1, the introduction
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 various kinds of household appliances shell, which has close relationship with mould. Mould shape determines the shape of the products, precision mold processing quality and also determines the quality of these products. Because the products all kinds of material, appearance, specifications and usage of different, mould into casting die, forging die, plastic injection mold, die-casting mould, stamping die, etc, as well as plastic mold.
In recent years, with the rapid development of plastic industry and general engineering plastic in the aspects of improving strength and precision, the application range of the plastic products are also growing, such as: household electrical appliances, instrumentation, construction equipment, many fields such as automotive industry, daily hardware, plastic products such as the proportion of is rapidly increasing. A rational design of plastic parts often can replace more traditional metal pieces. Industrial products and daily products rising trend of plastic.
General definition: 2, mold in the industrial production, with all kinds of press and in a pressure on the special tool, metallic or non-metallic materials produced through pressure required shape parts or products, this kind of special tools are collectively referred to as mold.
Description: 3, injection molding process is a production of plastic products mould tool. It consists of several groups of parts, the combination with molding cavity. Clamped injection molding, mold in injection molding machine, the molten plastic is injected molding die cavity, and the cavity cooling stereotypes, and then separated from mould, through the ejector system will be products from the mold cavity ejector left, the last mould and closed for the next injection, the injection molding process is a cycle.
4, mold of the general classification: can be divided into the plastic mold and plastic mold:
Plastic injection mold are: (1) the casting die, forging die, stamping die, die mold etc.
A. the casting mould, cast iron platform - tap
B. forging die, car body
C. stamping mold, computer panels
Die casting - d. super alloy, the cylinder body
(2) plastic moulds according to the different production technology and production products is divided into:
A. injection molding die, TV shell, keyboard button (the most common application)
B. blow mold - beverage bottle
C. bowls disc compression molding mold, bakelite switches, science
D. transfer molding mould, IC products
E. extrusion die - glue tube, plastic bags
F. thermoforming mould, transparent packaging shell molding
G. rotational molding mold, soft plastic doll toys
Pieces of injection molding is the most widely used in plastic processing methods. This method is applicable to all thermoplastics and some thermosetting plastic, made of plastic products 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 product quality, yield, cost and product updates, at the same time also determines the enterprise in competition in the market response capacity and speed.
Pieces of injection mold is made up of several pieces of steel plate with various parts, basic is divided into:
A forming device (die and punch)
B positioning device, guide pin, guide sleeve)
C fixtures (h board, code modules pit)
D cooling system (hole)
E thermostatic system (heating tube, hot line)
F runner system (pumping, nozzle hole flow channel slot and port holes)
G ejection system (thimble, top stick)
5, depending on the system of pouring system type mould can be divided into three categories:
Gate mold (1) : the runner and gate on the parting line, together with product when open mold demoulding, design simple, easy processing, low cost, so more people with big nozzle system operation.
(2) nozzle mould, runner and sprue is not in the parting line, generally directly on the product, so to design a set of shuikou parting line, design is relatively complex, processing more difficult, depending on product requirements and choose fine nozzle system.
(3) the hot runner mold: this kind of mold is approximately the same structure and fine shuikou, the difference is the biggest port in one or more heat flow but with constant temperature and heat pumping mouth, no cold feeding demoulding, runner and sprue directly on the product, so the port don't need mold release, also known as no nozzle system, the system can save raw materials, applicable to the raw material is more expensive, high requirement of products, design and processing difficulties, the mold cost is higher.
Hot runner system, also known as hot runner system, mainly composed of hot runner, hot water, but temperature control electric box. Our common hot runner system with single point hot runner and hot runner 2 more forms. Single point gate is to use a single hot runner set the molten plastic into the cavity directly, it is a single cavity of a single gate plastic mould; Multipoint hot sprue is by hot water but the molten material branch to the hot runner set in again into the cavity, it is suitable for single cavity more into the material or multi-cavity mould.
Pieces of hot runner system advantage
(1) no shuikou expected, don't need after processing, make the whole process fully automated molding, save the working time, improve work efficiency.
(2) the pressure loss is small. Hot runner temperature and the injection molding machine nozzle equal temperature, avoid the material surface condensation phenomenon within the runner, minimum loss in injection pressure.
(3) material floolwing repeated use can make plastic performance degradation, while the use of hot runner system no 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 a smaller injection pressure, the shorter molding, 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 machine to produce larger products.
(4) hot nozzle adopt standardization and seriation design, equipped with a variety of selection of the nozzle head, good interchangeability. Unique design processing electric heating coil, heating temperature uniformity can be obtained, 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.
Pieces of hot runner system deficiencies
(1) the whole die shut height increasing, because of 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 an important subject need to solve.
(3) thermal expansion, heat bilges cold shrink is our design problem to consider.
(4) mold manufacturing costs have gone up, the hot runner system standard spare parts price is higher, affect the popularity of hot runner molds.