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DETAILED CASE STUDY: PLC-Cardboard Cartons

International Paper makes corrugated boxes and was beginning to suffer costly downtime because of aging equipment. The machine itself is known as a “flexo,” short for flexographic printer. It die cuts the cardboard, creases and folds a box, then unfolds it to lay it flat and stacks it on a pallet. Also, during the process it prints onto the box the product or branding information the customer requires.

the-pointPROJECT DETAILS

ROI: Less than 12 months

Project duration: 8 months culminating with 14-day startup

Team
Client: 4
Concept Systems: 2 engineers

Concept Systems’ time on site: 14 days

Pain points

  • Downtime from failure of old parts
  • Hard to source replacement parts
  • Long product changeover time
  • Difficult interface slowed new operator training
  • Replacement machine would be very costly

Results

  • Nearly doubled production output per shift
  • Less downtime
  • Fewer expensive repairs and maintenance
  • Reduced changeover time between different products
  • Improved training time for new operators

Technology used

  • ControlLogix PLC
  • Kinetix 6000 and 7000 motion (drives and motors)
  • Absolute position encoders and Ethernet-based remote I/O
  • PanelView Plus touch screen

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The plant typically made fairly large boxes, for everything from watermelons to lawnmowers. These box types are a high margin product.

Hard to find parts

The existing machine was many decades old and very large, about 100 yards long. It used an obsolete control processor. Any failure of an electrical component could result in a long downtime because electrical distributors no longer stocked the parts, and plant staff sometimes had to try to hunt down parts on eBay.

“There’s sort of a black market for these components on eBay, and they get to be very expensive,” said Tim Dykstra, a sales engineer who works in Concept Systems southeast office in Charlotte, N.C.

Costly training and servicing

Moreover, the original machine builder was based in Germany. Service for the system came from overseas, and technicians had to fly to the United States at least once a year to do maintenance.

As for the day-to-day operations, the system had a clumsy interface with push-button stations at various parts of the machine. An operator had to walk around to different stations to make adjustments when it was time to change from one type of box to another. The changeover time was typically 45 to 50 minutes.

Training new operators was time-consuming, as well.

Overall, it was getting increasingly costly to run this machine.

The solution: a retrofit

Because the machine itself was so large and had many years left in terms of mechanical lifespan, Concept Systems worked with corporate and factory engineers to design a retrofit, adding a new control system to the existing machine.

Concept Systems replaced the main PLC controller, remote IO, servo drives, variable frequency drives, and added absolute encoders and touch-screen interfaces, along with customizing all the necessary software.

“A retrofit makes sense when there is a ton of steel in the machine — many tons, actually — and a lot parts,” Dykstra said. “The cost of a new machine might be $6 or $7 million. Whereas retrofitting came in at about $800,000. It will add another 15 to 20 years of life to that machine.”

“The biggest thing is the recipe system,” he said. The new control system has all the settings for the various types and styles of boxes, saved in a recipe management system. This allows operations to quickly select a new box and the machine automatically positions itself to accommodate the new box type. This shaved more than half an hour off changeover time and was one of the main factors in increasing shift capacity.

Changeover time cut by more than 80 percent

Changeover from one type of box to another now takes 8 to 10 minutes, compared to the 45 to 50 minutes previously.

Not only are replacement parts much easier to find for the new system, they are much less likely to fail in the first place.

“The new touch screen interface is far more intuitive. A new operator can pick it up quickly, so training time was reduced,” Dykstra said.

The installation challenge

Another challenge was a tight timeframe for the installation of the new system. With this machine producing the highest margin boxes for the plant, its uptime was essential for the plants’ profitability.

“The plant could only be down for 14 days,” Dykstra said. “We worked around the clock for those 14 days to meet the deadline.”