When it’s time to buy paper towels and bath tissue, you want lots of choices: one-ply, two-ply or even four-ply. You might opt for super-strong or ultra-absorbent, and decide whether you prefer a smooth surface or a quilted design. So Paper Converting Machine Co. (PCMC, www.pcmc.com) designed its next-generation Forte surface rewinder for flexibility, speed and rapid changeovers.
The controller combines motion and sequential control, eliminating the need for a separate motion controller and the costs associated with programming, installing, synchronizing and stocking spare parts for it.
A typical converting line begins with the unwind stand, which unwinds the web of tissue or towel material from the parent roll. The next step is the embosser, which adds texture and bulk to the paper. The rewinder applies perforations, then wraps the paper around a cardboard core into long, tight rolls of adjustable diameter and length — called “logs.” A tail sealer applies a thin layer of glue to the end of the roll to keep it from unraveling, and the accumulator then stores the rolls until they can go through the log saw, which cuts the rolls into consumer sizes.
One of the more complex parts of the line is the rewinder. Tissue paper is relatively fragile and can be easily damaged or torn during the rewinding process. The challenge was to design a rewinder that operated reliably at high output rates with precise handling of the fragile tissue web, yet was fast and flexible enough to change over from one product to the next within minutes.
“When our customers are in production, they require fast and consistent performance,” says Jon Vander Pas, tissue product line engineer leader at PCMC. “We knew we needed to look beyond center-driven winding technology, which places too much tension on a web.”
“Previously, we focused on center-driven technology, but after conducting extensive market research, we saw an opportunity to create a unique machine — leveraging PCMC surface winding technology — that could better meet our customers’ needs,” says Vander Pas.
To address the need for a lean, easier-to-use design, PCMC standardized on the Allen-Bradley Logix control platform from Rockwell Automation (www.rockwellautomation.com), which includes an integrated suite of control, networking and visualization technologies. As part of this platform, the rewinder has multiple ControlLogix programmable automation controllers that cover discrete, process, motion and drive control. The controller combines motion and sequential control into a single control environment, helping to eliminate the need for a separate motion controller and the costs associated with programming, installing, synchronizing and stocking spare parts for it.
A high-speed SERCOS interface links the controller to Allen Bradley Kinetix 6000 multi-axis servo drives and PowerFlex 700 AC drives to help precisely guide the position and profiling of the paper rolls.
Adhering to open-access design and modular software design principles means maintenance and operations can use the Allen Bradley PanelView Plus operator interface terminals and PCMC custom-developed Active X controls to quickly access hundreds of machine variables and diagnostics. In addition, the components inside the rewinder have front-mounted connectors and other features that make them easier to access for both routine and unscheduled maintenance activities.
Traditional rewinders crank out about 50 logs per minute (lpm), but the Forte can produce more than 60 lpm at web speeds as high as 800 meters per minute. “Guiding a web at near-zero tension, it practically floats around the core,” says Vander Pas. “It maintains caliber and bulk even at high converting speeds.”
Standardizing the control platform and components reduced the number of parts in the rewinder by one-third. This minimizes the number of spare parts needed in inventory, saving space and capital, and shortens training time for both PCMC personnel and the end customer.
The servo drive enclosures are as much as 50% smaller than their competitors’, reducing the machine’s footprint. The integrated motion-control capabilities of the ControlLogix controller further reduce panel space by eliminating the need for a separate motion controller.
Integrated motion-control capabilities also helped PCMC meet its performance standards more quickly. “The seamless integration helped reduce testing time by nearly 70%,” says Vander Pas. Using the Logix Position Caming (PCAM) capability and a new interpolation method, PCMC can implement a CAM profile for the rewinding process using only 100 segments instead of the 900 segments required with the old solution. The approach helps reduce memory usage and smoothes the rewinding process, increasing production speed and reducing the likelihood of torn paper.
Because of the open design of the Forte, customers have access to hundreds of variables, allowing them the flexibility to customize the machine’s basic settings. The Forte also can store recipes, giving customers the ability to change over their lines from one product to the next seamlessly, with little or no downtime.
Orders for the Forte already have started to roll in.