The screw of the extruder rotates in the barrel, and the friction between the material and the two causes the working surface of the screw and the barrel to gradually wear. However, because the inner surface of the extruder barrel is harder than that of screw, its damage comes later than the screw. In addition, because the extruder barrel is cylindrical, the area under stress and friction is large, while the area under friction of the screw ridge is small. Besides, the raw material is in the screw groove, and the thrust surface of the screw is designed to move upwards. In light of these reasons, the damage to the extruder barrel comes later than the screw.
The damage of the extruder barrel is the increase in the inner diameter due to wear after a period of time.
(1) For the extruder barrel with increased diameter due to wear, if there is a certain nitriding layer, the inner hole of the extruder barrel can be directly bored, and ground to a new diameter size, and then a new screw should be prepared according to this diameter.
(2) The inner diameter of the extruder barrel is machined and trimmed to recast the alloy with a thickness of between 1 to 2mm, and then finished to the applicable size. This method is expensive.
(3) Under normal circumstances, the homogenization section of the extruder barrel wears quickly. This section (the length is 5 to 7D) can be trimmed by boring a hole, and then equipped with a nitrided alloy steel bushing. The inner hole diameter refers to the screw diameter. In the normal matching gap, processing and preparation can be conducted. The feeding section of the high-efficiency extruder barrel wears quickly, so it should be checked frequently during use.
