Power source analysis of Hydraulic multi-piston moulding machine

Hydraulic is to use liquid as working medium and use the pressure energy of liquid to transmit power.
The hydraulic system consists of five parts, namely energy device, executive device, control and adjustment device, auxiliary device, and liquid medium. Hydraulics are widely used in industrial and civil industries due to their large transmission power, easy transmission and configuration. The function of the actuators (hydraulic cylinders and hydraulic motors) of the hydraulic system is to convert the pressure energy of the liquid into mechanical energy, so as to obtain the required linear reciprocating motion or rotary motion. The function of the energy device (hydraulic pump) of the hydraulic system is to convert the mechanical energy of the prime mover into the pressure energy of the liquid.

Hydraulic advantages:
1. From the structural point of view, the output power per unit weight and the output power per unit size are overwhelming among the four types of transmission modes, and have a large moment-to-inertia ratio. Small size, light weight, small inertia, compact structure and flexible layout.
2. From the point of view of work performance, speed, torque and power can be adjusted steplessly, the action response is fast, the direction and speed can be changed quickly, the speed regulation range is wide, and the speed regulation range can reach 100:1 to 2000:1; action It has good rapidity, simple control and adjustment, convenient operation and labor saving, easy to cooperate with electrical control and connection with CPU (computer), and easy to realize automation.
3. From the point of view of use and maintenance, the self-lubrication of the components is good, and it is easy to realize overload protection and pressure keeping, which is safe and reliable; the components are easy to realize serialization, standardization and generalization.
4. All equipment using hydraulic technology is safe and reliable.
5. Economy: The plasticity and variability of hydraulic technology is very strong, which can increase the flexibility of flexible production, and it is easy to change and adjust the production process. The manufacturing cost of hydraulic components is relatively low, and the adaptability is relatively strong.
6. The combination of hydraulic and microcomputer control and other new technologies to form the integration of "mechanical-electrical-hydraulic-optical" has become the trend of world development, which is convenient for digitalization.

Hydraulic Disadvantages:
1. The hydraulic transmission inevitably leaks due to the relatively moving surface, and the oil is not absolutely incompressible. In addition to the elastic deformation of the oil pipe, the hydraulic transmission cannot obtain a strict transmission ratio, so it cannot be used for machine tools such as threaded gears. in the inline drive chain.
2. Under the conditions of high temperature and low temperature, it is difficult to use hydraulic transmission.
3. In order to prevent oil leakage and meet certain performance requirements, the manufacturing precision of hydraulic components is required to be high, which brings certain difficulties to use and maintenance.

Pneumatic is the use of compressed air as a power source to drive machinery to complete telescopic or rotating actions.
Pneumatic is the use of the compressibility of air. When the air is inhaled and compressed and stored, the air has elastic force like a spring, and then the direction of the control element is controlled to drive the rotation and expansion of the actuator. How much air is inhaled from the atmosphere will be discharged into the atmosphere, no chemical reaction will occur, and no components of polluted air will be consumed. In addition, the viscosity of gas is smaller than that of liquid, so the flow speed is fast, and it is also very environmentally friendly.

Air pressure advantages:
1. Using air as the working medium, the working medium is relatively easy to obtain, and the air after use is discharged into the atmosphere, which is convenient to handle.
2. Because the viscosity of air is very small (about 1/10,000 of the dynamic viscosity of hydraulic oil), its loss is also very small, so it is convenient for centralized air supply and long-distance transportation.
3. Good adaptability to working environment, especially in flammable, explosive, dusty, strong magnetic, radiation, vibration and other harsh working environments, it is superior to hydraulic, electronic and electrical control.
4. Low cost, automatic overload protection.

Disadvantages of air press:
1. Due to the compressibility of air, the working speed is slightly less stable. But the use of gas-liquid linkage device will get more satisfactory results.
2. Because the working pressure is low (usually 0.31.0MPa) and the structure size should not be too large, the total output force should not be greater than 10 ~ 40kN.
3. The noise is large, and a muffler should be added when exhausting at high speed.
4. The transmission speed of the air signal in the pneumatic device is slower than the speed of electrons and light within the speed of sound. Therefore, the pneumatic control system should not be used in complex circuits with too many components.

Summarize:
1. The medium used in pneumatic transmission is air, and the medium used in hydraulic transmission is hydraulic oil.
2. The hydraulic pressure is higher than the pneumatic pressure, the power is large, and the hydraulic pressure must be used for the heavy load. By improving the screw air compressor, the air storage tank, and the air inlet hole of the contact box, the sand mold manufacturing of special castings can basically be realized by increasing the pressure.
3. Hydraulic has higher precision than pneumatic. The cylinder generally has two actions of extending and retracting. The hydraulic action can be varied. After adding a proportional valve or a servo valve, the acceleration and deceleration of the action can be realized.
4. There is a pause during the action. The oil cylinder must be used if the oil cylinder is required to have a pause in the middle position. The cylinder can also stop but the position is biased, and the contact stops pressing down after the sand mold compactness is satisfied.
5. The volume change rate of the gas is too large during compression, and the volume change rate during hydraulic compression is very small.
6. Hydraulic multi-contact molding machine can obtain a large pressing force through the hydraulic cylinder. During compaction, each contact exerts corresponding pressure according to the height of the pattern below it (that is, the thickness of the compressed sand layer), so that the sand mold can obtain high and uniform compactness and hardness.
7. The jarring mechanism of the worktable adopts pneumatic as the power source, which can adapt to complex shapes. The sand mold has a high compaction rate and can cast castings with thin walls, precise dimensions and smooth surfaces.

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