The relationship between hydraulic oil temperature rise and viscosity index in injection molding machines?
October 25, 2023
In the injection molding industry, the problem of oil temperature rise is very troublesome for us. The increase in oil temperature not only affects the operation of the machine, but also seriously affects the service life of the machine. So how do we prevent the temperature of injection molding oil from rising? We need to analyze from aspects such as viscosity index, whether there is a good hydraulic heat dissipation system, viscosity, and other comprehensive performance.
1. Viscosity index (VI) This indicator directly reflects the nature of oil viscosity changing with temperature, i.e. the viscosity temperature characteristics of oil. The high viscosity index of oil indicates that the viscosity of this type of oil changes less with temperature; On the contrary, it is larger. The viscosity index of anti wear hydraulic oils from well-known foreign manufacturers such as Mobil and Shell is VI ≥ 110, while the viscosity index of domestic advanced anti wear hydraulic oils is around 95. The viscosity index of high viscosity index hydraulic oil (HV) and multi-stage engine oil produced abroad is VI>140; The domestic lamp oil cannot reach this level. This point requires special attention for users of injection molding machines using domestically produced hydraulic oil. A decrease in viscosity index will narrow the range of ambient temperatures that the oil can adapt to. If it is not necessary to use it, relevant information should be consulted with the oil manufacturer. The range of use of the oil must be adjusted appropriately, and if necessary, the relevant setting values of the equipment should also be changed (such as extreme temperature). 2. Good hydraulic oil heat dissipation system For the improvement of the hydraulic oil heat dissipation system (more specifically, the hydraulic oil temperature control system) of injection molding machines, although the specific methods adopted by various manufacturers are different, the basic idea is the same. Whether the hydraulic oil radiator is blocked by dirt, which leads to a decrease in heat dissipation efficiency, it is necessary to clean the radiator promptly. 3. Hydraulic oil viscosity The principle for determining the viscosity of hydraulic oil (ISO VG, viscosity unit: mm2/s) is to keep the viscosity of hydraulic oil (used for components such as pumps and motors) in the optimal range (16-36x10-6mm2/s) while considering the working temperature and efficiency of the hydraulic circuit; The viscosity of short time cold start corresponding to the lowest ambient temperature is ≤ 1000X10-6mm2/s; And the viscosity corresponding to the maximum allowable leakage oil temperature of 90 ℃ in a short period of time is ≥ 10X10-6mm2/s. 4. Other comprehensive performance Due to the high working pressure (≥ 14MPa) of the hydraulic system of modern injection molding machines, the maximum allowable working oil temperature of the hydraulic oil is also high (around 50 ℃). Therefore, in order to ensure the normal operation of the hydraulic system during the normal oil change cycle, it is required to have good quality in terms of lubrication, oxidation stability, wear resistance, rust prevention and corrosion resistance, emulsification resistance, foam resistance, shear stability, and extreme pressure load resistance of the selected oil for the system. Especially when choosing alternative oils, it is important to pay attention to meeting the requirements of the standards for the substituted oil. Otherwise, serious problems such as system overheating and component damage may occur during the use of the equipment due to unsatisfactory oil quality.
