Many components and processes give us trouble in our web industry. For example, both tension control and winding have been the priority problem in hundreds of my assignments as a consultant. Rollers and slitters also trouble more than a few. Processes such coating and drying are near continuous challenges for people who own them. Calendering and printing seem to run a bit more smoothly, but are nowhere near trouble-free.

It might be instructive to ask why we have these problems, and to look for trends. However, the complexity and uniqueness of the products, process and machinery in our industry make it difficult to draw general conclusions. Let's try a different approach. Let's see if we can find something that works relatively well and ask why. The reasons may be applicable to other areas of web handling.

My first candidate would be edge guides. Of the thousands of calls I've answered, only one was for an edge guide. It turned out to be a simple application error with not so simple consequences, once you build a machine. While I've worked on more than a few guides, they were not the main reason for a visit to a plant.

This is not to say that guides are totally free of problems. I am sure if you ask the guide manufacturers they will be able to supply scores of troubled references. Sometimes this is a matter of unrealistic expectations. People want hairsbreadth positioning tolerances when these can only be achieved under ideal circumstances of a good web, good guide, good edge and modest incoming position error rates. Sometimes it is a simple matter of maintenance or application. In any case, however, guides are almost never mentioned in most daily production meetings. Why?

The first and most obvious difference is lack of complexity. Guides just don't have as much going on as, say, coaters or winders. However, rollers and slitters are also simple and they don't have such rock-solid performance. There must be something else also at work.

The second difference would be known only to those well-schooled in web handling. It's a wealth of research. That is, guides have been researched for decades. Ph.D. level work at Fife, the Web Handling Research Center, and other organizations has been done as far back as the mid 1960's and continues to the present. While winding has been the subject of even more study, winding is also far more complicated. The higher ratio of study to complexity for guides compared to winding means that we know the subject better.

The third difference is that guides are almost always turnkey applications under the direction of experts, i.e., the guide manufacturers. One of the common ingredients for failure is do-it-yourself. People may do-it-yourself on rollers because they look simple and on winders to save money. For some unknown reason, guides seemed to have escaped that pitfall.

The fourth difference is lack of interference. Guides are only infrequently touched by maintenance personnel or operators. Slitters are also relatively simple. However, the short mean-time-between repair of slitters gets people involved who are not always properly trained or motivated. I am certain that if maintenance and operators had better training and took better care with slitters, we would have only a tiny fraction of the problems we now have.

I believe that these principles for reliable performance also apply to other areas of web handling and web processing. While we can do nothing about inherent complexity, we can make use of the other findings. To summarize, people who work on stuff must study it enough so that they understand it well. If you are not sure, turn to the builder who may be better equipped in regard to specialized expertise. If that builder does not have the expertise, find another. Keep looking until you find what you need. It is not machinery we buy, it is the expertise to avoid and solve problems.

David Roisum, Ph.D., Consulting Technical Editor 920/725-7671, DRroisum@aol.com, www.roisum.com