How to choose the spring intercepting nozzle 0 of

2022-08-13
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How to choose the spring shut-off nozzle of injection molding machine

the spring shut-off nozzle is easy to install and maintain, so it is widely used in the field of injection molding, especially in low viscosity material injection and vertical injection. However, many users do not know how to choose the appropriate nozzle model and specification very well, which often leads to improper selection. 9. Ensure that the driving air is clean and dry. Improper model selection may lead to difficulties in injection molding, lower than expected nozzle life, lower production efficiency and product quality, and even destroy the nozzle structure in a short time, resulting in unnecessary waste of human and material resources

type and application

according to the different interception methods, the spring interception nozzle can be divided into needle interception and bolt interception

1. Needle type intercepting spring nozzle

this type of nozzle is the most commonly used and well-known type by users. Its applicable occasions include: during the whole injection molding process, salivation and filaments are not allowed at the nozzle mouth; It is required to adopt the production process of taking materials while opening the mold and pre molding (or storing materials) at the same time, so as to shorten the production cycle; During foaming molding, the nozzle is required to be closed reliably to prevent foaming agent from foaming in the material pipe; After the end of the previous the first mock examination, there should be no cold material left at the front end of the nozzle mouth, so as not to affect the product quality of the next the first mock examination

in order to improve aerodynamics Figure 1 the use of needle type intercepting nozzle can eliminate the residual cold head produced by the open nozzle

needle type intercepting spring nozzle mainly has two types: inner spring type and outer spring type. The maximum working temperature of the former is 350 ℃, and the maximum injection pressure does not exceed 200MPa; In order to seek a longer-term future, the latter is suitable for occasions with a maximum working temperature of 400 ℃ and a maximum injection pressure of no more than 300mpa. For example, when used in the molding of conventional PA materials, the inner spring nozzle is usually competent, but when used in LCP or Teflon materials with higher molding temperature, the outer spring nozzle is more suitable

2. Bolt type intercepting spring nozzle

compared with needle type nozzle, this kind of nozzle does not have the function of preventing filaments. It is usually used in micro injection occasions, and the injection rate is generally less than 45cm3/s, and the screw diameter is less than 20mm. For micro injection molding process, salivation will affect the injection volume, injection accuracy and process repeatability

Fig. 2 inner spring needle type intercepting spring nozzle

basic principle of type selection

because plastic melt will produce additional shear when flowing through the spring intercepting nozzle, it is generally not recommended for users to use it in PVC injection occasions. In other words, only for non PVC injection occasions, spring intercepting nozzle should be considered. In addition, users should pay attention to the following points when selecting the type of spring intercepting nozzle:

1 Specify the application occasion to determine the nozzle type

2. The nozzle size is determined based on the maximum injection rate of the machine (based on PS). It is necessary to ensure that the injection pressure drop of the nozzle (in order to open the needle valve of the nozzle and maintain the opening of the nozzle, the pressure must be provided by the plastic melt, which will cause partial pressure loss of the melt) is maintained within the generally acceptable range, and to take into account the injection volume and the volume of the nozzle cavity as much as possible to ensure the stability of the injection process

Figure 3 outer spring needle type intercepting spring nozzle

3 In order to ensure the structural strength and service life of the nozzle, the maximum injection pressure of the machine and the maximum working temperature of the nozzle must be considered

4. A good nozzle design should fully consider the parts, so each face can only be formed once for wear resistance, and at the same time, dead corners should be avoided in the whole flow channel structure. In addition, the nozzle shall be able to withstand the long-term scouring of 30% glass fiber

5. Whether the nozzle can work normally is closely related to the advantages and disadvantages of its temperature control system, especially for occasions with high molding temperature and narrow temperature control range (requiring accurate temperature control). It is recommended to consult relevant professional manufacturers about how to select the appropriate type of heating ring and temperature measurement means

as the world's leading manufacturer of spring intercepting nozzles, Hezhuo nozzles can provide injection molding users with high-quality and economical needle and bolt products and related technical services

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