Solid Bleached Sulfate Board Bending Stiffness Evaluation Methods
SBS bending stiffness scales with the third power of caliper and dictates carton bulking resistance, requiring verification via ISO 2493 load-cell testing.
Receiving Inspection Protocol
Intake Standard
Material verification at the dock begins when a carrier unloads palletized folding boxboard or coated freesheet, checking grammage variations against the purchasing specification before any freight ticket receives a signature. The receiving inspection protocol establishes whether incoming paper reels or stacked sheets meet moisture content thresholds and dimensional tolerances required by high speed printing presses. Without this preliminary gatekeeping, variable curl tendencies and off center caliper measurements enter the converting plant unchecked, leading to catastrophic web breaks and misregister during subsequent offset operations.
Coated art papers require rigorous surface strength testing alongside brightness evaluations to confirm the coating layer stays anchored during high tack lithographic runs. Mills frequently ship paper with variable relative humidity levels that differ substantially from converting room atmospheres, making acclimation checks mandatory during the initial dock audit.
Dimensional Verification
Caliper micrometer measurements taken across five distinct points on a delivered pallet expose variations in thickness that would otherwise cause uneven impression cylinder pressure on press. Reel width measurements must match the maximum diameter permitted by the sheeter or press unwinding stand to prevent web edge damage and costly downtime caused by telescoping rolls. Squareness deviations in sheeted stock create gripper edge registration failures that ruin multi pass color printing, necessitating diagonal tape checks on every fifth skid.
When basis weight falls below the contractual lower tolerance limit, the resulting folding carton loses the stiffness required for automatic packaging lines.
Defect Classification
Surface contamination, grease spots and slime holes are categorized by size and frequency to determine whether a paper delivery warrants total rejection or a negotiated price adjustment. Visual defects receive numerical ratings based on visibility under standardized daylight lamps, separating mill side dirt inclusions from handling damage incurred during transit. Core damage on paper reels prevents proper mounting on shaftless unwind stands, forcing operators to scrap the outer layers until sound substrate appears.
Laboratory testing for Cobb water absorption confirms whether surface sizing agents function correctly, preventing excessive fountain solution absorption that leads to linting and blanket piling on press.