Direct gate, also known as direct gate, large gate, it is generally located in plastic parts, and is also called feed gate in multi-cavity injection molds. The body is directly injected into the cavity, the pressure loss is small, the pressure holding and shrinkage is strong, the structure is simple, and the manufacture is convenient, but the cooling time is long, it is difficult to remove the gate, the gate marks are obvious, and sink marks, shrinkage holes and residues are easily generated near the gate. Stress is high.
(1) Advantages of straight gate
The melt enters the cavity directly from the nozzle through the gate, the process is very short, the feeding speed is fast, and the molding effect is good; The injection mold has a simple structure, is easy to manufacture, and has a low cost.
(2) Disadvantages of straight gate
The cross-sectional area of the sprue gate is large, it is difficult to remove the gate, and the trace after the gate is removed is obvious, which affects the appearance of the product; the gate part has a lot of melt, the heat is concentrated, and the internal stress after cooling is large, and it is easy to produce pores and shrinkage holes. ; For the molding of flat and thin-walled plastic parts, the sprue is prone to warpage deformation, especially if it is crystalline plastic.
2. Edge gate
Edge gate, also known as side gate, is one of the most widely used gate types, so it is also called ordinary gate. Its cross-sectional shape is generally processed into a rectangle, so it is also called a rectangular gate. It is generally opened on the parting surface and fed from the outside of the cavity. Since the size of the side gate is generally small, the relationship between the cross-sectional shape and the pressure and heat loss can be ignored.
(1) Advantages of side gate
The cross-sectional shape is simple, the processing is convenient, the gate size can be finely processed, and the surface roughness is small; the gate location can be flexibly selected according to the shape characteristics of the plastic parts and the filling needs, such as frame-shaped or annular plastic parts. The mouth can be set on the outside or on the inside; due to the small cross-sectional size, it is easy to remove the gate, the traces are small, the product has no fusion line, and the quality is good; Dongguan Machike Injection Mould Factory For the unbalanced pouring system, it is reasonable to change the pouring system. The size of the mouth can change the filling conditions and filling state; the side gate is generally suitable for multi-cavity injection molds, with high production efficiency, and is sometimes used in single-cavity injection molds.
(2) Disadvantages of side gate
For shell-shaped plastic parts, the use of this gate is not easy to exhaust, and it is easy to produce defects such as weld lines and shrinkage holes; the side gate can only be used when there are traces of feeding on the parting surface of the plastic part, otherwise , only another gate is selected; the pressure loss during injection is large, and the pressure-holding and feeding effect is smaller than that of the straight gate.
(3) Application of side gate: The application of side gate is very wide, especially suitable for two-plate multi-cavity injection mold, mostly used for casting and molding of small and medium-sized plastic parts.
3. Overlapping gate
Also known as lap gate, it can be arranged as an impact gate, which can effectively prevent jet flow, but it is easy to produce sink marks at the gate, it is difficult to remove the gate, and the gate trace is obvious.
4. Fan gate
The fan gate is a gate that gradually expands, like a folding fan, which is derived from the side gate. The gate gradually widens along the feeding direction, and the thickness gradually becomes thinner, and the melt enters the cavity through the gate step of about 1mm. The gate depth depends on the thickness of the product.
(1) Advantages of fan gate
The melt enters the cavity through a gradually expanding fan shape. Therefore, the melt can be distributed more evenly in the lateral direction, which can reduce the internal stress of the product and reduce deformation; The effect of grain and orientation is greatly reduced; the possibility of bringing in air can be reduced, and the cavity is well vented to avoid gas mixing into the melt.
(2) Disadvantages of fan gate
Because the gate is very wide, the workload of removing the gate after molding is large, which is troublesome and increases the cost; there are long shear marks along the side of the product, which affects the appearance of the product.
