The Basis For Setting The Cooling Time In Injection Molding In injection production, the cooling time of plastic injection molding parts accounts for about 80%
Major Hazards and Solutions of Excessive Temperature Rise of Injection Molding Machine
# Major hazards of excessive temperature rise of injection molding machine
1. Thermal deformation of machinery
The moving parts with different coefficients of thermal expansion in the hydraulic components are stuck due to their smaller fitting clearances. And that causes malfunctions, affects the transmission accuracy of the hydraulic system, and deteriorates the working quality of the parts.
2. Reduce oil viscosity
Excessive temperature rise of the injection molding machine will result in the decrease of the oil viscosity. What’s more, it will increase the leakage, and reduce the volumetric efficiency of the pump and the efficiency of the entire system significantly. As the oil viscosity decreases, the oil film of moving parts like slide valves becomes thinner and cut. Besides, the frictional resistance increases, leading to increased wear.
3. Deform the rubber seal
Excessive temperature rise of the injection molding machine will deform the rubber seals. Then, accelerates aging failure, reduces the sealing performance and service life, and causes leakage.
4. Accelerate the oxidation and deterioration of oil
Excessive temperature rise of the injection molding machine will accelerate the oxidative deterioration of the oil. Then, precipitates asphalt substances, and reduces the service life of the hydraulic oil. The precipitates block the damping orifice and the slit valve port, causing the pressure valve to become stuck and unable to move. While the metal pipe is stretched and bent, or even ruptured.
5. Cause the poor work quality of components
Excessive temperature rise of the injection molding machine will cause the deterioration of quality of the parts. And the dissolved air in the oil will escape, resulting in air pockets, which will reduce the working performance of the hydraulic system. The ideal working temperature of the hydraulic system should be between 45 degrees and 50 degrees. Because the hydraulic system is designed according to a selected pressure oil viscosity. But the viscosity will change with the oil temperature, which will affect the work of components in the system like oil cylinders, hydraulic valves, etc.. And it reduces control accuracy and response sensitivity, especially for precision injection machines.
At the same time, if the temperature is too high, it will accelerate the aging of the seal and cause it to harden and crack. If the temperature is too low, the consume of processing energy will be large and the operating speed will be reduced. Therefore, it is necessary to pay close attention to the working temperature of hydraulic oil. There are many reasons for high oil temperature, but most of them are due to oil circuit failure or cooling system failure.
# Solutions of excessive temperature of injection molding machine
(1) According to different load requirements, frequently check and adjust the pressure of the overflow valve to make it just right.
(2) Choose hydraulic oil reasonably, especially the viscosity of oil. If conditions permit, try to use a lower viscosity to reduce viscosity friction loss.
(3) Improve the lubrication conditions of moving parts to reduce friction loss. Because it is conducive to reducing work load and heating.
(4) Improve the assembly quality and accuracy of hydraulic components and hydraulic systems. Strictly control the clearance of matching parts and improve lubrication conditions. Use the sealing materials with a small friction coefficient and improved sealing structure. And reduce the starting force of the hydraulic cylinder as much as possible. Finally, reduce the heat generated by the mechanical friction loss.