What Is a Hydraulic Press?
A hydraulic press is a machine that uses liquid as the working medium and is based on Pascal's principle to transfer energy to achieve various processes. Hydraulic machine is generally composed of three parts: the machine (main machine), power system and hydraulic control system. The hydraulic presses are classified into valve hydraulic presses, liquid hydraulic presses, and engineering hydraulic presses.
- Chinese name
- Hydraulic Press
- Alias
- Hydraulic press
- Principle
- Pascal's Law
- Use
- Forging
- Make up
- Main engine, power system and hydraulic control system
- A hydraulic press is a machine that uses liquid as the working medium and is based on Pascal's principle to transfer energy to achieve various processes. Hydraulic machine is generally composed of three parts: the machine (main machine), power system and hydraulic control system. The hydraulic presses are classified into valve hydraulic presses, liquid hydraulic presses, and engineering hydraulic presses.
Introduction to hydraulic press
- Hydraulic press (also known as hydraulic press) Hydraulic press is a kind of machinery that uses hydrostatic pressure to process metal, plastic, rubber, wood, powder and other products. It is commonly used in pressing and forming processes, such as: forging, stamping, cold extrusion, straightening, bending, flanging, sheet drawing, powder metallurgy, press fitting, and so on.
- Its principle is to use Pascal's law to make machinery using liquid pressure transmission, there are many types. Of course, the use is also rooted
- The total pressure generated by the hydraulic press is large, and it is often used for forging and stamping. Forging hydraulic presses are divided into die forging hydraulic presses and free forging hydraulic presses. The die forging hydraulic press uses a die, while the free forging hydraulic press does not use a die. The first hydraulic press of 10,000 tons made in China was a free forging hydraulic press.
Hydraulic machine use
- A hydraulic press is a machine that uses liquid as a working medium to transfer energy to achieve various processes. In addition to forging and forming, hydraulic presses can also be used for correction, press fitting, packing, briquetting and pressing plates. Hydraulic presses include hydraulic and hydraulic presses. Water-based liquids are called hydraulic presses, and oil-based liquids are called hydraulic presses. The specifications of hydraulic presses are generally expressed in nominal working force (kilonewtons) or nominal tonnage (tons). Forging hydraulic presses are mostly hydraulic presses, and the tonnage is relatively high. In order to reduce the size of the equipment, large forging hydraulic presses often use higher pressures (about 35 MPa), and sometimes ultra-high pressures of more than 100 MPa are also used. Hydraulic presses for other uses generally use a working pressure of 6 to 25 MPa. The hydraulic press has a lower tonnage than the hydraulic press.
Brief History of Hydraulic Press
- In 1795, British J. Brammer applied the Pascal principle to invent a hydraulic press for packing and squeezing vegetable oil. By the middle of the 19th century, the British began to use hydraulic presses for forging, and the hydraulic presses gradually replaced super-large steam forging hammers. By the end of the 19th century, the United States had made 126,000 kN free forging hydraulic presses. Since then, the world has manufactured more than 20 100,000 kN free forging hydraulic presses, of which 2 are made in China (see color chart). With the advent and improvement of electric high-pressure pumps, forging hydraulic presses have also developed towards smaller tonnages. After the 1950s, small-scale rapid forging hydraulic presses appeared, which can perform the work equivalent to a forging hammer of 30-50 kN. In the 1940s, Germany made a giant die forging hydraulic press of 180,000 kN. Since then, the world has made 18 die forging hydraulic presses of more than 180,000 kN, of which one in China is 300,000 kN.
Working principle of hydraulic press
- How hydraulic machines work. The areas of the large and small plungers are S 2, S 1, respectively.
