The functional structure of the plastic mold system mainly consists of six systems: pouring system, temperature control system, formed parts system, exhaust system, guide system, and ejection system. Among them, the pouring system and formed parts are the parts that come into direct contact with plastic and change with plastic and products. They are the complex and variable parts in the plastic mold that require high processing smoothness and accuracy.
1. Pouring system:
The pouring system refers to the part of the flow channel before plastic enters the mold cavity from the nozzle, including the main flow channel, cold material hole, diversion channel, and gate.
2. Formed parts system:
The formed parts system refers to various combinations of parts that make up the shape of a product, including moving molds, fixed molds, 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:
The temperature control system is required to meet the temperature requirements of the injection process for the mold, and it is necessary to have a temperature control system 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, using 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:
The exhaust system is set up to exhaust the air and gas generated by the melting of plastic in the injection molding process into the outside of the mold. When the exhaust is not smooth, the surface of the product will form defects such as air marks (air marks) and burning; 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 connections, insufficient mold filling, and even the accumulated air to 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 there, 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. Guidance system:
The guiding system is established 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:
The ejection system generally consists of several parts, including the ejector pin, front and rear ejector pin plates, ejector pin guide rods, ejector pin reset springs, and ejector pin plate locking screws. 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.
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