Hydraulic press (also known as: Hydraulic Press) hydraulic press is a kind of machine that uses hydrostatic pressure to process metal, plastic, rubber, wood, powder and other products. It is commonly used in pressing process and pressing forming process, such as forging, stamping, cold extrusion, straightening, bending, flanging, sheet drawing, powder metallurgy, pressing, etc.
Its principle is to make use of Pascal's law to make use of liquid pressure transmission machinery, there are many kinds. Of course, there are various uses according to the needs. For example, according to the type of liquid to transmit pressure, there are two categories: oil press and hydraulic press.
The total pressure produced by hydraulic press is large, which is often used in forging and stamping. Forging hydraulic press is divided into die forging hydraulic press and free forging hydraulic press. Die forging hydraulic press should use die, while free forging hydraulic press does not use die. The first 10000 ton hydraulic press made in China is the free forging hydraulic press
Working principle of hydraulic press. The area of big and small plunger is S2 and S1 respectively, and the force of hydraulic press on plunger is F2 and F1 respectively. According to Pascal principle, the pressure of closed liquid is equal everywhere, that is, F2 / S2 = F1 / S1 = p; F2 = F1 (S2 / S1). It indicates the gain effect of hydraulic pressure. Like the mechanical gain, the force increases, but the work does not gain. Therefore, the movement distance of large plunger is S1 / S2 times of that of small plunger.
The basic principle is that the oil pump transmits the hydraulic oil to the integrated cartridge valve block, distributes the hydraulic oil to the upper or lower cavity of the oil cylinder through each check valve and overflow valve, and makes the oil cylinder move under the action of high pressure oil. The hydraulic press is a device that uses the liquid to transmit the pressure. When liquid transfers pressure in a closed container, it follows Pascal's law. The hydraulic transmission system of four column hydraulic press consists of power mechanism, control mechanism, actuator, auxiliary mechanism and working medium. The power mechanism usually uses the oil pump as the power mechanism, generally the integral oil pump. In order to meet the requirements of the moving speed of the actuator, one or more oil pumps are selected. Gear pump for low pressure (oil pressure less than 2.5MP); vane pump for medium pressure (oil pressure less than 6.3mp); plunger pump for high pressure (oil pressure less than 32.0mp). Pressure processing and forming of various plastic materials, such as extrusion, bending, drawing of stainless steel plate and cold forming of metal parts, can also be used for pressing of powder products, grinding wheel, bakelite and resin thermosetting products.
The function of working medium used in hydraulic press is not only to transfer pressure, but also to ensure that the working parts of the machine work sensitively, reliably, with long service life and less leakage. The basic requirements of hydraulic press for working medium are: proper fluidity and low compressibility to improve transmission efficiency; anti rust; good lubrication performance; easy to seal; stable performance, long-term operation without deterioration. At first, water was used as working medium for hydraulic press. Later, a small amount of emulsion oil was added into water to increase lubricity and reduce corrosion. In the late 19th century, the oil press with mineral oil as working medium appeared. Oil has good lubricity, corrosion resistance and moderate viscosity, which is conducive to improving the performance of hydraulic press. In the second half of the 20th century, a new type of water-based emulsion appeared. Its emulsification form is "oil in water", not the original "oil in water". The external phase of "water in oil" emulsion is oil, its lubricity and corrosion resistance are close to oil, and its oil content is very small, so it is not easy to burn. But the price of water-based emulsion is expensive, which limits its popularization.