- Hydraulic Press
- The basic principle is that the oil pump delivers hydraulic oil to the integrated cartridge valve block, and distributes the hydraulic oil to the upper or lower chamber of the cylinder through each check valve and relief valve, and makes the cylinder move under the action of high-pressure oil. It is a device that uses liquid to transmit pressure. When a liquid transfers pressure in a closed container, it follows Pascal's law. The hydraulic transmission system of a four-column hydraulic press is composed of a power mechanism, a control mechanism, an executive mechanism, an auxiliary mechanism and a working medium. The power mechanism usually uses an oil pump as the power mechanism, and is generally an integrated oil pump. In order to meet the requirements of the actuator's movement speed, one oil pump or multiple 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, deep drawing of stainless steel plates and cold pressing of metal parts. It can also be used for pressing powder products, grinding wheels, bakelite, and resin thermosetting products.
Working medium of hydraulic press
- The function of the working medium used in the hydraulic press is not only to transmit pressure, but also to ensure that the working parts of the machine are sensitive, reliable, long life and low leakage. The basic requirements of the hydraulic press for the working medium are: suitable fluidity and low compressibility to improve the efficiency of the transmission; anti-rust; good lubrication; easy to seal; stable performance and long-term work And not degenerate. The hydraulic press used water as the working medium initially, and later changed to an emulsion made by adding a small amount of emulsified oil to the water to increase lubricity and reduce rust. In the late 19th century, hydraulic presses with mineral oil as the working medium appeared. The oil has good lubricity, corrosion resistance and moderate viscosity, which is helpful to improve the performance of the hydraulic machine. A new type of water-based emulsion appeared in the second half of the 20th century. Its emulsified form was "water-in-oil" instead of the original "oil-in-water". The external phase of the "water-in-oil" emulsion is oil, and its lubricity and corrosion resistance are close to oil, and its oil content is very small, and it is not easy to burn. But water-based emulsions are more expensive, which limits their promotion.
Hydraulic machine structure
Hydraulic drive system
- There are two types of drive systems for hydraulic presses: direct pump drive and pump-accumulator drive. The pump directly drives this drive
- Drive System
- Pump-accumulator drive There is one or a group of accumulators in this drive system. When there is a surplus of the high-pressure working fluid supplied by the pump, it is stored by the accumulator; when the supply is not enough, it is supplemented by the accumulator. With this system, the capacity of the pump and motor can be selected according to the average amount of high-pressure working fluid, but because the pressure of the working fluid is constant, the power consumption is large, and the system has many links and the structure is complicated. This drive system is mostly used in large hydraulic machines, or a set of drive systems to drive several hydraulic machines.
Hydraulic machine structure
- According to the direction of the force, there are two types of hydraulic machines: vertical and horizontal. Most hydraulic presses are vertical
- structure
Classification of hydraulic press
- According to the structure, it is mainly divided into: four-column type, single-column type (C type), horizontal type, vertical frame, universal hydraulic machine, etc.
- According to the application, it is mainly divided into metal forming, bending, stretching, punching, powder (metal, non-metal) forming, press fitting, extrusion and so on.
- Hot forging hydraulic press
- Large forging hydraulic press is a forging equipment capable of completing various free forging processes and is one of the most widely used equipment in the forging industry. Currently there are 800T, 1600T, 2000T, 2500T, 3150T, 4000T, 5000T and other series of forging hydraulic presses.
- Four-column hydraulic press
- The 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, and lateral pressing, bending, turning through, correction and other processes.
- 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 and so on.
- Single arm hydraulic press (single column hydraulic press)
- Expandable working range, using three sides of space, lengthened hydraulic cylinder stroke (optional), maximum retractable 260mm-800mm, preset working pressure; hydraulic system cooling device.
- Gantry hydraulic press
- The machine parts can be assembled, disassembled, straightened, rolled, stretched, bent, punched, etc., realizing multiple uses of one machine. The worktable of the machine can move up and down, the size of the machine expands the opening and closing height, and it is more convenient to use.
- Double-column hydraulic press
- This series of products are suitable for processing of various parts such as press-fitting, bending and shaping, embossing, creasing, punching and shallow drawing of small parts; forming of metal powder products. It adopts electric control, equipped with jog and semi-automatic cycle, can maintain pressure delay, and has good slider guidance, convenient operation, easy maintenance, economical and durable. Functions such as thermal instrumentation, ejection cylinder, stroke digital display, and counting can be added according to the needs of users.
