Manufacturing Process expanded

Expanded metal sheet is made by first creating multiple slits in the sheet, and then stretching the sheet. The stretching creates a unique diamond pattern opening with one of the strands protruding at a slight angle. These raised strands can be flattened later in the process if desired. As you can see this process creates no waste (thus keeping down production costs) and it can add structural strength to the product.
Perforated metal sheet
Perforated metal sheet is a product that is made from sheet steel that has been fed through a machine that punches out round holes (or other designs). These holes can be straight rows or staggered to increase the amount of the openings. Typically the perimeter of the sheet has a boundary where holes are not punched; this adds stability to the sheet. The removed metal from the holes can be recycled but it also increases the cost of the product. The larger the hole size (or increased amount of holes), the greater scrap volume, and therefore costs can be increased.