Leakage causetreatment of hydraulic system of injection molding machine
2018-06-12 07:12:40
1. General overview
Leakage is a common failure phenomenon in injection molding machine, which is mainly due to the leakage of pressure and the existence of gaps in the flow of liquid in hydraulic components and pipelines. In addition, bad working conditions will also affect the sealing of injection molding machine. Once the leakage of the hydraulic system, the pressure of the system will not be established, and the leakage of the hydraulic oil will cause environmental pollution, which will affect the production and even produce serious consequences that can not be estimated. The following are some factors that affect the leakage of the hydraulic system of the injection molding machine to briefly talk about the causes and Countermeasures of its leakage. Two, the classification of leaks
There are two kinds of leakage in the hydraulic system of the injection molding machine, the leakage of the fixed seal and the leakage of the moving seal. The leakage parts of the fixed seal mainly include the bottom of the cylinder and the connection of the joints of the pipes. The main parts of the movement seal include the parts of the piston rod of the cylinder and the valve stem of the multiple valve. The leakage of oil can also be divided into external leakage and internal leakage. Leakage mainly refers to the leakage of hydraulic oil from the system to the environment. Internal leakage refers to the existence of pressure difference in the high and low pressure side and the failure of the seal, so that the hydraulic oil flows from the high pressure side to the low pressure side.
Three. The cause of the leakage
(I) design factors
(1) selection of seals
The reliability of the hydraulic system depends to a great extent on the design of the seal of the hydraulic system and the selection of the seals. Because the selection of the sealing structure is not reasonable in the design, the selection of the seal is not standard. In the design, the compatibility type, load, limit pressure and working speed of the hydraulic oil and the sealing material are not taken into account. The change of the size, the temperature of the environment, etc. All these directly or indirectly cause the leakage of hydraulic system. In addition, due to the use of dust and impurities in the injection molding machine environment, the proper dust proof seal should be selected in the design to avoid the dust and other dirt entering the system to destroy the seal and contaminate the oil, thus producing the leakage.
(2) other design reasons
In the design, the geometric precision and roughness of the motion surface are not comprehensive enough, and the strength checking of the connection parts is not carried out in the design. These will cause the leakage in the mechanical work.
(two) manufacturing and assembly factors
(1) manufacturing factors
All hydraulic components and seals have strict dimensional tolerances, surface treatments, surface finish and geometric tolerances. If there is a difference in the manufacturing process, such as the piston radius of the cylinder, the depth or width of the sealing groove, the oversize of the hole size of the sealing ring, or the loss of the circle due to the processing problem, the burr itself, the depressions, the chromium plating and so on, the seal will be deformed, scratched, crushed or untrue, so that the seal will lose its sealing work. Yes. It will cause the part itself to have a congenital leakage point and leak after assembly or use.
(2) assembly factors
In the assembly of the hydraulic components, the barbaric operation should be eliminated. If the parts are overexerted, the parts will be deformed, especially the cylinder and sealing flanges, such as copper rods, etc.; the parts should be carefully checked before assembly, and the parts should be dipped in a little hydraulic oil, gently pressed into the assembly, and the use of diesel oil, especially the seal ring and dust ring when cleaning. Rubber elements such as O ring and so on. If gasoline is used, it will be easy to age and lose its original elasticity, thereby losing its sealing function.
(three) oil pollution and damage of parts
(1) gas pollution
At atmospheric pressure, the hydraulic oil can dissolve about 10% of the air. Under the high pressure of the hydraulic system, it will dissolve more air or gas in the oil. Air forms bubbles in the oil. If the hydraulic support is in a very short period of time in the working process, the rapid transformation of pressure between high and low pressure causes the bubble to produce high temperature at the high pressure side and burst at the low pressure side. If the surface of the hydraulic system has a concave point and damage, the liquid pressure oil will speed to the surface of the component. The wear of the surface caused the leakage.
(2) particle pollution
The hydraulic cylinder is the main component of the hydraulic system of some injection molding machines. Because the piston rod exposed in the working process is exposed directly to the environment, the dust and dirt are brought into the hydraulic system, and the scratches and wear of the seals and the piston rods are accelerated. And leakage, particle pollution is one of the most damaging factors of hydraulic components.
(3) water pollution
Because of the influence of humidity and other factors, the water may enter the hydraulic system, the water will react with the hydraulic oil, form acid and oil sludge, reduce the lubrication performance of the hydraulic oil, accelerate the wear of the components, and water also cause the valve stem of the control valve to bond, so that the control valve is difficult to manipulate the seal and causes the leakage.
(4) part damage
The seal is made of oil resistant rubber and other materials. Aging, cracking and damage will result in system leakage due to prolonged use. If the parts are damaged by collision during the working process, they will scratch the sealing elements and cause leakage.
Four, the main prevention and control measures of leakage
The leakage of the hydraulic system of the injection molding machine is the result of many comprehensive effects. It is difficult to eliminate the leakage of the hydraulic system of the injection molding machine with the existing technology and materials. Only from the above factors affecting the leakage of hydraulic system, take reasonable measures to minimize leakage of hydraulic system. In the design and processing links, we should give full consideration to the important factors affecting the leakage, the design and processing of the sealing groove. In addition, the selection of seals is also very important. If the factors of leakage are not fully considered at the beginning, it will bring no future production.
