The molding processing methods of plastic products for home appliances mainly include injection molding, extrusion molding, thermal molding, hollow molding, lamination molding, compression molding, transfer molding, foam molding, pouring molding, inlay casting, sealing casting, etc., of which injection molding is the main.

In recent years, some new plastic processing technologies and new equipment have been widely used in the molding of household appliances plastic products, such as precision injection molding, rapid prototyping technology, core injection molding technology, gas-assisted/water-assisted injection molding technology, electromagnetic dynamic injection molding technology and laminating injection molding technology.

1, precision injection molding

can ensure that the product has high precision and high repeatability in terms of size and weight. The injection molding machine using this technology can achieve high pressure and high speed injection. Because its control mode is usually open loop or closed loop control, the injection molding process parameters can be controlled with high precision. Usually, precision injection molding requires higher accuracy of the mold. At present, China has been able to produce small and medium-sized precision injection molding machines.

2, rapid prototyping technology

is accompanied by the development of household appliance varieties to the direction of diversification and continuous upgrading and rapid development, mainly used for the preparation of household appliance plastic shell. The advantage of this technology is that small batch production of plastic parts can be achieved without mold. At present, the more mature rapid prototyping methods are laser scanning molding and liquid light curing molding, of which laser scanning molding method is more used. Laser scanning equipment is composed of laser light source, scanning device, dusting device and computer. The processing process is that the computer-controlled laser head is scanned according to a certain track, in the position of the laser, the plastic powder is heated and melted and bonded together, every scanning is completed, the powder device is scattered with a thin layer of powder, so that after repeated scanning, it forms a product with a certain shape and size. At present, some enterprises in China can produce laser scanning molding machines and plastic powder, but the performance of the equipment is unstable, and the varieties of micro-powder are less.

3, core injection molding technology

is usually used to shape the cavity roughness and precision requirements of higher, can not be processed by hollow molding or rotary molding method of special-shaped cavity products. At present, the application of this technology in foreign countries has been relatively mature, but in China is still in a state of individual application. The processing principle of this technology is that the core form of the cavity is formed first, and then the core is used as an insert injection molding. Under the heating action of the injection part, the core melts and flows out, thus forming the cavity. The most important point to use this technology is to master the melting point of the core material and the plastic part. Usually, the core material can be selected according to the specific situation and general plastic, thermoplastic elastomer or low melting point metal such as lead, tin and so on.

4, gas-assisted/water-assisted injection molding

widely used, can be formed a variety of types of injection parts, the typical product is the TV shell. When injection molding, gas or superhot water can be injected into the cavity almost synchronously with the plastic melt. At this time, the plastic melt will be covered by gas or superhot water, and the molded plastic products are sandwich structures. After the plastic parts are shaped, the gas or water can be demoulded. Such products have the advantages of material saving, shrinkage, good appearance and good rigidity. The key part of the molding equipment is the gas-assisted or water-assisted device and its control software. In recent years, although China has more research on this, the application speed is also faster, but the domestic equipment is still unstable. The technology makes the screw vibrate reciprocally in the axial direction through the action of electromagnetic force. Because the plastic can be micro-plasticized in the pre-plasticization stage, the structure of the plastic parts in the pressure holding stage is more dense, and the internal stress of the product is reduced. This technology can be used for molding products with high requirements, such as optical discs. When it is used to form ordinary products, the quality of the products can be improved.

6, film injection molding technology

and the application of equipment in foreign countries has been more mature. When using this technology, it is necessary to clip the special printing decorative plastic film in the mold before injection molding, and then injection molding. The printing film can be affixed to the surface of the plastic part after heat deformation, which is not only beautiful and firm, but also saves the decoration step.

Under normal circumstances, the demand for plastic molds of household appliances plastic products is very large, for example, a refrigerator or a fully automatic washing machine required plastic molds usually more than 100 pairs, an air conditioner needs more than 20 pairs, a color TV needs 50-70 pairs of plastic molds. At the same time, the technical requirements for plastic molds are relatively high, and often require the processing cycle of the mold to be as short as possible, which greatly promotes the mold design and the development of modern mold manufacturing technology. In addition, the application of some difficult molds such as hot runner injection mold and laminated injection mold in China is gradually increasing.

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