Injection hot injection nozzle classification
As a key component of the hot runner system, there are many types of injection molding hot nozzles. Different types of hot nozzles are suitable for different injection molding scenarios and material properties. According to the structural form, injection molding hot nozzles can be divided into two categories: open hot nozzles and needle valve hot nozzles. The open hot nozzle has a simple structure and low cost. It is suitable for the production of plastic parts that do not require high gate marks, such as daily necessities and industrial accessories. Its characteristic is that the hot nozzle is directly connected to the mold cavity, and the melt enters the mold cavity directly through the nozzle, and the gate mark is relatively obvious. For example, when a factory produces PP plastic barrels, it uses an open hot nozzle, which not only reduces the mold cost but also meets the product’s usage requirements.
Needle-valve hot-shooting nozzles control the opening and closing of the gate through the movement of a needle valve, effectively eliminating gate marks and improving the appearance quality of the plastic part. They are suitable for producing plastic parts with high aesthetic requirements, such as automotive interiors and electrical appliance housings. The needle valve of a needle-valve hot-shooting nozzle is typically driven by an oil or air cylinder, precisely controlling the opening and closing time of the gate, facilitating the control of the melt filling and pressure-holding process. An automotive interior manufacturer uses a needle-valve hot-shooting nozzle in the production of instrument panels, making the gate marks on the instrument panel surface virtually invisible. This significantly improves the product’s appearance and enhances its market competitiveness.
Based on the heating method, injection molding hot nozzles can be divided into internally heated and externally heated types. Internally heated nozzles have the heating element located inside the nozzle, resulting in minimal heat loss, high heating efficiency, and precise temperature control. They are suitable for processing temperature-sensitive materials such as PVC and POM. However, their disadvantages are their relatively complex structure and increased maintenance difficulties. A chemical plant uses internally heated nozzles in the production of PVC pipe fittings. This allows for precise control of the melt temperature, preventing PVC decomposition due to excessive temperatures, and achieving a product qualification rate exceeding 99%.
Externally heated hot nozzles, with the heating element wrapped around the nozzle, offer a simple structure, easy maintenance, and low cost. They are suitable for processing most common plastics, such as PE, PP, and ABS. However, because heat is easily transferred to the mold, heat loss is significant, resulting in relatively low temperature control accuracy. A toy factory using an externally heated hot nozzle in the production of PE toys not only reduced mold manufacturing costs but also met production requirements and achieved higher production efficiency.
In addition, there are some special types of injection molding hot nozzles, such as micro hot nozzles, multi-gate hot nozzles, and high-temperature hot nozzles, depending on the applicable materials and the characteristics of the plastic parts. Micro hot nozzles are suitable for the production of small precision plastic parts, such as electronic connectors and medical device parts. Their gate diameter can be as small as 0.5mm or less, and they can precisely control the filling of the melt. Multi-gate hot nozzles have multiple gates on a single nozzle and are suitable for the production of large or complex plastic parts. They allow the melt to evenly fill the mold cavity and reduce internal stress in the plastic part. High-temperature hot nozzles are suitable for processing high-temperature engineering plastics such as PEEK and PI. Their operating temperature can reach over 400°C, ensuring good fluidity of high-temperature materials. An aerospace company uses high-temperature hot nozzles to produce PEEK parts, ensuring the fluidity and stability of the material during the molding process and meeting the high-performance requirements of the parts.
