Web Works

• Roller release: How can I improve it?
  David Roisum, Ph.D. Consulting Technical Editor, 06/01/2009
  Sticky or tacky materials, such as coatings and adhesives, can cause enormous operational and runnability headaches. At the modest level, the tacky coating causes a delayed tangent of the web as it departs from the roller (or wound roll). This will quite likely upset the surface of the coating. More
• Roller traction: How can I improve it?
  David Roisum, Ph.D., Consulting Technical Editor, 05/01/2009
  Traction is as important in web handling as it is in driving your car. Without traction, you lose control of braking, steering, speed and other vital concerns. In either case, losing traction is an invitation to a crash. It matters little whether the loss of traction is on the driven or undriven rollers (wheels). More
• Helper drives: What are they and how do they work?
  David Roisum, Ph.D. Consulting Technical Editor, 04/01/2009
  One way to think of a helper drive is as a poor man's dancer or load-cell tension control. However, it's not always the case that we can't afford load cells; it's more often the case that we can't fit them in, literally. There's no space for a sensor, or we don't want to make the space by adding rollers that are needed to set up the geometry of a dancer or load cell. More
• Master-speed reference: What is it?
  David Roisum, Ph.D. Consulting Technical Editor, 03/01/2009
  Most web machines have one and only one master-speed reference. This master drive is the timekeeper/pacer of all other drive motors and elements in the line. When the master moves, everyone else must move. When it comes to a stop, everyone else must stop. It's the one drive that directly follows the speed command input by operators. More
• Wound-roll diameter: How do you measure it?
  By David R. Roisum, Technical Editor, 02/01/2009
  Roll diameter is vital in commerce and in operation. For example, unwind-roll diameter is zero, which is needed to avoid runoff at the core when the operator is busy or inattentive. Here, we automatically shut down or go into a roll transfer on a preset diameter, usually a part of an inch above the core to avoid damaged material there. More
• Web and roll length: How do you measure it?
  David Roisum, Ph.D. Consulting Technical Editor, 01/01/2009
  Roll length is such a common measure that few even think about it until they get customer complaints for discrepancies. A common prophylactic response is to “pad” the roll with extra material... More
• What tension is best for laminators?
  David Roisum, Ph.D. Consulting Technical Editor, 12/01/2008
  Setting and controlling tension is more challenging on laminators than almost any other machine. The tensions at the two unwinds are set first by the guidelines of web handling. Most webs like to run at tensions of 10 percent to 25 percent of their MD breaking str engths. The laminate also would like to run in a similar range based on the strength of the laminate. More
• Web-Handling: Looking back and looking forward
  David Roisum, Ph.D., Consulting Technical Editor, 11/01/2008
  A quarter-century has brought many positive changes to web-handling. The most obvious is computer control of our machinery. However, the most important may be simple name recognition. No matter what the chemistry or the construction of your web, no matter whether you manufacture, convert or use; web-handling is fundamental to what you do. More
• What do I need to know about web accumulators?
  David Roisum, Ph.D., Consulting Technical Editor, 10/01/2008
  Accumulators are used to temporarily store web material on medium-speed, continuous-processing lines. This storage allows a manual roll change to be made on an unwind or winder while stopped and yet still keep the process running by drawing upon that stored material. At very low speeds, say less than 100 fpm, manual roll changes can sometimes be made at speed without accumulators. More
• What is the best winding curve?
  David Roisum, Ph.D., Consulting Technical Editor, 09/01/2008
  The best winding curve is one that straddles two types of defects at two different ends of the wound roll. Tight defects include some blocking, one type of core crush and many others. Loose defects include one type of loose cores, out-of-round rolls and a few others. Some defects don't respond to changes in tightness, such as cores not aligned with the roll edge, or product/process design iss... More
• What is gap winding?
  David Roisum, Ph.D., Consulting Technical Editor, 08/01/2008
  Gap winding is many things to many people. A common arrangement is a centerwind with a lay-on roller where the lay-on roller has been lifted from the winding roll. The lay-on roller makes the wind tighter. Perhaps you don't want a tighter wound roll, so then you would lift the lay-on roller to loosen. More
• What are the drawbacks to draw control?
  David Roisum, Ph.D., Consulting Technical Editor, 07/01/2008
  Speed or draw control is quite simple for electrical engineers. They merely need to make a motor turn at a target speed to an accuracy of a few parts per thousand. Maintenance is simply a matter of knowing roller diameters accurately to 4 or 5 digits. Speed control is exceptionally complex for everyone else, including those ranging from operators to process-control people. More
• What is draw control?
  David Roisum, Ph.D., Consulting Technical Editor, 06/01/2008
  Draw control should be called what it actually is: Speed control. The word draw is ambiguous. It could mean the intentional and permanent elongation of material, which is a web-forming concern. Alternatively, it could be an alias for speed control. In speed control, we make adjacent motors go an ever-so-slightly different speed. More
• What do you mean by web machine quality?
  David Roisum, Ph.D., Consulting Technical Editor, 05/01/2008
  We have lots of ways to define web quality. But how do we judge the machine's quality? Here, we can seldom use any conventional web or uptime measurements. For example, let's say that you have side-by-side machines with drastic differences in runnability. It could be due to a different product mix or raw material, neither of which is the machine's fault. More
• What do you mean by process and product quality?
  David Roisum, Ph.D., Consulting Technical Editor, 04/01/2008
  Everyone has an idea about what constitutes process quality. It's often defined as the absence of negatives. However, if the machine crashes, the cause may be related to man (operator), machine, material, method or some combination. So who or what is at fault (i.e., lacking in some key quality)? Leaving the operator out for the moment, the problem is almost always machine and material. More
• When do I need to align my machine?
  David Roisum, Ph.D., Consulting Technical Editor, 03/01/2008
  Roller alignment costs money. It takes a couple of technicians something like an hour to move a typical roller into alignment. This is not a large cost if the machine is already down because it is being installed or rebuilt, or it is not fully utilized. Thus, there is absolutely no excuse not to align to precision ingoing standards in those situations. More
• How closely do I need to align my machine?
  David Roisum, Ph.D., Consulting Technical Editor, 02/01/2008
  A decade ago in this column I tried to answer this complicated question and did not do a very good job. I can now answer this question definitively: It depends. More
• Can you apply DFM to winding?
  David Roisum, Ph.D., Consulting Technical Editor, 01/01/2008
  Of course you can. However, you really have to think outside the box so that the winder is considered a vital step in manufacturing instead of an after-thought. DFM (or Design For Manufacturability) recognizes the futility of making a product that the end-user really likes if manufacturing costs prohibit profitability. More
• How can I wind material with bad gauge profile?
  David Roisum, Ph.D. Consulting Technical Editor, 12/01/2007
  You really only have a few options: Wind very short rolls (a few dozen wraps ought to be okay), send the ugly raw material back to the supplier, or wind soft and live with the remaining gauge-related defects. Our greatest fear in winding is being asked to wind a material with a profile problem. The word “profile” means variation of ____ across the width, where ___ could be thickne... More
• What is the best taper tension that I should run on my winder?
  David Roisum, Ph.D., Consulting Technical Editor, 11/01/2007
  I wish taper tension had never been invented. It was invented solely as a convenience to the electrical people decades ago when cams and proportional controls were about all there was available. There are far better ways to do things now. Taper tension has two settings that must be selected by an operator: starting tension and percent (%) taper. More
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