Introduction of precision injection mold runner system


In the manufacture of plastic molds, the flow channel design can be said to be a large group of mold designers. When the design is large, the material consumption is large, and the design is small, and the product will have problems such as filling. When designing plastic molds, a clear understanding of the runner system is an extremely important basic skill.

Ordinary runner system (Runner System) is also called runner system or pouring system, which is the necessary channel for molten plastic from the nozzle of the injection machine to the mold cavity. In plastic molds, the runner system includes the primary runner (Primary Runner), the sub-runner (Sub-Runner) and the gate (Gate).

   Main runner: Also called sprue, sprue or down runner, it refers to the runner from the part where the nozzle of the injection machine is in contact with the main runner bushing of the mold to the branch runner. This part is the first part that the molten plastic flows through after entering the mold.

   Split runner: also known as sub-runner or secondary runner, which can be further divided into first runner and second runner (Secondary Runner) according to the mold design. The runner is the transition area between the main runner and the gate, which can make the flow direction of the molten plastic change smoothly; for the multi-cavity mold, it has the function of uniformly distributing the plastic to each cavity.

   Gate: Also called the feed port. It is the narrow opening between the runner and the cavity, and it is also the shortest and thinner part. The function is to use the shrinkage of the flow surface to accelerate the plastic. The high shear rate can make the plastic good fluidity (due to the shear thinning characteristics of the plastic); the heating effect of the viscous heating also has the effect of increasing the material temperature and reducing the viscosity. After the molding is completed, the gate is the first to be cured and sealed, which has the function of preventing the plastic from reflowing and preventing the mold cavity pressure from falling too fast to cause the molded product to shrink. After forming, it is convenient to cut to separate runner system and plastic parts.

Cold slug well: also called cold slug hole. The purpose is to store and replenish the colder plastic wavefront at the initial stage of filling, to prevent the cold material from directly entering the mold cavity, affecting the filling quality or blocking the gate. The cold material well is usually set at the end of the main runner. When the plastic mold has a long branch runner length, A cold slug well should also be opened at the end.