Environmental improvement has become the main target of this year's national cleanup. How to address the noise pollution from hydraulic machines? Here are several factors of precision shared by the Shandong Guowei CNC Machine Tool editors.

The pressure relief valve is unstable, which may be caused by improper fit between the slide valve of the molding small hydraulic press and the valve bore, or by debris causing the cone valve to stick at the contact point with the valve seat, clogged damping holes, bent or failed springs, etc., leading to the valve core getting stuck or not moving smoothly within the valve bore, resulting in fluctuations in system pressure and noise. In response, attention should be given to cleaning and clearing the damping holes; inspect the pressure relief valve for any damage or excessive wear beyond specifications, and repair or replace it promptly if necessary.
 
Poor quality hydraulic pumps or hydraulic motors are often the main sources of noise in hydraulic transmission. The manufacturing quality of the hydraulic pump in the game coin molding small hydraulic press is not good, the precision does not meet the technical requirements, pressure and flow fluctuations are significant, the phenomenon of trapped oil has not been effectively eliminated, the sealing is poor, and poor bearing quality are all major causes of noise. During operation, due to the wear of hydraulic pump components, excessive gaps, insufficient flow, and easy pressure fluctuations, noise can also be induced. To address these issues, first, choose high-quality hydraulic pumps or hydraulic motors, and second, strengthen maintenance and upkeep, such as: if the gear tooth shape precision is low, the gears should be lapped to meet the contact surface requirements; if the vane pump has the phenomenon of trapped oil, the triangular slots of the oil distribution plate should be corrected to eliminate the trapped oil; if the hydraulic pump has excessive axial clearance and insufficient oil delivery, repairs should be made to ensure the axial clearance is within the permissible range; if the wrong hydraulic pump is selected, it should be replaced.
 
3. Air intrusion into the hydraulic system is a major cause of noise. When the hydraulic system of a coin molding miniature hydraulic press intrudes air, the air occupies a larger volume in the low-pressure area. As it flows into the high-pressure area, it is compressed, causing its volume to suddenly decrease. When it returns to the low-pressure area, its volume suddenly increases. This sudden change in bubble volume results in an "explosion" phenomenon, thus generating noise, which is commonly referred to as "cavitation." To address this issue, exhaust devices are often installed on hydraulic cylinders for air release. Additionally, after starting the machine, executing a rapid full-stroke reciprocation several times to exhaust air is also a commonly used method.
 
4. Improper adjustment of the directional valve led to the valve core moving too quickly, resulting in directional shock and consequently, noise and vibration. In this situation, if the directional valve of the mold hydraulic press is a hydraulic directional valve, the throttle element in the control oil circuit should be adjusted to ensure smooth and shock-free directional changes. During operation, the valve core of the hydraulic valve is supported by a spring. When its frequency is close to the pulsation frequency of the hydraulic pump's oil delivery rate or the frequency of other vibration sources, vibration and noise may occur. At this point, changing the natural frequency of the pipeline system, adjusting the position of the control valve, or appropriately adding a surge tank can prevent vibration and reduce noise.