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Causes Of Screw Barrel Damage Due To Improper Operation

1.screw in the barrel rotation, the friction between the material and the two, the screw and the barrel of the working surface gradually wear: screw diameter gradually reduced, cylinder bore diameter gradually increased. In this way, the diameter and clearance of the screw and the cylinder are slightly increased with the gradual wear of the two. However, because the resistance of the front head and the splitter plate of the barrel does not change, this increases the leakage flow when the extruded material moves forward, that is, the flow of material increases from the diameter gap to the feed direction. As a result, the extruder output decreased. This phenomenon increases the residence time of the material in the barrel, resulting in the decomposition of the material.  If it is polyethylene, the decomposition of hydrogen chloride gas strengthens the corrosion of the screw and cylinder.

2.the material such as calcium carbonate and glass fiber filler, can speed up the screw and barrel wear.

3.because the material has no uniform plasticizing, or metal contamination material, so that the rotation of the screw torque suddenly increases, the torque exceed the strength limit of the screw, the screw barrel is broken. This is a non conventional accident damage


Repair of screw barrel The broken screw 


1.according to the actual diameter of the barrel to consider, made according to new screw diameter deviation of normal clearance and cylinder are given.

2.The surface of the screw thread whose diameter is smaller than that of the worn screw is treated by thermal spraying, and then it is machined to size by grinding. This method generally has professional spraying factory processing and repair, the cost is relatively low

3. Wear resistant alloy on the threaded part of the worn screw.  According to the degree of screw wear, 1~2mm thickness is deposited, and then grinding screw to size. The wear resistant alloy is composed of C, Cr, Vi, Co, W and B, which can increase the wear resistance and corrosion resistance of the screw. The cost of this kind of machining is very high in the professional surfacing factory, except for the special requirements of the screw, it is seldom used.

4.repair screw can also be plated hard chromium method, chromium is wear and corrosion resistant metal, but hard chromium layer is easy to fall off. Three. Repair of cylinder

The inner surface hardness of the barrel is higher than that of the screw, and its damage is later than that of the screw. The discarding of the barrel is that the diameter of the inner diameter increases due to the wear of the time. Its repair methods are as follows:

1.because the wear increases the diameter of the barrel, if there is a certain nitriding layer, the barrel bore can be directly boring, grinding to a new diameter size, and then according to the diameter of the new screw.

2.The inner diameter of the barrel is machined and re casted. The thickness of the alloy is between 1~2mm, and then machined to the size.

3.under normal circumstances, the homogenization of the barrel wear faster, you can take this paragraph (take 5~7D long) through boring, and then with a nitriding alloy steel bushing, the diameter of the hole reference screw barrel diameter, stay in the normal fit gap, processing and preparation.