The molding methods of plastic products for household appliances mainly include injection molding, extrusion molding, thermal molding, hollow molding, laminated molding, compression molding, transfer molding, foam molding, pouring molding, inlay molding, sealed casting, etc., of which injection molding is the main method.

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

One. Precision injection molding

It can ensure high precision and repeatability of product size and weight. The injection machine using this technology can achieve high-pressure and high-speed injection. Due to its control method usually being open-loop or closed-loop control, high-precision control of injection molding process parameters can be achieved.

Generally speaking, precision injection requires high precision of molds. At present, China is able to produce small and medium-sized precision injection molding machines.

2。 Rapid prototyping technology has developed rapidly with the diversification and continuous upgrading of household appliances, and is mainly used for the preparation of plastic shells of household appliances. The advantage of this process is that it can achieve small batch production of plastic parts without the need for molds.

At present, the relatively mature rapid prototyping methods include laser scanning molding and liquid light curing molding, of which laser scanning molding is widely used. The laser scanning equipment consists of a laser light source, a scanning device, a dust removal device, and a computer. The processing process is carried out by a computer-controlled laser head scanning along a certain path. At the location where the laser passes, plastic powder is heated, melted, and bonded together. After each scan, the micro powder device will sprinkle a thin layer of powder. In this way, after repeated scanning, a product with a certain shape and size is formed.

At present, some domestic enterprises are able to produce laser scanning molding machines and plastic micro powders, but the equipment performance is unstable, and there are few types and brands of micro powders.

III. Fusible core injection molding technology

Usually used for forming irregular cavity products with high requirements for cavity roughness and accuracy, they cannot be processed through hollow or rotary forming.

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 process is to first form the core of the cavity, and then use the core as an injection mold insert.

Under the heating effect of the injection molded part, the core mold melts and flows out, forming a cavity. Mastering the melting point of core materials and plastic parts is the key to using this technology. Generally speaking, the core material can be ordinary plastic, thermoplastic elastomer, or low melting point metals such as lead and tin.

Four. Gas assisted water assisted injection molding has a wide range of applications. It can form various injection molded parts, and its typical product is the TV casing. During the injection molding process, gas or overheated water can be injected into the mold cavity almost simultaneously with the plastic melt.

At this point, the plastic melt will cover the gas or overheated water. The plastic products formed are sandwich structures. After the plastic parts are shaped, gas or water can be discharged and demolded. This product has the advantages of material saving, small shrinkage, good appearance, and good rigidity. The key part of the forming equipment is the gas assisted or water assisted equipment and its control software.

In recent years, although China has conducted a large amount of research and application, domestic equipment is not stable.

5. The electromagnetic dynamic injection molding technology//technology causes the screw to undergo axial reciprocating vibration under the action of electromagnetic force. Due to the ability to microplasticize the plastic during the pre plasticization stage, the structure of the plastic parts during the compression stage is more compact, reducing the internal stress of the product.

This technology can be used to form products with high requirements such as optical discs. Applied to the forming of ordinary products, it can improve product quality.

6。 Laminated injection molding technology

When using this technology, it is necessary to clamp the specialized printing decorative plastic film into the mold after injection molding, and then proceed with injection molding. The printed film after thermal deformation can fit onto the surface of plastic parts, which not only looks beautiful and firm, but also saves the final decoration steps.

Generally speaking, there is a high demand for plastic molds for home appliance plastic products. For example, refrigerators or fully automatic washing machines typically require over 100 plastic molds, air conditioners require over 20, and color televisions require 50-70 plastic molds.

At the same time, the technical requirements for plastic molds are high, often requiring the processing cycle of molds to be as short as possible, greatly promoting the development of mold design and modern mold manufacturing technology. In addition, some difficult molds such as hot runner injection molds and stacked injection molds in China are gradually increasing.