⚙️The working principle can be summarized as follows:
Solid plastic raw materials (granules or powder) are converted into a uniform and viscous melt in the barrel through heating, screw shearing, and external heat. Driven by the screw, the melt is continuously and stably extruded through a flat die (flat die head). Finally, after cooling, traction, and cutting, plastic sheets or plates are obtained.
🔧Detailed Explanation of Core Components：
Screw and Barrel:
These are the "heart" of the extruder. The screw is generally divided into the feeding section, compression section, and homogenizing section (metering section), each with distinct functions that collectively accomplish solid conveying, melting and plasticizing, as well as metering and pressure boosting. The screw design (such as length-diameter ratio and compression ratio) directly affects the plasticizing quality and output of plastics.
Heating and Cooling System:
The exterior of the barrel is surrounded by heaters (such as electric heating coils), which are used for startup heating and heat supplementation. Meanwhile, it is equipped with cooling devices (air cooling or water cooling) to prevent plastic degradation caused by excessive shear heat, serving as a key component for achieving precise temperature control.
Flat Die (Die Head):
This is the key component that determines the width and thickness of the sheet. The melt is "shaped" into the required flat sheet form here. The die lip is usually designed to be fine-tunable to precisely control the thickness uniformity of the sheet at all points.
Three-Roll Calender:
Installed immediately after the die head, it consists of three rolls with precise temperature control.
Subsequent Cooling, Traction and Cutting:
The sheet is further cooled to room temperature through a cooling roll group, then a tractor provides stable tension, and finally cut into sheets or wound into coils according to requirements.