Z94.12.4 Metal Forming

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DECARBURIZATION. The loss of carbon from the surface of a ferrous alloy as a result of heating in a medium that reacts with the carbon.

DEEP DRAWING. Characterized by production of a parallel-wall cup from a flat blank. The blank may be circular, rectangular, or of a more complex shape. The blank is drawn into the die cavity by action of a punch. Deformation is restricted to the flange areas of the blank. No deformation occurs under the bottom of the punch-the area of the blank that was originally within the die opening. As the punch forms the cut, the amount of material in the flange decreases. Also called cup drawing or radial drawing.

DEFLECTION. The amount of the deviation from a straight line or plane when a force is applied to a press member. Generally used to specify allowable bending of bed, slide, or frame at rated capacity with load of predetermined distribution.

DEFORMATION LIMIT. In drawing, the limit of deformation is reached when the load required to deform the flange becomes greater than the load-carrying capacity of the cut wall. The deformation limit (limiting drawing ratio, LDR) is defined as the ratio of the maximum blank diameter that can be drawn into a cup without failure to the diameter of the punch.

DIE. Generic term used to denote the entire press tooling used to cut or form material. This word is also used to denote just the female half of the press tool.

DIE-ENCLOSURE GUARD. An enclosure attached to the die shoe or stripper, or both, in a fixed position.

DIE PAD. A movable plate or pad in a female die, usually for part ejection by mechanical means, springs, or fluid cushions.

DIE SET. The assembly of the upper and lower die shoes (punch and dieholders), which usually includes the guide pins, guide pin bushings, and heel blocks. This assembly, which takes many forms, shapes, and sizes is frequently purchased as a commercially available unit.

DIESETTER. An individual who places dies in or removes dies from presses, and who makes the necessary adjustments to cause the tooling to function properly and safely.

DIE SINKING. Forming or machining a depressed pattern in a die.

DIE SHOES. The upper and lower plates or castings which make up a die set (punch and dieholder). Also a plate or block upon which a dieholder is mounted, functioning primarily as a base for the complete die assembly. It is bolted or clamped to the bolster plate or the face of the press side.

DIMPLING. A process of cupping sheet so as to permit the use of rivets that have countersunk heads. Dimpling differs from counters in that it is a cupping operation and no metal is cut away after the rivet holes have been drilled.

DIRECT EXTRUSION. Extrusion through a die placed at the opposite end of the billet from the ram.

DISHING. The act of forming a large-radiused concave surface in a part.

DISTORTION. Any deviation from a desired contour or shape.

DOUBLE SEAMING. The process of joining two edges of metal, each edge being flanged, curled, and crimped within the other.

DRAFT. (1) The amount of taper in the side walls of die impressions. (2) The taper given to the sides of a pattern to enable it to be withdrawn easily from the mold.

DRAW BEAD. An insert or riblike projection on the draw ring or hold-down surfaces that aids in controlling the rate of metal flow during draw operations. Draw beads are especially useful in controlling the rate of metal flow in irregular-shaped stampings. (See also BLANKHOLDER.)

DRAWING. In general terms, drawing describes the operations used to produce cups, cones, boxes and shell-like parts. The sheet metal being worked wraps around the punch as it descends into the die cavity. Essentially, the metal is drawn or pulled from the edges into the cavity. Shallow drawing applies when the depth of the part is less than one-half of the part radius. Deepdrawn parts are deeper than one-half the part radius. the inner edge of the metal is drawn by the punch.

DRAWABILITY. (1) A quantitative measure of the maximum possible reduction in a drawing process. (2) Reduction in diameter from a blank to a deep-drawn shell of maximum depth.

DUCTILITY. The property that permits permanent deformation before fracture by stress in tension.

DWELL. A portion of the press cycle during which the movement of a member is zero or at least insignificant. Usually refers to the interval when the blankholder in a drawing operation is holding the blank while the punch is making the draw.

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