What are the types of screw gaps of conical twin-screw extruders and what are their functions?What are the types of screw gaps of conical twin-screw extruders and what are their functions?
In summary, there are the following four working gaps between the screw and barrel of the conical twin screw extruder:
(1) The radial clearance between the end surface of the screw rib and the inner diameter circumference of the barrel.
(2) The radial clearance between the end surface of the screw edge and the bottom surface of the screw groove when the two screws are engaged.
(3) The axial clearance between the screw rib and the side of the screw groove when the two screws are engaged.
(4) The axial gap between the small screw head and the top of the barrel.
Among them, the first two gaps not only play the role of calendering and rubbing the materials, but also play a role in preventing the backflow of the materials. Especially the first gap is very important.
The permissible limit will directly cause the material to leak or reverse flow, affect the product quality, and is also the dominant factor restricting the working life of the extruder. The third gap not only serves to shear the material, but also serves to transport the material. If the installation is improper, the gap on one side is too small, resulting in direct friction of the ribs and black lines on the profile. As the wear gap increases, to a certain extent, it will increase the amount of material conveyed, resulting in a decrease in the degree of melting and plasticization, reducing the extrusion efficiency. The fourth gap acts to squeeze the material. The second clearance is mainly determined by the processing, whether it is installed or after the wear is increased, it cannot be manually adjusted. The third gap must be adjusted accurately before installation, and the adjustment after wear is not effective. The fourth gap is adjusted synchronously with the first gap. The so-called extruder gap adjustment mainly refers to the adjustment of the first gap and the third gap when the new screw is installed. After the extruder runs normally, it mainly refers to the adjustment of the first gap.