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Mould Technical application/ Blow molding machine
- Jul 03, 2018 -

Mould Technical application/ Blow molding machine


All the tools and products we use in our daily production and life are as large as the base of the machine tool, the casing of the fuselage, small to a head screw, button and the shell of a variety of household appliances, all of which are closely related to the mold. The shape of the mold determines the shape of these products, and the quality and accuracy of the mold determine the quality of these products. Because of the different material, appearance, specification and use of various products, the mould is divided into non plastic moulds, such as casting mould, forging die, die casting mould, stamping die, etc., and plastic moulds.
In recent years, with the rapid development of the plastic industry and the continuous improvement of the strength and precision of general and engineering plastics, the application scope of plastic products is also expanding, such as household appliances, instruments, building equipment, automobile industry, daily hardware and so on, and the proportion of plastic products is rapid. Increase. A reasonable design of plastic parts can often replace several traditional metal parts. The trend of plasticization of industrial products and daily products is increasing.


Meaning


General definition of the mold: in industrial production, with a variety of press and the special tools installed on the press, the metal or non metal materials are made out of parts or products of the desired shape through pressure. This special tool is known as a mold.
Injection molding process description: mold is a tool for the production of plastic products. It consists of several parts, with a cavity formed in it. In injection molding, the mold is clamped on the injection molding machine. The molten plastic is injected into the mold cavity, and the mold is cooled in the cavity. Then the upper and lower dies are separated. The products are ejecting from the top of the die cavity by the top out system. Finally the mold is closed for the next injection. The whole injection process is carried out in a cycle.


Classification


A. injection moulds -- TV housing, keyboard buttons, electronic products, computer peripherals plastic products, toys, household products (most commonly used)


B. blow mold - a beverage bottle


C. compression molding die - bakelite switch, scientific porcelain bowl dish.


D.
transfer molding - integrated circuit products


E. extrusion mould -- rubber hose and plastic bag


F.
thermoforming mold - transparent molding package shell


G. rotary mold - Soft Doll Toy



According to the difference of gating system, the mould can be divided into three types.


(1)
large water mouth mold: flow channel and gate in the mold line, and the product in the mold opening together with the mold, the design is the simplest, easy to process, low cost, so a lot of people use large water port system operation.


(2)
fine water mouth mold: flow channel and gate are not in the mold line, generally directly in the product, so we should design a group of water nozzle mold line, the design is more complex, processing is difficult, generally depending on the product requirements and select the fine water system.


(3)
hot runner mold: this kind of die structure is roughly the same as that of fine water. The biggest difference is that the flow channel is in one or more hot runner plates with constant temperature and hot pump mouth, no cold material is removed, the runner and gate are directly on the product, so the flow path does not need to be demoulding. This system is also called a water free system and can save the raw material. It is difficult to design and process for high quality raw materials and products, and the cost of mould is high.


The hot runner system, also known as the hot runner system, is mainly composed of a hot runner sleeve, a hot runner plate and a temperature controlled electric box. Our common hot runner system has two forms: single point hot runner and multi point hot runner. The single point hot gate is used to shoot the molten plastic into the cavity directly with a single hot gate sleeve. It is suitable for a single cavity single gate plastic mold. The multi point hot gate is used to branch the molten material into the mold cavity through the hot runner plate and then enter into the cavity. It is suitable for single cavity multi point feeding or multi cavity mold.

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Advantages of the hot runner system


(1) no water outlet material, no need for post-processing, so that the entire molding process is fully automated, saving working hours and improving work efficiency.


(2)
the loss of pressure is small. The temperature of the hot runner is equal to the temperature of the injection nozzle of the injection molding machine, so that the surface condensation phenomenon of the raw material in the runner is avoided, and the injection pressure loss is small.


(3)
the reuse of the nozzle material will degrade the properties of the plastic, and the use of the hot runner system can reduce the loss of the raw material and reduce the cost of the product. In the cavity, the temperature and pressure are uniform, the plastic part stress is small and the density is uniform. Under the small injection pressure, the injection molding is better than the general injection molding system during the shorter molding time. For transparent parts, thin parts, large plastic parts or high requirement plastic parts, it can show its advantages and produce larger products with smaller models.


(4)
the heat nozzles are standardized and serialized, and are equipped with various nozzle heads with good interchangeability. The unique design and processing of the electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plate, temperature controller and so on. It has many advantages such as ingenious design, various kinds, convenient use and stable and reliable quality.


The disadvantages of the hot runner system


(1)
the overall height of the die is increased, and the overall height of the mold is increased due to the addition of hot runner plates.


(2) heat radiation is difficult to control. The main problem of hot runner is the heat loss of runner, which is a major issue to be solved.


(3)
thermal expansion, thermal expansion and cold shrinkage are the problems we should consider when designing.


(4)
the cost of mold manufacturing increases, and the price of standard parts of hot runner system is higher, which affects the popularity of hot runner mold.