Paperboard Creasing Mechanics and Physical Quality Inspection Fundamentals
Optimizing rule depth and matrix channel width induces internal ply delamination, preventing top liner crack failures during high-speed carton folding.
Bending Moment Ratio
Structural Property
Structural evaluation of paperboard stiffness relies on the comparison of resistance forces measured across different grain directions. The bending moment ratio expresses the relationship between the bending resistance in the machine direction and the cross direction. Resulting values determine how a carton maintains its shape under compression.
A high value suggests significant directional orientation of the fibres.
Directional Anisotropy
Folding operations and high speed packaging lines require predictable board behaviour to prevent bulging. When the bending moment ratio exceeds standard limits for a specific grade, the carton may fail to square up properly during the filling process. Creasing becomes more difficult if the resistance gap between directions is too wide.
Performance Calculation
Standardised testing involves a two point bending test where a sample is deflected through a set angle. Mechanical sensors record the force required to reach this deflection in both primary axes. Results provide a dimensionless figure that assists designers in selecting substrates for heavy vertical loads.
The test helps ensure that the chosen board provides sufficient bulge resistance for liquid packaging and heavy dry goods. Calculated values allow the mill to adjust the fibre refining process to meet the specific requirements of the converting line.