Extrusion, Injection Molding, Blow Molding Three Plastic Molding Process!

- May 08, 2018-

Plastic molding is an engineering technology, which involves the conversion of plastic into plastic products.

Injection molding

Injection molding, and its principle is that the raw material for the granular or powder added to the injection machine in the hopper, raw material through heat melt flow state, in the injection machine screw or piston driven by the nozzle and the mould gating system into the mold cavity, in the mold cavity hardening. Factors affecting injection molding quality: injection pressure, injection molding time, injection molding temperature.


1. Short molding cycle, high production efficiency and easy to realize automation.

2. Plastic parts with complex shapes, precise sizes, metal or non-metal inserts.

3. Stable product quality.

4. Wide adaptability.


1. The price of injection equipment is higher.

2. The structure of injection mold is complicated.

3. High production cost, long production cycle, unsuitable for single small batch production of plastic parts.


In industrial products, injection molding products are: kitchen supplies, garbage can, bowl, buckets and POTS, tableware and all kinds of containers), electrical equipment shell (hair dryers, vacuum cleaner, food mixer, etc.), toys and games, all products of the auto industry, many other parts of the product, etc.

Extrusion molding

Extrusion molding: also known as extrusion molding, it is mainly suitable for the forming of thermoplastic plastic, and also suitable for some of the more liquid thermosetting and reinforced plastic forming. Its forming process is using the rotation of the screw, will be heating molten thermoplastic materials, from have the cross section shape of the nose extrusion, and then finalize the design by shape, chill solidified by cooler again, become the required section products.

Technical features:

1. Low equipment cost;

2. Simple operation and easy control of the process, easy to realize continuous automatic production;

3. High production efficiency; Product quality is uniform and dense;

4. The product or semi-finished products can be formed by changing the shape of the die.


In the field of product design, extrusion molding has strong applicability. Extruded product types include tube, film, bar, single wire, flat belt, net, hollow container, window, door frame, sheet, cable cladding, single wire and other profiles.

Blow molding

From extruder extrusion blow moulding, is to the molten thermoplastic materials, clip into the mould, then blow into the air, in the raw material within the molten materials under the action of air pressure expansion, to mold cavity wall, the cooling and solidification become the method of product shape. Blow molding is divided into thin film blow molding and hollow blow molding:

Film blowing:

Film blowing molten plastic from extruder head mouth die circular gap in a cylindrical thin tube extrusion, at the same time from the central hole to the thin tube cavity into the compressed air blowing, blowing thin tube bulge into a larger diameter tubular membrane (commonly known as the bubble tube), cooling after coiling.

Hollow blow molding:

Hollow blow molding is with the aid of gas pressure, will be closed in the mold cavity in a kind of rubber state parison swell become hollow products molding technology, the production of hollow plastic products. The hollow blow moulding moulding machine is different in manufacturing method, with extrusion blow molding, injection blow molding, stretching blow molding.

1) extrusion blow molding: extrusion blow molding is extruded tubular billet, which is clamped in the mold cavity and sealed, and then compressed air into the billet cavity to blow up and form.

2) injection blow molding: the form used is made by injection molding. The mould is left on the core mould of the mould. After the mold is used to mould the mold, the mold is connected to the compressed air from the core mold, and the billet is blown up and cooled, and then the product is ready for release.

3) stretch blow molding, will have been heated to stretching temperature parison placed in blow molding mold, tensile rod with longitudinal tensile, using compressed air to blow into the transverse tensile huff, and then the method to get the product.


The product wall thickness is uniform, the weight tolerance is small, the rear processing is small, the waste side Angle is small; Suitable for production of large batch of small fine products.


Thin film blowing is mainly used to make plastic thin mold. The hollow blow molding is mainly used to make hollow plastic products (bottles, bottles, bottles, tanks, cans, toys, etc.).