Open-die forging can produce forgings from a few pounds up to more than 150 tons. Called open-die because the metal is not confined laterally by impression dies during forging, this process progressively works the starting stock into the desired shape, most commonly between flat-faced dies. In practice, open-die forging comprises many process variations, permitting an extremely broad range of shapes and sizes to be produced. When design criteria dictate optimum structural integrity for a huge metal component, the sheer size capability of open die drop forging makes it the clear process choice over non-forging alternatives. At the high end of the size range, open-die forgings are limited only by the size of the starting stock, namely, the largest ingot that can be cast.
Open-die shape capability is indeed wide in latitude. In addition to round, square, rectangular, hexagonal bars and other basic shapes, open-die processes can produce:
● Stepper shaft solid shaft (spindle or rotor) whose diameter increases or decreases (decreases) at multiple positions on the longitudinal axis.
● The shape of a hollow cylinder is usually much longer than the diameter of the part. Length, wall thickness, inner diameter, and outer diameter can be changed as needed.
● Depending on the height/wall thickness ratio, the shape of the ring-shaped part may resemble a gasket or close to a hollow cylinder.
● Profiled metal shells (such as pressure vessels) can be combined with extrusion nozzles and other design features.