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How to Choose Hydraulic Oil For Bending Machine

hydraulic oil

There will be wear and tear in normal machine operation, and all kinds of lubricants will show their talents at this time. Taking the bending machine as an example, choosing the right hydraulic oil for the bending machine can not only ensure the normal operation of the bending machine but also greatly extend its service life. If the quality of the additives is poor, it will affect the efficiency and use of the bending machine. Service life. Therefore, Mayo of the HARSLE bending machine department reminds everyone that you must be cautious when choosing hydraulic oil for the bending machine. What are the specific requirements?

First of all, we have a brief understanding of the structure and operating principle of the bending machine. The bending machine is divided into the manual bending machine, hydraulic bending machine, and CNC bending machine.

CNC Bending Machine
CNC Bending Machine

The bending machine includes a bracket, a workbench, and a clamping plate. The workbench is placed on the bracket. The workbench is composed of a base and a pressing plate. The base is connected to the clamping plate by a hinge. The base is composed of a housing, a coil, and a cover. In the recess of the seat shell, the top of the recess is covered with a cover plate. When in use, the wire is energized to the coil, and the gravitational force is generated on the pressing plate after being energized, so as to realize the clamping of the thin plate between the pressing plate and the base. Due to the electromagnetic clamping, the pressing plate can be made into a variety of workpiece requirements, and the workpiece with sidewalls can be processed. The pressure generated by the hydraulic system is transmitted through the mold, and finally, the desired material shape is obtained. Therefore, to lubricate the bending machine appropriately, improve the working efficiency of the equipment, reduce the wear of the machine tool, and extend the use of the equipment, 46# and 32# anti-wear hydraulic fluid must be used.

Hydraulic Oil
Hydraulic Oil

Performance characteristics of special hydraulic fluid for bending machine

  1. Various viscosity grades can meet the process requirements of different equipment.
  2. Excellent oil-water separation performance and anti-foaming performance to ensure stable equipment pressure.
  3. Very strong anti-rust performance, effectively protecting the oil pump and other hydraulic components from corrosion.
Hydraulic Oil

The importance of hydraulic oil selection for bending machine

Bending machine hydraulic oil is one of the important tasks for the hydraulic system to achieve power transmission. It also plays a role in lubrication, rust prevention, buffering, and cooling of the hydraulic system. With the continuous development of hydraulic technology, the requirements for the use of hydraulic fluid become more and more important.

Bending machine hydraulic oil is generally recommended to use L-HM32/46/68 low-condensing high-pressure anti-wear hydraulic oil, and different selections will be made as to the temperature changes. High-grade hydraulic oil is used in areas with relatively high temperatures, and the temperature is low. Select low-grade hydraulic oil.

L-HM32 Hydraulic Oil
L-HM32 Hydraulic Oil
  1. For indoor fixed equipment, use HL oil for hydraulic system pressure <7.0MPa and temperature below 50℃; choose HL or HM oil for system pressure 7.0-14.0Mpa and temperature below 50℃, choose HM for temperature 50-80℃; system pressure> Select HM or high pressure anti-wear hydraulic oil for 14.0MPa.
  2. Choose HV (above -30°C) or HS (above -40°C) low-temperature hydraulic fluid for open-air cold or severe cold areas. (Such as field engineering and ocean-going ships, CNC machine tools, cable well pumps, cranes, excavators, large cranes, etc., have good low-temperature startability).
  3. For equipment near high-temperature heat sources, fire-resistant hydraulic fluid should be used. (Suitable for high-temperature fire-resistant hydraulic systems in metallurgy, chemical and other industries, such as converters, electric furnaces and other high-temperature hydraulic systems, and also suitable for continuous casting machines, hot rolling mills, glass forming machines, etc.)
  4. For equipment with higher requirements in the food and pharmaceutical industries, choose food-grade hydraulic fluid.
  5. Choose first-class hydraulic oil for hydraulic equipment that requires long service life and harsh environmental conditions; choose first-class hydraulic oil for hydraulic equipment that requires short service life and mild working conditions.
  6. Hydraulic and rail lubrication share the same system, and hydraulic rail oil should be used.
  7. Open-loop CNC machine tools using electro-hydraulic pulse motors use CNC machine tool hydraulic oil, use electro-hydraulic servo mechanism closed-loop system, and use high-clean hydraulic oil.
  8. For hydraulic systems containing bronze or silver components, choose ash-free anti-wear hydraulic oil HMN (with zinc-containing additives below 0.03%).
L-HM46 Hydraulic Oil
L-HM46 Hydraulic Oil

