An impact is a product formed by striking a cold "slug" of aluminum, held in a die cavity, with a rapidly moving punch. The slug itself is a closely controlled volume of aluminum which is either cut from bar of a specific shape or punched from plate of exacting thickness.

Upon impact, the aluminum flows plastically through designed orifices between the punch and die to form the part. A finished impact is produced with each stroke of the press.

There are three basic forms of the impact process: reverse, forward and combination. By definition, each method specifies the direction of aluminum cold flow in relation to the pressure developed by the punch.