Calculating Substrate Compression Ratios in Embossing Operations
Substrate compression ratio measures z-axis compaction, balancing tool impression depth against fiber strain limits to maximize embossing height without shearing.
Surface Micro Cracking
Coating Failure
Structural defect refers to the appearance of tiny fissures on the top layer of a coated substrate. Surface micro cracking occurs when the brittle mineral coating on a paperboard fails to stretch as much as the underlying fibres during folding. These breaks are often invisible to the naked eye but become apparent when ink bleeds into them.
Strain Limit
Excessive tension during the creasing process triggers the separation of the coating particles. While the cellulose network may remain intact, surface micro cracking compromises the visual and functional integrity of the finish. Low humidity levels make coatings more brittle and increase the frequency of this defect.
Using a wider crease or a softer coating formulation can reduce the occurrence of these fissures. The depth of the crack determines whether the barrier properties of the coating are completely lost.
Print Quality
Integrity of the printed image depends on a continuous and smooth surface layer. Surface micro cracking allows moisture or oils to penetrate the board and cause localized swelling or staining. In high-end packaging, these cracks are rejected because they ruin the premium appearance of the solid ink coverage.
Correct adjustment of the creasing pressure and matrix width protects the delicate top layer.