Dimensional Reversion
Residual internal stress within freshly wound rolls of coated paperboard drives dimensional reversion during storage before conversion. Post press relaxation describes the dimensional stabilization period required immediately after calendering or winding, allowing elastic energy dissipation across the web matrix. Calender nips apply high compressive force that deforms individual cellulose fibres beyond their elastic recovery limit instantaneously.
Once tension drops upon the finishing winder, stored mechanical energy forces gradual thickness recovery and lateral expansion within the reels. Converting plants schedule a mandatory holding window before feeding these rolls into die cutters or high-speed lithographic presses to prevent registration drift. Thermal conditioning accelerates this molecular rearrangement, reducing warehouse holding time before downstream processing begins.
Elastic Recovery
Interlaminar friction prevents immediate dimensional equilibrium across heavy multi-ply carton board structures after winding operations. Post press relaxation alleviates radial pressure gradients built during high-speed web tensioning on paper machine finishing equipment. Paperboard exhibits viscoelastic behavior under mechanical stress, meaning deformation recovery occurs across hours rather than seconds.
Caliper measurements taken immediately after slitting consistently exceed nominal targets because secondary thickness expansion has not yet concluded. Converting specifications mandate specific aging durations prior to creasing to ensure carton stiffness matches structural design tolerances. Insufficient dwell time before folding carton production causes barrel distortion on finished blanks, leading to corrugated packaging rejections during automated filling.
Conversion Tolerance
Mechanical stability determines whether printed folding carton blanks maintain strict alignment throughout high-speed gluing and packaging lines. Post press relaxation minimizes register errors by ensuring sheet dimensions remain constant during subsequent offset printing operations. Press operators measure residual curl and transverse shrinkage before releasing master rolls to the printing department.
Paper mills adjust winding tension profiles to limit internal stress accumulation during jumbo roll formation. Final product quality relies on predictable dimensional behavior, making controlled stock conditioning an essential phase of paperboard manufacturing.
