Before we answer that question, we should first ask, why should we tape rollers? There are three common reasons given. First: to improve air handling at high speed. For this case, almost any rough tape, in almost any pattern, will do well provided that it does not cause wrinkles. The second reason is to spread using spiral tape. It is useless for that purpose. Spiral tape and spiral grooves do not spread, despite much folk wisdom to the contrary. The third reason given is to spread by taping the edges. We will use different language here, such as banding (bumpers or collars), to avoid any confusion for the type and purpose of taping. This will be the focus of this column.

Before taping rollers, know where it works well and where it does not. Taping the edges of the idler roller turns it into a concave spreader. While not a powerful spreader, it's perhaps all that's needed for thin, low-modulus materials. Polypropylene, elastomerics and some nonwovens all are good candidates, provided they are thin. Stiffer materials, such as polyester and paper, are marginal. Try it and see if it works. Heavy materials and even thin foils are out of the question. Don't even try as you will more likely make wrinkles than keep them at bay. One last limitation is width. This spreader does not work well at very narrow or very wide widths. Less than 10 in. seems to be marginal, as is anything greater than 100 in.

If I teach this subject to operators, we will spend about an hour on it. The reason is that letting tape into the plant is like letting cockroaches into a plant. Once in, always in. Thus, we had better get it right. Here, however, I will just give a summary for taping rollers to spread the web.

1. Determine which few rollers need tape. Those requiring treatment are only those that initiate wrinkles—probably less than 10 percent of the total.
2. Tape only well-wrapped rollers. There is no hard-and-fast rule that works everywhere, but let's start with at least 90 degs.
3. Both tape and roller must be grippy. Surprisingly, masking tape on plain idler rollers usually works if the wrap angle is large enough.
4. Use only 1–4 wraps of masking tape or similar thickness. Use less tape on stiff webs and small rollers. More is not better.
5. Band is as much as 5–10 percent of web width.
6. Web edge must end at maximum diameter buildup on roller. Some people taper thickness on the band to avoid an abrupt sharp inner edge.
7. Neatness counts in taping.
8. Evaluate results. All you need is your eyes to tell if spreading is needed/working, provided you look closely and without bias.
9. Remove tape, restart process, and evaluate results again using a different operator.
10. If consistently helpful on a certain roller, cut a permanent concave into that roller, provided that the usage always includes suitably thin, low-modulus and mid-width applications. Thus, the tape can be used to teach us how to make the concave roller, rather than just as an emergency band-aid.

920/725-7671, drroisum@aol.com, www.roisum.com