Eevery plastic injection molding engineer may meet the injection molding machine hydraulic leakage. Here we would like introduce the cause and treatment of injection molding machine hydraulic oil leakage, and how to find out and fixed the oil leakage issues.
1. General overview
Injection Molding Machine Hydraulic leakage is a common fault phenomenon in injection molding machines, mainly due to the pressure difference generated when the liquid flows in the hydraulic components and pipelines, and the existence of gaps between components. In addition, harsh working conditions will also have a certain impact on the sealing of the injection molding machine. Once the hydraulic system leaks, it will cause the system pressure to fail to build up, and the injection machine hydraulic oil leakage will also cause environmental pollution, affect production and even produce unpredictable serious consequences. The following is a brief talk about the causes and countermeasures of some factors that affect the leakage of the hydraulic system of the injection molding machine.
2. the classification of leakage
There are two main types of leakage in the hydraulic system of the injection molding machine, the leakage at the fixed seal and the leakage at the moving seal. The leakage at the fixed seal mainly includes the bottom of the cylinder, the connection of each pipe joint, etc. The moving seal mainly includes the piston rod of the cylinder, Multi-way valve stem and other parts. The leakage of oil can also be divided into external leakage and internal leakage. External leakage mainly refers to the leakage of hydraulic oil from the system to the environment. Internal leakage refers to the existence of pressure difference between high and low pressure sides and the failure of seals. Make the hydraulic oil flow from the high pressure side to the low pressure side in the system.
3. Reasons Affecting the Leakage
(1). Design factors
1). Selection of seals
The reliability of injection moulding machines` hydraulic system depends to a large extent on the design of the hydraulic system seal and the selection of the seals. Due to the unreasonable selection of the sealing structure in the design, the selection of the seals does not meet the specifications, and the hydraulic oil and the hydraulic oil are not considered in the design. Compatible types of sealing materials, load conditions, ultimate pressure, working speed, changes in ambient temperature, etc. These all cause hydraulic system leakage directly or indirectly to varying degrees. In addition, due to the dust and impurities in the operating environment of plasitc injection moulding machine, appropriate dust seals should be selected in the design to prevent dust and other contaminants from entering the system and cause damage to the seal and contaminate the oil, resulting in injection molding machine hydraulic leakage.
2). Other design reasons
In the design, the geometric accuracy and roughness of the moving surface are not comprehensive enough, and the strength check of the connection part is not carried out in the design, which will cause leakage in the work of the machine.
(2) Manufacturing and assembly factors
1). Manufacturing factors
All hydraulic components and sealing components have strict dimensional tolerances, surface treatment, surface finish and geometric tolerances. If it is out of tolerance during the manufacturing process, such as: the piston radius of the cylinder, the depth or width of the sealing groove, the hole size of the sealing ring is out of tolerance or out of round due to processing problems, there are burrs or depressions, chrome plating falls off, etc. The parts will be deformed, scratched, crushed or not compacted, which will cause them to lose their sealing function. The parts themselves will have congenital leak points, which will leak after assembly or during use.
2). Assembly factor
In the assembly of hydraulic components, brutal operation should be avoided. Excessive force will cause deformation of the parts, especially using copper rods to beat the cylinder body and sealing flanges. Before assembly, the parts should be carefully inspected, and the parts should be dipped in a little hydraulic pressure during assembly. Oil, gently press in, use diesel oil when cleaning, especially rubber components such as sealing rings, dust rings, O-rings, etc. If gasoline is used, it will easily age and lose its original elasticity, thereby losing its sealing function.
(3) Oil pollution and damage to parts
1). Gas pollution
Under atmospheric pressure, about 10% of the air can be dissolved in the hydraulic oil. Under the high pressure of the hydraulic system, more air or gas will be dissolved in the oil. Air forms bubbles in the oil. If the hydraulic support changes rapidly between high and low pressure in a very short time during the working process, the bubbles will generate high temperature on the high pressure side and burst on the low pressure side. If the components of the hydraulic system When there are pits and damage on the surface, the hydraulic oil will rush to the surface of the component at a high speed to accelerate the wear of the surface and cause injection molder hydraulic system leakage.
2). Particulate pollution
Hydraulic cylinders are the main components of the hydraulic system of some injection molding machines. Since the piston rod is exposed and directly in contact with the environment during the working process, although dust rings and seals are installed on the guide sleeves, it is inevitable that dust and dirt will be brought into the air. Enter the hydraulic system, accelerate the scratch and wear of seals and piston rods, etc., causing leakage, and particle contamination is one of the fastest damage factors for hydraulic components.
3). Water pollution
Due to the influence of factors such as humidity in the working environment, water may enter the hydraulic system, and the water will react with the hydraulic oil to form acidic substances and sludge, reduce the lubricating performance of the hydraulic oil, accelerate the wear of the components, and the water will also cause the valve of the control valve. The rod sticks, making it difficult to operate the control valve, scratching the seal, and causing leakage.
4). Parts damage
The seals are made of oil-resistant rubber and other materials. Due to long-term use, aging, cracks, and damage will cause system leakage. If the part is damaged by impact during operation, it will scratch the sealing element, resulting in leakage.
4. the main prevention and control measures of leakage
The factors that cause the leakage of the hydraulic system of the injection molding machine are the result of various comprehensive influences. With the existing technology and materials, it is difficult to fundamentally eliminate the leakage of the hydraulic system of the injection molding machine. Only from the above factors affecting the leakage of the hydraulic system, take reasonable measures to minimize the leakage of the hydraulic system. In the design and processing links, the important factors affecting the leakage should be fully considered in the design and processing of the sealing groove. In addition, the selection of seals is also very important. If the influencing factors of leakage are not fully considered at the beginning, it will bring immeasurable losses to subsequent production. Choose the right method of assembly and repair, drawing on past experience. For example, try to use special tools in the assembly of the sealing ring, and apply some grease on the sealing ring. In the pollution control of hydraulic oil, it is necessary to start from the source of pollution, strengthen the control of pollution source, and take effective filtering measures and regular oil quality inspection. In order to effectively cut off the pollution of the hydraulic cylinder by external factors (water, dust, particles, etc.), some protective measures can be added. In short, the prevention and control of leakage must be comprehensively started, and comprehensive consideration can be effective.
SPECIAL PROMOTION
