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All FAQs

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Why is traction so important for an idler roller?

Traction is important because it is the only way to control the web as it winds its way through a machine.  Without traction, a web is free to slide left and right and to slip over the roller. Printing registration is lost with side to side web movement and scratching occurs when the web slips over the slower moving roller.

What are the advantages of a dead shaft over a live shaft idler?

In addition to being less expensive, dead shaft idlers perform better in many applications. Since the bearings are installed inside the body of the roller they are closer to the web load which minimizes roller deflection. Placing the bearing inside the roll body also allows for the use of the latest self-adjusting bearing technology.

What is the best way to size an idler to minimize deflection?

The best way to size an idler is to use the WINertia Calculator.  This online tool lets you input five variables and it then recommends the best idler to use for your application. It is very quick and easy to use. If you have any questions about your application, you can contact one of our Idler Application Specialists at 608-884-2201 or email:

Why do you use two different part numbers for bearings in the same idler?

WINertia Self–Adjusting bearings are designed to use locking set screws at one end of the idler and a lock nut with plunger system at the other end. The locking side is designated “UFSSA” which stands for Ultra Free Spin Self-Adjusting and the floating side is designated “UFSSAP” which stands for Ultra Free Spin Self-Adjusting Plunger.

What is the best way to prevent bearing failure?

Using WINertia self-adjusting rollers is the best way to prevent bearing failure. This patented system allows a roller to expand and contract linearly while at the same time adjusting radially to compensate for shaft deflections.  The WINlock Bearing Protection system also helps prevent bearing failure by locking out unwanted dirt and grime particles.

Both of these unique systems minimize bearing wear for years of maintenance free service.

What is a free-spinning bearing?

A free-spinning bearing is designed to have a very low coefficient of friction. WINertia bearings are ultra free-spinning with a long lasting fluoropolymer lubricant.

Explain why you only lock one side of the bearing on your idlers?

This is done to keep the idler bearings from ever binding up and to keep the bearings from failing.  In the field, it is common to have misaligned idlers, idler thermal expansion and contraction, and conditions where the shaft bends more than the idler itself.  Ultimately, this leads to bearing failure.  Componex developed the Self-adjusting idlers to solve these three common problems.  The roll can expand and contract at different temperatures, and the bearings pivot to adjust for excessive shaft deflection.  This technology has solved many bearing problems for our customers.

What is the best way to install bearings in an idler roll?

The best way to install a bearing in a dead-shaft idler roll is to heat up the ends of the roller and allow the bore expand.  Aluminum has good expansion properties and once the aluminum reaches about 150 degrees F, the bearings slide in easily.  As the roll cools the WINertia bearing is then locked in place. Bearings should never be hammered or pressed in as this can cause damage to both the bearing bore and the bearing itself.

How can I prevent adhesives from sticking to our idler rolls?

WINtrac coatings are the best way to solve this problem.  The coatings are done in-house making them affordable and delivered in just 5 days.

What is the difference between hard coat anodizing and thermal coatings?

The biggest difference between hard coat anodized dead-shaft idlers and WINtrac coated rolls is traction.  Anodized rolls have a smooth surface and they lose traction at high speeds.  The anodized coating protects the idler from wear, but it does not protect the web.  With WINtrac thermal spray coatings both the idler and the web are protected as traction is constantly maintained.  In addition to constant traction WINtrac thermal spray coatings also have release properties for inks and adhesives.

Is there something we can do to prevent ink from sticking to the idlers?

Yes, we have high release WINtrac coatings for both ink and adhesive release that we apply in-house.  Other non-stick roll coverings can sometimes be effective at repelling ink, however because they also have a very low coefficient of friction they can cause the web to slip on the idler.

Are there applications when a Dead shaft roll can be used to replace a Live shaft roll?

Yes, in most applications where the roller is not driven, it is less expensive to use a Dead shaft idler in place of a Live shaft idler.

Why is Total Indicator Runout (TIR) important for an idler roller?

A low TIR is important because it keeps registration issues at a minimum.  If the rollers have high TIR, they can cause registration errors from one print station to the next.  This is especially critical with digital printing applications!

What is the most accurate way to balance an idler?

The most accurate way to balance a roller is to add weight where the roll is out of balance which can be anywhere along the length of the roller.  Because of the unique design of the WINertia tubing, balancing weight can be added across the entire roll face. Most other idler manufactures only add balancing weights at both ends of the roller.  Rolls that are not balanced across the entire roll face can cause whip and vibration at high speeds.

What are the advantages of aluminum idler rollers?

