The 6 common plastic injection molding process techniques for plastic products for home appliances are mainly injection molding, extrusion, thermoforming, hollow molding, lamination molding, compression molding, transfer molding, foam molding, embedded casting, sealing casting, etc., of which injection molding is the main.
In recent years, some new plastic injection molding process technologies and equipment have been applied in the molding of home appliances plastic products, such as precision injection molding, rapid molding technology, melt core injection molding technology, gas-assisted/water-assisted injection molding technology, electromagnetic dynamic injection molding technology, and overlay injection molding technology.
The following are the six common injection molding process technologies for plastic products.
Precision injection molding of the plastic injection molding process
It can ensure high precision and repeatability in terms of the size and weight of products. The injection molding machine using this technology can achieve high pressure and high-speed injection. Since the control method is usually open-loop or closed-loop control, high precision control of injection process parameters can be achieved.
Usually, precision injection molding requires high precision of the mold. At present, small and medium-sized precision injection molding machines can be produced in China.
Rapid prototyping technology of the plastic injection molding process
It is developed rapidly along with the diversification of home appliances and the continuous renewal of home appliances and is mainly used to prepare plastic shells for home appliances. The advantage of this technology is that it does not require a mold to achieve the small-volume production of plastic parts.
At present, the more mature rapid prototyping methods are laser scanning molding and liquid light-curing molding, among which the laser scanning molding method is more widely used.
Laser scanning equipment is composed of a laser light source, scanning device, powder spreading device, and computer.
The process is that the laser head controlled by the computer scans according to a certain trajectory, and at the position where the laser passes, the plastic micro-powder is heated and melted and bonded together, and after each scan, the micro powder device spreads a thin layer of powder, so that after repeated scans, products with a certain shape and size are formed.
Melt Core Injection Technology of the plastic injection molding process
It is usually used to mold 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 has been relatively mature in foreign countries, but it is still in the state of individual application in China. The processing principle of this technology is that the cavity core is formed first, and then the core is used as an insert for injection molding.
The cavity is formed by melting the core under the heating effect of the injection molded part. The most important point of using this technology is to master the core material and the melting point of the plastic part.
Usually, the core material can be available plastic, thermoplastic elastomer, or low melting point metal such as lead, tin, etc., depending on the specific situation.
Gas-assisted/water-assisted injection molding of the plastic injection molding process
It can be used for a wide range of injection molded parts, and a 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 molten plastic is covered with gas or superheated water, and the molded plastic product is a sandwich structure, which can be demolded by discharging the gas or water after the plastic part is set. These products have the advantages of material saving, small shrinkage, good appearance, and rigidity. The key part of the molding equipment is the gas-assisted or water-assisted device and its control software.
In recent years, although domestic research on this, the application rate is also faster, and the domestic equipment is not yet stable.
Electromagnetic dynamic injection molding technology of the plastic injection molding process
This electromagnetic dynamic injection molding technology of the plastic injection molding process makes the screw vibrate reciprocally in the axial direction through electromagnetic force. As the plastic is micro-plasticized in the pre-plasticization stage, the structure of the plastic part in the holding stage is denser, and the internal stress of the product is reduced.
This technique can be used to mold demanding products such as discs. When used in the molding of available products, it can improve the quality of the products.
Lamination injection molding technology of the plastic injection molding process
Using this technology, a special printed decorative plastic film is clamped inside the mold before injection molding. After heat deformation, the printed film can be attached to the plastic parts’ surface, which is beautiful and firm and eliminates the post-decoration step.
For example, a refrigerator or an automatic washing machine usually needs more than 100 pairs of plastic molds, an air conditioner needs more than 20 pairs, and a color TV needs 50-70 pairs of plastic molds.
At the same time, the Lamination injection molding technology of the plastic injection molding process technical requirements of plastic mold is relatively high, often requiring the processing cycle of the mold to be as short as possible, which greatly promotes the development of mold design and modern mold manufacturing technology.
In addition, some of the more difficult molds in domestic applications, such as hot runner injection mold, laminated injection mold, etc., are gradually increasing.
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