Views: 192 Author: Site Editor Publish Time: 2020-08-10 Origin: Site
Working principle of hydraulic press: the areas of large and small plungers are S2 and S1 respectively, and the acting forces on plungers are F2 and F1 respectively. According to Pascal's principle, the pressure of sealed liquid is equal everywhere, that is, F2/S2=F1/S1=p;F2=F1(S2/S1)。It indicates the gain effect of hydraulic pressure. Like mechanical gain, the force increases, but the work does not gain, so the moving distance of large plunger is S1/S2 times of that of small plunger.
The basic principle is that the oil pump delivers the hydraulic oil to the integrated cartridge valve block, distributes the hydraulic oil to the upper cavity or lower cavity of the oil cylinder through various one-way valves and overflow valves, and makes the oil cylinder move under the action of high-pressure oil. Hydraulic press is a device that uses liquid to transmit pressure. It follows Pascal's law when liquid transmits pressure in a closed container. 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 adopts oil pump as the power mechanism, which is generally an integral oil pump. In order to meet the requirements of the movement speed of the actuator, one oil pump or multiple oil pumps are selected. Gear pump for low pressure (oil pressure less than 2.5MP);Blade pump for medium pressure (oil pressure less than 6.3MP);Piston pump for high pressure (oil pressure less than 32.0MP).Pressure processing and forming of various plastic materials, such as extrusion, bending and deep drawing of stainless steel plates and cold pressing of metal parts, can also be used for pressing powder products, grinding wheels, Bakelite and thermosetting resin products.
Compared with the traditional stamping process, hydroforming process has obvious technical and economic advantages in reducing the weight, the number of parts and dies, improving the rigidity and strength, reducing the production cost, etc., and has been applied more and more in the industrial field, especially in the automobile industry.
In the fields of automobile industry, aviation, aerospace, etc., it is a long-term goal of people to reduce the structural mass to save energy in operation, and it is also one of the development trends of advanced manufacturing technology. Hydroforming is an advanced manufacturing technology to realize lightweight structure.
Hydroforming is also called "internal high pressure forming". Its basic principle is to use pipe as blank, apply ultra-high-pressure liquid inside the pipe, and at the same time, apply axial thrust to both ends of the pipe blank for feeding. Under the joint action of two kinds of external forces, the tube blank material is plastically deformed, and finally comes into contact with the inner wall of the die cavity, thus obtaining hollow parts with shape and precision meeting the technical requirements.
For the hollow structure with variable cross-section, the traditional manufacturing process is to press and form two halves first, and then weld them into a whole, while hydroforming can integrally form the hollow structure with variable cross-section at one time. Compared with stamping and welding process, hydroforming technology and process have the following main advantages:
(1) Reduce the quality and save materials. For typical parts such as automobile engine bracket and radiator bracket, hydroformed parts are 20% ~ 40% lighter than stamped parts; For hollow stepped shaft parts, the weight can be reduced by 40% ~ 50%.
(2) Reduce the number of parts and dies and the cost of dies. Hydroforming parts usually only need one set of dies, while stamping parts mostly need multiple sets of dies. The hydroformed engine bracket parts are reduced from 6 to 1, and the radiator bracket parts are reduced from 17 to 10.
(3) The welding amount of subsequent machining and assembly can be reduced. Taking the radiator bracket as an example, the heat dissipation area increased by 43%, the number of solder joints decreased from 174 to 20, the number of processes decreased from 13 to 6, and the productivity increased by 66%.
(4) Improve strength and rigidity, especially fatigue strength. For example, the rigidity of hydroformed radiator bracket can be increased by 39% in vertical direction and 50% in horizontal direction.
(5) Reduce the production cost. According to the statistical analysis of hydroformed parts, the production cost of hydroformed parts is reduced by 15% ~ 20% and the die cost is reduced by 20% ~ 30%.
| Common advantages and disadvantages of hydraulic press | |
| Advantage | Disadvantage |
| 1. It is easy to realize the automation of the machine. When the electro-hydraulic joint control is adopted, the degree of automatic control can be improved, and remote control can also be realized. | 1. Due to the large fluid flow resistance and leakage, the efficiency is low. If not handled properly, the leak will not only contaminate the site, but may also cause fire and explosion accidents. |
| 2. Generally, mineral oil is used as the working medium, the relative moving surface can be lubricated by itself, and the service life is long. | 2. As the working performance is easily affected by temperature changes, it is not suitable to work under very high or very low temperature conditions. |
| 3. Convenient operation and control, which can realize a wide range of stepless speed regulation (speed regulation range up to 2000:1). | 3. It is not easy to find out the cause when the hydraulic transmission fails; use and maintenance require a higher technical level. |
| 4. The hydraulic transmission to various components can be conveniently and flexibly arranged according to needs. | 4. Due to the influence of liquid leakage and compressibility, a strict transmission ratio cannot be obtained. |
| 5. Light weight, small size, small movement inertia and fast response speed. | 5. The manufacturing precision of hydraulic components is high, so the price is more expensive. |
| 6. It is easy to realize linear motion. | |
| 7. Can automatically realize overload protection. | |
According to the structural form, it is mainly divided into four columns, single column (C type), horizontal and vertical frame, universal hydraulic press, etc. It can be divided into metal forming, bending, stretching, blanking, powder (metal, non-metal) forming, press fitting, extrusion, etc. Common types are as follows:
Hot forging hydraulic press: Large forging hydraulic press is one of the most widely used equipment in forging industry. At present, there are 800T, 1600T, 2000T, 2500T, 3150T, 4000T and 5000T series of forging hydraulic machines.
