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Metal forming glossary - D

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Date of run

See run stamps.

Datums

Theoretically exact planes, lines or points from which other features are located on design drawings.

Daylight

The maximum clear distance between the pressing surfaces of a press when the surfaces are in the usable open position. Where a bolster plate is supplied, it is considered the pressing surface. See also shut height.

Deburr

To remove the sharp, knife-like edge from parts. Decrease the height of die space.

Dedicated tooling

Commonly referred to as hard tooling. This is tooling made to produce a specific part.

Deep drawing

The fabrication process of flat rolled steel to make drawn parts. The part is mechanically formed through or in a die. The blank diameter is reduced; the blank contracts circumferentially as it is drawn radially inward. Deep drawing is characterized by the production of a parallel-wall cup from a flat blank of sheet metal. The blank may be circular, rectangular, or a more complex shape. The blank is drawn into the die cavity by the 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 cup, the amount of material in the flange decreases. Deep drawing is also called cup drawing or radial draw forming. See deep drawing applications.

Deep drawing applications

Parts or applications that require deep drawing to meet their fabrication requirements. Examples would include are motor shells, fenders, quarter panels, and door panels for automotive parts and battery cases for AA or AAA batteries.

Deep drawn

Metals that have been subjected to the deep drawing metal stamping process.

Defect

Anything that renders the steel unfit for the specific use for its intended use such as punchmarks, roll marks, oil spots, and scratches. However, what is defective for one user may be prime steel for another.

Deflection

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

Deformation

The process of metal forming the solid material into shape by applying forces to it.

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 cup wall. The deformation limit (limiting draw 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.

Deformation processing

Deformation is forming the solid material into shape by applying forces to it. Because the material is in the solid state, the forces required are high and for this reason, metals with very high yield stresses are deformed hot. However, many commonly used metals can be deformed at room temperature eliminating the need for expensive heating equipment. The most well known deformation processes are forging, rolling and extrusion, which can produce components of a variety of shapes. Forming sheets into various shapes is also a type of deformation processes. Cold forming gives a better surface finish than hot forming and cold-formed parts generally have a higher yield strength than those that are hot-formed because the work hardening is retained.

Demarest process

A fluid forming process in which cylindrical and conical sheet metal parts are formed by a modified rubber bulging punch. The punch, equipped with a hydraulic cell, is placed inside the workpiece, which in turn is placed inside the die. Hydraulic pressure expands the punch.

Details

Individual parts of the die. Also known as steels, sections, die sections, and back-ups.

Developed blank

A sheet metal blank that yields a finished part without trimming or with the least amount of trimming.

Die

Tool with a void or cavity that is precisely fitted to a punch used to solid, molten, or powdered metal primarily because of the shape of the tool itself. Die-casting and powder metallurgy dies are sometimes referred to as molds.

Die ad

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

Die aid

See skin or cast.

Die assembly

The parts of a die stamp or press that hold the die and locate it for the punches.

Die block

A block, often made of heat treated steel, into which desired impressions are machined or sunk and from which closed die forgings or sheet metal stampings are produced using hammers or presses. In forging, die blocks are usually used in pairs, with part of the impression in one of the blocks and the rest of the impression in the other. In sheet metal forming, the female die is used in conjunction with a male punch.

Die button

See button.

Die cavity

The machined recess that gives a forging or stamping its shape.

Die clearance

Amount of space between the punch and die opening.

Die cushion

A large pressurized cylinder, generally housed beneath the bed of a press used to apply upward pressure to the lower die. The die cushion is actuated by air, oil, rubber, springs, or a combination of these.

Die cut inserts

Packaging elements, generally of cardboard, which are machine blanked to a specific shape in order to precisely fit a part contour.

Die height

The distance from the finished top face of the upper shoe to the finished bottom face of the lower shoe immediately after the die operation and with the work in the die.

Die holder

A plate or block, on which the die block is mounted, having holes or slots for fastening to the bolster plate or the bed of the press.

Die hooks

See turnover.

Die impression

The portion of the die surface that shapes a forging or sheet metal part.

Die life

The productive life of a die impression, usually expressed as the number of units produced before the impression has worn beyond permitted tolerances.

Die line

A line or scratch resulting from the use of a roughened tool or the drag of a foreign particle between tool and product.

Die lubricant

In forging or forming, a compound that is sprayed, swabbed, or otherwise applied on die surfaces or the workpiece during the forging or forming process to reduce friction. Lubricants also facilitate release of the part from the dies and provide thermal insulation. See also lubricant.

Die maker's friend or helper

See profile grinder.

Die marks

Scratches, scrub marks, indentations, galling or burnishing of sheet metal workpieces by tooling.

Die match

The alignment of the upper (moving) and lower (stationary) dies in a hammer or press. An allowance for misalignment (or mismatch) is included in forging tolerances.

Die post

Lower section of die on which the part nests. Also called an adapter, boss, horn, locator, master, master plug, and stool. Guide post where wear plates are attached.

Die proof (cast)

A casting of a die impression made to confirm the accuracy of the impression.

Die radius

The radius on the exposed edge of a deep drawing die, over which the sheet flows in forming drawn shells.

Die set

The assembly of the upper and lower die shoes (punch and die holders), usually including the guide pins, guide pin bushings, and heel blocks. This assembly takes many forms, shapes, and sizes and is frequently purchased as a commercially available unit. Two (or, for a mechanical upsetter, three) machined dies used together during the production of a die forging.

Die shoes

The upper and lower plates or castings that constitute a die set (punch and die holder). Also a plate or block upon which a die holder is mounted, functioning primarily as a base for the complete die assembly. This plate or block is bolted or clamped to the bolster plate or the face of the press slide.

