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Don't You Understand The Main Points Of Injection Mold Design?
Sep 12, 2018

Plastic injection moulds are the most widely used moulds of all plastic moulds, capable of forming complex high-precision plastic products. This article is only a cursory introduction.
Since it is a chain-like structure, the direction of shrinkage of plastics during processing is also related to the orientation and cooling contraction of polymer molecular chains under stress, and more contraction in flow direction than in vertical direction.
Product shrinkage is also related to product shape, gate, thermal expansion and contraction, temperature, pressure holding time and internal stress. Generally, the range of shrinkage rate provided in the book is wide. In practical application, the thickness, structure of the product and the size and orientation of temperature pressure are considered. In general, if there is no core support, the contraction will be larger. Plastic injection mold basically divided into static mold and dynamic mold.

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The injection head side of the injection molding machine with sprue cover is static mold, static mold generally with sprue cover, plate, template composition, simple mold (especially die without core) can also not use the plate, directly with a thicker template. Generally speaking, the sprue cap is a standard part. It is not recommended to cancel unless there is a special reason.
The use of sprue muzzle is conducive to the installation of molds, convenient replacement, without polishing. Some special moulds can be drilled out or cut with taper line. Part of the mold must be the static mold demoulding, also need to add the static mold demoulding mechanism. In general, the structure of the moving mold is the moving template, the moving mold plate, the demoulding mechanism, the die pin and the mounting fixed plate.
Gate is directly related to the appearance of plastic parts, gate design is not good, easy to produce defects. It's easy to produce snake-like flow without any blockages. For demanding products, overflow and exhaust should also be designed. Top bar can be used in overflow area, do not leave overflow flying edge on the template, so as not to affect the die life.
In the demoulding mechanism, in addition to the stripper bar, there is a return bar, part of the mold must increase springs to achieve such functions as automatic demoulding. There are also guide column, cooling water hole, flow channel, such as the basic structure of die. Of course, the inclined guide mould also has the inclined guide box, the inclined guide column and so on.

When designing a mold for a product, the basic structure size of the mold should be set first to prepare materials to speed up the mold manufacturing. Complex products should be drawn first, and then the size of the mold. The current mold basically needs to undergo heat treatment, increase the mold hardness, improve the die service life.
Before heat treatment, preliminary processing of the formwork is carried out first: drilling the guide hole, the return hole (dynamic mode), the cavity hole, the screw hole, the sprue sleeve hole (static mode), the blanking hole (dynamic mode), the cooling water hole, etc., milling the flow channel, the cavity, some molds should also milling the inclined guide box.