Extrusion molding: also known as extrusion molding, it is mainly suitable for the molding of thermoplastic plastics, as well as the molding of some thermosetting and reinforced plastics with good fluidity. The forming process is to use a rotating screw to extrude the thermoplastic raw material that has been heated and melted from the machine head with the desired cross-sectional shape, then shape it with a shaping device, and then solidify it through a cooler to become the desired cross-sectional product.

equipment

1. Host

Extrusion system: composed of screws and barrels, it is a key part of the extruder. Its function is to plasticize materials and extrude the melt in a quantitative, constant pressure, and constant temperature manner

Transmission system: Drive screws to provide the required torque and torque

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

2. Auxiliary equipment

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 motor to meet the required speed and power; Control the temperature, pressure, and flow rate of the main and auxiliary machines to ensure product quality; Realize automatic control of the extrusion unit to ensure coordinated operation of the main and auxiliary machines.

Related parameters

1. Temperature

The extrusion molding temperature includes the barrel temperature, plastic temperature, and screw temperature. Generally, we measure the barrel temperature. The temperature is controlled by the heating and cooling system. Due to the screw structure, unstable heating and cooling system, and changes in screw speed, the temperature of the extruded material fluctuates in both radial and axial directions, which affects the quality of the product. The strength of each point of the product is different, resulting in residual stress and a dull and dull surface. To ensure product quality, the temperature should be stable.

2. Pressure

Due to the screw and barrel structure, the resistance of the machine head, filter screen, and filter plate creates pressure inside the plastic. The pressure changes are shown in the figure, and there are also fluctuations in pressure.

3. Extrusion rate

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

There are fluctuations in temperature, pressure, and extrusion rate. In order to ensure product quality, it is necessary to design the screw correctly, control the heating and cooling system, and maintain the stability of screw speed to reduce parameter fluctuations.

Field of use

It is applied in industrial sectors such as agriculture, construction, petrochemicals, machinery manufacturing, medical devices, automobiles, electronics, and aerospace.