(3) Application of fan gate
Due to the wide feeding port and smooth feeding, the fan gate is often used to form long, flat and thin products, such as cover plates, rulers, trays, plates, etc. For plastics with poor fluidity, such as PC, PSF, etc., the fan gate can also be adapted.
5. Disc gate
The disc gate is used for round plastic parts with large inner holes, or plastic parts with large rectangular inner holes, and the gate is on the entire circumference of the inner hole. The plastic melt is injected into the cavity in a roughly synchronous manner from the periphery of the inner hole, the core is evenly stressed, the weld line can be avoided, and the exhaust is smooth, but there will be obvious gate marks on the inner edge of the plastic part.
6. Round gate
The annular gate, also known as the annular gate, is somewhat similar to the disc gate, except that the gate is set on the outside of the cavity, that is, the gate is set around the cavity, and the gate position is exactly the same as the disc gate. Corresponding to the gate, the annular gate can also be regarded as a variation of the rectangular gate. In the design, it can still be treated as a rectangular gate, and you can refer to the selection of the size of the disc gate.
(1) Advantages of annular gate
The melt enters the cavity evenly along the circumference of the gate, and the gas is discharged smoothly, and the exhaust effect is good; the melt can achieve approximately the same flow rate on the entire circumference, without ripples and weld lines; because the melt is in the cavity Smooth flow, so the internal stress of the product is small and the deformation is small.
(2) Disadvantages of annular gate
The cross-sectional area of the annular gate is large, which is difficult to remove, and leaves obvious traces on the side; since there are many gate residues, and it is on the outer surface of the product, in order to make it beautiful, it is often removed by turning and punching.
(3) Application of ring gate: Ring gate is mostly used for small, multi-cavity injection molds, and is suitable for cylindrical plastic parts with long molding cycle and thin wall thickness.
7. Sheet gate
Sheet gate, also known as flat slot gate, film gate, is also a variant of side gate. The distribution runner of the gate is parallel to the side of the cavity, which is called a parallel runner, and its length can be greater than or equal to the width of the plastic part. The melt is firstly distributed evenly in the parallel flow channels, and then uniformly enters the cavity at a lower rate. The thickness of the flat-slot gate is very small, generally 0.25~0.65mm, its width is 0.25~1 times the width of the cavity at the gate, and the length of the gate slit is 0.6~0.8mm.
(1) Advantages of sheet gate
The rate of the melt entering the cavity is uniform and stable, which reduces the internal stress of the plastic part and makes the plastic part look good. The melt enters the cavity from one direction, and the gas can be removed smoothly. Due to the large cross-sectional area of the gate, the flow state of the melt is changed, and the deformation of the plastic part is limited to a small range.
(2) Disadvantages of sheet gate
Due to the large cross-sectional area of the sheet gate, it is not easy to remove the gate after molding, and the injection molding process technology and production management work are heavy, so the cost increases. When removing the gate, there is a long shear mark along one side of the plastic part, which hinders the appearance of the plastic part.
(3) Application of flat-slot gate: The flat-slot gate is mainly suitable for thin-plate plastic parts with a large molding area. For plastics such as PE that are easy to deform, this gate can effectively control the deformation.
8. Pin point gate
Pin point gate, also known as olive gate or diamond gate, is a kind of circular section gate with extra small section size, and it is also a very widely used gate form. The size of the point gate is very important. If the point gate is opened too large, the plastic in the gate will be difficult to be broken when the mold is opened. Moreover, the product is subjected to the tensile force of the plastic at the gate, and its stress will affect the shape of the plastic part. . In addition, if the taper of the point gate is too small, when the mold is opened, it is difficult to determine where the plastic in the gate is broken, which will cause poor appearance of the product.
(1) Advantages of pin point gate
The location of the point gate can be determined according to the process requirements, which has little effect on the appearance quality of the product. When the melt passes through the gate with a small cross-sectional area, the flow rate increases, the friction increases, the melt temperature increases, and the fluidity increases, so that a plastic part with a clear shape and a glossy surface can be obtained.
