Injection molding is also a separate engineering technology, the purpose of which is to thermoplastic raw materials through the important process conditions of injection molding into products that can be used and maintain the original properties, so the preparation of injection molding process parameters is to ensure that the injection molding process is an important link. In the injection molding process parameters to pay particular attention to the preparation of several elements are: temperature, pressure, time.
Injection molding temperature control:
Injection molding process needs to control the temperature of the barrel temperature, nozzle temperature and mold temperature. Cylinder temperature and nozzle temperature control its main purpose is to make the material in the cylinder for full plasticization and flow.
Mold temperature control its purpose is: so that the molten material in the mold filling process to improve a certain mobility, to help the molten material can quickly fill all parts of the mold cavity. Secondly, it also makes the material filled with mold cavity to the fixed temperature can be fully cooled and shaped. Third, the mold temperature control on the inner properties of the product and the apparent quality has a great impact.
Pressure control:
Injection molded products processing process, the need to control pressure including injection pressure and plasticizing pressure (i.e., back pressure).
Injection pressure: through the hydraulic system of the injection molding machine (electric injection molding machine is the use of servo motors) the pressure is transferred to the end of the barrel, so that it pushes the screw to move forward, i.e., the pressure exerted on the end of the screw is called injection pressure. In injection molding, the role played by the injection pressure is to overcome the molten plastic from the barrel to the mold cavity, filling the process of flow resistance, to give the rate of molten mold filling and compaction of molten material.
Plasticizing pressure: refers to the top of the screw melt in the screw rotation back when the pressure received by the plasticizing pressure, also known as back pressure. Can also be said to overcome the resistance generated by the screw feed rotation called back pressure. In general, the appropriate increase in back pressure can make the melt temperature uniformity, color mixing uniformity, but also can be discharged from the melt in the gas, the normal production operation, the size of the back pressure should be in the premise of maintaining the quality of the product the smaller the better.
Time control:
Injection molding process needs to control the time including: injection time, holding time, plasticizing time, cooling time, cycle time.
Injection time: the barrel of molten material in the injection pressure under the action of the basic cavity filled with the time required is called injection time.
Holding time: is the time to apply pressure to the plastic in the cavity. However, it should be noted that, in the gate at the melt freeze before the length of holding time on the dimensional accuracy of the product has an impact, if to the gate at the melt freeze after the impact is not.
Plasticizing time: The time required from the beginning of the screw rotation to feed the material until the set metering position is called plasticizing time, the length of which is directly affected by the back pressure and screw speed. It is important to note that the plasticizing time must be completed within the cooling time.
Cooling time: cooling time refers to the cavity filled with solid plastic melt, at a constant temperature under the state of the product fully molded time required. The length of the cooling time depends mainly on the thickness of the product size, but also to ensure that the product does not cause changes when the principle of demolding.
Cycle time: Cycle time refers to the time required from the start of the injection molding machine to the end of the product demolding. Cycle time contains, as mentioned earlier, several times, namely, injection time, holding time, cooling time (cooling time has included plasticizing time). The length of cycle time is related to whether the process parameters are set reasonably or not. It is also related to the continuity and automation of the production process.
