They manufacture flexible packaging, labels, folding cartons and corrugated materials. They print, coat, laminate, sheet, slit and rewind those materials. Sometimes, what they deal with everyday has nothing to do with packaging, falling instead into product categories ranging from A to Z. But the one thing the scores of attendees at this month's AWEB 2008 conference had in common is a web.

The AWEB event, a biennial program for production professionals to learn the ins and outs of applied web-handling technology for tomorrow as well as troubleshooting skills for today, was held May 6-9 at the Radisson University Hotel in Minneapolis. Organized by the Association of Industrial Metallizers, Coaters & Laminators (www.aimcal.org), AWEB also included a short course on winding and a full-day seminar on TopWeb 2.0.

It's nearly impossible to capture the full volume of information presented during AIMCAL's Applied Web Handling Conference. The following abstracts of selected sessions should have special interest for Converting readers.

Dilwyn P. Jones, Emral Ltd.

The scientific understanding of winding has been developed over many decades on single ply webs. Nowadays, however, many webs are multilayered, and carry patterns and structures made by selective deposition and printing. Production of flexible electronics, displays and photovoltaic cells is being driven by cost toward continuous web processing, where rolls are used to store the partially-made product. Some of the component layer materials are very weak mechanically, and there is a tremendous variation in stiffness between them. The structure may be prone to wrink-ling of one layer or failure of an interface. This paper considers the potential problems of winding multi-layered and patterned webs and suggests how they may be overcome by application of winding science.

Stresses are generated from bending to conform to the cylindrical roll, winding tension, and addition of successive turns. The resulting tension, compression both radial and circumferential, and shear may all initiate product damage. Small-scale patterning will affect winding by altering the elastic properties, whereas larger-scale features will distort the roll. The winding process will require more control accuracy than traditionally, and the product structure and materials may need changing to reduce the susceptibility to mechanical damage.

Neal Michal, Kimberly Clark

This presentation focuses on zero-speed splice unwinds. It is common for unwind splices to be the number one source of waste and delay in a converting process. Many of the process upsets during an unwind splice are associated with poor tension control. Failure modes include troughing, wrinkling, neck down, “Z” folding, edge flip over, web collapse and web break.

Covered are answers to when this type of unwind is needed, how it works, challenges and optimization. This presentation also highlights the needs that industry has for better equipment. Fundamental research for web handling has been limited to a single roller in an open span. Several papers have described relationships for traction, air lubrication, and wrinkling. There have been a handful of publications for multi-span festoons and little to no information for zero-speed unwinds.

Dr. Lee Finney, Sigmala Ltd.

In recent years, significant progress has been made in micro servo control systems and artificial intelligence, enabling highly capable, low-cost actuators to be developed which outperform traditional pneumatically-driven products. Actuators as little as an inch across can incorporate as many as six micro servos, enabling higher levels of accuracy and remote-configurability than ever before. This paper describes how micro-servos have been applied to slitting and winding machines, and how their use, when combined with that of conventional servo-winding motors, can enable the implementation of advanced intelligent control.

Tim Walker, TJWalker and Associates

What is the right roller diameter? This seems like it should be one of the simplest of web-handling questions. The answer is minimizing deflections under the loads of roller weight, web tension, and nip load. However, roller diameter is a variable in an amazing number of calculations used to understand web handling. This presentation will cover the effects of roller diameter on roller costs, web tension, roller traction, scratching, nipped processes, air management and more.

Mark Daun, Preco, Inc.

Recent breakthroughs in vision, beam steering and on-the-fly power control have advanced the technology and created new uses for lasers in package design. In addition to scoring, lasers are particularly suited for kiss-cutting, through-cutting, and perforating or a combination. The laser beam works equally well in any direction and can be positioned with mirrors to create complex and unusual shapes at high speed. The pattern is easily changed or adjusted simply by modifying the program that controls the laser. Intricate shapes and hole patterns can also be created without distorting or losing registration with other package features. The “forceless” nature of the process permits fragile and/or thin materials to be worked with little support or tooling.

