The key to manufacturing fast running packaging lies in producing carton blanks with certain stiffness/crease ratios as described in BS6965
Understanding crease and board stiffness is essential for predicting how a carton will run on high‑speed packaging lines and how it will perform for the end user. The relationship between these two parameters determines whether cartons will fold cleanly, stay securely closed and maintain their shape throughout filling, packing, transport and on‑shelf display.
Board stiffness describes the resistance of the carton board to bending. It is influenced by factors such as thickness, fibre composition, coatings and manufacturing method. Stiffer boards help the pack keep its shape, improve stackability and provide a more premium, “rigid” feel. However, if the board is too stiff in relation to the crease, it becomes more difficult to fold and can cause problems on automated gluers and cartoners.
Crease stiffness (or crease resistance) indicates how much force is needed to fold a pre‑creased line and how well that fold will remain in place. A well‑designed crease weakens the board just enough so that panels fold accurately, without cracking or excessive spring‑back. If the crease is too strong, the pack may try to spring open and lead to poor closure or machine stoppages. If it is too weak, the carton may collapse or distort, compromising shelf appearance and product protection.
By measuring both board stiffness and crease resistance in the machine and cross directions and then looking at the ratio between them, packaging engineers can quickly assess how well a particular board/crease combination will run. Consistent, optimised ratios support faster line speeds, reduced downtime and more reliable, high‑quality cartons.
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