Release time：2021-11-05
General classification of moulds:
It can be divided into plastic mold and non plastic mold:
(1) Non plastic molds include: casting molds, forging molds, stamping molds, die-casting molds, etc.
A. Casting mold - faucet, pig iron platform
B. Forging die automobile body
C. Stamping die - computer panel
D. Die casting die - superalloy, cylinder block
(2) Plastic molds can be divided into:
A. Injection molding mold - TV shell, keyboard button (most widely used)
B. Blow mold - beverage bottle
C. Compression molding mold - bakelite switch, scientific porcelain bowl and dish
D. Transfer molding mold - integrated circuit products
E. Extrusion mold - glue cylinder, plastic bag
F. Thermoforming mold - transparent molding packaging shell
G. Rotary molding mold soft rubber doll toy
Injection molding is the most commonly used method in plastic processing. This method is applicable to all thermoplastics and some thermosetting plastics. The number of plastic products manufactured is unmatched by other molding methods. As one of the main tools of injection molding processing, the level of quality accuracy, manufacturing cycle and production efficiency in the injection molding process directly affects the product quality, output, cost and product update, It also determines the reaction ability and speed of enterprises in market competition.
The injection mold is composed of several steel plates and various parts, which are basically divided into:
A. Forming device (female die, male die)
B. Positioning device (guide post, guide sleeve)
C. Fixed device (I-shaped plate, code mold pit)
D. Cooling system (water delivery hole)
E. Thermostatic system (heating tube, heating wire)
F. Runner system (nozzle hole, runner groove, runner hole)
G. Ejection system (thimble, plunger)
According to different types of gating systems, molds can be divided into three categories:
(1) Large sprue mold: the runner and gate are on the parting line. When opening the mold, it is demoulded together with the product. The design is simple, the processing is easy, and the cost is low, so more people use the large sprue system for operation.
(2) Nozzle mold: the runner and gate are not on the parting line, but usually directly on the product. An additional set of nozzle parting line needs to be designed. The design is complex and the processing is difficult. Generally, the nozzle system should be selected according to the product requirements.
(3) Hot runner mold: the structure of this mold is roughly the same as that of the fine nozzle. The biggest difference is that the runner is located in one or more hot runner plates and hot runner pumps with constant temperature. There is no cold material for demoulding. The runner and gate are directly on the product. The runner does not need demoulding. This system is also known as the nozzle free system, which can save raw materials. It is suitable for the situation of expensive raw materials and high product requirements, and it is difficult to design and process, Mold cost is high.
Hot runner system, also known as hot runner system, is mainly composed of hot sprue sleeve, hot runner plate and temperature control electric box. Our common hot runner system includes two forms, which are divided into single point hot gate and multi-point hot gate. Single point hot sprue is a plastic mold that uses a single hot sprue sleeve to directly inject molten plastic into the mold cavity, which is suitable for a single cavity and single gate; Multipoint hot sprue refers to that the molten material enters each hot sprue sleeve through the branch of hot runner plate and then enters the mold cavity. It is suitable for single cavity multipoint feeding or multi cavity mold.
Advantages of hot runner system
(1) No nozzle material, no post-treatment, so that the whole molding process is fully automated, saving working time and improving work efficiency.
(2) Low pressure loss. The temperature of the hot runner is equal to that of the injection nozzle of the injection molding machine, which avoids the surface condensation of raw materials in the runner and reduces the injection pressure loss.
(3) The reuse of nozzle materials will degrade the plastic properties, and the use of hot runner system without nozzle materials can reduce the loss of raw materials and reduce the product cost. In the mold cavity, the temperature and pressure are uniform, the plastic parts bear little force and the density is uniform. Under a small injection pressure and a short molding time, products superior to general injection molding systems can be injected. Transparent parts, thin parts, large plastic parts or high demand plastic parts can better show their advantages, and smaller models can produce larger products.
(4) The hot nozzle adopts standardized and serialized design, and is equipped with a variety of nozzle heads for selection, with good interchangeability. The specially designed and processed electric heating coil has uniform heating temperature and long service life. The hot runner system is equipped with hot runner plate, temperature controller, etc., which is exquisite in design, wide in variety, easy to use, stable and reliable in quality.
Disadvantages of hot runner system application
(1) The closing height of the overall mold increases, and the overall height of the mold increases due to the installation of the hot runner plate.
(2) Thermal radiation is difficult to control. The biggest problem of hot runner is the heat loss of runner, which is a major problem to be solved.
(3) There is thermal expansion, thermal expansion and cold contraction, which should be considered in our design.
(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.
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