The molding processing methods for plastic products for home appliances mainly include injection molding, extrusion molding, thermoforming, hollow molding, lamination molding, compression molding, transfer molding, foam molding, casting molding, insert molding, encapsulation, etc. In the past few years, some new plastic processing technologies and new equipment have been widely used in the molding of household electrical appliances, such as precision injection molding, rapid prototyping technology, molten core injection molding technology, gas-assisted/water-assisted injection molding technology, electromagnetic Dynamic injection molding technology and film injection molding technology.
1. Precision injection molding guarantees high precision and repeatability in terms of size and weight. Injection molding machines using this technology can realize high pressure and high speed injection. Since the control method is usually open loop or closed loop control, it can be used for injection molding. Process parameters achieve high precision control. Generally, precision injection molding requires high precision for the mold. At present, domestic small and medium precision injection molding machines can be produced.
2, Rapid prototyping technology is rapidly developed along with the development of household appliances in various diversification directions and continuous upgrading. It is mainly used to prepare plastic casings for home appliances. The advantage of this technology is that plastic parts can be realized without molds. At present, the more mature rapid prototyping methods include laser scanning molding and liquid photocuring. Among them, laser scanning molding is applied more. 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 scans according to a certain trajectory. At the position where the laser passes, the plastic micro-powder is melted and bonded together by heat, and each time the scanning is finished, the micro-powder device is sprinkled with a thin layer of powder, so that After repeated scanning, it has formed a product with a certain shape and size. Now, some companies in China have been able to produce laser scanning molding machines and plastic micro-powders, but the performance of the equipment is unstable, and the number of micro-powders is also small.
3, Fuse injection molding technology is usually used to form shaped hollow cavity products that require high cavity roughness and precision and cannot be processed by hollow molding or rotary forming. At present, the application of this technology in foreign countries is relatively mature. However, it is still in an individual application state in China. The processing principle of this technology is that the core shape constituting the cavity is first formed, and then the core type is used as an insert for injection molding. Under the heating action of the injection molded part, the core type is melted and flowed out. , thus forming a cavity. The most important point of using this technology is to master the melting point of the core material and the plastic part. Generally, the core material can be selected from general plastic, thermoplastic elastomer or low melting point metal according to the specific conditions. Such as lead, tin, etc.
4, Gas-assisted/water-assisted injection molding is widely used, and can form many types of injection molded parts. The typical product is the TV casing. When injection molding, gas or superheated water can be injected into the cavity almost synchronously with the plastic melt. At this time, the plastic melt is coated with gas or superheated water, and the formed plastic product is a sandwich structure. After the plastic parts are shaped, the gas or water can be discharged to release the mold. Such products have the advantages of material saving, small shrinkage, and good appearance. Good rigidity. The key part of the molding equipment is gas-assisted or water-assisted device and its control software. In recent years, although there are many researches in China, the application speed is faster, but the domestic equipment is still unstable.
5, electromagnetic dynamic injection molding technology was invented by Mr. Jin Jinping from South China University of Technology. This technology causes the screw to reciprocate in the axial direction by the action of electromagnetic force. Because the plastic is microplasticized in the pre-plasticization stage, The plastic part structure in the pressing stage is more compact and reduces the internal stress of the product. This technology can be used for forming products with high requirements such as optical discs. When used for forming ordinary products, the quality of the products can be improved.
6. The application of film injection molding technology and equipment in foreign countries is relatively mature. When using this technology, it is necessary to clamp the special printed decorative plastic film into the mold before injection molding, and then injection molding. The printed film can be bonded after being thermally deformed. The surface of the plastic part is not only beautiful and firm, but also eliminates the post-decoration steps.
Under normal circumstances, the demand for plastic molds and flame retardant plastics for household electrical appliances is very large. The most used ones are: flame retardant PP, flame retardant ABS, followed by flame retardant PBT and other flame retardant materials.