Laser Triangulation Topography Principles for Boxboard Surface Evaluation
Laser triangulation delivers uncompressed 3D areal topography data, isolating micro-roughness and void volumes that drive print quality across coated boxboard.
Skewness
Fibre Distribution
Asymmetry in paper webs describes the directional imbalance of mass across a manufacturing machine width. Skewness measures this lateral variation by calculating the third standardized moment of grammage readings taken from cross-machine profiles. Production engineers apply the metric to quantify the degree of leaning in basis weight frequency curves.
High distribution asymmetry indicates a biased stock flow from the headbox or uneven drainage across the forming table. Standard quality thresholds demand absolute values below specific limits to prevent localized stretching during subsequent converting operations.
Caliper Deviation
Localized thickness fluctuations arise when excessive weight concentration occurs on one side of a reel. Skewness reveals whether caliper anomalies skew toward high or low extremes rather than following a normal Gaussian distribution. Converting lines running at high speeds suffer web breaks when asymmetrical caliper profiles pass through nip rollers.
Calender rolls apply uneven pressure across boards exhibiting high mass asymmetry, producing variable surface smoothness on folding boxboard.
Platen Stress
Uneven mass distribution induces asymmetric mechanical stress during corrugated board manufacturing and sheet-fed offset printing. Skewness dictates how flat a stack of paper remains after guillotine trimming and conditioning in climate-controlled warehouses. Die-cutting presses jam more frequently when incoming substrates possess elevated thickness asymmetry because gripper bars fail to register distorted sheets accurately.
Proper tension control during reeling mitigates the propagation of mass imbalances throughout subsequent finishing stages.