Internal Structure Analysis and Maintenance Matters Needing Attention of Screw Machine

I. Internal structure of extruder screw


(1) The extruder screw can be a structure or assembled in different parts. The additional mixing section installed at the end of the extruder screw is usually separated by threads or lasts in the appropriate position. This is the manufacture of the mixer and provides the possibility of modifying the terminal mixing. The modification of terminal mixing allows the shear and mixing degree to be customized according to the polymer and processing conditions.


(2) In order to integrate the extruder screw with cooling, it can be punched in the extruder screw, but this hole should not extend too long beyond the feeding pipe (about 4-5 laps).


Generally, it is not necessary to heat and cool of the extruder screw. If the polymer is at risk of premature melting, which will lead to the non-separation of particle feeding, then it makes sense to cool down strongly in the feeding section.


Due to the rotation of the extruder screw, it is difficult to cool the extruder screw with water or oil. Rotary installation and barrel pipes need to be installed in the cavity of the extruder screw. The width of the screw edge should be 0.08D~0.12D. A very narrow screw edge will increase the leakage of the polymer, and there is a risk that the screw edge will break, because the shear stress and the pressure difference between the front and rear edges of the screw edge will load it. Wide screw edges increase the risk of overheating of polymer parts. The typical screw groove section has a box shape and slightly rounded edges. The end of the extruder screw is circular or conical to prevent the polymer from stagnating in front of the extruder screw.


2. Main design characteristics of extruder screw


(1)Length of extruder screw.

(2) Distinguish the length of sections and regions.

(3) Thread depth and compression ratio.

(4) Number of threads.

(5) Screw pitch.

(6) Mixed local and shear local arrangement.

(7) Mixed local and shear local geometric shapes (pin mixer, long diamond mixer, groove mixer, shear appearance mixer, maddock mixer).


3. Points to note for maintenance of extruder screws


(1) When the extruder screw does not reach the preset temperature, do not use the engine.

(2) Avoid metal fragments and sundries falling into the hopper. If the recycled material is processed, a magnetic hopper needs to be added to prevent iron chips from entering the hopper.

(3) When using anti-salivation, make sure that the plastic in the barrel is completely melted to avoid damaging the transmission system parts when the extruder screw retreats.

(4) When using new plastics, the surplus of the extruder screw should be cleaned.

(5) When the temperature of the molten plastic is normal, but black spots or discoloration of the molten plastic are constantly found, the screw anti-reverse ring should be checked for damage.

(6) When processing, try to plasticize the material evenly, do not let metal foreign bodies mix into the material, and reduce the rotation torque of the extruder screw.


Our company specializes in the production of parallel and homogeneous rotating modular screw components, barrels and screws, involving various models from Ø20mm to Ø300mm. After ten years of vigorous development, our company now has a number of advanced CNC machine tools and screw manufacturing special processing equipment. If necessary, you are welcome to consult.

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