Music City plays host to converters attending the Flexographic Technical Assn.'s annual conference and exhibition.Read more
Folding carton and corrugated converters will find equipment displays and educational opportunities in die-cutting, foil stamping, embossing, and more.Read more
How well do you understand the relationship between your films and your corona treater?Read more
EVOH allows conversion from foil and metallized film laminations to co-extruded barrier films.Read more
News | New Products
VpCI-126 EM UV film provides high-tech corrosion protection from aggressive environments and UV exposure
With a number of co-located events and educational features, the show promises many offerings for those involved in processing and packaging
All operating units of the company are now branded under the Constantia Flexibles in an effort to present a consistent, clear image to the customer
Labels from around the world are honored in a competition the head judge calls “the Oscars of the global label industry”
The new survey points to confidence in?the foodservice packaging industry for 2015, and there is optimism despite economic and environmental challenges
The event, coming in September, will co-locate with Pharma EXPO, and organizers expect an improving economy will bolster both shows
OpenColor 2.0 multichannel profiling software comes with extensive color correction tools and a test chart generator, plus many other new features
Directories | Reports
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Visit Kelly on Static from Static control expert Dr. Kelly Robinson, president of Electrostatic Answers; Kelly has 27+ years of experience in problem-solving and consulting.
Visit Tim's Web Lines to handle and wind your paper, film, foil, and similar products. Take advantage of Tim’s 25+ years just like over 100 converters have.
Visit Mark's Coating Matters from fluid coating expert Mark D. Miller; Process improvement and project management for precision roll-to-roll coating applications.
Visit Marketing Mojo for dynamic marketing insights from Stephanie Millman that inspire new ideas on how to stay on top of your customer’s mind.
Visit Yo’s Yarns to share the thoughts, impressions, experiences, and news that impact the converting industry. . . or anything else that happens to be on her mind!
Visit Tom's Poly Ploys, where Tom will be writing on various topics that the typical polymer processor would encounter on the job.
- May 03, 2013
Have you ever heard of the TNTs of winding: Tension, Nip, and Torque? I'm not necessarily a big fan of this cute and catchy acronym, but it does help to describe what variables are important to a winding roll. I think the advocates of TNT come mainly from the paper industry based on their experience with two drum surface winders. Tension is the web tension upstream of the winder. Nip is the normal force between the winding roll and the surface drums.
But what is torque? Torque is the ft-lbs (or N-m) applied to the second drum. In two drum surface winders, this torque is important to cinch up the initial layers of a winding roll.
Let's back up a little. What does the winding roll care about? Stress and strain. One of the easiest ways to understanding winding is to imagine creating a roll as a series of tensioned hoops. You start with a core, add one tensioned hoop of material (like stretching a rubber band around a tube), then add another on top of the first hoop, then add another, and another, etc. Each of the hoops will add to the stresses and pressures within the building roll. Each layer has an initial length, tension, and radial position.
Where do the TNTs come in? The tensions, nip forces, and torques of winding determine the initial condition of each layer (or hoops, if you will) as they are added to the winding roll.
Imagine starting with a 3.5-in. OD tube. Take a 3.0-in. diameter rubber band and stretch it onto the tube. Now take four more 3.0-in. diameter rubber bands, stretch them, and add each on top of the earlier bands. You can imagine that the pressure exerted on the core could be five times the pressure from one band.
Now repeat this experiment, but do it with smaller rubber bands, say of 2.0 in. diameter. You will have to exert more stress to get the first rubber band out to 3.5 in. diameter, resulting in more pressure on the core. As you add four more 2.0-in. diameter bands to the others, you will again create a core pressure around five times the pressure of the first band and quite a bit higher than the pressure in your first experiment with 3.0-in. diameter bands.
So, what are the critical variables in the tightness of these rubber band rolls?
- Tensile stress required to stretch the hoop onto the core.
- Number of layers added to the core.
*In this experiment there was no nip or torque, just tension.