Predicting Set off Migration in Stacked Packaging Board under Non Uniform Compression
Predicting set-off migration requires calculating local pressure peaks across board caliper variations to set safe pile heights and barrier coat weights.
Paperboard Caliper Variation
Thickness Tolerance
Dimensional thickness deviation across manufactured paperboard webs represents a primary physical parameter governing structural uniformity and converting performance. On-line radiometric or optical gauges measure cross-machine and machine-direction thickness profiles continuously during board production. Uncontrolled paperboard caliper variation causes unpredictable changes in bending stiffness, feeding reliability, and crease quality across folding boxboard grades.
Fiber distribution fluctuations during wet end forming directly drive cross-directional profile deviations. Mill target specifications enforce strict tolerance limits to ensure consistent box performance on automated packaging lines.
Converting Impact
Automatic packaging machinery requires uniform board thickness to maintain precise carton blank feeding, folding, and gluing operations. Thick zones within a board lot cause jamming in high speed carton feeders, while thin zones result in loose creasing scoring and weak corner joints. Experiencing paperboard caliper variation compromises die cutting precision, leading to incomplete cut lines or severe knife wear on cutting plates.
Variations in caliper alter press nip pressure during offset printing, causing localized changes in dot gain and ink transfer density. Multi-ply paperboard structures require balanced layer formation to prevent caliper fluctuations from warping the finished board web. Controlling furnish consistency and headbox flow profiles minimizes web thickness deviations prior to drying.
Quality Control
Statistical process control charts track thickness profiles across web reels to identify mechanical roll wear or stock flow fluctuations. Minimizing paperboard caliper variation protects structural container rigidity while maximizing throughput on high speed packaging lines.