All-across perforating presses are so called because the entire width of the sheet or strip is perforated at each stroke. Automation of the perforating process is combined with the presence upstream of a decoiler which allows the automatic moving on of the coil to be perforated, and, downstream, of a shearing machine, a roller leveller and a recoiler. In this case we can talk of perforating lines, where the whole process is automatic and the characteristics of each perforation are set by computer.

Sectional perforating presses are equipped with press tools that do not cover the entire width of the sheet to be perforated. Sheets are therefore perforated in a series of passes. This was the first type of industrial process to be used for the production of perforated sheets, when technology couldn’t offer better performances. They are still used for difficult perforations, where the shape of the perforated areas means that all-across presses cannot be used, when the perforating force requiredby each punch is high or when production levels are limited. They can only be used for sheets and not for coils.

Perforation generates tensions inside the sheet which deform and ondulate it. To avoid these defects, the sheets must always be flattened on a roller levelling machine. The operation is carried out on multi-roller levellers which flatten the sheet between two sets of rollers, one above the other. The rollers are staggered with a reduced distance between centers. Wide unperforated margins, alternating perforated and unperforated areas, reduced hole pitch and cases in which the bridge is less than the thickness of the sheet make the process more difficult.