Q: How has the use of lighter webs changed idler roll design?
A: Idler rolls by definition are web-driven rolls. But lighter webs impart less force on an idler to start or keep it turning. In addition, wider webs require larger idlers. Lighter webs require lighter weight idlers that need very little force (or minimum PLI) to turn. This is achieved with lighter roll bodies made of aluminum or carbon fiber, as well as thinner body walls and/or special low friction bearings.
Yet, a thin-wall roll must have the structural integrity to be machined or ground to tight tolerances – there’s definitely a balance between lighter weight and precision tolerances. It’s not uncommon for us to produce a 6 inch diameter idler for 0.1 PLI today with tolerances to 0.001 inch TIR.
Q: How important are idlers in web handling?
A: As the backbone of web handling, idlers carry, turn, support and direct the web. As web-driven rolls, they must function correctly and not influence the web in any negative way – like marking, stretching or wrinkling. Idlers are routinely engineered for optimum performance in all sorts of web handling challenges, including low tension, minimum wrap applications.
Q: What converting applications or technologies have influenced roller engineering recently?
A: Today, we are seeing more applications using highly sensitive, lighter weight webs. For example, films for solar panels, optical film or pharmaceutical markets running epidermal patches or bio filter membranes.
Q: What misconceptions do customers often have about roller specifying?
A: Some think that any roll will work and anyone with a lathe can provide it – it just needs to be round and turn. In some cases, roll quality may not be that critical, but in most cases, it is. Some are surprised to learn that aluminum rolls can cost less than steel, and that carbon fiber rolls can be a real value. Carbon fiber is also not the solution to every lightweight roll design.
Q: How important is engineering in roller manufacturing?
A: The more critical the process, the more important an engineered roll becomes. Properly engineered rolls will not be under-designed, whereupon the roll could fail or even break – a real safety issue. Engineering helps nail down the exact roll specifications needed to do the job – including dimensions, materials, surface treatments or finishes, wall thicknesses, bearing types and much more.
Q: When should a dead shaft idler be used instead of a live shaft?
A: Dead shaft idlers typically cost less, have lower rotating inertias with less body mass, spin easier and are usually easier to install.
Live shaft idlers allow the bearings to be located further away from the process/web. They may be specified for greater loading, and are better with wider webs. Live shaft rolls are typically specified for more precision applications.
Webex Inc.
(920) 729-6666; www.webexinc.com
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