In impression die forging, which accounts for the vast majority of forging production, two dies are brought together and the workpiece undergoes plastic deformation until its enlarged sides touch the die side walls. Then, some material begins to flow outside the die impression, forming flash. The flash cools rapidly and presents increased resistance to deformation, effectively becoming a part of the tool. This builds pressure inside the bulk of the workpiece, aiding material flow into unfilled impressions.

Impression die forgings range in size from a few ounces to over 10,000 pounds, and vary in length from a fraction of an inch to over twenty-six feet. Impression die forging provides three-dimensional control of the workpiece, which provides much closer dimensional control than does open die forging. The control is achieved by a pair of matched dies with specially fabricated impressions, which form an impression, or cavity in the shape of the forging. The term "impression die" forging derives from the impressions. Sometimes called "closed die forging". KEYWORDS for this process: forgers