Lighter weight, lower rotational inertia and lower costs. WINertia extruded aluminum tubing is specifically designed to create the highest quality, lightest weight, best valued aluminum idler rollers available today.

How can we prevent accelerated wear on idlers (dog bone)?

Idler wear is mostly related to loss of traction between the idler and the web.  When the web is traveling at speeds of 750 feet per minute and the roll is running slower by 100 or 200 feet per minute, the material acts like very fine sandpaper, polishing the roll surface.  Over time the wear on the roll can form a dog bone shape. By using a handheld tachometer one can measure the speed of the roller and compare it to the speed of the web. To see examples of traction on different style idler rollers watch our Traction testing video.

What is a stub shaft and when would you use one?

As the name implies, it is a short shaft located on each end of a dead-shaft idler. If you have stout framework, it is a great alternative to through shafts.  It has the advantage of lower cost and easier installation.

What are the different ways to mount an idler shaft?

A Dead-shaft idler shaft can be mounted to a frame via two tapped ends with a hole in each end of a sideframe.  Additional accuracy can be obtained by using a shoulder screw with a precision hole being machined in the frame and the end of the shaft.  Another mounting technique is a block mount with saddle which makes for easier removal.

Dead-shaft idler shafts can also be mounted to existing pillow block bearings when converting a live-shaft to dead-shaft idler roll.

What is a Class B roller deflection?

The Class B roller deflection is an industry accepted deflection level used when calculating a dead-shaft idler.  The allowed deflection in the center of the roller is equal to or less than .00015 x the length of the idler roll.

When determining web tension what is the difference between PLI and total pounds of tension?

PLI is the pounds per lineal inch of web length.   To get PLI you divide the total web load in pounds by the length of the web.

How does web speed affect the sizing of idler shaft diameters?

Web speed affects the sizing of idlers by matching the shaft diameters for various web speeds.  The higher the web speed, the more need there is for shaft strength and stability.  For example a 5” WINertia idler 70 inches long with a 75 inch shaft length may be just fine at 200 feet per minute web speed with a 1” diameter shaft.   If the web speed were increase to 1,000 feet per minute, a 1.25” diameter shaft would work better for this application.

If the shaft length was increased to 80 inches and the web speed increased to 2,000 feet per minute, then a 1.5 inch diameter shaft would be a better option.  If you have any questions about sizing an idler, you can contact one of our Idler Application Specialists at 608-884-2201 or email:

What is Air Entrainment and how does it damage the web?

Air trapped between the web and the idler is one of the main causes of losing traction.  The trapped layer of air acts like a lubricant which causes the web to slide over the roller rather than turn it.  Once sliding occurs, traction is lost and the web is free to move left, right, and scratching occurs when the web slips over the slower moving roller.

How can I remove wrinkles from a web?

The WINertia AV roll with a reverse crown is a great way to spread a web and a very cost effective way to remove wrinkles.

How do Spiral Grooved rolls compare to lateral groove rolls?

Spiral grooves do not do an adequate job of eliminating air and hence, they lose traction at much lower speeds than a lateral groove roll.  When the spiral grooves lose traction, the film tracks into the groove and drives the web toward the center.  The WINertia AV lateral grooves are perpendicular to the web direction and the web cannot track down into the grooves. A video showing traction test results can be viewed on our resources page.

How can I prevent scratching on a web?

Using a WINertia AV roller which maintains constant traction is the best way to prevent scratching on a web.  To some this might be counterintuitive as one of the myths of preventing web scratching is to use a very fine finish on a smooth roller. The problem with smooth idler rolls is that at higher speeds the web lifts off the roller which results in web scratching.

What is a spreader roll?

A spreader roll is any roller that spreads the web from the center out.  Bowed and rubber covered spreader rolls can be effective but they are expensive to manufacture.  The most cost effective spreader roll is the WINertia AV roll with a reverse-crown.

How does the idler alignment affect the web, even with slight contact?

Idler Alignment affects web skewing with greater wrap angles.  The web needs traction with the idler in order to control it.  Greater surface contact between the web and the idler minimize slipping.  When wrap angles are less than < 15 degrees, there is so little contact between the web and the idler that misalignment of the idler becomes less of a factor.  Slipping is very common with low wrap angles and causes web scratching.  To maintain traction at low wrap angles use a WINertia AV roll or a WINtrac coated roll.

How does the wrap angle affect traction?

The higher the wrap angle the more surface area on the roller in contact with the web.  This contact area allows the web to drive the dead-shaft idler roll. However, at web speeds over 300 feet per minute air entrainment still causes a loss of traction even with higher wrap angles.