Idler Rollers FAQs
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What is the difference between a Dead shaft and a Live shaft idler roll?
With a Dead shaft idler, bearings are installed in each end of the roller body and the shaft passes through the body of the roll. The shaft is mounted to the framework of a machine and the roll body rotates around the fixed shaft. The shaft does not rotate so it is called a dead shaft.
With a Live shaft idler, the shaft ends are rigidly fixed on each end of the roller body. When a Live shaft roller rotates the shaft ends rotate with it, so it is called a Live shaft. The bearings for a Live shaft idler are mounted on the framework of a machine and they are not part of the roller body.
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.
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.