be precisely synchronized by one controller via a fiber-optic network (e.g., SERCOS), as shown for a typical can filler-sealer line in the "Synchronizing machine sections" diagram.

Bosch Rexroth motion/logic controllers for Gen 3 machines take either a rack-based or PC-based form. One controller handles up to 40 motion axes to unburden the system controller, though 20 axes are more typical, explains Throne. Multiple controllers can accommodate up to 1,280 axes.

In the past, packaging machines sections were not synchronized to form an integrated line, explains Tom Jensen, senior technology evangelist at Elau. "Packaging lines have depended on accumulation devices to queue work in process between machines. Now, packagers are recognizing the benefits of more tightly synchronizing the packaging line." Conveyors have often served as product accumulators between machine sections, including such clever variants as spiral conveyors that conserve floor space.

Synchronization among controllers in a packaging line is a separate concern from that of motor drives. This refers to OMAC's synchronization bus (based on IEEE 1588), which seeks to unify time clocks in different parts of distributed test, measurement, or control systems to ensure optimal data flow.

Manufacturers now design more modular, multifunctional machinery, which does away with accumulation bottlenecks and reduces footprint (unit size). Modular design also enables faster package format changes and future machine reconfigurations.

An OEM could, for example, incorporate a cartoner module to a filling/sealing machine, or add a case packing robot to a cartoner. At the control level, this extra functionality can come from adding a chunk of code, such as an IEC function block, without the need for more control hardware. "This level of control scalability is an important attribute of Generation 3 packaging machinery," Jensen adds.

He believes that to be competitive at the Gen 3 machine level, the minimum requirement is to adopt integrated motion and logic control. According to Jensen, automation architectures must go beyond PLC-type data structures to enable efficient interfaces to MES data, to upstream operations for their impact on throughput, and to see the big picture of equipment effectiveness.