Hydraulic machine product use
- This equipment is especially suitable for bending, forming, flanging and other processes of center-loaded parts. It can also be used for punching and blanking after being equipped with a punching buffer device. It is a shipbuilding industry, pressure vessel industry, chemical industry and other industries. Preferred product.
- It is used for the process of drawing, forming, tumbling, bending and stamping of sheet metal parts. It can also be used in the general pressing process. It can add punching buffer, blanking, moving table and other devices according to user needs.
- In addition to forging and forming, the three-beam four-column hydraulic press can also be used for correction, press fitting, packing, briquetting and pressing plates.
- It can also be used for the pressing process of shaft parts, the calibration, buckling, press-fitting process of profiles, and the bending, argumentation, shaping, embossing, forming, stretching, and pressing of plastic materials such as stamping, bending, turning Edge thin stretching and other operations can also be engaged in correction, press fitting, press molding of plastic products and powder products. Because of its wide range of applications, it is also known as a universal hydraulic machine.
Technical conditions of hydraulic press
- 1. The technical requirements of the drawings and technical documents of the hydraulic press shall meet the requirements of the relevant current standards and shall be approved in accordance with the prescribed procedures before they can be used for production.
- 2. The design should be reasonable in layout, beautiful in appearance, safe and reliable in use performance, sensitive and light in handling, and no more than 49N (5kgf) in hand and no more than 78? 4N (8kgf) in pedaling force.
- 3 Important guide rails, columns, and plugs should be wear-resistant. The slide rail guide (or purlin surface) and the tracking surface of the fuselage should maintain the necessary hardness difference.
- 4 Parts, components or equipment weighing more than 15kg must be easy to lift and install, and lifting holes or lifting hooks (rings) should be provided if necessary.
- 5. The whole or part of the packaged hydraulic press and its parts and components shall comply with the current standards and relevant regulations for transportation and loading.
- 6. Repacked parts and components shall have relevant installation identification marks. Among them, plate or tube valves shall be installed with correct orientation measures. Among them, the pipeline and the passage openings of hydraulic components shall be protected against dust.
Hydraulic forming technology
Advantages of hydraulic press
- Compared with the traditional stamping process, the hydroforming process has obvious technical and economic advantages in reducing weight, reducing the number of parts and molds, increasing rigidity and strength, and reducing production costs. It has been obtained in the industrial field, especially in the automotive industry. More and more applications.
- In the automotive industry, aviation, aerospace and other fields, reducing structural quality to save energy during operation is a long-term goal for people, and it is also one of the development trends of advanced manufacturing technology. Hydroforming is an advanced manufacturing technology to achieve lightweight structure.
- Hydroforming is also known as "internal high pressure forming". Its basic principle is to use the tube as a blank, while applying ultra-high pressure liquid inside the tube, and applying axial thrust to both ends of the blank to perform replenishment. Under the combined action of two external forces, the tube blank material undergoes plastic deformation, and finally adheres to the inner wall of the mold cavity to obtain a hollow part whose shape and accuracy meet the technical requirements.
Advantages of hydraulic press
- For hollow variable cross-section structural parts, the traditional manufacturing process is to press-form two halves first, and then weld them into a whole, while hydraulic forming can be used to integrally form hollow structural parts that change along the cross-section of the component at one time. Compared with the stamping and welding process, the hydroforming technology and process have the following main advantages:
- 1. Reduce quality and save materials. For automotive engine brackets, radiator brackets and other typical parts, hydroformed parts are 20% to 40% lighter than stamped parts; for hollow stepped shaft parts, they can be 40% to 50% lighter.
- 2. Reduce the number of parts and molds, and reduce mold costs. Hydroformed parts usually require only one set of dies, while stamped parts mostly require multiple sets of dies. The number of hydroformed engine bracket parts was reduced from 6 to 1, and the radiator bracket parts were reduced from 17 to 10.
- 3. It can reduce the welding amount of subsequent machining and assembly. Taking the radiator bracket as an example, the heat dissipation area increased by 43%, the number of solder joints was reduced from 174 to 20, the number of processes was reduced from 13 to 6, and the productivity increased by 66%.
