Dynamic Platen Impression Adjustments for High-Speed Multi-Ply Creasing Operations
Dynamic platen impression adjustment balances platen bow and speed-dependent viscoelastic strain to eliminate liner cracking in multi-ply cartonboard.
Folding Endurance ISO 5626
Standardized Testing
Laboratory testing standards define mechanical resistance parameters for paper materials subjected to double folds under constant tension. Methodological testing under folding endurance ISO 5626 measures the logarithm to base 10 of the number of double folds a paper strip withstands before breaking. Packaging papers, currency stocks, and book papers undergo this evaluation to predict durability during repeated physical handling.
Mechanical tension applied during testing simulates functional stress encountered in bookbinding or flexible packaging hinges.
Test Execution
Testing apparatus configurations specified in the standard include Schopper, Lhomargy, Kohler-Molin, and MIT instruments, each applying distinct folding geometry and tension clamps. A standardized paper strip measuring fifteen millimeters in width is clamped under specified spring tension and folded back and forth through a set angular range until physical fracture occurs. Standard test folding endurance ISO 5626 requires strict environmental conditioning at twenty-three degrees Celsius and fifty percent relative humidity, as ambient moisture softens paper fibers and alters fold counts.
Fiber length, refining degree, and inter-fiber bonding within kraft or sulfite pulps govern the resulting folding resistance values. High filler content reduces double fold values by interrupting hydrogen bonding between cellulose fibers.
Material Limitation
Rigid paperboards and thick containerboards exceeding specified grammage limits cannot be evaluated accurately with this test protocol. Excessive substrate thickness induces severe surface cracking on initial bending, rendering double fold counts meaningless for structural stiffness assessment. Modified creasing tests replace folding endurance ISO 5626 when evaluating heavy folding boxboard and solid bleached sulphate grades.