Abnormal noise during injection molding operation is a common equipment fault signal on the production floor. Noise not only affects the working environment but also often indicates potential issues in the hydraulic system or mechanical transmission components. If not addressed promptly, it can lead to accelerated equipment wear or even unplanned downtime. This article systematically reviews the core causes of noise and corresponding elimination measures from the perspective of the hydraulic vibration pump.
1. Analysis of Primary Noise Causes
The root cause of abnormal noise in injection molding machines is mostly concentrated in the hydraulic vibration pump and its associated pipeline system. The causes can be summarized into the following seven categories:
First, the installation concentricity of the oil pump motor exceeds the allowable tolerance, generating periodic vibration noise during operation.
Second, the coupling is loose, resulting in uneven power transmission and causing mechanical impact sounds.
Third, internal components of the oil pump are worn or damaged, leading to abnormal hydraulic pulsation.
Fourth, the oil tank level is too low, causing the filter screen or joint connections to be exposed above the oil surface. Air is drawn into the oil, forming cavitation noise.
Fifth, the motor drive shaft seal has failed, allowing external air to seep into the hydraulic system along the shaft end.
Sixth, the filter screen is clogged with oil contaminants, restricting oil flow and producing high-frequency whistling sounds.
Seventh, the return oil pipeline is loose or the pipe opening is above the oil surface, allowing air to mix into the oil and causing unstable hydraulic system noise.
2. Systematic Elimination Procedures
To address the above causes, it is recommended to troubleshoot and resolve each item step by step:
First, recalibrate the installation concentricity between the motor and the oil pump, ensuring the deviation is controlled within 0.1 millimeter.
Second, inspect and correct the coupling fit condition to eliminate any clearance or looseness.
Third, disassemble and inspect the oil pump to confirm the condition of internal components, and replace it if necessary.
Fourth, replenish hydraulic oil to the specified level, ensuring that the filter screen and all joint positions are submerged at least 400 millimeters below the oil surface.
Fifth, replace the motor drive shaft seal ring to block the external air intrusion path.
Sixth, remove the filter screen for thorough cleaning, and replace the filter element if necessary, to ensure oil cleanliness.
Seventh, tighten all connection points of the return oil pipeline and extend the return pipe end below the oil surface to prevent air back-suction.
3. Preventive Maintenance Recommendations
Noise troubleshooting should not be limited to post-fault response. It is recommended to incorporate hydraulic oil level checks, filter screen cleaning, and concentricity verification into the daily inspection checklist. A systematic maintenance cycle every 2,000 operating hours can effectively reduce the frequency of noise-related faults.
Frequently Asked Questions
Q: When the injection molding machine noise suddenly increases, which component should be checked first?
A: The hydraulic oil level and filter screen status should be checked first. Insufficient oil level or a clogged filter screen is the most common cause of noise on site. The troubleshooting cost is low and results are quick.
Q: What is the difference between the noise caused by a loose coupling and that caused by an internal oil pump failure?
A: A loose coupling typically produces irregular mechanical impact sounds, with frequency varying with rotation speed. An internal oil pump failure usually produces a continuous hydraulic pulsation sound accompanied by pressure fluctuations. A stethoscope can assist in identifying the noise source.
Q: Why does a return oil pipe above the oil surface cause noise? Can the return oil simply not be connected?
A: When the return pipe opening is exposed above the oil surface, air is drawn into the oil, creating a cavitation effect that causes obvious hydraulic noise. The return pipe end must be extended below the oil surface. This is a fundamental requirement of hydraulic system design and cannot be omitted.
