Control Systems

Control system integrates PLCs and PACs

In this installment of What Works, a control system upgrade improves reliability and reduces maintenance costs.

As food and beverage manufacturers adapt to meet changing consumer demands for freshness and convenience, they rely on packaging suppliers to deliver cartons and containers comprised of a variety of materials and in a range of shapes and sizes. Evergreen Packaging (www.evergreenpackaging.com) works with many manufacturers to develop fiber-based packaging for everything from juice and candy to specialty products such as liquid eggs and fabric softener.

View more content on PlantServices.com

At its Olmsted Falls, Ohio, plant, Evergreen produces milk cartons from rolls of paperboard supplied by one of its paper mills. The plant uses eight sealers and converting machines to fold, print, die cut and seal the cardboard cartons (Figure 1). The high-speed converting operation produces cartons ranging in volume from four ounces to one-half gallon, with an average output capacity of approximately 400,000 cartons per hour.

Figure 1. An integrated control platform provides benefits for a plant that manufactures milk cartons and other converted paper products.
Figure 1. An integrated control platform provides benefits for a plant that manufactures milk cartons and other converted paper products.

After a converting machine prints the words and images on the paperboard, the same machine scores the paperboard along what will be the edges of the milk carton, where the box will fold later. A die lowers and stamps out a flat, scored and printed piece called a blank.

The blanks are loaded into a sealer, which takes the blank and folds it laterally into an overlapping side seam. The seam is heated and squeezed. The sealed and folded blanks are then loaded into corrugated cartons and shipped to the dairy. The dairy uses specialized machinery to transform the blanks into open containers, where they’re filled and top-sealed.

Challenge

Over the years, Evergreen machines have used a mix of control technologies from different suppliers. Most recently, the machines consisted of outdated drives, relay logic and PLCs running on proprietary software, which was making them increasingly difficult to operate, maintain and support. To make changes to the machines, engineers had to perform complex reprogramming for each new control function.

Access to reliable support also was a growing concern as the company was finding it increasingly difficult to find engineers with the knowledge and skills needed to support the older, diverse technologies. In addition, limited diagnostic capabilities made troubleshooting an ongoing challenge.

Another area of complexity centered on the extensive amount of wiring required with the existing control system design, which complicated maintenance and repair, and multiplied the potential points of failure.

“Some of our machines had 15 e-stop buttons wired in series, which produced a troubleshooting nightmare,” says Richard Stewart, senior project engineer, Evergreen Packaging. “Even a simple problem, such as a failed sensor, could be extremely difficult to identify and locate, putting the entire operation at risk for incurring substantial downtime losses.”

With most of the technology more than a decade old, Evergreen wanted to upgrade its production machinery with a standard control platform. This would help simplify programming and configuration, improve troubleshooting capabilities and ensure wider availability of support and replacement parts.

Solution

To make changes to the machines, engineers had to perform complex reprogramming for each new control function.

Evergreen turned to Rockwell Automation (www.rockwellautomation.com) for a standard control system that would significantly enhance the performance, reliability and ease of use of its production machinery (Figure 2). At the heart of each machine is an Allen-Bradley CompactLogix programmable automation controller (PAC), which allows Evergreen to connect machine components in an open, integrated environment. The controller tracks the sequence of machine events and allows operators to monitor variables and status information in real time to easily identify and diagnose problems.

System programming is performed using Rockwell Software RSLogix 5000 programming software; engineers select the motors and drives the machine will use, and encoder information and drive parameters are automatically uploaded.

“Using a single programming package across all of our machines significantly minimized the learning curve for our operators,” says Stewart. “The software’s easy-to-use features proved to be a huge timesaver, especially the ability to integrate all the drives and interfaces into a single project file.”

As part of the upgrade, the machines are equipped with Allen-Bradley PowerFlex 70 and PowerFlex 40 AC drives, which provide smooth, efficient motor control. The drives help maximize throughput, reduce the wear and tear on machine mechanics, and provide enhanced diagnostic and monitoring capabilities. The drives are connected to the controller via an EtherNet/IP network, providing operators with access to detailed drive and motor status information.

“With the EtherNet/IP connectivity enabled by the drives, we’re able to access a wide range of operating and performance data,” says Stewart. “We can track run time off the drives themselves and monitor loads and other variables for better diagnostics and more proactive maintenance.”

Operators have a window into the machines through an Allen-Bradley PanelView Plus human-machine interface running the FactoryTalk View HMI software.

To help improve machine safety and reliability, each machine is equipped with an Allen-Bradley SmartGuard 600 safety controller. Connected to the machine controller via DeviceNet, the SmartGuard controller simplifies safety functions, eases troubleshooting and minimizes downtime by giving operators clear identification and status of each e-stop event.

Results

The integrated control technology allows Evergreen to reduce the size of its installation by 50%. It also minimized the number of spares needed in inventory, saving space and capital.

With improved access to machine performance data, managers can view run-time variables easily and check throughput and scrap rates. This allows the facility to plan downtime based on actual run times, resulting in more cost-effective preventive maintenance.

The improved monitoring and diagnostic capabilities helped Evergreen reduce its maintenance costs and increase its uptime by 25%. Equally important is the increased reliability, attributable in large part to the significant reduction in the amount of wiring required.

As part of the control system upgrade, Evergreen enrolled in the Rockwell Automation TechConnect Support program, which provides the plant with around-the-clock access to a global network of support centers and technical resources.

“I can’t say enough about the support we’ve received from Rockwell Automation,” says Stewart. “From start to finish, they’ve been right there with us, giving expert insight and analysis. This support has been instrumental in helping us maximize the value of our existing plant assets, as well as our new technology investments.”

Ultimately, the controls help Evergreen reduce maintenance and support costs and improve machine reliability. As product quality and speed of delivery become more important for its customers, Evergreen is now better positioned to meet these demands while significantly enhancing its competitive position and strengthening its bottom line.