A major advantage of perforated metal plates is that they can be produced with unperforated or plain margins on 4 sides or with perforated areas of various shapes alternating with unperforated areas. This is particularly important if the metal plates must subsequently be finished by bending &/or flanging or by adding fixing holes.
Designers can exploit the capabilities of modern punching presses to obtain a perforated plate that can be directly transformed into a finished product, without the need for additional components.
A technical drawing is certainly needed to define the shape & size of a metal sheet with irregular full areas alternating with perforated areas. The full areas & margins are always measured outside edge of the holes. Technical drawings show perforated metal plates from the punch entry side. It is in any case advisable to specify the burr side for asymmetrical perforated plates. This becomes mandatory if the plates are to undergo additional operations such as bending. We should note that wide margins or large unperforated areas make it difficult to obtain perfectly flat sheets. The mechanical stress of perforation causes bulging & buckling that, in extreme cases, cannot be corrected even with highly sophisticated leveling rolls. Large unperforated areas can also produce dimensional changes during perforation & leveling. A final trimming operation therefore becomes necessary when tolerances are tight. Because of the substantial irregularities that result from perforation, trimming causes the size of the margins to differ from the nominal values.