Machinery's Handbook, 31st Edition
1464 Presses for Sheet Metal Working Single action: One ram operated by a mechanism located in the crown or bed of a press. These presses are used for blanking, bending, forming, and other operations. They perform a single action with each cycle of the press. Double action: One inner ram and one outer ram are operated by a mechanism located in the crown or bed on the press. The rams move from the crown towards the bed on the downstroke. They are used for severe forming and drawing operations. Triple action: Same as double action with the addition of a third ram located in the bed of the press. The third ram moves upward in the bed soon after the other two rams lower. Large presses (like those used in the automotive industry) have a die cushion integrated in the bolster plate to apply the blank holder force. This is necessary when a single acting press is used for deep drawing. Fig. 74 schematically illustrates a mechanical press with its basic components.
Drive
Flywheel
Ram
Frame
Bed Boster plate
Fig. 74. Schematic Illustration of Mechanical Drive Presses with Basic Components
Gap-Frame Presses.— The most noticeable characteristic of a press is the frame’s style of construction. The frame is the supporting element of a press. All of the shafts and bear- ings, as well as the ram and gearing, are mounted in the frame. Frames may be fabricated by casting or by welding heavy rolled steel plates. The cast frame has excellent rigidity but is expensive. The welded frame is lower in cost in most cases. Due to the greater toughness of rolled steel, welded frames have more resis tance to shock loading. The C-frame press gets its name from its shape. The most common types of C-frame are the inclinable or open-back inclinable (OBI), the solid frame or open-back stationary (OBS), the open-end press, and the adjustable bed or knee frame press. Inclinable-frame press: The frame of an inclinable press can be tilted backward to an angle of around 30 ° . This inclination permits finished parts, slugs, or both, to slide to the rear of the machine upon completion. As the name implies, a fixed-position, or noninclin able machine does not tilt, and parts and/or slugs must either drop vertically or be removed by some other means. Solid-frame press: Because of the more rigid base and solid construction, solid frame presses or OBS presses are built in higher tonnages than inclinable presses. These presses have larger beds and frame openings than inclinable presses and can handle larger dies. Adjustable-bed press: The third type of C-frame press is the adjustable bed or knee press. The lower leg of the C-frame forms an adjustable table or bed, and thus a wide range of shut heights may be obtained. Because of possible lack of rigidity, only smaller tonnages are made with this style of frame. The adjustable bed press is one of the most versatile presses. Open-end press: This press has the unusual feature of having the driveshaft located from front to back. Most presses of the C-frame type have the driveshaft from right to left. The
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