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Extrusion molding process and equipment


Extrusion, also known as extrusion molding or extrusion, plastic molding is an important method. It is suitable for most thermoplastics, thermoplastic molding three methods (injection, extrusion, calendering) one, but also for a small number of thermosetting plastics.

·Extrusion process
1, pipe molding process
Pipe is one of the main products of extrusion molding, pipe diameter from a few millimeters to several hundred millimeters.
a, Process flow
The forming process of the pipe is slightly different due to different raw materials, the main process is as follows: plastic extrusion → head forming → vacuum sizing set → tank cooling shaping → traction machine traction → fixed length cutting → inspection → packaging storage.
b, Process control factors
One molding temperature, screw speed, traction speed, compressed air pressure, are important process control factors.

2, bar molding process
Bar generally refers to solid round bar, there are square, rectangular, triangular bar, mainly for the manufacture of machine parts.
a, Process flow
Plastic bar extrusion process is as follows: plastic extrusion molding → → → cooling head shaping → drawing traction → fixed length cutting → inspection → finished warehousing.
b, Process control factors
To extrude a plastic bar at a constant rate, it is necessary to keep the axial force pushing the bar forward and the radial frictional resistance between the sleeve wall surface and the bar to a suitable equilibrium pressure.

3, plate (sheet) material molding process
Plastic sheet (sheet) material has a single layer and multi-layer, flat and corrugated board, foam and non-foam, a single material and composite materials.
a, Process flow
Plastic sheet (sheet) Extrusion process is roughly as follows, different raw materials slightly different: plastic extrusion → head molding → three rollers → calendering → cooling conveying → traction → cutting → inspection → packaging.
b, Process control factors
Extrusion is usually die temperature should be higher than the body temperature of 5 ~ 10 ℃ or so. The roller temperature of the three-roll calender is related to the forming raw material, the thickness of the plate and the arrangement position of the roller. The thickness of the plate is related to the die lip and the three-roll spacing. Die lips are generally equal to or slightly less than the required thickness of the plate, the plate after extrusion from the die expansion, traction and calendering to achieve the required thickness.

4, blow molding film forming process
Plastic film production methods are rolling, blow molding and direct extrusion and other forms.
a, Process flow
Blowing film production process and process methods, raw materials and product categories are closely related. According to the different extrusion and traction direction, blow molding method can be divided into flat blow, flat down and down the blowing flat blowing method.
b, Process control factors
Extrusion temperature is an important factor in the control of product yield and quality.

5, extrusion molding process conditions
In determining the process conditions of extruded products, the raw and auxiliary materials by the molding performance, processing equipment, molding characteristics, as well as the design and mold design and processing methods and other factors, the situation is more complex.

·Extrusion molding equipment
1, the structural characteristics of the extruder
a, transmission
Extruder drive is to drive the screw rotation of the components, mainly by the motor, bearings and gears and other components.
b, Feeding device
Extruder feeding device is usually used hopper.
c, Barrel
Cartridge is an important part of the extruder, plastic is in the barrel to complete the plasticization and pressure.
d, Screw
The screw is the "heart" part of the extruder. Through the rotation of the screw, the material in the barrel is moved, and the pressure and the partial heat are obtained.
e, Head and die
The head is the transition between the cylinder and die, its structure depends on the form and size of the extruder, and the variety of plastic, heating methods, the shape of products.
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