Several reasons for the damage to the injection molding machine oil pump:
air mixed in
Air mixing refers to a phenomenon in which air bubbles are dispersed in the hydraulic oil of the system. This bursting effect occurs when compressed air bubbles in the oil system face the pump outlet pressure. And this cracking effect will cause the pressure side plate, wear-resistant side plate, and other metal surfaces close to each other's cracking points inside the pump to peel off and cause extremely high temperatures there.
The phenomenon of air mixing, the pump will produce a loud crackling noise. The pitch of this noise increases with pressure, and excessive air entrainment can cause hydraulic oil to emulsify (because the air contains a lot of water vapor). Moreover, due to the air compression phenomenon in hydraulic oil, problems such as the unsmooth operation of various hydraulic components are caused.
Possible ways that air can get mixed into the pump are:
Bad shaft seal.
Leaking at the junction of the oil tank to the pump inlet section.
The oil level is too low or the oil return pipe that returns to the oil tank is installed on the oil surface, causing the hydraulic oil in the oil tank to generate air bubbles, which will be sucked again by the pump before the air bubbles are eliminated.
Cavitation refers to a local gasification phenomenon that occurs in the fluid of hydraulic oil when the pressure is reduced below the saturated vapor pressure. Simply put, when the hydraulic oil is not completely filled with the space it should occupy, there is a vacuum in the oil circuit, which will cause this cavitation phenomenon.
The noise caused by cavitation is roughly similar to the noise caused by air mixing. The factors that cause the phenomenon of cavitation are:
There is a problem with the matching of the pump and the electric motor, causing the pump speed to be too high.
The pump suction line is too long, or the suction port is restricted.
Hydraulic oil viscosity is too high.
Is the exhaust port on the fuel tank plugged in?
Check the pump suction filter.
The presence of any foreign matter in the circuit of the hydraulic system will have an adverse effect on the efficiency of the hydraulic components and their circuits. Contaminating foreign objects may be solids, liquids, or gases. Most of the foreign matter contamination will cause frictional movement caused by the tight gap between the workpiece and the workpiece, which will lead to accelerated wear and cracking of the workpiece.
The pollution sources in the oil circuit can be roughly divided into:
Casting oil cylinder, oil block, inside of oil tank, pipeline joints, etc.
The oil seal or O-ring is brittle and fractured.
Hydraulic oil deteriorates under high temperatures for a long time, resulting in oil pollution.
The pump causes the material to be stripped from the metal surface due to air incorporation or cavitation.
Overheating is a thermal phenomenon that causes fluid viscosity to change due to exceeding the specified upper limit temperature. Overheating will cause accelerated oxidation of hydraulic oil and deterioration of hydraulic oil viscosity, and cause a chain reaction. Therefore, the real root cause of overheating needs to be eliminated and the problem can be corrected effectively.
Causes of overheating are:
Overload operation, overpressure use.
Caused by air mixing and cavitation.
caused by oil pollution.
Overpressure refers to the operating pressure greater than the design pressure of the pump. Overpressure will subject the internal components of the pump to extreme forces and cause premature failure of the internal components.