Technology application
development
All kinds of tools and products we use in our daily production and life are closely related to molds, from the base of the machine tool, the shell of the machine body, the small screw, button and the shell of various household appliances. The shape of the mold determines the shape 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, the mold is divided into casting mold, forging mold, die casting mold, stamping mold and other non plastic mold, as well as plastic mold.
In recent years, with the rapid development of plastic industry and the continuous improvement of 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 other fields, the proportion of plastic products is increasing rapidly. A well-designed plastic part can often replace multiple traditional metal parts. The plastic trend of industrial products and daily-use products is on the rise.
meaning
General definition of mold: in industrial production, metal or non-metallic materials are made into parts or products with required shape by using various presses and special tools installed on the press. This special tool is collectively referred to as mold.
Injection molding process description: mold is a tool to produce plastic products. It is composed of several groups of parts, and the combination has a forming cavity. During injection molding, the mold is clamped on the injection molding machine, and the molten plastic is injected into the injection mold cavity, and cooled and shaped in the cavity. Then, the upper and lower molds are separated, and the products are ejected from the mold cavity through the ejection system. Finally, the mold is closed for the next injection. The whole injection process is cyclic.
classification
A. Injection molding mold -- TV shell, keyboard and button, electronic products, computer peripheral plastic products, toys, household products (most commonly used)
B. Blowing mold -- beverage bottle
C. Compression molding mould: bakelite switch, scientific porcelain bowl and dish
Automobile bumper mold
Automobile bumper mold
D. Transfer molding die -- integrated circuit products
E. Extrusion molding mould -- glue pipe and plastic bag
F. Thermoforming mould -- transparent packaging shell
G. Rotary molding mold -- soft rubber doll toy
According to the different types of gating system, the mould can be divided into three types
(1) Large gate mold: the runner and gate are on the parting line, and demould together with the product when opening the mold. The design is the simplest, easy to process, and the cost is low. Therefore, many people use the large water gate system for operation.
(2) Fine nozzle mold: the runner and gate are not on the parting line, but directly on the product. Therefore, it is necessary to design an additional set of nozzle parting lines. The design is more complicated and the processing is more difficult. Generally, the fine nozzle system should be selected according to the product requirements.
(3) Hot runner mold: this kind of mold structure is roughly the same as the fine nozzle, its biggest difference is that the runner is located in one or more hot runner plates and hot pump mouth with constant temperature, there is no cold material demoulding, the runner and gate are directly on the product, so the runner does not need demoulding. This system is also called no nozzle system, which can save raw materials, and is suitable for the situation of expensive raw materials and high product requirements However, it is difficult to design and process, and the mold cost is high.
Hot runner system, also known as hot runner system, is mainly composed of hot runner 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 runner. Single point hot gate is to use a single hot gate sleeve to directly inject the molten plastic into the mold cavity, which is suitable for the plastic mold with single cavity and single gate; the multi-point hot gate is to branch the molten material into each sub Heat Gate sleeve and then into the cavity through the hot runner plate, which is suitable for single cavity multi-point feeding or multi cavity mold
Advantages of hot runner system
(1) No water mouth material, no need for post-processing, so that the entire molding process is fully automated, save working time and improve work efficiency.
(2) The pressure loss is small. The temperature of the hot runner is equal to that of the nozzle of the injection molding machine, which avoids the surface condensation of the raw materials in the runner and reduces the injection pressure loss.
(3) The reuse of nozzle material will degrade the properties of plastic, but the use of hot runner system without nozzle material can reduce the loss of raw materials and reduce the cost of products. In the mold cavity, the temperature and pressure are uniform, the stress of plastic parts is small, and the density is uniform. Under the small injection pressure and short molding time, the injection molding can produce better products than the general injection molding system. 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 machines.
(4) The hot nozzle adopts standardized and series design, equipped with various nozzle heads for selection, and has good interchangeability. The electric heating ring with unique design and processing can achieve uniform heating temperature and long service life. The hot runner system is equipped with hot runner plate, temperature controller, etc., with exquisite design, various types, convenient use, stable and reliable quality.
Deficiency of hot runner system application
(1) The closing height of the whole mold is increased, and the overall height of the mold is increased due to the installation of hot runner plate.
(2) Thermal radiation is difficult to control, the biggest problem of hot runner is the heat loss of runner, which is an important issue to be solved.
(3) The existence of thermal expansion, thermal expansion and cold contraction is the problem we should consider when designing.
(4) The increase of mold manufacturing cost and the high price of standard accessories of hot runner system affect the popularity of hot runner mold.
