2015年3月2日星期一

The basic knowledge of injection mould and technical application

That we use in our daily life and production to the various tools and products, to the base of the machine tool, the fuselage shell, small to a germ head screws, buttons, and all kinds of household appliances shell, which has close relation with the mould. The shape of the die decides the shape of the products, precision mold processing quality and determines the quality of these products. Because the material of all kinds of products, appearance, specifications, and different purposes of mould into casting die, forging die, die-casting mould, stamping mould of plastic moulds, such as, and plastic moulds.
In recent years, with the rapid development of plastic industry and general engineering plastics in the aspects of improving strength and precision, the application range of the plastic products are also constantly expanding, such as household appliances, instrumentation, construction equipment, automotive industry, daily hardware, and many other fields, proportion of plastics is rapidly increasing. A reasonable design of plastic parts often can replace more traditional metal pieces. Industrial products and daily products rising trend of plastic.


Injection molding is the most widely used method in plastic processing. This method is applicable to all thermoplastics and part of thermosetting plastics, plastic products made the great number of them is the other forming methods of dust, as the main tool of injection molding processing, one of the injection mould, the quality of precision, manufacturing cycle and injection molding production efficiency in the process of the level of high and low, directly affect the product quality, yield, cost and product updates, at the same time also determines the enterprise in the market competition ability and speed of reaction.

Injection mould is made up of several steel plate with various parts, basic is divided into:
A forming device (die, die)
B positioning device (guide pin, guide sleeve)
C fixtures (h board, code die hole)
D cooling system (hole)
E thermostatic system (heating tube, hot line)
F runner system (pumping of nozzle hole flow channel slot and port holes)
G ejection system (thimble, top stick)

5, depending on the system of pouring system type of mould can be divided into three categories:
(1) the gate of mould, the runner and gate on the parting line, together with the product in the mould stripping, the simplest design, easy processing, low cost, so more people using gate system operation.
(2) nozzle mould: the runner and gate is not the parting line, generally directly on the product, so to design a set of shuikou parting line, design is relatively complex, processing more difficult, often depending on the product requirements to choose fine runner system.
(3) the hot runner mold: this kind of mold is approximately the same structure and fine shuikou, the biggest difference is that flow into one or more of the temperature of heat flow but and heat pumping mouth, no cold feeding demoulding, runner and gate directly on the product, so the port don't need mold release, also known as no runner system, this system can save raw materials, applicable to the raw material is more expensive, high requirement of products, design and processing difficulties, mould cost is high. Hot runner system, also called hot runner system, mainly composed of hot runner, hot water but, temperature control box. Our common hot runner system there is a single point of hot runner and hot runner 2 more forms. Single point gate is to use a single hot runner of the molten plastic into the cavity directly, it is a single cavity of a single gate of plastic mold; Multipoint hot runner by hot water but the molten material branch to various points in the hot runner set into the cavity, it is suitable for single cavity more into the material or multi-cavity mold

The advantage of hot runner system


1) material floolwing does not need after processing, the whole forming process is fully automated, save the working time, improve work efficiency.

(2) the pressure loss is small. Hot runner temperature and the temperature of the plastic injection machine nozzle is equal, to avoid the surface of the material in the runner, condensate loss in injection pressure.

(3) material floolwing repeated use can make plastic performance degradation, and the use of hot runner system is not shuikou expected, can reduce the loss of raw materials, thereby reducing the product cost. Uniform temperature and pressure in the cavity, plastic stress is small, uniform density, in smaller injection pressure, the shorter the forming time, injection molding injection system is better than the general products. For transparent, thin pieces, large plastic parts or high demand parts can show its advantage more, and with small models produce larger products.
(4) hot nozzle adopt standardization, seriation design, equipped with a variety of selection of the nozzle head, good interchangeability. Unique design and processing of electric heating circle, can achieve uniform heating temperature, long service life. Hot runner system is equipped with heat flow but, thermostat, etc., the design is exquisite, species diversity, use convenient, stable and reliable quality.

Application of hot runner system deficiencies
(1) the whole mould height increasing, by adding hot water but, mold the overall height increase.
(2) the thermal radiation is hard to control, is the biggest trouble of hot runner gating heat loss, is a major issue to solve.
(3) thermal expansion, heat bilges cold shrink is to consider when we design problem.

(4) the mold manufacturing costs have gone up, hot runner system standard accessories price is higher, affect the popularity of hot runner mold.

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