Characteristics of Hydraulic Oil for Bending Machine

  • The hydraulic oil of the bending machine should have good anti-wear and lubricity. The purpose is to reduce mechanical friction and ensure the service life of the hydraulic system of the shearing and bending machine.
  • The hydraulic oil of the press brake should maintain the proper viscosity. Viscosity is the size of the frictional resistance between molecules when the oil flows. If the viscosity is too high, it will increase the conveying resistance in the pipeline, increase the energy loss during the working process, increase the no-load loss of the main engine, rapid temperature rise and high working temperature, and “cavitation” may appear at the oil suction end of the main pump. If the viscosity of the hydraulic fluid of the plate machine is too small, the good lubrication condition of the plate shearing machine cannot be guaranteed, which will aggravate the wear of the shearing machine hydraulic system parts and increase the system leakage, which will cause the volumetric efficiency of the oil pump to decrease. The specific use depends on the working pressure of the shear hydraulic system, the working temperature and the movement speed of the actuator. High viscosity should be selected for high pressure and high temperature, and low viscosity for high speed movement.
  • The hydraulic oil of the bending machine has good viscosity and temperature. Viscosity temperature refers to the degree to which the oil viscosity rises and falls with temperature, usually expressed by the viscosity index. The greater the viscosity index, the smaller the oil viscosity decreases with the increase in temperature during the work of the shear hydraulic system, so that the internal leakage of the hydraulic system will not be too large. ) The working conditions of the hydraulic system of the shearing machine are generally harsh. The temperature of the hydraulic oil changes with the load and the ambient temperature during the operation, and the viscosity index is generally not less than 90.
  • The hydraulic oil of the bending machine has good anti-oxidation stability. Antioxidant stability refers to the ability of the oil to react chemically with oxygenates when the temperature of the oil rises. Practice has shown that for every 10°C increase in oil temperature, the chemical reaction speed is approximately doubled. The hydraulic fluid of the shearing machine with good oxidation resistance and stability is not easy to be oxidized and deteriorated after long-term use, which can ensure the normal circulation of the hydraulic oil.
  • The hydraulic oil of the bending machine has good shear resistance and stability. In order to improve the viscosity index of the oil, high molecular polymers such as polymethacrylic ester and polyisobutylene are often added to the oil. The molecular chain of these substances is long, and the oil is severely sheared when it flows through the slits of the hydraulic components. The effect will often cause molecular chain scission and oil viscosity-temperature characteristics to decrease. The frequent reversing of the reversing valve and the throttling of the throttling element during the shearing machine operation require the hydraulic fluid to have strong shear resistance.
  • Hydraulic oil for press brakes with good demulsibility and foam resistance. Demulsibility refers to the ability of the oil to be mixed with water and become an emulsion after agitation, and the water can be separated from it. Anti-foaming property refers to the ability of the oil mixed with air and agitated to form an emulsion, and the bubbles are separated from the oil. After mixing with water or air, the volume modulus of the oil will be reduced, the compressibility will increase, the hydraulic components of the shearing machine will move slowly, and it is prone to shock and vibration.
L-HM68 Hydraulic Oil
L-HM68 Hydraulic Oil

The hydraulic oil is commonly used as the working medium in the hydraulic transmission of the CNC bending machine. When the liquid flows under the action of external force, the cohesion between the molecules will hinder the relative movement between the molecules and present internal frictional resistance. This characteristic is called the viscosity of the liquid. Viscosity is an important physical property of liquids. The size of viscosity is expressed by viscosity. There are three commonly used viscosity, namely dynamic viscosity, kinematic viscosity, and relative viscosity. The dynamic viscosity refers to the internal friction force per unit area of the liquid layer in which the liquid flows; the kinematic viscosity is the ratio of the dynamic viscosity to the density of the liquid; the relative viscosity is the viscosity measured by a specific viscometer. Engel’s viscosity has been used The viscosity is measured by an Engler viscometer.

The performance index of the hydraulic oil of the bending machine is the viscosity, and the kinematic viscosity (unit is mm²/s) is commonly used to determine the grade of the hydraulic fluid. For example, hydraulic oil N32 means that the average kinematic viscosity of this hydraulic fluid at 40°C is 32mm²/s. The most significant factor that affects the viscosity of a hydraulic fluid is temperature, and the viscosity decreases with increasing temperature. The change of oil viscosity directly affects the performance and leakage of the hydraulic system.

There are many types of hydraulic oils for bending machines. As the working medium in the hydraulic transmission of CNC bending machines, the following aspects should be considered in the reasonable selection of hydraulic oil: In normal temperature, the viscosity changes with temperature as small as possible; lubrication performance Good; good chemical stability, not easy to oxidize and deteriorate; oil contains fewer impurities. The choice of hydraulic fluid for a CNC bending machine is mainly the choice of viscosity, which depends on the structure of the hydraulic pump, working temperature, pressure, and working characteristics. To use the hydraulic fluid of the CNC bending machine correctly, the appropriate hydraulic fluid must be selected according to the equipment manual. When using, prevent the intrusion of water, emulsion, dust, and other impurities.

The normal working oil temperature of the bending machine is 15-65°, and the kinematic viscosity is 27-43mm²/s. When the oil works at a normal working temperature, the kinematic viscosity should not be lower than 27mm²/s at 65°C and not high at 15°C. At 43mm²/s, the self-priming vacuum caused by the high kinematic viscosity of the oil during cold start should not be greater than 0.016Mpa. The cleanliness of the oil should be controlled within NAS10 (or 19/16). The contamination of the hydraulic fluid in the hydraulic system of the press brake is the main reason for the failure of the hydraulic system and the reduction of working life.

When the CNC bending machine is working, the temperature of the hydraulic oil should not be too high and the fluid should be replaced regularly. The service life of domestic hydraulic oil can generally reach more than one year. After one year of use, it can be considered whether to replace the oil according to the actual situation. When replacing new oil, the oil tank and system pipes should be cleaned as necessary, and the new oil should be filtered before being injected into the oil tank. The density of hydraulic fluid decreases with increasing temperature and increases with increasing pressure. However, when the working oil pressure is below the medium pressure (2.5X106Pa), the oil can generally be regarded as incompressible.

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2 thoughts on “How to Choose Hydraulic Oil For Bending Machine

  1. Prakash says:

    Thanks for your sharing, It’s useful for me to choose a bending machine

    1. Mayo says:

      my pleasure, if you need the press brake, no hesitation to tell me, thanks!

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