Treatment of Excessive Noise in the Hydraulic System of Injection Molding Machines

1、 Noise from pumps or motors
(1) The phenomenon of suction is one of the main reasons for high pump noise. When air is mixed into the oil, it is easy to form cavitation in its high-pressure area and propagate in the form of pressure waves, causing oil oscillation and causing cavitation noise in the hydraulic system of the injection molding machine. The main reasons for this are:
① Blockage of the oil filter and inlet pipe of the hydraulic pump, or high viscosity of the oil can cause high vacuum at the inlet of the pump, causing air infiltration.
② The oil seal at the shaft end of the hydraulic pump is damaged, or the sealing of the oil inlet pipe is poor, causing air to enter
② The oil level in the fuel tank is too low, causing the hydraulic pump inlet pipe to directly empty.
When high noise occurs during the operation of the hydraulic pump, the above parts should be inspected first, and any problems found should be promptly addressed.
(2) Excessive wear and tear on the internal components of the hydraulic pump, such as the wear and tear on the pump body and valve plate, can cause serious internal leakage in the hydraulic pump. When the hydraulic pump outputs high-pressure and low flow oil, flow pulsation will occur, causing high hydraulic noise in the injection molding machine. At this point, the triangular groove can be appropriately increased to improve the impact of internal leakage on the pump output flow.
(3) The hydraulic pump port plate is also an important component that can easily cause hydraulic noise in injection molding machines. Due to surface wear or oil sludge deposition at the opening of the unloading groove during use, the port plate can shorten the unloading groove and change the unloading position, resulting in oil trapping and subsequently causing high noise. During the normal repair process, the port plate repaired by flat grinding may also have the consequence of the unloading groove becoming shorter. If it is not properly lengthened in a timely manner, it will also generate significant noise. During the assembly process, the large unloading groove of the valve plate must be installed in the high-pressure chamber of the pump, and its sharp angle direction must be opposite to the rotation direction of the cylinder body, otherwise it will also cause significant noise to the hydraulic system of the injection molding machine.
2、 Noise of overflow valve
The overflow valve is prone to high-frequency noise, mainly caused by the unstable performance of the pilot valve, which is caused by the high-frequency oscillation of the front chamber pressure of the pilot valve and the air vibration. The main reasons for this are:
(1) Air is mixed in the oil and forms cavitation in the front chamber of the pilot valve, causing high-frequency noise. At this point, timely exhaust the air and prevent external air from re-entering.
(2) During use, the needle valve is excessively worn due to frequent opening, causing the cone surface of the needle valve to not fit tightly with the valve seat, causing unstable pilot flow and pressure fluctuations, leading to noise. In this case, it should be repaired or replaced in a timely manner.
(3) The pilot valve's pressure regulating function is unstable due to the fatigue and deformation of the spring, causing large pressure fluctuations and causing noise. At this time, the spring should be replaced.
3、 Noise from hydraulic cylinders
(1) Air is mixed in the oil or the air in the hydraulic cylinder is not completely discharged, resulting in cavitation under high pressure and causing significant noise. At this point, it is necessary to exhaust the air in a timely manner.
(2) The cylinder head oil seal is too tight or the piston rod is bent, which can also cause noise during movement due to other forces. At this point, it is necessary to replace the oil seal or align the piston rod in a timely manner.
4、 Pipeline noise
Excessive dead bends or loose fixing clips in the pipeline can also cause vibration and noise. Therefore, in the pipeline layout, dead bends should be avoided as much as possible, and loose clips should be tightened in a timely manner.