How many kinds of moulds and gates are there in Shandong? Gate, also known as feed gate, is a thin and short flow between the distributor and the die cavity (except for the direct gate), which is the key component of the gating system. Its main functions are:
(1) After filling the cavity, the first condensation is melted at the gate to prevent its reflux.
(2)容易在浇口系统中切割冷凝水。闸门截面积约为分流截面积的0.03 ~ 0.09。浇口长度约0.5 mm ~ 2mm，浇口的具体尺寸一般根据经验确定。取下下限，在试模时逐步修正。
(2) It is easy to cut condensate in gate system. The section area of the gate is about 0.03-0.09 of that of the diversion section. The gate length is about 0.5 mm ~ 2 mm. The specific size of the gate is generally determined by experience. Take the lower limit and correct it step by step during the test.
When the plastic melt passes through the gate, the shear rate increases, the friction in the melt increases, the material flow temperature increases, the viscosity decreases, the flowability improves, and the filling is beneficial. However, too small gate size will increase pressure loss, accelerate the speed of condensation water, make it difficult to feed, and even form spray phenomenon, which will affect the quality of plastic parts.
The gate forms are as follows:
Direct gate, also known as center gate, has small flow resistance and fast feeding speed. It is often used to form large and deep plastic parts in single cavity dies. It is suitable for all kinds of plastics, especially those with high viscosity and low fluidity, such as PC, PSF, etc.
Straight door shallow shallow shaping when plastic parts will produce bending and distortion phenomenon, while removing inconvenience door, there are obvious traces, sometimes because of the heat concentration of the door location, cavity seal, internal pressure and become the source of cracks, so the design of the door should be as small as possible. When forming thin-walled plastic parts, the diameter of gate root is at most twice the thickness of plastic parts.
(2) side door
侧浇口，又称边浇口，其断面为矩形，一般开在分型面上，由塑料部分的侧浇口进料，可合理选择浇口位置，特别适用于多个型腔。如图10-12所示，一般宽度B= 1.5mm ~ 5mm，厚度h= 0.5mm ~ 2mm(或塑料件壁厚的1/3 ~ 2/3)，长度L= 0.7mm ~ 2mm。
Side gate, also known as side gate, its cross-section is rectangular, generally separated on the parting surface, feeding by the side gate of the plastic part, can reasonably select the gate location, especially suitable for multiple cavities. As shown in Figure 10-12, the general width B = 1.5mm-5mm, thickness h = 0.5mm-2mm (or 1/3-2/3 of the wall thickness of plastic parts), length L = 0.7mm-2mm.
Point gate, also known as pin gate, is a small size gate, as shown in Figure 10-14. Plastic melt has a high shear rate. It is widely used in various shell forming parts. When the die is opened, the gate can be opened by itself.
The door is connected with plastic parts. In order to prevent the breakage and damage of plastic parts at the point gate, a small bump gate can be designed with a small cross-sectional area. The boss's form condensates quickly, which is not conducive to feeding. Thick plastic parts on the wall should not be used.
(4) Potential doors
It is also called shear gate, which evolved from the point gate used for three-plate die, while the submerged gate is used for two-plate die, thus simplifying the die structure. The latent door is arranged inside and outside the plastic part without affecting the appearance of the plastic part. When releasing plastic parts, the gate is cut off, but strong thrust is needed. It is not suitable to use stronger and harder plastics.