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Leakage of Injection Molding Machine

Leakage is a common fault phenomenon of the injection molding machine, mainly because of the liquid in the hydraulic components and pipeline activities when the pressure difference and the gap between the components are caused by leakage. 

Other harsh working conditions will also have a particular impact on the sealing of the injection molding machine. Once the hydraulic system leakage causes the system pressure can not be established, hydraulic oil leakage will also constitute environmental pollution, affecting the production and even immeasurable serious consequences.

Let’s briefly talk about the countermeasures for some of the reasons that affect the leakage of the hydraulic system of the injection molding machine.


Classification of leakage 


There are two main types of leakage in the hydraulic system of the injection molding machine, leakage at the fixed seal and leakage at the motion seal.

A. The fixed seal leakage parts mainly include the bottom of the cylinder, the interface of the pipe joints, etc.

B. The primary parts of the motion seal include the piston rod part of the cylinder and the valve stem of the multiway valve. 

The fluid leakage can also be divided into external and internal leakage. External leakage refers to the leakage of hydraulic fluid from the system to the environment, and internal leakage refers to the existence of pressure difference between the high and low-pressure sides and the failure of the seal so that the hydraulic fluid flows from the high-pressure side to the low-pressure side inside the system.


Reasons affecting leakage


1. Planning factors.

The selection of seals and the reliability of the hydraulic system largely depend on the planning of the hydraulic system seal and the selection of seals. Because the planning of the seal structure is not reasonable, the selection of seals is not in line with the specifications in the planning of the hydraulic oil and the seal material compatibility type, load conditions, ultimate pressure, operating speed size, changes in ambient temperature, etc.

These are in varying degrees directly or indirectly constitute the hydraulic system leakage. Because the injection molding machine environment has dust and impurities, in the planning, choose the appropriate dustproof seal to avoid dust and other dirt into the system to damage the seal, contamination of the fluid, and then the onset of leakage. 


Other planning reasons

Planning to consider the movement of the appearance of the little accuracy and roughness is not comprehensive enough. In the planning of the articulation parts of the strength check, etc., these will cause leakage in the operation of the machinery.


2. Production and installation elements.

Production elements: all hydraulic components and sealing components have strict scale tolerances, appearance treatment, appearance finish, and shape tolerance requirements. 

Suppose it is out of tolerance in the production process. For example, the piston radius of a cylinder. The depth or width of the seal groove. The hole size of the sealing ring is out of tolerance or out of round due to processing problems. It has burrs or depressions, chrome plating, etc.

The seal will be deformed, scratched, crushed or unpressed, and other phenomena to make it lose its sealing function. Will make the parts themselves have innate leakage points after the installation or use in the leakage process. 

Installation elements: hydraulic components should be installed in the rough operation if excessive force will make parts deformation, especially with copper rods and other strike’s cylinder body, sealing flange, etc.

Installation should be carefully checked before the parts. The installation should be dipped in a little hydraulic oil, gently pressed into the parts, cleaning the application of diesel oil, especially the seals, dust rings, O-rings, and other rubber components. If you use gasoline, it is accessible to age, loses the original elasticity, and then loses the sealing function.


3. Oil pollution and damage to parts. 

Gas pollution 

The hydraulic oil can dissolve about 10% of the air at atmospheric pressure. In the hydraulic system, the fluid will dissolve more air or gas under high pressure. 

Air in the fluid constitutes a bubble. If the hydraulic support is in the process of operation in a brief period, the pressure in the high and low pressure between the rapid change will make the air bubble in the high-pressure side of the high temperature in the low-pressure side of the burst.

Suppose the hydraulic system components have dents and damage on the exterior. In that case, the hydraulic oil will rush to the components at high speed to accelerate the wear of the exterior, causing leakage. 



Particle contamination 

Hydraulic cylinder as some injection molding machine hydraulic system of the primary executive element, because the operation process of the piston rod exposed directly and environmental contact.

Although the guide sleeve is equipped with a dust ring and seals, the dust and dirt into the hydraulic system speed up the seals and piston rod and other scratches and wear and then cause leakage. Particle contamination is one of the fastest elements of hydraulic components damage. 



Water contamination 

Because the operating environment is wet and other factors may make water into the hydraulic system.

Water will react with the hydraulic fluid, constitute acid and sludge, reduce the lubricating performance of the hydraulic fluid, and accelerate the wear of the components. Water can also constitute the control valve stem bonding so that the control valve operating difficulties scratch the seals, constituting leakage.



4. Parts damage. 

Seals are made of oil-resistant rubber and other materials because the long-term use of aging, cracking, damage, etc., will cause the system to leak. If the parts are knocked and damaged during the operation, they will scratch the sealing components and constitute leakage. 



Leakage primary prevention and control measures 


The elements that constitute the leakage of the hydraulic system of the injection molding machine are the result of the generalized influence of many aspects, with the existing technology and information, to fundamentally eliminate the leakage of the injection molding machine’s hydraulic system very difficult to do.

Only from the above factors affecting the hydraulic system leakage, adopt reasonable measures to reduce the leakage of the hydraulic system as much as possible. 

In the planning and processing links, consider the critical elements affecting the leakage of the seal groove planning and processing. The selection of sealing parts is also significant. If you do not consider the influence of leakage comprehensively initially, it will bring incalculable losses in future production. 

Select the correct installation and repair method, and learn from experience, for example, in installing the seal as far as possible to use particular tools and in the seal on some grease. 

In the hydraulic oil pollution control, we should start from the source of pollution, strengthen the control of pollution sources, and adopt effective filtration measures and regular fluid quality inspection.

To effectively cut off the external elements (water, dust, particles, etc.) on the hydraulic cylinder pollution, you can add protective measures. In short, preventing and controlling leakage should be a comprehensive approach, inductive consideration to do practically.

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