The location of the gate determines the quality of the MIM injection molded product
time：2020-06-08Views：476 Author：Best Seiko
The gate, also known as the feed port, is a channel connecting the runner and the melt in the cavity. The proper choice of gate is directly related to whether the metal powder injection molded products are intact and injection molded with high quality. Gate design includes: 1. Determination of gate cross-sectional shape and size; 2. Choice of gate location. The location of the gate plays a decisive role in the shape of the melt flow front and the effect of holding pressure, so it also determines the strength and other properties of metal powder injection molded products. Shenzhen Best believes that the factors affecting the determination of the gate position include the shape, size, wall thickness, dimensional accuracy, appearance quality and mechanical properties of the product. In addition, the processing of the gate, demolding, and the difficulty of removing the gate should also be considered. The correct gate position can avoid those foreseeable problems. According to the characteristics of different metal powder injection molded products, Shenzhen Best compares the differences between various types of gates and introduces the advantages and disadvantages of the gate position and its structure. In the design of metal powder injection molding molds, according to the structure and characteristics of the gate, the commonly used gate forms are as follows: 1. Straight gate: It is a mainstream gate, which is a non-limiting gate. (1) Advantages: The plastic melt enters the cavity directly from the large end of the main channel, so it has the characteristics of low flow resistance, short flow and long replenishment time. Such a gate has a good melt flow state, and the melt flows from the center of the bottom surface of the cavity to the parting surface, which is conducive to exhaust; this gate form makes the metal powder injection molded products and the pouring system on the parting surface The projection area is very small, the mold structure is compact, and the metal powder injection molding machine is evenly stressed. (2) Disadvantages: There is a large residual stress at the feed, which can easily lead to warpage and deformation of metal powder injection molded products. At the same time, the gate is large, it is difficult to remove the gate traces and the traces are large, which affects the appearance, so this type of pouring Metal powder injection molding manufacturers are mostly used for injection molding of large and medium-sized long-flow, deep cavity, cylindrical or shell metal powder injection molding products, especially suitable for high viscosity plastics such as polycarbonate and polysulfone. In addition, this type of gate is only suitable for single cavity molds. When metal powder injection molding manufacturers design such gates, in order to reduce the gate area where they come in contact with metal powder injection molded products and prevent defects such as shrinkage and deformation, on the one hand, the mainstream with a smaller taper should be used as much as possible. Road cone angle (2 ~ 4 °), on the other hand, the thickness of the fixed template and fixed mold base should be minimized. 2. Side gate: The side gate is called a standard gate in foreign countries. The side gate is generally opened on the parting surface.The plastic melt fills the mold cavity from the inside or the outside.The cross-sectional shape is mostly rectangular (flat groove).Change the gate width and thickness to adjust the shear rate and pouring of the melt. The freezing time of the mouth. This type of gate can choose its position according to the shape characteristics of metal powder injection molded products, and it is convenient to process and trim, so it is widely used. (1) Advantages: The gate cross section is small, which can reduce the consumption of molten material in the pouring system, the gate is easily removed, and the trace is not obvious. Shenzhen Best believes that this gate is suitable for metal powder injection molding products of various shapes, but it is not suitable for metal powder injection molding products of slender barrel shape. (2) Disadvantages: Metal powder injection molded products and gates cannot be separated on their own, there are welding marks, metal powder injection molding pressure loss is large, which is unfavorable for the exhaust of deep cavity metal powder injection molded products. 3. Fan-shaped gate: generally opened on the parting surface, feeding from the outer side of the cavity, the gate gradually widens in the feeding direction, and the thickness gradually decreases. The wave front of the plastic melt entering the cavity from the gate is relatively straight, which can reduce warpage and deformation, and is suitable for forming a plate-shaped plastic product with a large width. 4. Thin gate: also known as flat seam gate. The distribution runner of the gate is parallel to the side of the cavity, and its length is usually greater than the width of the plastic product. (1) Advantages: The plastic melt enters the cavity uniformly at a low speed through the thin gate. Shenzhen Best believes that its material flow is parallel, which can avoid warpage and deformation, and is commonly used to form flat large-area thin walls. Metal powder injection molded products. (2) Disadvantages: It is difficult to remove the gate, which increases the production cost of metal powder injection molded products. 5. Ear protector gate: mainly used for highly transparent flat metal powder injection molded products and metal powder injection molded products with small deformation requirements. (1) Advantage: The ear protection gate is provided with ear grooves on the side of the cavity, and the melt generates frictional heat on the side of the ear groove through the gate impact, thereby improving the fluidity. After adjusting the direction and speed, the ear grooves are uniform and Entering the cavity smoothly can avoid jet flow. (2) Disadvantages: gate removal is more difficult and gate traces are larger.