Chain of Custody Credit Allocation Ledger Audit Procedures
Verify credit allocation ledgers by auditing dock scale moisture corrections, empirical conversion yield factors, and the rolling 24-month expiration limit.
Paperboard Caliper Variance
Tolerance Metric
Mill production records track the physical divergence in thickness across a finished roll or sheet of paperboard, determining whether the output maintains the uniformity required for consistent downstream machine performance. Paperboard caliper variance denotes the measurable deviation between the minimum and maximum thickness points within a single production unit. This property limits the utility of a stock for high speed offset printing or automated folder gluer operations where mechanical interference occurs if the substrate thickness drifts beyond narrow tolerances.
Suppliers provide a target value for the stock and define the allowable deviation range based on the board grade and the manufacturing process.
Production Mechanism
Manufacturing plants control this thickness profile through the precise adjustment of the headbox slice and the pressing section of the paper machine. Proper loading of the calender stack governs how much the fiber mat compresses as the web passes through steel rolls under pressure. Uniform distribution of water weight across the forming wire affects how much the sheet compacts, as uneven moisture retention leads to soft or hard zones in the final roll.
Operators monitor these variables to prevent density fluctuations that create localized thickness variations. Sensors scan the moving web to map the thickness profile and generate feedback loops that adjust the slice opening automatically. Higher pressure at the center or edges of the roll can correct specific thickness profiles before the board reaches the winding stage.
Operational Consequence
Automatic packaging equipment relies on a predictable and uniform material profile to maintain the integrity of mechanical seals and fold geometries. Thickness shifts outside the established tolerance range often cause feeding jams or failed glue applications because the equipment setting remains fixed for the nominal thickness. Printers notice register issues when the web deviates in thickness, as the pressure exerted by the plate cylinder changes in response to the altered substrate depth.
Uniformity serves as the primary technical requirement for heavy gauge packaging materials. Dense and even board ensures the converter achieves consistent performance on high speed production lines.