Basic knowledge and technical application of plastic mold
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Basic knowledge and technical application of plastic mold

Author:小编    Release date:2021-08-20 11:34:10     Number of views :

All kinds of tools and products used in our daily life are large enough for the base of the machine tool, the shell of the fuselage, and the outer shell screws, buttons and the housing of all kinds of household appliances, all of which are closely related to the mold. The shape of the mould determines the shape of these products. The quality and precision of the mold are determined by the quality of the products. Because all kinds of products have different materials, appearance, specifications and uses, molds are divided into casting moulds, forging dies, die-casting dies, stamping dies and other plastic moulds, and plastic moulds.

In recent years, with the rapid development of plastic industry and general and engineering plastics in the continuous improvement of the intensity and precision, the application of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, many fields of automobile industry, daily hardware, the proportion of plastic products is rapidly increasing. A reasonable design of plastic parts can often replace a number of traditional metal parts. The trend of the plastic production of industrial products and daily products is increasing.

2, the general definition of molds: in industrial production, all kinds of presses and special tools installed on the press are used to produce parts or products of the desired shape by pressing metal or non-metallic materials. This special tool is collectively referred to as dies.

3. The injection molding process shows that the mold is a tool for the production of plastic products. It consists of several parts, which have a molding cavity. Injection molding, mold clamping in injection molding machine, the molten plastic is injected into the molding cavity, and cooling in the cavity shape, and then die down to separate out the system through the top products from the top of the left mold cavity, the mold is closed again for the next injection, the injection molding process is carried out of the cycle.

4, the general classification of the mold: can be divided into plastic mold and non plastic mold:

1) non plastic moulds are: casting mould, forging die, stamping die, die casting die and so on.

A. casting mould -- water faucet and pig iron platform

B. forging die - car body

C. stamping die - computer panel

D. die casting mould -- superalloy, cylinder body

2) the plastic mold is divided into the production process and the production product.

A. injection molding - TV shell, keyboard button (most commonly used)

B. blow mold - a beverage bottle

C. compression molding, bakelite switch, science 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 molding -- soft toy doll

Injection molding is the most commonly used method in plastic processing. This method is applicable to all parts of thermoplastic and thermosetting plastics, the number of plastic products obtained large than other forming methods, as one of the main tools of injection mold injection molding processing, production efficiency and the level of quality in accuracy, manufacturing cycle and injection molding process, directly affect the cost and the product quality, yield, update, and also determines the response ability and speed in the market competition.

The injection mold is composed of several pieces of steel plate with various parts, which are basically divided into:

A forming device (concave die, punch)

B positioning device (guide, guide sleeve)

C fixtures (i-board, code pits)

D cooling system (water transport hole)

E constant temperature system (heating pipe, hotline)

F runner system (Jack Tsui hole channels, channel hole)

G ejection system (thimble, top stick)

5. The mold can be divided into three types according to the different casting system.

1) the big water outlet mold: the runner and gate are on the parting line, and the product is demoulding with the product when opening the mould. The design is the most simple, easy to process and the cost is low, so many people use the big water system operation.

2) the fine nozzle mold: the runner and gate are not on the parting line, usually directly on the product, so we need to design more than one group of water outlet parting line, the design is more complex, and the processing is more difficult. Generally, we need to select the fine nozzle system according to the product requirements.

3): this kind of hot runner mold mold structure and fine nozzle is roughly the same, the biggest difference is the flow in one or more of the constant temperature hot runner plate and heat pump mouth, no cold material stripping, runner and gate directly on the product, so the channel need not release, this system also called a gate system, can save raw materials, suitable for raw materials more expensive, higher requirements of products, design and processing difficulties, the mold cost is higher.

The hot runner system, also known as the hot runner system, is mainly composed of a hot gate sleeve, a hot runner plate, and a temperature controlled electric box. The common hot runner system has two forms of single point hot gate and multi point hot gate. Single point hot runner is a single heat gate directly to the molten plastic into the cavity, which is suitable for plastic mould cavity single single gate; multipoint hot runner hot runner plate by molten material to the branched heat gate again into the cavity, it is suitable for single cavity multi point feeding or multi cavity mold

The advantages of the hot runner system

1) no water mouth material, do not need post processing, make the whole forming process complete automation, save working time, improve work efficiency.

2) the pressure loss is small. The temperature of the hot runner is equal to the injection temperature of the injection machine, which avoids the condensation phenomenon of the surface of the raw material in the runner, and the loss of injection pressure is small.

3) the repeated use of water will make the performance of plastics degraded, while the use of hot runner system can not reduce the loss of raw materials and reduce the cost of products. In the cavity, the temperature and pressure are uniform, and the stress of the plastic parts is small and the density is uniform. Under smaller injection pressure, a better product is injected in the shorter molding time than the general injection system. For transparent parts, thin parts, large plastic parts or high requirements for plastic parts, the advantages can be shown more, and larger products can be produced with smaller models.

4) the hot nozzle is standardized and serialized, with all kinds of nozzle head which can be chosen, and the interchangeability is good. The unique design and processing electric heating ring can achieve uniform heating temperature and long service life.  The hot runner system is equipped with hot runner plate, thermostat and so on. The design is exquisite, the variety is varied, the use is convenient, the quality is stable and reliable.

Inadequacies of the application of the hot runner system

1) the height of the whole die is increased, and the overall height of the die is increased because of adding hot runner plate and so on.

2) the heat radiation is difficult to control. The biggest problem of the hot runner is the heat loss of the runner. It is a major problem to be solved.

3) the existence of thermal expansion, thermal expansion and contraction is a problem to be considered in our design.

4) the cost of mould manufacturing is increased, and the standard parts of the hot runner system are more expensive, which affects the popularity of hot runner mold.

technical support : Ju Shang Juyou information technology