Expanded metal, also known as expanded grate, is defined by openings in the surface, so-called meshes that are the result of staggered cuts and simultaneous expanding deformation. They are generally diamond-shaped, round or square and neither plaited nor welded. Stretching (“cold drawing”) causes the material to exhibit significant strength and surface stability, as metals generally become brittle and become more resistant to bending. There are various types of mesh in the grates consisting of sheets or strips: diamond mesh, long-bond mesh, hexagonal mesh, round mesh and square mesh. Generally, expanded metal grates have ribbed, plastically structured surfaces, however, flat rolling of the grate is also possible. Expanded metal can achieve free cross sections between 4 and 90 percent; in contract to perforated metal sheets, however, there is no waste during production (cut punching).
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The term “expanded metal” (expanded grating) is defined in the standard DIN 791, BS 405, and BS 4592 part 2. Expanded metal is available in standard or flat-rolled design.
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TOLERANCES OF THE STANDARD SHEETS
Group 2 (< 2 mm thickness)
Group 2 (>2 mm thickness)
Expanded metal is considered flat, if, when placed on an even area with the curvature facing upwards, the distance between the metal sheet and the area does not exceed 20mm (heat-resistant metal sheets 40mm).
Expanded metal is considered even above the longitudinal edge, if the centre of the curvature does not deviate from the straight line by more than 1.5 % of the length at a sheet thickness of 3 mm, and not more than 2 % of the length at a sheet thickness of more than 3 mm.
The type of cut of the expanded metal (open / closed mesh per metal sheet side to be specified) must be discussed and defined in relation to the order.