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Technical application of plastic mold

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development of
The various tools and products used in our daily production and daily life, ranging from the base of the machine tool, the body shell, to a small screw, button and the shell of various household appliances, are all closely related to the mold. The shape of the mold determines the appearance of these products, and the processing quality and precision of the mold also determines the quality of these products. Because of the different materials, appearance, specifications and uses of various products, molds are divided into non-plastic molds such as casting molds, forging molds, die-casting molds, and stamping molds, as well as plastic mold.

In recent years, with the rapid development of the plastics industry and the continuous improvement of the strength and precision of general and engineering plastics, the application range of plastic products is also expanding, such as: household appliances, instruments, construction equipment, automobile industry, In many fields such as household hardware, the proportion of plastic products is increasing rapidly. A reasonably designed plastic part can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily-use products continues to rise.

meaning
The general definition of mold: In industrial production, various presses and special tools installed on the press are used to make metal or non-metallic materials into parts or products of the required shape through pressure. Such special tools are collectively called molds.

Description of the injection molding process: A mold is a tool for producing plastic products. It is composed of several groups of parts, and there is a molding cavity in this combination. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, cooled and shaped in the cavity, and then the upper and lower molds are separated, and the product is ejected from the cavity and out of the mold through the ejection system, and finally the plastic mold is closed For the next injection, the entire injection molding process is carried out cyclically.

classification
A. Blow mold-beverage bottle
B. Compression molding mold-bakelite switch, scientific porcelain dishes
C. Injection molding mold-TV shell, keyboard buttons, electronic products, computer peripheral plastic products, toys, housewares (most commonly used)
D. Thermoforming mold-transparent molded packaging shell
E. Rotary forming mold-soft doll toy
F. Transfer molding mold-integrated circuit products
G. Extrusion mould-glue pipe, plastic bag

  • According to different types of gating system, molds can be divided into three categories:
    (1) Nozzle mold: runners and gates are not on the parting line, usually directly on the product, so it is necessary to design an additional set of nozzle parting lines, the design is more complicated and the processing is more difficult, and generally depends on the product requirements Fine nozzle system.
    (2) Large nozzle mold: The runner and gate are on the parting line and are demolded together with the product when the mold is opened. The design is the simplest, easy to process, and low cost, so more people use the large nozzle system to work.
    (3) Hot runner mold: The structure of this type of mold is roughly the same as that of the nozzle. The biggest difference is that the runner is in one or more hot runner plates and hot nozzles with constant temperature. There is no cold material demoulding, runner and pouring. The port is directly on the product, so the runner does not need to be demolded. This system is also called a nozzleless system, which can save raw materials. It is suitable for situations where raw materials are more expensive and products require higher requirements. Design and processing are difficult, and mold costs are higher.

Hot runner system, also known as hot runner system, is mainly composed of hot sprue sleeve, hot runner plate and temperature control electric box. Our common hot runner system has two forms: single-point hot gate and multi-point hot gate. The single-point hot gate uses a single hot sprue sleeve to directly inject the molten plastic into the cavity. It is suitable for plastic mold with a single cavity and single gate; the multi-point hot gate branches the molten material to each The sub-heat sprue sleeve then enters the cavity, which is suitable for single cavity multi-point feeding or multi-cavity molds.

  • Advantages of hot runner system
    (1) No nozzle material, no need for post-processing, so that the entire molding process is fully automated, saving working time and improving work efficiency.
    (2) The pressure loss is small. The temperature of the hot runner is equal to the nozzle temperature of the injection molding machine, which avoids the surface condensation of the raw materials in the runner, and the injection pressure loss is small.
    (3) The repeated use of the nozzle material will degrade the performance of the plastic, and the use of the hot runner system without nozzle material can reduce the loss of raw materials, thereby reducing product costs. The temperature and pressure in the cavity are uniform, the stress of the plastic part is small, and the density is uniform. Under a small injection pressure, a shorter molding time can produce better products than ordinary injection molding systems. For transparent parts, thin parts, large plastic parts or high-demand plastic parts, it can show its advantages, and can produce larger products with smaller models.
    (4) The hot nozzle adopts standardized and serialized design and is equipped with various nozzle heads to choose from, which has good interchangeability. The uniquely designed and processed electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plates, thermostats, etc., with exquisite design, diverse types, convenient use, and stable and reliable quality.

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