Die space

The maximum space (volume), or any part of the maximum space, within a press for mounting a die.

Die stamping

The general term for a sheet metal part that is formed, shaped, or cut by a die in a press in one or more operations.

Differential coatings

Coatings on flat rolled products where the thickness of the coating on the one side is heavier than the other side.

Dimension

A measurement describing size and/or appearance of a part feature.

Dimensional tolerance

A range by which a product's width and gauge can deviate from those ordered and still meet the order's requirements. Also see commercial tolerance.

Dimpling

The stretching of a relatively small, shallow indentation into sheet metal. In aircraft/aerospace industries, the stretching of metal into a conical flange for a countersunk head rivet.

Dings

A small unwanted mark or dimple in a completed part. These are usually caused by dirt or material in the die.

Distortion:

Any deviation from a desired contour or shape.

Doctor blade steel strip:

A hardened and tempered spring steel strip, usually blued, produced from approximately .85 carbon cold rolled spring steel strip specially selected for straightness and good edges. Sometimes hand straightened or straightened by grinding and cut to desired lengths. This product is used in the printing trade as a blade to uniformly remove excess ink, called dope, from the rolls providing the origination of the name.

Dog leg cam

A cam attached to the upper half of the die with a driver on the bottom half of the die. Also called an aerial cam, flying cam, or walking cam.

Dog leg driver

A cam driver designed to ensure positive cam-slide travel in both directions.

Dope

A drawing compound used to lubricate the stock during a forming operation.

Double burned

A condition that may occur on a laser wherein the laser essentially produces a feature twice destroying the part's edge and causing out of dimension condition.

Double-action

Press utilizing two moving elements.

Double-action die

A die in which pressure is first applied to a blank through the blank holder and is then applied to the punch.

Double-action mechanical press

A press having two independent parallel movements by means of two slides, one moving within the other. The inner slide or plunger is usually operated by a crankshaft and the outer or blank holder slide, which dwells during the drawing operation, is usually operated by a toggle mechanism or by cams. See slide, triple action press.

Double-action press

Same as double action mechanical press that is run automatically.

Dowel

A round pin, usually case hardened, that fits into a corresponding hole to align two die members.

Dowel puller

A weight that slides along a rod with a head on one end and threads on the other end that is normally used to pull dowels and details. This weight and rod combination is commonly called a dowel puller. See slide hammer.

Draft

The taper given to a die so as to allow the part to fall through the die or be removed.

Drain holes

Holes placed in the part that are nonfunctional except to allow for drainage.

Draw

See drawing, deep drawing.

Draw bead

An insert or rib-like projection on the draw ring or hold-down surfaces that aids in controlling the rate of metal flow during deep draw operations. Draw beads are especially useful in controlling the rate of metal flow in irregularly shaped stampings.

Draw die

A specific type of form die that basically involves forcing the flat sheet of metal into a die cavity with a punch while holding the workpiece around the cavity to control metal flow.

Draw die punch

A punch that is tied to the inner press ram.

Draw line

See impact line.

Draw marks

Impressions such as scratches, burnished areas, and similar marks left on the surface of the workpiece, part, or panel by a draw die. Also called skid marks.

Draw plate

A circular plate with a hole in the center contoured to fit a forming punch used to support the blank during the forming cycle.

Draw radius

The radius at the edge of a die or punch over which sheet metal is drawn.

Draw ring

Holding device in a die to control material flow and wrinkling during forming. Also referred to as a binder.

Drawability

A measure of the feasible deformation of a blank during a drawing process. A measure of the percentage of reduction in diameter of a blank when it is drawn to a shell of maximum practical depth. The general formability and ductility of a metal.

Drawing

A term used for a variety of forming operations, such as deep drawing a sheet metal blank; redrawing a tubular part; and drawing rod, wire, and tube. The usual drawing process with regard to sheet metal working in a press is a method for producing a cup-like form from a sheet metal disk by holding it firmly between blank holding surfaces to prevent the formation of wrinkles while the punch travel produces the required shape. In metal forming, the stretch rig or compressing of a sheet metal part into a die by a punch to create a 3-dimensional part. The process of cold forming a flat pre-cut metal blank into a hollow vessel without excessive wrinkling, thinning, or fracturing.

Drawing compound

A substance applied to prevent pickup and scoring during deep drawing or pressing operations by preventing metal-to-metal contact of the workpiece and die. Also known as die lubricant.

Drawing quality (DQ)

Draw quality steel that is a more flexible grade of steel. Flat-rolled products produced from either deep drawing rimmed steel or extra deep drawing aluminum killed steels. Special rolling and processing operations aid in producing a product that can withstand extreme pressing, drawing or forming, without creating defects.

Drawn

A process where material is mechanically formed by tension through or in a die.

Drawn sheet

Sheet metal that has been mechanically formed by use of tension though a die or in a die.

Driver

A block with one or more angular surfaces that applies force by the vertical movement of the press to mating angular surfaces on a cam slide.

Ductility

A qualitative, subjective, property of material that indicates the extent that it can be deformed without fracture in normal metal working operations such as rolling, extrusion, or fabrication.

Dutch bend

See hem.

Dutchman

A unshaped device for tying sections of dies together either by design or to repair a die which has been broken.

Dwell

Portion of a press cycle during which the movement of a member is zero or at least insignificant. Usually refers to the interval when the blank holder in a drawing operation is holding the blank while the punch is making the draw or the interval between the completion of the forging stroke and the retraction of the ram.

Dwell cam

A cam that can be moved into position and held there while the press continues its cycle. Also see filler cam.

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