The barrel of the twin-screw extruder is the same as in the extrusion compression molding system, and is an important part of the extruder. The barrel and the extruder screw work together, the barrel contains the screw, and the screw rotates in the barrel.
When the screw rotates and pushes the plastic to move forward in the barrel, the outside of the extruder barrel heats and conducts heat to the plastic in the barrel. In addition, the volume of the screw thread on the extruder is gradually reduced, so that the plastic in the screw groove is affected. After the action of various forces such as extrusion, turning and shearing, it is uniformly mixed and plasticized. As it moves to the front of the barrel, it gradually melts into a viscous fluid state to complete the plasticization of the plastic.
The normal cooperation of the extruder barrel and screw ensures the continuous extrusion of raw materials and molding production of the extruder screw.
The structure is relatively simple. In a large extruder, the structure of the twin-screw extruder barrel can be composed of several sections. Since the barrel is divided into several sections, the length of each section of the barrel is reduced, which brings convenience to the machining of the barrel.
However, for this type of extruder barrel composed of several sections, the inner diameter size after machining and the concentricity accuracy of the inner holes of the several sections of the barrel are difficult to be consistent.
In addition, the barrel of the segmented twin-screw extruder is connected by a flange, which will bring some difficulties to the layout of the heating and cooling equipment of the barrel, and the temperature control will not be too uniform.
In order to save more expensive alloy steel, the barrel of some large extruders adopts the method of inner hole lining or casting wear-resistant alloy layer. The outer casing of the extruder barrel can be cast from ordinary steel to achieve the purpose of reducing the manufacturing cost of the barrel.