Advanced Calendering Technology for Cross Direction Caliper Profiling, 2000 Papermakers Conference Proceedings

Rex A. Robertson--Recent advances in calender roll design and process development are providing papermakers with enhanced caliper control capability. The use of narrow-zone, hydraulic profiling rolls to control cross direction (CD) caliper uniformity continues to grow. Some aspects that make this an attractive approach to profile control include:

· Internal hydraulic profiling elements provide excellent CD resolution, rapid response and fast recovery from web breaks. · The use of counter zones enables effective profiling across the entire operating range for nip loading. · Closed-loop caliper control based on existing scanner measurement of caliper is readily accomplished. · Control elements are internal to the roll, avoiding the machine space restrictions associated with conventional external profilers. · Dependence on hydraulic profiling avoids the high energy costs of conventional electric systems. · The technology is effective in both hard and soft nip calenders, supercalenders, and the new advanced multinip calenders.

The technology has now been applied to a variety of paper and board grades with excellent operating results.