Molding And Processing Methods Of Plastic Products For Household Appliances

The molding and processing methods of plastic products for household appliances mainly include injection molding, extrusion molding, thermoforming, hollow molding, lamination molding, compression molding, transfer molding, foam molding, casting molding, insert casting, encapsulation, etc., among which Mainly injection molding. In recent years, some new plastic processing technologies and new equipment have been widely used in the molding of home appliance plastic products, such as precision injection molding, rapid prototyping technology, melt core injection molding technology, gas-assisted/water-assisted injection molding technology, electromagnetic dynamic injection molding technology and overlay technology. Film injection molding technology, etc.

1. Precision injection molding can ensure that the product has high precision and high repeatability in terms of size and weight. Injection molding machines using this technology can achieve high-pressure, high-speed injection. Because its control method is usually open-loop or closed-loop control, it can achieve high-precision control of injection molding process parameters. Generally, precision injection molding requires higher precision of the mold. At present, China has been able to produce small and medium-sized precision injection molding machines.

2. Rapid prototyping technology has developed rapidly along with the diversification of household appliances and the continuous upgrading, and is mainly used to prepare plastic housings for household appliances. The advantage of this technology is that small batches of plastic parts can be produced without the need for molds. At present, the more mature rapid prototyping methods include laser scanning molding and liquid photocuring molding, among which the laser scanning molding method is widely used. Laser scanning equipment is composed of laser light source, scanning device, dusting device and computer. The processing process is that the laser head controlled by the computer scans according to a certain trajectory. At the position where the laser passes, the plastic micropowder is heated and melted and bonded together. After each scan, the micropowder device sprinkles a thin layer of powder, so that, After repeated scanning, a product with a certain shape and size is formed. At present, there are some domestic enterprises that can produce laser scanning molding machines and plastic micropowders, but the performance of the equipment is unstable, and the varieties and brands of micropowders are also few.

3. Melt core injection molding technology is usually used to form special-shaped cavity products that require high cavity roughness and precision and cannot be processed by hollow molding or rotational molding methods. At present, the application of this technology in foreign countries is relatively mature, but it is still in a state of individual application in China. The processing principle of this technology is to form a core that forms a cavity first, and then use the core as an insert for injection molding. Under the heating effect of the injection molded part, the core is melted and flowed out, thereby forming a cavity. The most important point in 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-purpose plastics, thermoplastic elastomers or low-melting metals such as lead and tin according to specific conditions.

4. Gas-assisted/water-assisted injection molding has a wide range of uses, and can form various types of injection molded parts, and its typical product is a TV casing. During injection molding, gas or superheated water can be injected into the cavity almost simultaneously with the plastic melt. At this time, the plastic melt covers the gas or superheated water, and the molded plastic product has a sandwich structure. Such products have the advantages of material saving, small 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 there have been many studies on this topic in China and the application speed is also fast, the domestic equipment is still unstable.

5. Electromagnetic dynamic injection molding technology was invented by Mr. Qu Jinping from South China University of Technology. This technology makes the screw vibrate back and forth in the axial direction through the action of electromagnetic force. Because the plastic is microplasticized in the pre-plasticizing stage, the structure of the plastic part in the pressure-holding stage is more compact, and the internal stress of the product is reduced. This technology can be used to form more demanding products such as optical discs. When used in the molding of ordinary products, it can improve the quality of the products.

6. The application of laminating injection molding technology and equipment in foreign countries has been relatively mature. When using this technology, a special printed decorative plastic film needs to be clamped in the mold before injection molding, and then injection molded. The printed film can be attached to the surface of the plastic part after being deformed by heat, which is not only beautiful and firm, but also saves the post-decoration step.

Under normal circumstances, the demand for plastic molds and flame retardant plastics for home appliance plastic products is very large. The most used are: flame retardant PP, flame retardant ABS, followed by flame retardant PBT and other flame retardant materials.