By Jason Vanderpoel, web guide sales manager, BST North America

Web guiding is a critical aspect of many converting processes, ensuring that materials such as films, foils, rubber and textiles are directed accurately through various manufacturing stages. While standard web types like an unwind/winder package, positive displacement guide and steering rolls are common in most applications, certain specialized methods are crucial for optimizing performance in specific tasks. This article will cover several less common but highly valuable web guiding techniques, perfect for optimizing precision, efficiency and product quality in a variety of converting applications.

Master-Slave web guiding system

In industries such as laminating, coating and flexible packaging, the Master-Slave guiding system is crucial for ensuring precise alignment between two material webs; this is essential for quality and efficiency. This system operates by maintaining either a constant offset or perfect alignment between the edges of the webs. “Master” refers to the primary web, while the “Slave” is the secondary web that follows the Master’s movement. Two sensors track the positions of both webs, ensuring continuous, accurate alignment (see Figure 1).

The system begins by aligning both webs to a predefined position, using wide-array edge sensors or CCD cameras to detect their edges. During production, if the Master web shifts laterally, the system automatically adjusts the Slave web’s position to maintain the desired alignment. This continuous monitoring and adjustment will ensure that the edges remain in line with each other or maintain a consistent offset throughout the production process, regardless of conditions.

The Master-Slave system provides several key benefits. It offers enhanced precision, especially in laminating applications, where misalignment can negatively affect product quality. By automating alignment, it improves efficiency, reducing the need for manual adjustments and minimizing the risk of human error. The system also ensures consistency in high-speed production applications and, most importantly, offers cost-effectiveness by eliminating the need for two web-guide controllers.

Common applications for this system include laminating films, paper or textiles, where precise positioning is necessary for high-quality bonds. It also is widely used in printing to maintain edge alignment for multilayer printing and in packaging to ensure accurate cutting, folding and sealing.

Overall, the Master-Slave guiding system is a vital tool in modern manufacturing, offering automated precision to improve quality, efficiency and consistency across various industries.

Web-width monitor

Web-width monitoring is crucial for ensuring that the correct width is maintained throughout the guiding and processing stages, especially in applications where material width is critical to product success. This system tracks the web’s width as it moves through production, helping operators verify proper machine set-up and material size (see Figure 2). It also can detect issues such as “necking,” where the web narrows, indicating a set-up problem or defect.

The system is particularly valuable when working with high-value materials, such as optical films, foils for battery production or custom non-woven materials, where maintaining consistent width is vital for product quality. It also is essential in coating applications, where precise width control prevents inconsistencies and reduces material waste. Another common place for these systems is on seamer machines that make labels for cans and bottles. Running too narrow of a web would yield poor results and unusable products.

The typical system uses a CCD camera(s), wide-array sensor(s) or simple edge detectors on a positioning unit with linear feedback. The camera or sensor(s) will pick up the edges of the material, and the position data is fed back to the controller to calculate a web-width value. Typical accuracy is +/-0.1 mm or better, and oftentimes the data is fed back to a host PC or PLC over a fieldbus like Ethernet or ProfiNET for data acquisition. Setpoints can be used for various cases, like the web being too wide, too narrow or the material is off to one side. The controller then can trigger an output for a tree light or audible alarm to notify operators that something is wrong in their process.

Belt guide control system

An advanced guiding system is essential for industries that rely on conveyor belts, such as food processing, or operations involving large ovens or chillers. Conveyor belts in these environments often are very expensive, and even a small misalignment or overrun on the idler can lead to significant damage, costly downtime and expensive belt replacements. By guiding the conveyor belts, converters can extend the life of the belt and ensure a consistent, reliable production process.

The belt guide control system typically uses a wide array sensor or camera in combination with an actuator that provides linear feedback, often in the form of a steering roll or an end pivot steering roll web guide system, depending on the specific application (see Figure 3a and 3b). In this set-up, the sensor or camera detects the position of the belt, and the controller compares this information with feedback from a potentiometer in the linear actuator, which tracks the actuator’s position. The comparison between the edge detector’s output and the potentiometer’s output identifies any misalignment or error, which then sends a command signal to adjust the actuator’s position. This adjustment ensures that the belt’s position is correctly aligned, as both outputs now will match.

When the system is switched to auto mode, a closed-loop servo control is established. The combined outputs from the edge detector and the actuator potentiometer control the motor of the linear actuator. If the edge detector detects any misalignment or belt error, it compares this information with the actuator’s current position. The system then adjusts the position of the guide mechanism by a proportional amount, correcting the belt’s alignment. This continuous feedback loop ensures that the belt remains properly aligned throughout the process, automatically compensating for any detected errors and maintaining a consistent and reliable operation.

Turn bar

The turning bar is a critical component in advanced web guiding systems, specifically designed to redirect the web by 90° while ensuring smooth and continuous material flow. Installed at a precise 45° angle to both the entry and exit direction of the web, the turning bar allows the web to travel around it in a controlled 180° arc, exiting the guiding device at a right angle (see Figure 4). This method is particularly beneficial in applications where a change in direction is required without disrupting the web’s integrity or process efficiency.

By guiding the web over a 45° angled idler or air-turn bar, the system effectively handles sharp directional changes, ensuring a seamless transition while maintaining the web’s trajectory, even under high-speed conditions. This smooth redirection capability is essential in optimizing material handling and minimizing potential web defects during the manufacturing or processing stages. They often are found on printing press applications where a release liner, foil stamping process, etc., needs to be added, and operators must have an easy way to add material rolls. They also are ideal for applications where operators are transporting webs from one machine to another and have limited floor space to keep the process flowing.

Edge chaser

The edge chaser is a specialized web guiding system designed to detect and track the edge of the web during a roll-to-roll process. Unlike traditional web guiding systems, which primarily focus on centering or controlling the entire web, the edge chaser targets the precise tracking of the web’s edge. This technique especially is valuable in applications where monitoring the movement of the web’s edge is critical, such as in inspection and defect detection processes.

Edge chaser systems operate by using sensors or cameras that identify the edge of the web. These sensors are mounted on a shifting base assembly or a rodless-style actuator, which moves laterally in response to the web’s motion. As the web moves through the roll-to-roll process, the actuator continuously tracks the edge, ensuring that the web remains properly aligned for subsequent operations. This real-time tracking capability allows for seamless integration with inspection cameras, printing modules or defect tabbing machines, which rely on precise edge detection to effectively function.

A common application is the inspection of the web edge for printed features such as bar codes and critical text on high-end materials used in battery and electronic manufacturing. Any cases where defects are found, the web then is flagged and removed downstream, where a finished roll can be run through a doctor machine. Operators then are able to remove the bad sections for the web and splice the web back together to ensure a consistent, error-free product. 

Jason Vanderpoel has more than 25 years of experience in the converting/automation industry and is a proud University of Wisconsin-Madison graduate with a BS in Mechanical Engineering. He presently holds the position of web guide sales manager at BST North America, a global provider of AccuWeb and BST web guides. Vanderpoel can be contacted at email: jason.vanderpoel@bst.group or linkedin.com/in/jason-vanderpoel-2423272/.