Metalforming Glossary
A variety of functions may be performed by any press, depending upon the tooling. Typical press operations and other terms referring to press features and functions are defined below:
Slide Adjustment -
The distance a mechanical press slide can be moved from its maximum shut height to reduce the die space height. The adjustment can be performed by hand or with a power mechanism.
Press Bed -
The stationary portion or "table" of the press to which the bolster is attached.
Blanking -
Blanks are produced from the shearing or cutting of outside contours or shapes out of sheet or strip stock. For larger production runs, blanking is often done in multiple dies, and is combined with
other operations such as piercing and forming in combination and progressive dies.
Bolster Plate -
A plate or block attached to the top of the press bed where the die is fastened. In some rare cases the die is fastened directly to the bed.
Press Brake -
The friction mechanism used to stop or control the motion of a press, feed or other mechanism.
Press Capacity -
Rated press capacity is the tonnage pressure the slide can safely exert at the bottom of the stroke. Mechanical press capacity is typically based on the bending capacity
of the main shaft (crank, toggle, or eccentric shaft).
Press Clutch -
A coupling used to connect or disconnect a driving machine-member, such as a shaft or wheel, to or from a driven machine-member, such as another wheel or shaft. The engaging or disengaging can be done by a hand operated controlling device operated manually or automatically.
Connecting Rod or Connection -
See Pitman
Coining -
A squeezing operation, usually performed in a closed die in which the metal is forced to flow and fill the shape and profile of the die. There is a definite change in metal thickness.
Crimping -
An operation in which the open end of a can or shell is forced tight over or around a mating part. This type of work is limited largely to assembly operations.
Curling -
The forming of an edge having a circular cross section along a sheet or around the end of a shell or tube. This operation is sometimes called false wiring.
Deep Drawing -
Forming of deep recessed parts from sheet material by means of a plastic flow of the material worked in presses and dies.
Deflection -
The amount of bending or the deviation from a straight line or a plane when a force or load is applied to a surface of a machine member or part.
Die -
1. A tool used on a press for any operation or series of operations, such as forming, drawing, piercing and cutting. The upper member (or members) are attached to the slide (or slides) of the press, with the lower member clamped or bolted to the bed or bolster, shaped so that the material placed between them is cut or formed when the press makes a stroke.
2. The female part of a complete die assembly as described in (1).
3. A tool for cutting external threads.
Die Cushion -
An attachment or press accessory which gives additional motion or pressure required in many compound press operations. The pressure medium can be rubber, springs, air or liquid (usually oil). Air (pneumatic) cushions are the most commonly used. Uses include blank holding, drawing, maintaining uniform pressure on a die part, knock-out, and stripping. Typically mounted in order on the press bed, they can sometimes be mounted on the top of a press slide flange.
Die Height -
The closed height of a die during the working portion of the press or completed operation in the die. Die Height is measured from the top of the bolster plate to the bottom of the slide.
Eccentric -
Essentially a disk arranged to rotate around a center, not the center of dish but parallel to it. An eccentric should crank with a crankpin of such size that it contains or surrounds the shaft. The eccentric with its strap or connection is used in the eccentric press and for driving auxiliary attachments, such as liftouts and various types of feeds.
Embossing -
A process for producing raised or sunken designs in sheet metal by means of a male and female die.
Extrusion -
A process in which pressure is applied to a slug of metal causing the metal to flow either up around the punch (toothpaste tubes) or down in the direction of pressure (cartridge cases - Hooker process).
Flywheel -
A wheel used on an engine or machine with a rotation energy or inertia able to prevent excessive or sudden changes in speed. In modern mechanical presses the flywheel is usually belted, chained or geared to the driving motor. A clutch is mounted on or within the flywheel.
Gibs -
Guides or shoes that insure the proper sliding fit between two machine parts and which usually are adjustable for taking up excessive wear, e.g., press gibs that guide the press slide.
Inching -
A machine control process used to adjust and set dies and other tools in by precisely controlling the working members of the press in short increments usually by rapidly engaging and disengaging the clutch or using electric or pneumatic push buttons.
Ironing -
A process in which the wall thickness of the shell is reduced without changing the O.D. of the shell (cartridge case work for example).
Lancing -
Slitting and forming a pocket shaped opening in sheet metal, without removing metal.
Link Motion -
A modified slide motion that produces either constant velocity or increased slow down through the working part of the press stroke.
Necking -
Reducing the diameter of a portion of the length of a cylindrical shell or tube.
Piercing -
A general term for cutting (shearing or punching) openings, such as holes and slots in sheet material, plate or parts. Similar to blanking; the slug or piece produced by piercing is scrap, whereas the blank produced by blanking is the useful part. In both cases the burr is opposite.
Pitman -
A connecting rod to convey motion and pressure from a revolving crank of eccentric to a sliding or swinging member, such as a slide or lever. A press connecting rod.
Pneumatic Die Cushion -
Pneumatic (air) attachment consisting essentially of cylinder piston, pressure plate and accessories generally used with a press for clamping, blank holding or ejecting.
Progressive Dies -
A series of two or more dies arranged in line for performing two or more operations on a part, one operation (single or compound) performed in each die, at each station. Work in the form of a strip is usually fed to progressive dies automatically by a roll feed.
Redrawing -
The second operation following deep-drawing operations, in which cups are deepened and reduced in cross section.
Tie Rod -
Four long rods, with threads and nuts on both ends, which hold the frame members of a straightside press together. These rods are stretched to place the frame members under compressive load.
Slide -
The most common name for the main reciprocating member of a press, guided in the press frame and to which the punch or upper die is fastened. It is also referred to as the ram. The inner slide of a double action press is called the plunger; the outer slide of a double action press is called the blank holder slide, and the slide of a hydraulic press is often called the platen.
Shut Height -
The shut height of an upright press is the distance from the top of the bed to the bottom of the slide with stroke down and adjustment up. The shut height must always be defined either from the top of the bed or from the top of the bolster. The shut height of a horizontal or inverted press, or of a press with adjustable bed, can be defined in a similar manner. Generally the shut height is equal to the maximum die-height of the die that can be accommodated, taking the bolster into consideration.
Staking -
An operation in which two or more parts are assembled permanently by upsetting a small portion of metal over the mating part, causing the compression on the assembled parts.
Stroke -
The reciprocating motion of a press slide, usually specified as the number of inches between the terminal points of the motion.
Swaging -
Forming a metal by the rapid striking of a large number of successive blows. In the case of aircraft cable fittings, the fitting is rotated while the press blows are being struck.
Throat (gap) -
The open space in a gap frame press back of the slide centerline. The depth of throat (gap) is the distance from the slide centerline back to the frame metal of the upright section.
Trimming -
A secondary operation on drawn or formed parts to remove excess metal on the flange or axial length.
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