Ever wonder how a massive roll of paper converts to stunning labels that pop on crowded shelves? Web handling plays a massive role in the label converting process, especially when accounting for speed, efficiency and waste. Unlike sheetfed manufacturing, web handling processes a constant stream of materials present in roll-to-roll label printing. Web handling is the guiding, controlling and converting  of web materials such as papers and films. Plus, there are numerous components in a converting line that make up the web handling process.

“Web handling refers to the act of moving a web through the process from its raw state – unprinted and in roll form – to a finished state – decorated and converted for its eventual use as a package or label,” states Gavin Rittmeyer, VP of sales and marketing, Martin Automatic. “At minimum, transporting a web through the process involves unwinds, rewinds, idler rollers, driven nip points and tension control devices. When properly designed, web transport systems allow processes to achieve their highest possible speeds and convert lighter, thinner substrates when packaging and label designs allow.”

“Tension is the most critical factor to consider in web handling,” explains Dave Grenwis, marketing manager, Delta ModTech. “It affects all aspects of web converting – lamination, diecutting, registration, printing, winding, steering, etc.”

“Web handling starts at the unwind,” explains Bill McCroskey, engineering fellow, Mark Andy, adding, “And the unwind tension system provides the setup for the entire process. The roll is unwound and given enough tension to let the guiding system work, and a dancer system is usually used so a lower inertia item can move to accommodate the imperfections in the roll.

“Once the product is guided, the web is brought to a processing tension by an infeed pacing system,” says McCroskey. “This is usually at a higher tension than the unwind since the core and roll limit the amount of tension that can be used during unwinding. The infeed further processes the tension and feed rate. Usually from this point, impression, pacing, and anvil rolls are at a constant rate or draw control. Special pacing to condition the web for digital or critical processes and semi-rotary isolation are often employed. The web is then paced by an exit pacing roll to isolate the process zones from the rewind, sheeter, turret, etc. Careful consideration to brakes, web guides, tension transducers, and tension control systems must be made for successful web handling.”

According to Maxcess, manufacturers can incorporate various tools into their processes to effectively transform raw web material into final products. These processes often include coating, slitting, cutting, stamping, laminating, plating and more. Each process requires a component carefully chosen to meet the needs of the material and converting line. The solutions have also been engineered to account for a wide range of challenging variables.

“Changes in materials create new demands and parameters for existing machines,” comments Darrell Whiteside, regional sales director, Maxcess. “Running thinner, more sensitive materials on machines designed to run something else creates an endless parade of issues and bottlenecks. Having a partner/supplier who understands the process and offers end-to-end solutions is more important than ever.

“Web handling is not simply throwing individual components at the process,” adds Whiteside.  “It is about the systems and how they function together to create an efficient, consistent workflow through the machine.”

There are a number of considerations for label converters to keep in mind when addressing web handling. The type of work and substrate are chief among them, as the requirements involved in delamination, lamination, reverse print, foiling and embossing, to name a few, will all impact press pacing.

“There must be controls in place to help accommodate these changes to the base material so waste is reduced,” states McCroskey. “Tension systems, variable pacing, and image length adjustment of some modern servo-driven machines can help the converter waste less and accommodate a greater variety of applications and substrates.”

“The main process specifications, like process type, speed and web width, must be reviewed. However, substrate properties are equally important – material caliper, adhesive weight, coatings and modulus will affect everything in the system,” notes Rittmeyer. “A properly designed system will move the web through without damaging the web or adversely affecting the process. The web is the only part of the system that actually contacts the equipment, and that contact is through the idler rollers. Even choosing, for example, the wrong idler roller bearings can degrade the system, resulting in tension disturbances, wrinkling or other problems in the web.”

In addition to common concerns like tension control and web alignment/tracking, mill roll quality is another aspect of web handling that cannot be ignored. “Mill roll quality is often overlooked by converters when specifying or purchasing new equipment, but this factor can often define what is needed to successfully control tension and web alignment through the machine,” explains Chris Plude, product engineer, KTI. “For instance, if a converter often receives mill rolls that have minor dishing or roll edge misalignment, the equipment they purchase must be equipped to manage those defects. For this case, the KTI Z Series butt splicers come with an automatic roll side lay feature to keep the roll edge running straight into the machine. This is a rough course correction but precise correction can be obtained by adding a servo-driven web guide system at the point where the web enters the first print station.”

The supply chain constraints have not eluded web handling processes, either. The difficulty in sourcing paper has prompted many converters to turn to alternative materials.

“These substitutes may react differently to the machine’s pacing and processing,” says McCroskey. “Filmic materials or liners may be more sensitive to tension, float over pacing rollers at speed, and be subject to wrinkling and more. Material handling items, such as nips, variable pacing, length adjust, and higher traction, low drag, web spreading idlers, may be needed. Heavier or stiffer material substitutions may be more sensitive to transmission errors in pacing and idler runout, too.”

As Plude notes, thinner materials, such as films, often deal with the challenge of web wrinkling, which is often caused by speed and web stiffness. “The lateral, cross-web stiffness of thin substrates is relatively low, thus making it unable to resist external forces that cause wrinkling,” remarks Plude. “The most common source of such a force is air entrainment between the web and roller surfaces that cause a bubble to form and that bubble can turn into a wrinkle. This effect becomes more pronounced with higher speeds and may not even appear at low speeds. The solution to this problem is to use idler rollers with surface grooving that allow the air to escape without causing a bubble in the web.”

Another challenge involves tension control associated with the splicer. “The typical zero-speed unwind splicers deployed inherently do not provide good tension control at the time of splice,” adds Plude. “If the press infeed is not designed to manage these tension variations, it can result in a registration shift in the press. In this case, a KTI Constant Tension Infeed placed between the splicer and the press can provide the precise control to manage these tension variations.”

