What is the injection pressure? The injection pressure is provided by the hydraulic system of the injection molding machine. The pressure of the hydraulic cylinder is transmitted to the injection melt through the screw of the injection molding machine. The plastic melt is pushed by the nozzle into the main flow path of the mold and injected into the mold cavity through the nozzle. The pressure is to allow the melt to be injected into the cavity as required and to ensure complete filling.
Injection time: Reasonable injection time is helpful for the filling of the plastic melt. The injection time is generally about 1/10 of the cooling time. It should be determined according to different injection molding materials.
Injection temperature: Injection temperature is an important factor affecting the injection pressure. The injection temperature must be controlled within a reasonable range. The temperature is too low, the raw material is not plasticized; the temperature is too high, and the raw material is easily decomposed. Therefore, temperature control requires reasonable control from an experienced master.
Holding pressure and time: At the end of injection molding, the screw stops rotating, just advances and enters the pressure holding phase. During the pressure keeping process, the nozzle constantly wants to replenish the raw material melt to ensure the integrity of the product after molding. The holding pressure is generally about 80% of the maximum filling pressure, which is determined according to the requirements of the actual raw materials and products.
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Back pressure: Back pressure refers to the pressure that the screw needs to overcome when reversing the material. The high back pressure facilitates the dispersion of the colorant and the melting of the plastic.
PP plastic injection temperature, injection pressure and other technical parameters
Drying temperature (°C) 65～75
Drying time approx. (hr) 0.5 to 1
Mold temperature (°C) 35～65
Residual material amount (mm) 3~10
Melt temperature (°C) 200～250
Back pressure (MPa) 9 to 17
Injection pressure (MPa) 80 ~ 130
Clamping force approx. (ton/in2)2
Medium injection speed
Return speed (rpm) 60~90
Screw type standard screw (straight-through nozzle)
Stop the processing and close the brakes.
Crushed material reuse (%) 15 ~ 30