In our world, we use tape-slitting machines that allow us to convert tape widths according to specification and the material itself. After the application of various coatings – which the backing material receives during the processing – the final coated product is delivered to the slitting machine in widths of 60 inches or more. In order to process these widths on a slitter, some tension must be applied to the material in order to keep it under control, and this tends to put a slight stretch in the tape. The tension and stretch will remain in the tape in the roll form. Or to think of it another way, the roll of tape has the same energy in it as a clock spring, but to a very minor extent.
How Much Stretch is Needed?
How much stretch the tape will receive during slitting will depend on many factors.
With the modern sophisticated slitting machine, every precaution is taken to keep the stretch to a minimum by automatic settings of the rolls that pull the tape through the slitter, and by the controlled speed of the machine. But not every machine is so sophisticated, and the settings of the machine tensions may be over-compensated, giving a very soft roll. The settings can also be under-compensated, which results in a firm, tightly wound tape.
A Closer Look at Winding Challenges: Gapping, Gearing, and Telescoping
In nature, wherever there is a continual stress, objects will move to relieve that stress. And so it is with the energy that has been built into the roll of tape. It will want to dissipate that stress. For example, a soft-wound roll has its place, as in the case of cloth surgical tape with a soft adhesive. If it were tightly wound, that clock-spring gradually tightens with time, squeezing the soft adhesive into the cloth backing, resulting in tape that can’t be unwound.
However, a very soft wind in an industrial adhesive tape can be the cause of two problems. There is a still energy in that roll, and the roll gradually rebalances itself with time to dissipate that energy. This may take weeks or months. In the rebalancing process, gaps can begin to appear between the layers, and those gaps concentrate in very specific areas. So we wind up with a roll problem that is known as “gapping”.
There is a second problem, too. As the gradual movement begins to distort and misshape the roll so that it is no longer circular, and can result in one or two bumps around the circumference. This is known as “gearing”.
When the opposite occurs – when the roll is wound too tight – the stress in the roll results in a vector force at right angles, and the tape layers begin to slide over one another in the direction of the stress, the tape no longer remains flat, and eventually begins to take on a pyramid shape, known as “telescoping.”
Distortion … and How to Avoid It
The softer the adhesive, the more pronounced the distortion becomes. It is also encouraged by a high percentage of elongation in the backing or by more narrow widths of slit tape. Half-inch wide vinyl tape with a soft adhesive wound too tight can telescope in a minute or two. Only the tape-slitting department can overcome these problems, but the effect can be slowed down considerably by storing the tape at cool temperatures – in fact, the cooler the better. At colder temperatures, the adhesive firms up and restricts movement. Warmer temperatures will accelerate the deformations.
At the end of the day, we deliver a pallet of tape on which every roll is perfectly wound and ready to go!
You can find more information about adhesive tape by visiting our post The Complete Technical Guide to Adhesive Tape. To learn more about ECHOtape and how we help customers find the right tape for their job, you can read about us here or contact us with any questions you may have.