- 4. Improve the strength and stiffness, especially the fatigue strength. For example, the rigidity of the hydroformed radiator bracket can be increased by 39% in the vertical direction and 50% in the horizontal direction.
- 5. Reduce production costs. According to the statistical analysis of the applied hydroformed parts, the production cost of hydroformed parts has been reduced by 15% to 20% on average, and the mold costs have been reduced by 20% to 30%.
Hydraulic press process application
Hydraulic machine range
- The hydroforming process has a wide range of applications in the automotive, aerospace, aerospace, and pipeline industries. It is mainly suitable for: circular, rectangular, or shaped hollow structural parts that change along the component axis, such as shaped parts for automotive exhaust systems; non-circular sections Hollow frames, such as engine brackets, instrument panel supports, body frames (approximately 11% to 15% of automobile mass); hollow shaft parts and complex pipe fittings. Figure 2 shows some typical parts manufactured by the hydroforming process in the automotive industry.
- Suitable materials for the hydroforming process include carbon steel, stainless steel, aluminum alloy, copper alloy, and nickel alloy. Materials that are suitable for cold forming are in principle suitable for hydroforming. Mainly targeted at auto parts factory, electronics factory, electrical appliance factory, heat treatment factory, vehicle parts factory, gear factory, air-conditioning parts factory
Hydraulic machine characteristics
- 1. According to the function and use, the score can be:
- Powder molding hydraulic press, automobile heavy beam hydraulic press, non-metal special hydraulic press, mechanical repair hydraulic press, carbon product hydraulic press, hydraulic press, hydraulic press, ceramic product hydraulic press
- 2. According to the type, it can be divided into:
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- 3. According to the size of the tonnage:
| 63 tons hydraulic press |
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| 250 ton hydraulic press |
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| 630 ton hydraulic press |
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Optional equipment for hydraulic press
- The main function
- Anti-cylinder electronic device
- Press fit large transmission gears and shafts
- Correcting the front axle
- Correct deformed workpiece
- Disassembly of cylindrical tapered bearings
- Change the car clutch film spring
- Press-fit bearing Bearing outer ring
- Replace the reaction rod rubber assembly
- Disassembly and assembly of various tight-fitting parts
- Clutch plate stop pin buffer spring
- Riveting, cutting and throwing rivets for rear basin teeth
- Press-fitted piston pin, knuckle pin and various pin sleeves
- The main parts are made of 45 # cast steel and quenched and tempered
- Worktable adopts movable heart plate structure
Hydraulic press reference
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Hydraulic machine maintenance system
Hydraulic machine care and maintenance
- 1. It is recommended to use 32 # and 46 # anti-wear hydraulic oil for working oil, and the oil temperature should be in the range of 15 ~ 60 degrees Celsius.
- 2. The oil is allowed to be added to the tank only after it has been strictly filtered.
- 3 The working oil is changed every year, and the first replacement time should not exceed three months;
- 4 The slide block should be filled with lubricating oil frequently. The exposed surface of the column should be kept clean frequently. The oil should be sprayed before each work.
- 5. Under the nominal pressure of 500T, the maximum allowable eccentricity of concentrated load is 40mm. Excessive eccentricity may easily cause injury to the column or other undesirable phenomena.
- 6. Correct and check the pressure gauge every six months;
- 7. If the machine is not used for a long period of time, the surface of each added part should be cleaned and coated with anti-rust oil.
Safe operation of hydraulic press
- 1. Those who do not understand the machine's structural performance or operating procedures should not start the machine without authorization;
- 2. During the work of the machine, it should not be overhauled and adjusted the mold;
- 3 When the machine finds serious oil leakage or other abnormalities (such as unreliable movement, loud noise, vibration, etc.), it should stop and analyze the cause, try to eliminate it, and not put it 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 mold closing height must not be less than 600mm.
- 6. The grounding of electrical equipment must be firm and reliable:
- 7. End of the day: Move the slider to the lowest position.
