Plastic extrusion principle

Release Date:2020-11-21


Extrusion molding: also known as extrusion molding, it is mainly suitable for the molding of thermoplastics, but also for the molding of some thermoset and reinforced plastics with better fluidity. The molding process is to use a rotating screw to extrude the heated and melted thermoplastic material from a die with the required cross-sectional shape, and then it is shaped by a shaper, and then cooled and solidified by a cooler to become the required cross-sectional shape. product.


1. Host

Extrusion system: Composed of screw and barrel, it is the key part of the extruder. Its function is to plasticize the material, and extrude the melt in quantitative, constant pressure and constant temperature

Transmission system: drive the screw to provide the required torque and torque

Heating and cooling system: to ensure that the temperature of the plastic and extrusion system meets the process requirements during the molding process

2. Auxiliary machine

Composed of machine head, shaping device, cooling device, traction device, coiling device and cutting device

3. Control system

Composed of electrical appliances, instruments and actuators

Function: Control the main and auxiliary motors to meet the required speed and power; control the temperature, pressure, and flow of the main and auxiliary machines to ensure product quality; realize automatic control of the extrusion unit to ensure the coordinated operation of the main and auxiliary machines.

Related parameters

1. Temperature

Extrusion molding temperature includes barrel temperature, plastic temperature, screw temperature, generally we measure barrel temperature. The temperature is controlled by the heating and cooling system. Due to the screw structure, the instability of the heating and cooling system, and the change of the screw speed, the temperature of the extruded material fluctuates in the radial and axial directions, which affects the quality of the product. The strength of the product is different. Residual stress, the surface is dull and dull. To ensure product quality, the temperature should be stable.

2. Pressure

Due to the structure of the screw and barrel, the resistance of the machine head, filter screen, and filter plate causes pressure inside the plastic. The pressure change is shown in the figure, and the pressure also fluctuates.

3. Extrusion rate

The mass or length of the plastic extruded from the die of the extruder per unit time. Factors affecting extrusion rate: head resistance, screw and barrel structure, screw speed, heating and cooling system, plastic characteristics. But when the product has been determined, the extrusion rate is only related to the screw speed. The extrusion rate also fluctuates, which affects the product geometry and size.

There are fluctuations in temperature, pressure, and extrusion rate. In order to ensure product quality, the screw should be designed correctly, the heating and cooling system and the stability of the screw speed should be controlled to reduce parameter fluctuations.

Use field

Agriculture, construction, petrochemical, machinery manufacturing, medical equipment, automobiles, electronics, aerospace and other industrial sectors have applications.

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Dongguan Shangyu Plastic hardware Products Co. LTD

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