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. Mainly injection molding.
In recent years, some new plastic processing technologies and new equipment have been widely used in 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 lamination injection molding technology.

 

High precision and repeatability in terms of size and weight can be guaranteed. 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 mold. At present, China has been able to produce small and medium-sized precision injection molding machines.

It has developed rapidly with diversified development of household appliances and continuous upgrading, and is mainly used to prepare plastic casings for household appliances. Advantage of this technology is that small batches of plastic parts can be produced without need for molds.
At present, more mature rapid prototyping methods include laser scanning molding and liquid photocuring molding, among which laser scanning molding method is widely used. Laser scanning equipment is composed of laser light source, scanning device, dusting device and computer. Processing process is that laser head controlled by computer scans according to a certain trajectory. At position where laser passes, plastic micropowder is heated, melted and bonded together. After each scan, micropowder device sprinkles a thin layer of powder. In this way, 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 performance of equipment is unstable, varieties and brands of micropowders are also few.

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

 

It 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 cavity almost simultaneously with plastic melt.
At this time, plastic melt covers gas or superheated water, and molded plastic product has a sandwich structure. Such products have advantages of material saving, small shrinkage, good appearance and good rigidity. Key part of molding equipment is 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 application speed is also fast, domestic equipment is still unstable.

This technology makes screw vibrate back and forth in axial direction through action of electromagnetic force. Because plastic is microplasticized in pre-plasticizing stage, structure of plastic part in pressure-holding stage is more compact, and internal stress of product is reduced.
This technology can be used to form more demanding products such as optical discs. When used in molding of ordinary products, it can improve quality of products.

When using this technology, a special printed decorative plastic film needs to be clamped in mold before injection molding, and then injection molded. Printed film can be attached to surface of plastic part after being deformed by heat, which is not only beautiful and firm, but also saves post-decoration step.
Under normal circumstances, demand for plastic molds for home appliance plastic products is very large. For example, a refrigerator or a fully automatic washing machine usually needs more than 100 plastic molds, an air conditioner needs more than 20 plastic molds, and a color TV needs 50-70 plastic molds.
At the same time, technical requirements for plastic molds are relatively high, and processing cycle of mold is often required to be as short as possible, which greatly promotes development of mold design and modern mold manufacturing technology. In addition, domestic application of some difficult molds such as hot runner injection molds and laminated injection molds is gradually increasing.