Four-column hydraulic press: This hydraulic press is suitable for the pressing process of plastic materials. Such as powder product molding, plastic product molding, cold (hot) extrusion metal molding, sheet stretching, transverse pressing, bending pressing, turning over and correcting, etc. Four-column hydraulic press can be divided into four-column two-beam hydraulic press, four-column three-beam hydraulic press, four-column four-beam hydraulic press, etc.
Single-column hydraulic press (single-arm hydraulic press): the working range can be expanded, and the hydraulic cylinder stroke can be lengthened by using three-sided space (optional installation), and the maximum expansion can be 260mm-800mm, and the working pressure can be preset; Heat sink of hydraulic system.
Gantry hydraulic press: It can assemble, disassemble, straighten, roll, stretch, bend and punch machine parts, thus realizing multi-purpose of one machine. The workbench of the machine can move up and down, which expands the opening and closing height of the machine and is more convenient to use.
Double-column hydraulic press: this series of products is suitable for pressing, bending, stamping, flanging, punching and shallow stretching of small parts; Processing technology such as forming of metal powder products. Electric control is adopted, with point movement and semi-automatic circulation, which can guarantee rolling, and has good slider guiding property, convenient operation, easy maintenance, economy and durability. According to users' needs, functions such as thermal instrumentation, ejection cylinder, stroke digital display and counting can be added.
This equipment is especially suitable for bending, forming, flanging and other processes of central load parts. With blanking buffer device, it can also be used for punching and blanking processing. It is the first-choice product in shipbuilding industry, pressure vessel industry, chemical industry and other industries. It can be used for drawing, flanging, bending, stamping and other processes of sheet metal parts, and can also be used for general pressing processes, and devices such as blanking buffer, punching and moving worktable can be added according to the needs of users. In addition to forging, the hydraulic press with three beams and four columns can also be used for straightening, pressing, packing, pressing and pressing. It can also be used for pressing process of shaft parts, calibration, buckling and pressing process of profiles, bending, setting, stamping, nesting and stretching of plate parts, pressing process of plastic materials, such as stamping, bending, flanging and stretching, etc., and can also be engaged in calibration, pressing and pressing operations of plastic products and powder products. Because of its wide application range, it is also called universal hydraulic press.
Suitable materials for hydroforming process include carbon steel, stainless steel, aluminum alloy, copper alloy and nickel alloy, etc. In principle, materials suitable for cold forming are all suitable for hydroforming process. Mainly for auto parts factory, electronics factory, electrical appliance factory, heat treatment factory, vehicle parts factory, gear factory and air conditioning parts factory. Hydroforming technology is widely used in automobile, aviation, aerospace and pipeline industries, which is mainly suitable for: round, rectangular or special-shaped cross-section hollow structural parts changing along the axis of components, such as special-shaped pipe fittings of automobile exhaust system; Non-circular cross-section hollow frames, such as engine bracket, instrument panel bracket and body frame (accounting for about 11% ~ 15% of automobile mass);Hollow shaft workpieces and complex pipe fittings, etc.
Maintenance
1. No.32 and No.46 anti-wear hydraulic oil is recommended as working oil, and the working oil temperature is within the range of 15 ~ 60℃.
2. The oil is allowed to be added to the oil tank after being strictly filtered.
3. The working oil should be replaced once a year, and the first replacement time should not exceed three months.
4. Lubricating oil should be frequently injected into the slider, and the appearance of the column should always be kept clean. Oil should be injected before each work.
5. Under the nominal pressure of 500T, the maximum allowable eccentricity of concentrated load is 40mm.Excessive eccentricity can easily cause column strain or other undesirable phenomena.
6. Check the pressure gauge once every six months.
7. When the machine is out of service for a long time, the surface of each part should be scrubbed clean and coated with antirust oil.
Safety operations
1. Those who don't know the structural performance or operating procedures of the machine should not start the machine without authorization.
2. During the working process, the machine should not be overhauled or adjusted.
3. When the machine finds serious oil leakage or other abnormalities (such as unreliable action, loud noise, vibration, etc.), it should stop and analyze the reasons, try to eliminate them, and may not put them into production with illness.
4. Do not overload or exceed the maximum eccentricity.
5. It is forbidden to exceed the maximum stroke of the slider, and the minimum closing height of the mold shall not be less than 600mm.
6. Electrical equipment grounding must be firm and reliable.
7. Put the slider to the lowest position at the end of every day's work.
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