Design of No Runner and Hot Runner Gating System for Injection Mold

The design of injection mold without runner and hot runner gating system, Shanghai Mulan Injection Mold Factory, in order to save plastic, facilitate high-speed automatic molding, shorten molding cycle, improve production efficiency and facilitate operation. In the design of injection molds, the structure of no runner and hot runner can be considered to ensure that the melt of the gating system is in a normal melting state. So that after each injection molded part is formed, there is no need to set up the process of taking out the condensate in the runner and cleaning the gate.





1. Application of plastics without runners and hot runners and their requirements


1. Requirements for the application of plastics with no runner and hot runner structure


①Wide molding temperature range: It is easy to mold at low temperature, that is, it has good fluidity at low temperature and good stability at high temperature;


② The fluidity of the melt at low temperature is sensitive to pressure: it does not flow when no pressure is applied, and it can flow as long as a little pressure is applied;


③ Good thermal conductivity: the molten plastic can quickly transfer heat to the mold and cool down quickly;


④The thermal deformation temperature of the plastic should be high: so that the molded injection molded parts can be quickly demoulded from the mold;


⑤The specific heat of plastic is low: it means that it is easy to melt and solidify.


2. Adaptable to non-runner and hot runner structures The factors that various plastics affect the structure of no runners and hot runners in injection molds depend on the thermal properties and fluidity of plastics. Plastics used for runnerless and hot runner structures include PE, PP, PS, and ABS, while less commonly used plastics include heat-sensitive plastics such as PVC, PC, and POM. This structural form is related to the plastic molding characteristics, and various plastics are suitable for the structure of no runner and hot runner.





2. Design of non-runner gating system


The design of the injection mold without runner and hot runner gating system, when the length of the main channel exceeds 60mm, the distance between the melt flow and the injection mold at room temperature is long, and the melt fluidity will be reduced after the melt is cooled too much, resulting in Various defects of injection molded parts. In order to avoid various defects of injection molded parts, Shanghai Mulan Injection Mold Factory should adopt measures such as no runner or thermal extension nozzle.


①Adoption of non-runner gating system: Because too long runners have a long distance between the melt flow and the mold at room temperature, after the melt cools down too much, the fluidity of the melt will be reduced, and at the same time, it will cause various defects in the injection molded parts. defect. In order to avoid various defects of injection molded parts, when the length of the main runner exceeds 60mm, measures such as no runner or thermal extension nozzle should be adopted.


② Well nozzle: The well nozzle is another form of point gate that makes the feed gate into the form of a well pit for storing materials.


a. Well nozzle pouring characteristics. When the plastic in the storage pit is injected, the plastic in the pit remains in a molten state, and the plastic that contacts the outer layer of the injection mold becomes a semi-condensed state due to cooling. This semi-frozen plastic plays a role of heat insulation, so that the nozzle of the injection molding machine can be continuously injected without leaving the sprue sleeve of the injection mold. This type of nozzle is often used in single cavity molds.





b. Well nozzle form. It can be divided into four types: general, extended, spring and expanded area. The molding cycle of injection molded parts is long and the nozzle is solidified. It shows that the volume at the front end of the nozzle is increased, so that the molten material of the accumulation is not in order to extend the nozzle of the injection molding machine to directly contact the mold. A special nozzle for the cavity, whose extended part replaces the runner, is better than the well nozzle for preventing the solidification of the molten material in the storage well and the clogging of the gate.


In the design of injection mold without runner and hot runner gating system, Shanghai Mulan Injection Mold Factory said that the design of gating system should not be underestimated. Its structural form, size and position all affect the structure and defects of injection molds.