Optimizing Multi-Ply Layering for Enhanced Post-Consumer Containerboard Performance
Multi-ply layering of post-consumer containerboard optimizes flexural stiffness and crush resistance by concentrating long fibers in outer faces.
Basis Weight Split
Ply Distribution
Multi-ply paperboard manufacturing relies on the precise allocation of fibre mass across individual layers during sheet formation. This allocation, termed the basis weight split, determines the ratio of fibre allocated to the outer and core plies of the board. Proper distribution ensures that the finished sheet achieves the target stiffness and surface smoothness required for high-speed printing and converting.
The boundary of this practice is dictated by the limits of the multi-fourdrinier forming section, where inadequate control of individual ply weights leads to curl and poor ply bond strength.
Structural Integrity
Mechanical properties of a folding boxboard depend directly on the density contrast between the outer plies and the core layer. By positioning high-density chemical pulp on the outer surfaces and high-bulk mechanical pulp in the center, a basis weight split optimises the bending resistance of the material per unit of total weight. The outer plies endure the tensile and compressive stresses during bending, while the bulky core provides the necessary separation between these faces.
A common proportion allocates fifteen percent of the total weight to each outer layer and seventy percent to the core.
Converting Behavior
Creasing and scoring performance during carton production is determined by how the sheet responds to localized compression. If the basis weight split deviates from the specified balance, the scoring tools will fail to create a clean hinge. Tight monitoring of ply weights at the wet end prevents subsequent line stoppages.