If you coat, slit, print, laminate, inspect, metalize or otherwise convert paper, film, foil, textile or nonwoven webs; make sure your idler rollers turn!
It is important to check all your idler rollers rotate synchronous with your web in almost ANY converting application. In other words, when it comes to idler rollers, your web should operate as if it were a drive belt and positively drive each idler in your machine. This ensures your web is in traction and is properly controlled through various tension zones and processes in your machine.
Inspect your machine(s) often. Idlers can slow or stop turning all together over time. Factors that can slow or stop idler rollers can include problems with the idlers themselves - if a bearing goes bad or becomes worn for example. Other factors may be due to the web itself. As you process thinner materials, tensions become less and there may no longer be enough tension to turn your idlers or maybe your web is too slippery to drive your idler rolls.
It is extremely important to keep all webs in traction with all idler rollers. Wrinkling and web tracking problems will accumulate as rollers have problems and roller surface speed does not equal web speed.
There are several ways to fix idler roller problems. Check your bearings - make sure they all spin freely. Invest in low-coefficient bearings. Invest in low inertia idlers either with thin wall metals or use carbon fiber idlers. Roller coatings like rubber or plasma can increase the coefficient of the webs surface to the idler roller face, aiding in web to roller traction. Roller face patterns, like grooves, knurls and spirals can also help.
Remember the web handling principal we have discussed in prior articles? Well, here it is again. A web will seek to be perpendicular to a roller in its entry span to that roller. That is how your web is controlled through your machine with idlers. However, the web handling principle only applies if the web is IN TRACTION with the rollers. If the web is not in traction with rollers it will become unstable and web handling problems will occur. Think of your web like your car tires; as long as your tires are in traction with the road - no problems - hit an ice patch and you lose control. Your web acts much the same as it is processed through your machine.
Jeff Damour
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