FACTS Tech Blog

Keep the calender running – stops cause the rolls to become egg shaped and introduce significant gauge thickness variation.

When the calender is stopped, roll heat loss is not uniform around the roll. Heat loss along the circumference near adjacent rolls is minimal while heat loss in other areas is much higher. This leads to different temperatures and therefore different degrees of roll expansion. A few degrees on a 24” to 30” diameter will result in measurable “out-of-roundness” of each roll. This is true when the calender is empty but even more so when there is a hot bank of rubber between the rolls. The longer the calender is stopped the worse the condition. Read more…

Force induced variations result from

• the way the calender is operated and
• from previous process steps such as feed mill operation
• compound consistency from mixing

In rubber calendering, separating forces generated are quite high; typically 160,000 lbs to 300,000 lbs at each actuator for a 66 inch active roll face producing a 60-inch wide rubber sheet. Those forces literally stretch the calender frame. Variations in these forces will therefore vary the amount of frame stretch and thus vary roll position and calendered gauge. Read more…