Variations in Paper and in Print

In the task of achieving a more stable and repeatable print process, an insight in all possible sources of variation is necessary. Quality variations in paper and in printed sheets, causes for them and consequences of them are discussed in this paper. E.g. in LWC paper, sinusoidal variations repeating every several meters can often be seen in coating amount and consecutively in gloss, in which variations can easily be even 10 %-units. This type of paper variation can consecutively be seen in the print quality in a similar way. In addition to paper related variations, the rotation of the printing cylinders cause variations in the print quality (e.g. density, gloss). By reducing quality variations, savings can normally be seen e.g. in raw material and energy costs, downtime, and as faster start-ups.