Influence Of Fibre Properties Of Paper On The Folding Quality Of Digitally Printed On-demand Products

During folding, the paper is subjected to mechanical stress. Excessive stretching or compression of the paper fibres can cause the coating of the paper to crack or, in the case of uncoated papers, the fibres to rupture or the ink to split from the fibres. The degree of fibre or coating cracking and/or ink splitting are informed by the type of fibres, lignin content, the humidity of the paper, and by various chemical compounds used for filling, sizing and finishing. Quality defects occur in the spine or in the fold of single layer brochures and covers. The defects may result in the product no longer being usable or sellable, which may lead to technical complaints. The objective of this work is to analyze and compare the influence of the fiber direction of the paper (in machine direction [MD] and cross machine [CD] direction) by investigating the formation of cracks after folding. The aim is to identify other influencing factors besides the fibre direction (running direction) that can affect the quality of the fold.