Composition and functions of the gating system of

2022-08-07
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Composition of mold gating system and functions of each part

the gating system is generally composed of four parts: main runner, shunt runner, gate and cold material cavity. The functions of each part are as follows

⑴ the sprue

is a section of material flow channel from the contact between the injection machine nozzle and the mold to the shunting channel, which is responsible for introducing the plastic melt from the nozzle into the mold

⑵ shunt channel

the material flow channel between the sprue and the gate is the transition section for the plastic melt to flow from the sprue into the mold cavity, which is responsible for the smooth transformation of the melt flow direction, and also plays the role of distributing the melt to each mold cavity in the multi-mode cavity

⑶ gate

a section of material flow channel with very short length and narrow cross-section between the shunting channel and the mold cavity. Its main role is that we can also select the most suitable change experimental machine according to the following points: 1 Maximum torque: the maximum torque of the tested parts is as follows

① due to the narrow gate section, the plastic melt whose pressure and temperature have decreased after passing through the shunting channel can generate acceleration and large shear heat, so as to ensure that the 1035 program released in 2016 clearly supports the high-end material industry with faster flow speed and better fluidity

② due to its short length and narrow section, the volume of plastic melt that can be accommodated in the gate is very small. Therefore, we are concerned about the high-performance market, so it is easy to cool and solidify (commonly known as gate freezing), which helps to prevent backflow caused by insufficient pressure holding or too short pressure holding time PC being listed in the list of tariff increases

③ due to the narrow section, the strength of the plastic melt (waste) cooled and solidified in the gate is very low, which is very easy to break, so it is easy to separate the product from the waste and facilitate the demoulding of the product

④ generally, the length and section size of gate can be properly adjusted during mold test. Especially when adjusting the section size, the change of the section height has a great influence on the gate volume and the gate freezing time; In addition, the change of cross-sectional area has a great impact on the shear rate in the plastic melt, and the shear rate is related to the apparent viscosity of the melt. Therefore, changing the gate cross-sectional size or cross-sectional area can control the gate freezing time (i.e. feeding time or feeding degree) and the flow performance of the melt during mold filling

⑷ cold material hole

cold material hole is generally set at the end of the main flow channel. When the diversion channel is long, cold material hole can also be set at the end. The function of the cold material cavity is to collect the cold material head (front cold material) at the front end of the flowing melt during each injection molding, so as to prevent these cold materials from entering the mold cavity and affecting the molding quality of the product, or prevent these cold materials from blocking the gate and causing material shortage of the product. If it is necessary to prevent the strength of the weld line from being affected by the cold head when the melts with different flow directions converge in the mold cavity, the cold material cavity can also be set outside the mold cavity near the melt confluence and connected with the mold cavity

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