During folding process several folds (up to 8 if necessary) are formed on a printed sheet in a sequential order.
Usually folding is performed on special equipment with rollers (a folding machine) where the printed sheet passes between pressure rollers. Folding is necessary to reduce or avoid cracking and breaking of printed products with high density (from 170 g/m2 and more).
Folding is usually preceded by creasing procedure to make folding lines more accurate and thin. Then no wrinkles appear along the folds of the bended sheet, and as a result there will be no harm caused to quality.