The structure of the hot runner mold is generally the same as that of the thin nozzle. The biggest difference is that the runner is located in one or more hot runner plates and hot nozzles with constant temperature. There is no cold material demoulding, the runner and gate are directly on the product.
Therefore, the runner does not need to be demolded. This system is also known as the nozzleless system, which can save raw materials. It is suitable for the product that the raw materials are expensive and the product requirements are high.
Hot runner system, also known as hot sprue system, is mainly composed of hot runner sleeve, hot runner plate and temperature control electric box. There are two types of hot runner system: single point hot sprue and multi-point hot sprue.
Single-point hot sprue is to use a single hot sprue sleeve to inject molten plastic into the cavity directly. It is suitable for plastic molds with single-cavity and single-gate; multi-point hot-gate is to branch the molten material to each through hot runner plate. It is suitable for single cavity multi-point feeding or multi-cavity mold.
Advantages of hot runner systems
1. No regrind material, no post-processing is needed, the entire molding process is fully automated, saving working time and improving work efficiency.
2. Low pressure loss. The hot runner temperature is same as the nozzle temperature of the injection molding machine, which avoids the condensation of the raw material on the surface of the runner and reduces the loss of injection pressure.
3. Reuse of regrind material can improve the degradation of plastic performance, while the use of hot runner system without nozzle materials can reduce the consumption of raw materials and thus reduce product costs.
4. In the cavity, the temperature and pressure are uniform, the plastic parts have low stress and uniform density, and the molding in series is continuous under a small injection pressure. For transparent parts, thin parts, large plastic parts or highly demanding plastic parts, it can show its advantages, and can produce bonded products with a small number of sheets.
5. The thermal nozzle adopts standardized and serialized design and adopts various alternative nozzle tips, which has good interchangeability. Uniquely designed and processed electric heating coil can achieve uniform heating temperature and replace long.
Disadvantages of Hot Runner System Applications
1. The overall mold closing height is increased, and the overall height of the mold has increased due to the installation of hot runner plates.
2. Heat radiation is difficult to control. The biggest problem of hot runner is the heat loss of runner, which is a major problem to be solved.
3. There is thermal expansion, thermal expansion and contraction are issues to be considered in our design.
4. The increase of mold manufacturing cost and the high price of standard accessories of the hot runner system have affected the popularity of hot runner molds.
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