Secondary maintenance of hydraulic press
- 1. The machine tool runs for 5000 hours for secondary maintenance. Mainly maintenance workers, operators participate. In addition to performing the first-level maintenance content, the following tasks should be done, and the wearing parts should be surveyed and mapped. Presenting spare parts.
- 2. First cut off the power for maintenance work. (See table below)
- Maintenance content and requirements of maintenance part
- A beam beam column guide 1. Check and adjust the plane of the row beam, column rail, guide sleeve, slider, and pressure plate to make it move smoothly and meet the technical requirements.
- 2. Repair or replace defective parts.
- 2.Hydraulic lubrication 1.Remove, repair and repair solenoid valve, grind valve and valve core.
- 2. Clean and inspect the oil pump cylinder plunger to smooth out burrs and replace the oil seal.
- 3 calibration pressure gauge
- 4. Repair or replace severely worn parts
- 5. Drive to check that each oil cylinder and plunger runs smoothly without creeping. The support valve can make the movable beam accurately stop at any position, and the pressure drop can meet the process requirements.
- Three electrical appliances 1. Clean the motor, check the bearings, and renew the grease
- 2. Repair or replace damaged components.
- 3. The appliance meets the requirements for equipment intact standards.
- Four precisions 1. Calibrate the level of the machine and check the adjustment and repair accuracy.
- 2. Accuracy meets the requirements of equipment intact standards.
- The maintenance and maintenance of the hydraulic press still needs special, professional and full-time maintenance, so that it can take longer!
Common faults of hydraulic press
- During the operation of the metal extrusion hydraulic press, sometimes the bolts fall off and fall into the hydraulic cylinder, causing serious damage to the plunger wall. After the problem appeared, the traditional method could not achieve on-site repair at all. It could only be dismantled and shipped to the manufacturer for repair welding or replacement. Because there is no replacement of spare parts, the time for remanufacturing parts or returning to the factory for maintenance cannot be controlled, and long-term downtime causes severe economic losses to the enterprise, and at the same time, high processing or repair costs must be paid. In order to meet the requirements of continuous production of the enterprise, it is necessary to find convenient, fast, simple and effective maintenance methods to solve the equipment problem, minimize the downtime of the enterprise and reduce the maintenance costs. Can be repaired on site using polymer composites
- Steps:
- 1. Use oxygen-acetylene flame to bake the scratched area (control the temperature and avoid surface annealing), bake the oil that permeates the metal surface all year round, and bake until there are no sparks.
- 2. The scratched part is surface-treated with an angle grinder, the depth of grinding is more than 1 mm, and the groove is polished along the outer wall of the cylinder barrel, preferably a dovetail groove. Scratch the holes at both ends to deepen and change the force situation.
- 3 Clean the surface with absorbent cotton dipped in acetone or absolute ethanol.
- 4 Apply the harmonized and uniform repair material to the scratched surface; the first layer should be thin, and the scratched surface should be evenly and completely covered to ensure the best adhesion of the material to the metal surface. Then apply the material to the entire repaired area and press repeatedly. Make sure the material is filled and reaches the required thickness, making it slightly higher than the outer wall surface of the cylinder.
- 5. It takes 24 hours for the material to fully reach various properties at 24 ° C. In order to save time, the temperature can be increased by a tungsten halogen lamp. For every 11 ° C increase in temperature, the curing time will be reduced by half, and the optimal curing temperature is 70 ° C.
- 6. After the material is solidified, use a fine grindstone or scraper to repair and level the material higher than the outer wall surface of the cylinder barrel, and the construction is completed.
Stress analysis of single-column hydraulic press
- The single-column hydraulic machine frame can be simplified into a flat frame according to its symmetry plane, and its simplified force diagram can be called a combination of flat curved rods and straight rods, as shown in the figure.
- The OO part of the crank is mainly affected by the axial force and bending moment, and the shear force is negligible. According to the calculation formula of the curved rod, the bending moment M and the axial force N at any section (determined by the angle ) of the OO section are M = P (l + rcos)
- Stress analysis chart of single column hydraulic press
For the straight part (see OB section in Figure 2-72)
M = P (l + r)
N = P