Calculating Matrix Depth Ratios for Co-Extruded Film Laminates under Pressure
Matrix depth ratios dictate counter-die selection by balancing polymer yield strain against substrate compaction to preserve layer integrity under pressure.
Matrix Depth Ratio
Tooling Proportionality
The mathematical proportion comparing female counter-channel groove depth to the original caliper of the paperboard substrate guides die-cutting tooling selection. Matrix depth ratio establishes the optimal vertical penetration of the creasing rule required to fracture internal fiber bonds without tearing the reverse side liner. Calculated by dividing channel depth by board thickness, this dimensional metric typically falls between 0.85 and 1.15 for standard folding boxboard and solid bleached sulfate grades.
Crease Definition
Structural definition in scored paperboard hinges on correct vertical tooling proportions. An insufficient matrix depth ratio under-compresses the sheet core, preventing effective horizontal shear delamination among fiber plies. This deficiency produces stiff, high-resistance scores that crack along the outer face when folded ninety degrees.
Conversely, an excessive ratio over-stretches the board, resulting in base liner shearing and score burst under rapid mechanical deflection.
Liner Preservation
Converters adjust depth ratios based on board furnish, coating thickness, and atmospheric humidity levels. Recycled board containing high mechanical pulp fractions requires higher depth ratios to induce ply separation than long-fiber virgin chemical board. Matrix selection charts correlate board caliper directly with matrix channel dimensions to standardize tooling prepress operations.
Maintaining proper depth ratios guarantees clean, uncracked folds on coated retail packaging.