Paperboard Converting Mass Balance Accounting and Scrap Yield Baselines
Paperboard mass balance accounting requires deducting real converting process scrap and moisture variations from credit ledgers to prevent invalid claims.
Folding Boxboard Deckle Trim Loss
Process Definition
Manufacturing yield loss occurs when paperboard web width exceeds the combined width of scheduled packaging rolls or sheets. In board mill operations, folding boxboard deckle trim loss represents the unslit edge material removed at the winder to achieve uniform roll edges and exact customer width specifications. This web offcut returns directly to the pulper as internal broke.
Yield Calculation
Papermaking machines operate at fixed maximum deckle widths, while customer orders demand variable reel configurations. Converting a full-width master roll into finished product widths leaves narrow longitudinal strips along the deckle edges. For example, a machine deckle of 420 centimetres running a combination of three 130 centimetre rolls produces a remaining edge strip of 30 centimetres.
That edge strip equals a deckle loss of seven percent of total reel width. Efficient trim scheduling software balances reel combinations to minimize this unallocated margin, though minimum edge slitting margins of two to three centimetres remain mandatory to prevent structural edge tear during high-speed rewinding.
Financial Impact
Fibre repulping recovers raw material stock but forfeits the thermal energy and chemical additives consumed during initial sheet formation. High-caliper multi-ply board requires considerable refining power, meaning trim re-wetting incurs measurable re-processing costs. Excess trim waste reduces net machine output and raises production costs per tonne.