Due to the small cross-sectional area of the gate, the gate can be automatically broken when the mold is opened, which is conducive to automatic operation. Since the gate exerts less force when breaking, the residual stress of the product at the gate is small. The melt at the gate solidifies quickly, which can reduce the residual stress in the mold and is conducive to the demoulding of the product.
(2) Disadvantages of pin point gate
The pressure loss is large, which is unfavorable for the molding of plastic parts, and requires a higher injection pressure. The structure of the injection mold is relatively complex, and a three-plate mold is generally required to be successfully demolded, but a two-plate mold can still be used in a runnerless injection mold. Due to the high flow rate at the gate, the molecules are highly oriented, which increases the local stress and is prone to cracking. Dongguan Machike Injection Mould Factory For large plastic parts or plastic parts that are easily deformed, it is easy to warp and deform by using one point gate. At this time, several more point gates can be opened at the same time for feeding.
(3) Application of pin gate: Pin gate is suitable for low viscosity plastics and plastics whose viscosity is sensitive to shear rate, and is suitable for multi-cavity feeding injection molds.
9. Latent gate
The latent gate, also known as the tunnel gate, is evolved from the point gate. It not only overcomes the shortcomings of the complex point gate injection mold, but also maintains the advantages of the point gate. The latent gate can be set on the side of the movable mold or on the side of the fixed mold. It can be placed on the inner surface or hidden side of the plastic part, it can also be placed on the ribs and columns of the plastic part, and it can also be placed on the parting surface, and the use of the ejector rod of the injection mold to set the gate is also a an easy way. The volt gate is generally tapered and has a certain angle to the cavity.
(1) Advantages of latent gate
The feed gate is generally hidden on the inner surface or side of the plastic part, and does not affect the appearance of the product. After the product is formed, the plastic part will automatically break when it is ejected. Therefore, it is easy to realize production automation. Since the latent gate can be set on the ribs and columns that cannot be seen on the surface of the product, the spray marks and air marks caused by spraying will not be left on the surface of the product during molding.
(2) Disadvantages of latent gate
Since the latent gate sneaks under the parting surface and enters the cavity in an oblique direction, it is difficult to process. Since the shape of the gate is a cone, it is easy to cut off when it is ejected, so the diameter should be small, but for thin-walled products, it is not suitable because the pressure loss is too large and it is easy to condense.
(3) Application of latent gate
The latent gate is especially suitable for plastic parts fed from one side, and is generally suitable for two-plate molds. Due to the strong impact on the plastic parts during ejection, it is difficult to cut off too strong plastics such as PA, while for brittle plastics such as PS, it is easy to break and block the gate.
10. Lug gate
The lug gate, also known as the tap gate or the adjustment gate, has an ear groove on the side of the cavity, and the melt impacts on the side of the ear groove through the gate. After entering the cavity after the speed, it can prevent the spray phenomenon when the small gate is pouring into the cavity. It is a typical impact gate. The lug gate can be regarded as an evolution from the side gate. The gate should generally be opened at the thick wall of the plastic part. The gate is usually square or rectangular, the ear groove is rectangular or semi-circular, and the runner is circular.
(1). Advantages of lug gate
The melt enters the lug through a narrow gate, which increases the temperature and improves the flow of the melt. Since the gate is at right angles to the lugs, when the melt hits the opposite wall of the lug, the direction changes and the flow rate decreases, allowing the melt to enter the cavity smoothly and evenly. The gate is far away from the cavity, so the residual stress at the gate will not affect the quality of the plastic parts. When the melt enters the cavity, the flow is smooth and no eddy current is generated, so the internal stress in the plastic is very small.
(2) Disadvantages of the lug gate: Due to the large cross-sectional area of the gate, it is difficult to remove and leave large traces, which is detrimental to the appearance. The runner is longer and more complicated.
Post time: Apr-15-2022