The age of automation

With automation ever-present on the minds of converters – especially with ongoing workforce challenges – the web handling process is even more critical than in years past.

The automated nature of this equipment has also helped drive efficiency and simplicity for label converters. For example, the newest machinery has eliminated the guesswork from the web handling process.

“Enhanced web handling allows the customer to track and monitor the process,” says Maxcess’ Whiteside. “This allows for making improvements where they are needed to directly impact the ROI without guessing where the problem might be.”

“Martin Automatic has recently added an operator performance package to its non-stop, automatic unwind splicers, which has grown in popularity around the world,” says Rittmeyer. “This package helps operators to more quickly, efficiently and repeatedly prepare splices, leading to less process waste and greater operation satisfaction.”

According to Delta ModTech’s Grenwis, the company’s new Delta Mod-Botics modular robots allow discrete part placement and liquid dispense in full rotary motion. “We’ve also developed an IOT reporting system, ModTech Connect, that ties directly into our controls for machine performance reporting,” he explains. “This software allows remote access to data that is crucial to production, operation and maintenance to help increase your OEE.”

Currently, one of the greatest challenges facing the industry centers on labor. Automation is not necessarily designed to replace employees, rather it allows them to more easily produce the work. Plus, enhanced automation speaks to a new workforce that has grown up in a technological age. “Keeping and finding skilled employees who understand the process is one of the industry’s biggest challenges,” explains Whiteside. “Having suppliers who can support the process as much as possible while not being limited to one piece of individual equipment is another challenge. As an end-to-end solution provider, we are developing many automated products that are easier to use for the next generation of operators who grew up with and are used to interacting with intuitive touch screen interfaces.”

Maxcess has addressed converting challenges with automation in mind. “We have been releasing solutions to help our customers tackle this growing challenge in the market with our new AccuAdjust and RotoAdjust automated adjustable anvils, designed to easily adjust and cut any liner you need to run with ease,” remarks Whiteside. “In addition, we have a new web guide (FIFE-500 MAX) that gives customers even more accurate guiding to reduce scrap of hard-to-get-material, and 100% vision inspection to ensure you’re delivering less scrap and better product quality to your customers.”

Web Cleaning

Maintaining a clean web, and press environment as a whole, is imperative for generating high-quality print. Typical cleaning arrangements range from tack cloths to collection rollers and vacuum solutions.

“The type of material should be the first thing to be addressed,” explains Matt Fyffe, VP and general manager, Meech USA. “For example, paperstocks are typically much ‘dirtier’ than films, which means that they will require a cleaning system that is better suited for high contaminant levels.

“We should then also consider if the material is sensitive or prone to marking,” he adds. “This will then help us to determine if we can use a less expensive contact cleaner or need to upgrade to a
non-contact system.”

Other factors to consider include the need for single- or double-sided cleaning, web tension, speed of the web, and the maximum size of the contaminant that needs to be removed. 

The downside to ignoring this aspect of production can be catastrophic. “Contamination causes downtime of the press due to debris sticking to the printing plates, causing repeating defects,” comments Chris Greco, sales manager, web cleaning, Simco-Ion, Industrial. “It is critical to remove all contamination in high-value films as it causes faults in the final product.

“Contamination is becoming a larger source of concern for many converters due to the increase in quality requirements and the use of more recycled materials,” adds Greco. “Web cleaning is also very important for digital printing to prevent debris from clogging the print head. Outside of label manufacturing, web cleaning is very important for high-value coating and battery manufacturing.”

According to Fyffe, all web cleaners must have certain requirements for successful cleaning. Static elimination of the web and contamination is imperative, and then it’s important to break the boundary layer of air on the web surface.

Fyffe adds that contact and non-contact cleaners work on different principles. Contact cleaners include tacky roll systems, vacuum-based systems, and rotary brush cleaners.

“Non-Contact cleaners use high velocity positive air flows to clean off the web with a turbulent air flow,” says Fyffe. “Negative pressure is then used to extract the removed contaminants, which are then conveyed away and stored in a collection system. Non-Contact systems are also ideal for use with low tension applications or in tight fitting areas of the press. They are typically the best solution for retrofitting on existing machinery.”

“Contact cleaning is designed to remove dry unattached particles below 1 micron,” adds Greco. “Contact cleaning breaks the boundary layer, which holds the debris to the substrate. It accomplishes this by the proprietary elastomer compounds, reverse wound adhesive roll and static neutralization. It is also recommended to install a double-side cleaner, even if only one side of the web is being printed.”

Important to keep in mind

When reviewing the web handling process, label converters should be aware of several factors. Proper web handling is critical for minimizing waste in a production facility, which is paramount for sustainability.

“The greatest benefit of enhanced web handling is waste reduction,” states Delta ModTech’s Grenwis. “Whether that be in raw materials or man hours, a well running machine setup properly will create higher yield and less waste than any manual manufacturing process. If operators have to visually inspect product on a running machine, the possibility of errors is multiplied. The use of advanced servo controls and automated registration of diecutting is essential for quality, speed and throughput.”

“One often overlooked item is chilled rollers, which make the web handling process stable,” remarks Mark Andy’s McCroskey. “Being able to employ the proper tools and practices will give you a more consistent product and allow a wider range of substrates and applications to be run. Overlooking good web handling will always result in increased waste and often failure to successfully run.”

There are other considerations worth noting, as well. Job saves, pre-tensioning, torque/tension monitoring/control are all vital attributes of the web handling process. Mark Andy has recognized “great improvements” in idlers and coatings. Length compensation and other items have been made easier with servo technology, too. Modern equipment also features better sensors and accuracy for web guiding.

“All of these enable the presses to run a variety of applications without physical modifications,” says McCroskey.