Thickness Deviation
Dimensional uniformity across paperboard webs defines the baseline mechanical performance required for high-speed folding carton converting. In commercial paperboard manufacturing, calliper variation describes the non-uniform cross-direction or machine-direction thickness profile within a single sheet or reel. Standard testing methods specify micrometre measurements under controlled press pressure to isolate structural thickness changes from surface roughness effects.
Uncontrolled thickness profiles impair feeder stability and alter creasing forces during high-speed printing.
Converting Boundary
Folded carton blanking and automatic cartoning lines operate within narrow mechanical tolerances. When calliper variation exceeds five percent of nominal board thickness, feeder suction cups miss sheets or double-feed blanks into the transport section. Die-cutting cylinders apply uneven pressure across the web.
This force imbalance causes incomplete cut-through on thin sections while crushing the solid board structure on thicker sections. Gluing units suffer from inconsistent adhesive film transfer because applicator rolls maintain a fixed gap that demands strict thickness uniformity.
Process Mechanism
Paper mills manage thickness profiles through automated headbox slice lip adjustments and zonal induction heating rolls. Refining intensity determines fibre swelling and network density, which directly impacts compressibility across the sheet width. Wet pressing nips remove water unevenly if felts suffer from localized compaction.
Calender stacks compensate for web profile defects by applying targeted thermal expansion to specific roll zones.
