Industry Q&A: Tension Control
Lesli Riehemann has been president of Mach III for 11 years, and has offered her expertise to Mach III for 21 years
Q: What kind of problems can occur with improper tension control?
A: When I explain the role of tension control to someone outside the industry, I ask if they have ever attempted to rewind a roll of toilet tissue after a child (or pet) has merrily twirled the contents onto the floor. Most people have experienced this and know that the resulting roll bears little resemblance to the original. It is then easy to explain how applying the proper amount of traction on the tissue (i.e., torque on the rewind roll) would have improved the finished product.
Without proper web tension, the following problems can occur:Telescoped or Dished Finished Rolls; Wrinkles; Web Drift; Web Breaks; Poor Printing Registration; Laminated Roll Curl.
The first three or four of these would apply to the toilet tissue example and, if house guests are due at any moment, you would likely just toss the roll in the trash because the cost is negligible. Converters, on the other hand, risk the waste of valuable material and precious time.
Q: What are your customers requesting in terms of products or service? What’s new and exciting at the company?
A: Mach III’s customers have chosen to maintain tension on the web using friction brakes and clutches that are engaged with air. Torque output is linear in relation to the air pressure applied. On the unwind, the torque output required of the brake decreases as the roll depletes. On the rewind, the torque output required of the clutch increases as the roll builds. In both cases, to maintain constant tension, the air pressure to the brake or clutch must be adjusted throughout the converting process.
We encountered numerous requests from both narrow web converting machine users and builders for a rewind clutch that would provide high resolution adjustment of tension under conditions where the torque range required between core and full roll was very narrow. Our SensiFlex product design is optimized to provide smooth torque output and high response to slight changes in air pressure, but in some cases the torque was still too high, even at the lowest possible pressures. After development of a new ultra-low coefficient friction material, Mach III expanded the SensiFlex line of tension control clutches and brakes to include nineteen new “ULOW” models. With 45 percent lower overall torque capacity than the original SensiFlex models, the ULOW models provide the solution for those needing very light, highly responsive tension control.
Q: What can be improved upon when a converter is looking for better tension control? Any troubleshooting tips to offer?
A: If a machine utilizes a manually controlled air actuated clutch or brake to control tension, the installation of a high precision air pressure regulator can improve performance dramatically. High precision regulators allow pressure changes in smaller increments than standard regulators.
As a result, smaller changes in torque output are achievable. The next level of improving tension control would be the installation of an automatic system that electronically adjusts air pressure to the clutch or brake using feedback from a variety of possible sources such as a load cell that measures web tension or an ultrasonic sensor which measures roll diameter.
(859) 291-0849; www.machiii.com