Live Shafts Versus Dead Shafts
This section is meant to provide our customers insight into the advantages of the two different styles of idler roll shafts. "Live Shaft" means that the shaft is fixed to the idler roll and therefore rotates with the roller body. The roller bearing is mounted to the machine frame, generally a pillow block or flange mounted bearing. "Dead Shaft" means that the bearing is in the idler roll body and therefore the dead shaft remains stationary. The shaft is fixed to the machine frame in various manners.
Dead Shaft Advantages
- Less Expensive!!!
The number one advantage of a dead shaft idler is the lower cost. This advantage makes dead shaft rolls more popular than live shaft rolls.
- Lower Rolling Inertia
Since the roll body is the only rotating object on an idler, the rolling inertia is much less than a live shaft roll.
- Free Spinning
Epoch dead shaft idler rolls with replaceable bearing carriers are one of the most free spinning designs available.
Live Shaft Advantages
- Elevated Temperatures
Since high temperatures are a main cause of reduced bearing life in any application, having roller bearings located away from high temperatures is good design practice. Roller bearings mounted on the machine frame can be lubed regularly, or can have special lubricating units to extend the expected life of the bearing. Be sure to identify high temperature applications when ordering so that the idler can be properly vented.
- Harmful Environments
The most popular reason for using live shafts is to move the bearings out of the web path, away from any environment that can damage the roller bearings. Live shafts are ideal in applications where there are damaging chemicals or vapors, excessive dust, or extreme moisture.
- Quicker Bearing Replacement
Whenever the roller bearings do wear out, replacement is quick and easy with live shafts.
- Higher Allowable Loads
On a live shaft idler, the bearing size isn't limited to the size of the idler roll body. Therefore, larger bearings with higher load ratings can be used. Also, the customer is allowed to choose between multitudes of bearing styles to best fit his/her application. On rolls with long shafts, self-aligning bearings are often used to manage the increased shaft deflections.
- Longer Rolls Possible
Thru shaft deflection can sometimes limit the length of a Dead Shaft Idler roll assembly, because the bearings only allow a small amount of angular slope. Live shaft idlers can increase the permissible overall length since self-aligning bearings can be used.
- Drive Rolls
Live shafts are ideal when driving a roll.