Thoughts on the design of plastic bottle cap mold

The requirements for bottle cap mold planning are based on the shape, precision, size, technical requirements and production batch of plastic parts. Mold planning should consider the following aspects:

A. Number and placement of cavities: Bottle caps are mass-produced as packaging containers, so it is recommended to choose one mold with multiple cavities. Considering the clamping force, injection volume, precision and economy of the existing injection molding machine, it is determined that one mold has 10 cavities, and the placement of the cavities is straight line layout.

B. Casting system planning: According to the layout of plastic parts, the mold is planned as a three-plate type with a point gate, which is set at the top center of the plastic part. The point gate can significantly increase the shear rate of the melt, greatly reduce the viscosity of the melt, and is conducive to filling. It is particularly useful for melts that are sensitive to shear rates, such as polyethylene. Moreover, plastic parts are packaging containers, which have high requirements for appearance quality. The point gate has small residual traces, which can ensure the surface quality of plastic parts. The gate is actively broken during demoulding, which facilitates the initiative of completing the product production process, improves production power, and increases economic benefits. The unbalanced gating system is selected, and the cavity is placed compactly, which reduces the mold size. In order to make each cavity evenly filled together, the method is selected to achieve balance by manually correcting the gate size of each cavity. Use a cold material cavity to store the front cold material.

C. Cooling system planning: The mold temperature control system of the bottle cap mold directly affects the product quality and output power. In order to improve the cooling capacity of the cavity, a cooling circuit is selected, and the inlet of one circuit is adjacent to the outlet of another circuit. According to the shape of the plastic part and the constraints of the mold layout, the cooling channel diameter of the fixed mold is φ12mm, which is connected to the hose outside the mold to form a circulating cooling. The moving core has a small diameter and adopts a steel pipe cooling method. A soft copper core rod with good thermal conductivity is pressed in the middle of the core, and one end of the core rod is inserted into the cooling water hole for cooling.