Roll barring is a serious blight for rolls used by industry. Not only does it compromise the calender and the life of the rolls, but it also threatens the efficiency of your production line and the consistency of your final product. The quality of your final product (strength and finish) is greatly enhanced with the removal of the barring. In some instances, when the barring gets bad enough, the severe noise also puts your workers at risk.
Calender barring is a self-excited vibration, which means that energy from the drive is converted to vibrational energy. For this to occur, a vibration feedback mechanism must exist where the vibration is sustained. The mechanism may be induced by:
- Caliper variation in the upper nips of the calender stack, forcing the lower nips to vibrate
- Barring patterns worn into the calender rolls
- Both events occurring simultaneously
- Frequency or vibration resulting from the framework, drive, gears, bearings, etc.
Why eliminate barring?
The benefits of eliminating roll barring from your production line are seemingly endless, but here are sixmajor ones:
- Customer Satisfaction
Eliminating roll barring from your production line results in a more uniform final product that your customers expect.
- Sheet And Web Strength
Roll barring dramatically decreases the tensile strength of your finished sheets and wet webs. By providing a truly uniform and concentric roll surface, you increase sheet and web strength for your machine and your customers.
- Improved Printability
Calender roll barring creates sheet inconsistencies that decrease the overall printability of your final product. Reducing these inconsistencies by eliminating press and calender roll variations drastically improves the uniformity and printability of your final product.
- Less Grinding
The smallest inconsistency can start roll barring, which then extends and expands across and around the surface of your rolls. That sets you up for more frequent roll grinding to keep your rolls in spec.
- Reduced Waste
As the rolls age, barred rolls require considerable fine-tuning and adjustment, which creates waste. Eliminating roll barring from the process reduces this waste and improves production efficiency.
- Easier Caliper Control
When you eliminate roll barring, you enhance the profile of the product during production – both cross direction (CD) and machine direction (MD). This allows for uniform printing and, once again, amps up production efficiency.
How to eliminate barring?
Traditional roll grinding methods are inconsistent and don’t work. For example, grinding rolls on bearings is a common practice to clean up rolls and try to reestablish the original specifications. However, this is far from effective, and simply does not work.
Bearing and housing removal must be implemented first. Bearing seats and roll faces must be ground round and concentric.
To prevent damage to the bearings and housings, leave the removal process to the precision grinding experts. Professional removal and inspection of bearings and housings not only sets you up for tighter tolerances when you grind your rolls, but also greatly reduces the opportunity for failure in the machine. This means less maintenance, less machine downtime and, most important, more consistent and higher-quality production.
SEE IT TO BELIEVE IT.
Watch PRG’s short, informative video on how to prevent barring and achieve tighter tolerances from your production line.
Ready to turn round into revenue? Click below to learn how Precision Roll Grinders wipes barring from your line with comprehensive roll grinding, inspection and repair – for manufacturers obsessed with quality and serious about profitability.