Brief discussion on plastic molding: types of plastic molding

Feb 16, 2023

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Injection molding

It is a method that plastic materials are heated and melted in the heating barrel of the injection molding machine, and then the melt is pushed into the cavity of the closed mold by the reciprocating screw.

It can not only produce high-precision and high-quality products at high productivity, but also process a wide variety of plastics with large output (about 1/3 of the total amount of plastics) and wide use. Therefore, injection molding is one of the important molding methods in plastic processing.

Extrusion molding

Extrusion is a method of continuous plastic molding through the die in a flowing state by heating and pressurizing in the extruder.

It is generally used for the molding of plates, pipes, monofilament, flat wire, film, wire and cable, etc. It has a wide range of uses and high output. Therefore, it is one of the important molding methods in plastic processing.

Foaming molding

It refers to adding appropriate foaming agent into the foaming material to produce porous or foaming products. The foaming products have the advantages of low relative density, high specific strength, low consumption of raw materials, sound insulation and heat insulation. The foaming materials include PVC, PE and PS.

Products include: films, plates, pipes, and profiles. Foaming can be divided into chemical foaming and physical foaming.

Blow molding

Blow (film expansion) molding (or hollow blow molding) refers to a molding method that uses the pressure of fluid (compressed air) to blow the hot thermoplastic blank or sheet in the closed mold into hollow products.

Plastic containers produced by this method. Such as various bottles, square, round or flat barrels, gasoline tanks, etc. have been widely used. Newly developed various industrial components and daily products, such as double-wall box products, L-ring large barrels, pallets, surfboards, seat backrests and desks, as well as front baffle plates, belt covers, instrument panels, air conditioning ventilation pipes, etc., have been applied in practice. The processed materials have developed from daily plastics to engineering plastics. Now blow molding has become one of the important molding methods in plastic processing.

However, the basic steps of the blow molding process are:

1. Melting material

2. Forming molten resin into tubular or parison

3. Melt and seal the hollow parison in the blowing mold

4. Blow the parison in the mold

5. Cooling blow molding products

6. Remove the product from the mold

7. Finishing

Injection Blow Molding

Injection blow molding is a blow molding method. First, the plastic is made into a bottomed parison by injection molding, and then it is moved into a blowing mold to blow into a hollow product.

This method can produce packaging containers for daily necessities, cosmetics, medicine, food, etc., but its volume should not exceed 1L. The commonly used plastics include polyethylene, polystyrene and PVC.

extrusion blow molding

Extrusion blow molding is a blow molding method. Unlike injection blow molding, its parison is made by extrusion.

stretch blow molding

Stretch blow molding is a blow molding method. It is to make parison by extrusion, injection molding and other methods, and then heat the parison to the drawing temperature, and carry out the longitudinal stretching by the mechanical force of the internal (such as mandrel) or external (such as clamp), and at the same time or later, carry out the transverse stretching by the blowing of compressed air.