Automating Your Packaging Lines
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.
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.
Planning is paramount
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 before the 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.
Role of motion control
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.
Vision systems, sensors, and more
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.
Variable-speed operation upgrades cleaning-swab packaging line
Medical and industrial cleaning swabs made at Solon Manufacturing's main packaging facility in Skowhegan, ME, must be produced to exact specs—as well as quickly and with minimal waste.
Solon's cotton-tip applicator process involved several wheels (for pickup, gluing, and spinning fiber around swab sticks from a continuous coil), a forming rail to shape the tip, and a station to apply binding agent. A fixed-speed motor and a set of adjustable belts and pulleys provided control for this machine section. If a change in swab count, fiber type, or tip configuration was needed, the required mechanical adjustments took 20 to 40 minutes (inset photo).
In the next sorter stage, a mechanical collection arm, photo eye, and counter separated swabs into groups of 100 and moved them onto a conveyor belt. However, substantial waste occurred due to the mechanism's jerky motion that scattered some swabs. Also, the process provided no clear separation between swab batches on the conveyor, causing machine operators to over-pack swab packages up to 2% to ensure that customers were not shortchanged.
In mid-2001, Solon partnered with Horizon Solutions Corp. (a Rockwell Automation product and service distributor) to analyze the existing controls and assess improvements. It was determined that an Allen-Bradley PowerFlex 4 variable-frequency drive (VFD) from Rockwell Automation would more precisely control the swab-tipping equipment and speed up changes for different fibers and tip configurations. With variable-speed operation such changes are now made with the push of a button. PowerFlex 4 ac microdrives are rated up to 5 hp.
A second PowerFlex 4 VFD upgraded the sorting belt, allowing variable speed (up to 40 Hz for one second and 2 Hz for about 10 seconds) to separate sets of swabs so machine operators could easily determine the correct number of swabs per package. The variable-speed drive also eliminated the mechanical arm and air cylinder, dramatically reducing scattered swabs. New machine operators benefit from being easily "brought up to speed" as they learn; machines benefit from reduced wear due to fewer shutdowns.
Peter Martell, process engineer at Solon Manufacturing, says, "To be flexible enough to meet our customers' needs and produce the optimum product, we also realized that we needed variable-speed control on the machine for some of the specialty fiber swabs." Results of the cotton-tipped applicator line upgrade beat expectations: production was raised by 10% and waste cut by 50%.
Three steps to effectively automate a packaging line
Determine your needs
Determine the level of throughput, accuracy and changeover you will need in your packaging line—that is, the number of lines and type of flexibility to run different products down the same line. This will help you determine the type of line layout and the level of automated machines you will need. If you’re running a dedicated line that produces one product at slow speeds, then you should run a fixed mechanical setup on your machine.
Investigate original equipment manufacturers (OEMs) that make machines in your area of automation level. For example:
Generation 1–Non-servo, mechanically line-shafted machines;
Generation 2–Hybrid, mechanical machines with a few servos used in critical areas of the machines; or
Generation 3—All electric servo-based machines that offer the highest throughput and flexible changeover.
Notice which controls supplier (or automation partner) the OEMs are using—for motion, logic, servo, HMIs, I/O lines, motors, etc. Look for an automation supplier used by most of your OEMs; the supplier stands the best chance of offering you a lower-cost controls solution because of OEM acceptance. Look into the automation supplier’s technology and see if it’s right for your needs and flexibility. Once OEM warrantees expire, you will have to support the automation you chose.
Choose the right automation partner
Choose an automation partner before selecting your OEMs.
a) Select a partner who knows the industry and specializes in food and packaging applications. You want a supplier who talks your language and can manage harsh production environments.
b) Demand an open architecture motion-controller system, not proprietary architecture where you are locked into using specific controls, drives and motors, etc.
c) Choose a partner who offers the right technology for your applications, such as ac servo drives for high-speed lines like flow wrappers and cartoners, and pneumatics for casepackers and palletizers that require the lowest cost automation. Mechanical solutions should also be considered for conveyors and components for your machines.
d) Pick a partner who will provide worldwide support and give you the proper attention. Your partner should be dedicated and hard working, providing appropriate resources to get the job done right.
e) Pick a truly global partner, with strong establishments in North America, Europe, and Asia. Why? Because some of your OEMs might supply equipment from other countries.
f) Chose a partner who focuses on higher performance systems, not one who can address only 60-70% of your applications, leaving tougher applications to another supplier. In this scenario, you will need two control systems to meet your needs–and you’ll end up limiting your throughput.
g) Demand key technologies supplied by today’s top automation partners:
Multi-axis synchronization of up to 40 axes of servos on a single controller;
Digital SERCOS fiber-optic communications interface to the drives;
Higher voltage drives with a 230-480 V ac (auto ranging), three-phase input, which eliminates the need for a transformer;
Built-in, absolute motor feedbacks to eliminate homing for your machines, which saves time and money;
Removable flash memory feature on controls, drives, and motors for quick and easy replacement. This eliminates the need to use a laptop computer to download the latest program revision; and
Ability to synchronize one machine control to another, significantly reducing interfacing issues when you’re trying to integrate machines from different OEMs. This can save months of integration time on the plant floor and bring your products to market quicker.
Don’t step over dollars to pick up pennies
Select OEMs which are easy to do business with and have stable management. Make sure your OEMs understand your long-term goals and can apply their resources in a timely manner.
Select one OEM partner, if possible, for the automation of your entire line—unless your process is so specialized that it requires OEMs unique to the application. Consider using the largest, most capable OEM who can subcontract work to smaller OEMs. This gives you a single point of responsibility, avoiding communication and integration issues.
Once you’ve chosen an automation partner and an OEM, have a “line-up meeting” before the project begins. Include the OEM, system integrator (if there is one), automation partner, and the project manager from your company. The results of this meeting should include:
Ensuring each representative agrees to his/her responsibilities;
Developing and agreeing to a list of milestones for the project;
Setting up communication ground rules;
Agreeing to reconvene the group if any major issues arise during the project; and
Meeting again after the project is complete to identify good and bad practices. If all goes well, you may be working together again in the future.
This will help the project run smoothly, and minimize surprises.
Dan Throne, Food and Packaging industry manager, Electric Drives and Controls business unit,