1. Introduction: All kinds of tools and products we use in our daily production and life, ranging from the base of the machine tool, the shell of the machine body, to the shell of a blank head screw, button and various household appliances, are all related to the mold. close relationship. The shape of the mold determines the shape of these products, and the processing quality and precision of the mold also determine the quality of these products. Due to the different materials, appearance, specifications and uses of various products, molds are divided into non-plastic molds such as casting molds, forging molds, die-casting molds, stamping molds, and plastic molds.
In recent years, with the rapid development of the plastics industry and the continuous improvement of the strength and precision of general-purpose and engineering plastics, the application scope of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, automobile industry, daily In many fields such as hardware, the proportion of plastic products is increasing rapidly. A well-designed plastic part can often replace multiple traditional metal parts. The trend towards plasticization of industrial and daily products is on the rise.
2. General definition of mold: In industrial production, various presses and special tools mounted on the press are used to make metal or non-metallic materials into parts or products of the desired shape through pressure. Such special tools are collectively referred to as mold.
3. Description of the injection molding process: The mold is a tool for producing plastic products. It consists of several sets of component parts, which have forming cavities within this set. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, and cooled and shaped in the cavity, and then the upper and lower molds are separated, and the product is ejected from the cavity through the ejection system to leave the mold, and finally the mold is closed again. For the next injection, the entire injection process is cyclic.
4. General classification of molds: It can be divided into plastic molds and non-plastic molds:
(1) Non-plastic molds include: casting molds, forging molds, stamping molds, die-casting molds, etc.
A. Casting molds - faucets, pig iron platforms
b. Forging die - car body
C. Stamping Dies - Computer Panels
D. Die Casting Die - Super Alloy, Cylinder Block
(2) Plastic molds are divided into:
A. Injection molding mold - TV casing, keyboard buttons (the most common application)
b. Blow mold - beverage bottle
C. Compression molding molds - bakelite switches, scientific porcelain dishes
D. Transfer Molding - Integrated Circuit Products
E. Extrusion Dies - Glue Tubes, Plastic Bags
F. Thermoforming molds - transparent molding packaging shells
G. Rotary forming mold - soft doll toy
Injection molding is the most commonly used method in plastics processing. This method is suitable for all thermoplastics and some thermosetting plastics. The number of plastic products produced is beyond the reach of other molding methods. As one of the main tools for injection molding, the injection mold has a great impact on quality accuracy, manufacturing cycle and injection molding process. The level of production efficiency in China directly affects the quality, output, cost and product renewal of products, and also determines the response ability and speed of enterprises in market competition.
The injection mold is composed of several steel plates with various parts, which are basically divided into:
A Forming device (die, punch)
B positioning device (guide post, guide bush)
C Fixing device (I-shaped plate, code mold pit)
D Cooling system (water port)
E constant temperature system (heating tube, heating wire)
F runner system (spout hole, runner groove, runner hole)
G ejector system (thimble, ejector)
5. According to the different types of pouring systems, the molds can be divided into three categories:
(1) Large nozzle mold: The runner and gate are on the parting line, and the mold is released together with the product when the mold is opened. The design is the simplest, easy to process, and the cost is low. Therefore, many people use the large nozzle system for operation.
(2) Small nozzle mold: The runner and gate are not on the parting line, and are generally directly on the product. Therefore, it is necessary to design more than one set of nozzle parting lines. The design is more complicated and the processing is more difficult. Generally, it should be selected according to the requirements of the product. Fine nozzle system.
(3) Hot runner mold: The structure of this type of mold is basically 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 nozzles with constant temperature, and there is no cold material demoulding, runner and pouring. The mouth is directly on the product, so the runner does not need to be demolded. This system is also called a nozzleless system, which can save raw materials. It is suitable for the situation where the raw materials are expensive and the product requirements are high, the design and processing are difficult, and the mold cost is high.
, The hot runner system, also known as the hot runner system, is mainly composed of a hot sprue sleeve, a hot runner plate, and a temperature control electric box. Our common hot runner system has two types of single-point hot gate and multi-point hot gate. The single-point hot gate uses a single hot gate sleeve to directly inject the molten plastic into the cavity, which is suitable for plastic molds with a single cavity and a single gate; Divided into the heat sprue sleeve and then into the cavity, it is suitable for single-cavity multi-point feeding or multi-cavity molds.
, the advantages of hot runner system
(1) No water mouth material, no post-processing is required, the entire molding process is fully automated, working time is saved, and work efficiency is improved.
(2) The pressure loss is small. The temperature of the hot runner is equal to the nozzle temperature of the injection molding machine, which avoids the condensation of the raw material on the surface of the runner, and the injection pressure loss is small.
(3) The repeated use of runner materials will degrade the performance of plastics, and the use of hot runner systems without runner materials can reduce the loss of raw materials, thereby reducing product costs. The temperature and pressure in the cavity are uniform, the stress of the plastic part is small, and the density is uniform. Under the smaller injection pressure and the shorter molding time, the injection molding system 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 it can produce larger products with smaller models.
