Injection molding is a very important process. As soon as the material enters the mold, the temperature of the melt drops rapidly and the density and viscosity of the melt increase continuously. The ability to compensate for the melt depends on the amount of holding pressure and the entire filling time at which the melt continues to transfer into the mold. This process continues until the gate is solidified and closed. Therefore, it can be considered that the holding pressure and the dwell time have a great relationship with the shrinkage at this stage. If the holding pressure is large and the dwell time is long, the shrinkage rate of the product is relatively low.
During the injection molding process, it is inevitable that the temperature will be extremely high, and there will be many bad effects when the temperature is high:
1. Thermal deformation of the machine: The moving parts with different thermal expansion coefficients in the hydraulic components are stuck due to their small training, which causes malfunction and affects the transmission precision of the hydraulic system, resulting in poor working quality of the components.
2. Reduce the viscosity of the oil: If the temperature rise of the injection molding machine is too high, the viscosity of the oil will decrease, the leakage will increase, and the volumetric efficiency of the pump and the efficiency of the entire system will be significantly reduced. As the viscosity of the oil is lowered, the oil film of the moving parts such as the spool is thinned and cut, and the frictional resistance is increased, resulting in an increase in wear.
3. Deformation of the rubber seal: If the temperature rise of the injection molding machine is too high, the rubber seal will be deformed, the aging failure will be accelerated, the sealing performance and service life will be reduced, and leakage will occur.
4. Accelerate oil oxidation and deterioration: When the temperature rise of the injection molding machine is too high, it will accelerate the oxidation and deterioration of the oil, precipitate the asphalt material, and reduce the service life of the hydraulic oil. The precipitate blocks the damper orifice and the slit valve port, causing the pressure valve to become stuck and unable to move, the metal pipe to be elongated and bent, or even broken.
5. The working quality of the components is deteriorated: if the temperature rise of the injection molding machine is too high, the working quality of the components will be deteriorated, the dissolved air in the oil will escape, and air pockets will be generated, resulting in a decrease in the working performance of the hydraulic system.