The structural composition of plastic molds

1. Pouring system: refers to the flow channel part of plastic before entering the mold cavity from the nozzle, including the main flow channel, diversion channel, cold material hole, gate, etc.

2. Formed parts system: refers to various combinations of parts that form the shape of a product, including moving molds, fixed molds, and cavities (concave molds), cores (convex molds), forming rods, etc. The core forms the inner surface of the product, and the cavity (concave mold) forms the outer surface shape of the product. After the mold is closed, the core and cavity form the cavity of the mold. According to the requirements of technology and manufacturing, sometimes the core and die are composed of several assembled blocks, and sometimes they are made into a whole. Only inserts are used in areas that are prone to damage and difficult to machine.

3. Temperature control system: In order to meet the temperature requirements of the injection process for the mold, a temperature control system is required to adjust the temperature of the mold. For injection molds for thermoplastic materials, the main approach is to design a cooling system to cool the mold (which can also be heated). The common method of mold cooling is to set up a cooling water channel inside the mold, and use the circulating cooling water to take away the heat of the mold; The heating of the mold can not only utilize cooling water to pass through hot water or oil, but also install electric heating elements inside and around the mold.

4. Exhaust system: It is set up to exhaust the air and gas generated by the melting of plastic inside the injection molding process to the outside of the mold. When the exhaust is not smooth, the surface of the product will form air marks (air marks), burning and other defects; The exhaust system of plastic molds is usually a groove shaped air outlet set up in the mold to exhaust the air in the original cavity and the gas brought in by the molten material.

When the molten material is injected into the mold cavity, the air originally stored in the cavity and the gas brought in by the molten material must be discharged out of the mold through the exhaust port at the end of the material flow. Otherwise, it will cause the product to have pores, poor fusion, insufficient filling of the mold, and even the accumulated air will be compressed and generate high temperature, which will burn the product. In general, the exhaust hole can be located at the end of the molten material flow in the mold cavity or on the parting surface of the plastic mold.

The latter involves opening a shallow groove on one side of the concave mold, with a depth of 0.03-0.2mm and a width of 1.5-6mm. During injection, there will not be a lot of molten material seeping out of the exhaust hole, as the molten material will cool and solidify at that location, blocking the channel. The opening position of the exhaust port should not face the operator to prevent accidental spraying of molten material and injury. In addition, the clearance between the ejection rod and the ejection hole, as well as the clearance between the ejection block, the template, and the core can also be used for exhaust.

5. Guiding system: It is set up to ensure accurate alignment between the moving and fixed molds during mold closing, and guiding components must be installed in the mold. In injection molding, four sets of guide pillars and guide sleeves are usually used to form guiding components. Sometimes, matching inner and outer conical surfaces need to be set on the moving and fixed molds to assist in positioning.

6. Ejection system: generally consists of several parts, including: ejector pin, front and rear ejector pin plates, ejector pin guide rods, ejector pin reset springs, ejector pin plate locking screws, etc. After the product is formed and cooled in the mold, the front and rear molds of the mold separate and open. The ejection mechanism - the ejector pin - pushes the plastic product and its condensate in the flow channel out or out of the mold opening and flow channel position under the push of the top rod of the injection molding machine, so as to proceed with the next injection molding work cycle.