What is inside the injection mold?
The structure of the mold may vary greatly depending on the type and properties of the plastic, the shape and structure of the plastic product, and the type of injection machine, but the basic structure is consistent.The mold is mainly composed of pouring system, tempering system, molding parts and structural parts.The casting system and molding parts are the parts that contact with plastics directly and change with plastics and products. They are the most complex part in the mold with the greatest change and require the highest degree of finish and precision.
Injection mold processing consists of two parts, dynamic mold installed in the injection molding machine mobile template, fixed mold installed in the injection molding machine fixed template.During the injection molding, the dynamic mold and the fixed mold close to form the casting system and cavity.In order to reduce the heavy work of die design and manufacture, most of injection moulds adopt standard formwork.
1. Pouring system
The pouring system refers to the part of the flow channel before the plastic enters the mold cavity from the nozzle, including the main channel, the cold material hole, the diverging channel and the sprue.
The pouring system, also known as the flow channel system, is a group of feeding channels that guide the plastic melt from the injector nozzle to the mold cavity, which is usually composed of the main channel, diverging channel, sprue and cold material hole.It is directly related to the molding quality and production efficiency of plastic products.
2. Mainstream
It is a section of the die connected injection molding machine injection nozzle to the shunt or cavity.The top of the main channel is concave to connect with the nozzle.The inlet diameter of the main channel should be slightly larger than that of the nozzle (0.8mm) to avoid overflows and to prevent interconnection between the two.Inlet diameter depends on product size, generally 4-8mm.Mainstream way to expand inside diameter are 3 ° to 5 ° Angle, so that the flow channel in January release.
3. Cold slug
It is a hole located at the end of the main channel to capture the cold material produced between two injections at the end of the nozzle to prevent blockage of the runner or sprue.If the cold material is mixed into the cavity, it is easy to produce internal stress in the manufactured product.The diameter of the cold slug is about 8-10mm and the depth is 6mm.In order to facilitate demoulding, its bottom is often taken by the demoulding rod.The top of the stripper should be designed as a zigzag hook or a sunken groove, so that the main channel can be pulled out smoothly.
4. Diverging path
It is the channel connecting the main channel and each cavity in the multi-slot module.In order to fill the cavity with molten material at the same speed, the distribution of diverging channel on the mold should be symmetrical and equidistant.The shape and size of the diverging section affect the flow of the plastic melt, the ease of product demoulding and the difficulty of mold making.
If the same amount of material flow, then the circular section of the flow path to the minimum resistance.However, because the cylindrical flow channel is smaller than the surface, it is not good for the cooling of the tripping channel.
Therefore, a trapezoid or semicircular section of the shunt is often used, and is set on half of the die with the stripper bar.The surface of the runner must be polished to reduce flow resistance and provide a faster filling rate.The size of the runner depends on the size and thickness of the plastic.For most thermoplastic plastics, the width of the shunt section is no more than 8m, the very large is 10-12m, and the very small is 2-3m.The cross-sectional area should be reduced as much as possible to increase shunt redundancy and extend cooling time.