Dimensional Trait
Dimensional measurements taken across paperboard substrates under cyclic mechanical loading reveal asymmetric recovery paths between compression and decompression phases. Thickness measurements vary depending on whether the sheet reaches a given pressure from a lower state or a higher state. Caliper hysteresis defines this path-dependent thickness discrepancy observed during platen loading and release cycles.
The phenomenon sets the boundary for thickness measurement accuracy on compressible paperboard grades.
Compressive Cycle
Mechanical pressing forces cellulose fibers into closer proximity while compressing internal air voids. Upon releasing the platen force, viscoelastic fiber recovery proceeds slowly, leaving a residual deformation during immediate unloading. Internal micro-friction between overlapping fiber walls resists immediate elastic rebound.
Consequently, paperboard thickness at a specific load remains smaller during unloading than during initial loading.
Calibration Deviation
Thickness tolerances on high-speed carton converting equipment require strict control of sheet caliper under feeding nip pressure. Caliper hysteresis causes unexpected thickness variance when substrates pass through multiple compression stages in print nips and creasing stations. Laboratory testing standards specify standardized dwell times and loading sequences to neutralize path-dependent thickness errors.
Ignoring this mechanical lag produces inaccurate density calculations and improper scoring matrix selection on folding carton lines. Substrate thickness stability under dynamic load cycles determines crease depth accuracy and carton squareness during high-speed automated erection.
