Classification of hydraulic presses according to application characteristics

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Hydraulic presses can be classified according to their application characteristics into double-acting drawing presses, multi-station automatic presses, rotary head presses, cold extrusion presses, and hot die forging presses. ①Double-acting drawing press: It has inner and outer sliders, which are used for the drawing formation of cup-shaped parts. Before drawing, the outer slider first compresses the outer edge of the sheet metal, after which the inner slider drives the punch to draw the cup shape, thereby preventing wrinkling at the outer edge of the sheet. After drawing is completed, the inner slider retracts first, followed by the release of the outer slider. The ratio of the nominal working forces of the inner and outer sliders is (1～1.7):1. ②Multi-station automatic press: A single press is equipped with multiple stations, each fitted with different forming dies, and the blank moves automatically to the next station one after another. During one stroke of the press, each forming step is carried out simultaneously at the respective stations to produce one workpiece. ③Swing head press: A swing head capable of holding dozens of sets of molds is installed between the slider and the worktable, allowing for the selection of molds as needed. The blank is placed on the mold and no longer moves. After each cycle is completed, the swivel head rotates by one position to finish one process step. This press features high positioning accuracy, making it easy to adjust products; it can be used for multiple purposes and is commonly used for stamping instrument bases and panels. A rotary press can be equipped with a CNC system, which allows for the selection of the appropriate molds and the areas of the sheet metal to be shaped based on pre-programmed instructions, thereby automating complex stamping tasks. ④Cold extruder: Used for cold and warm-state extrusion of metal parts, such as cartridge cases and toothpaste tubes. Cold extruders are generally vertical in design, featuring good stiffness, high guiding precision, high operating pressure, a small worktable surface, and a long working stroke. ⑤Hot die forging press: used for the production of die-forged parts. It has high fuselage stiffness, long guiding surfaces, and strong capacity to withstand off-center loads. In the past, crank-slider mechanisms were commonly used; to improve rigidity, double-slider and wedge types have been adopted instead. The dual-slider structure is relatively simple and lightweight ； The wedge-shaped structure has a large supporting area, but low transmission efficiency. During die forging, the slider tends to get stuck near the lower dead center (commonly known as sticking), so an escape mechanism is provided. The machine is equipped with upper and lower ejection devices, enabling multi-cavity forging; it yields forgings of high precision and is suitable for mass production. The maximum specification is 160 meganewtons.