Darrell Whiteside, Maxcess Intl.

Closed-loop tension control doesn't just mean PID anymore. Many new features are now available offering improved controllability, ease of use and overall gains in process efficiency. This presentation outlines those new technologies and identifies the benefits of each. The information provided is aimed at top-level engineers but in a manner that the benefits are clearly understood down to the operator level. Technologies covered: weightless load-cell calibration, auto-tuning, gain scheduling and out-of-round roll compensation.

Scott Hansen. Goldenrod Corp.

Air shafts are made from several materials: aluminum, steel and composites. Each possesses unique characteristics—cost, weight, stiffness, strength and critical speed—for specific applications. Several applications are presented to demonstrate which material should be used. The last part of the presentation deals with the area of composites. In the last 10 years, the composite window of stiffness and strength has expanded, opening many more options for lightweight and higher machine throughput.

Luis Teixeira, Dienes Corp.

Automatic slitting systems have been around for more than 10 years and have truly revolutionized slitting set-up efficiencies and slit-width consistency and accuracy. Menus can be downloaded from production departments, the computer system can warn operators when blade changes are needed, and contact forces of knife blades can be regulated. In one sense, this level of automation is astounding compared to the old “dovetail-mounted” manual systems in the field. But in a wider sense, is this full automation? Operators still must enter certain data and trigger slitter movement with the machine stopped.

Imagine a vision system (camera) dutifully positioned and watching, always at attention, waiting for a change to a programmed pattern on a fast moving web. Then it happens, the distance watched widens, or the printed line shifts out of limit, the camera acts and signals the shear-knife system that a predetermined tolerance has been exceeded. The shear-knife system is signaled and reacts to move all the knives back to within tolerance. This paper presents the coordination (marriage) of vision systems and automated slitter-positioning technology as the next step in productivity advancement.

David Roisum, Finishing Technologies, Inc.

We want to be able to literally touch the specific element that is responsible for a particular baggy (or tight) lane. This presentation begins by listing all of the elements that touch the web prior to the observed bagginess. That list is pared down in three steps to the responsible element. The first: Eliminate all elements that do not form or deform the web. Second: Eliminate all elements which are known not to have the correct shape. Third (and most challenging): Have the bold creativity to identify and verify the responsible element from the final candidate list by bending elements and noting response. These generic steps are amply illustrated by case histories from several different web-manufacturing processes.

Webs are often unwound and rewound several times in subsequent web-processing operations before they are converted to a final product. If profit losses due to web handling are compared based upon location in a process machine, the losses at unwinds and rewinds comprise the majority. Winders and unwinders are often the least perfect sections of a machine and are also the most difficult to control because they have varying parameters. Losses are also higher in winders because the web will be subject to stresses, strains, slippage or buckling in the winding roll that is not present elsewhere in a web-process machine.

Winding models help us understand how the winder type, the winder-control parameters and web-material properties act together to produce a pattern of pressure and stress as a function of radius in a roll. Many roll defects are quantifiable in terms of stress, and hence, winding models can be used to avert those defects. Often, a critical issue in converting is the precise amount of web length stored in a wound roll. Winding models can help us predict the wound-in length precisely as a function of the extensibility and compressibility of a web material. We can use models to explore what the effects of entrained air will be on the wound roll and what steps we must take if we wish to wind at higher velocities or lower web tensions.

The perfect extruder/orienter and the perfect coater are still in development, thus we may have web thickness non-uniformity, coating non-uniformity, and combinations thereof. Winders are integrators of thickness variation and minor variations in thickness can result in major hard bands where blocking or inelastic deformation occurs. Most webs spend the majority of their time stored in wound-roll form awaiting conversion. Some wound-roll defects are apparent immediately after the wind, but others may not appear until the roll has been stored for considerable time, quite possibly at elevated temperatures. Models are being used to study these defects as well.