Any one or a combination of preliminary The machined recess in a die that gives the forging its shape. impressions used in producing a (1) The forging operation in which stock is preformed or shaped to a predetermined size and contour prior to subsequent die forging operations. When a preform operation is required, it will precede a forging operation and will be performed in conjunction with the forging operation and in the same heat. (2) Ring blanks of a specific shape for profile (contour) ring rolling. (3) The initially pressed powder metallurgy compact to be subjected to repressing.... More. Also known as blocker, buster, scalebreak, and The process of forcing metal to flow through a die orifice in the same direction in which energy is being applied (forward extrusion); or in the reverse direction (backward extrusion), in which case the metal usually follows the contour of the punch or moving forming tool. The extrusion principle is used in many impression die forging applications.... More.