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As we all know, the screw and barrel are two important parts of the plastic extruder. If damaged, it will affect the operation of the machine. So what do we need to pay attention to during maintenance?
Screw repair
1The twisted screw should be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw should be given according to the normal clearance with the barrel and manufactured.
2. After the surface of the thread with reduced diameter of the worn screw is treated, the wear-resistant alloy is thermally sprayed, and then ground to size. This method is generally processed and repaired by professional spraying factories, and the cost is relatively low.
3. Overlay wear-resistant alloy on the threaded part of the worn screw. According to the degree of screw wear, surfacing welding is 1~2mm thick, and then grinding the screw to size. This wear-resistant alloy is composed of materials such as C, Cr, Vi, Co, W and B, which increases the wear resistance and corrosion resistance of the screw. Professional surfacing factories have a high cost for this kind of processing, except for special required screws, they are rarely used.
4.The surface of the screw can also be repaired by hard chromium plating. Chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easier to fall off.
Barrel Repair
The inner surface hardness of the barrel is higher than that of the screw, and its damage will occur later than that of the screw. The scrapping of the barrel is that the inner diameter increases due to wear and tear over time. It can be fixed as follows:
1For the barrel whose diameter is increased due to wear, if there is still a certain nitriding layer, the inner hole of the barrel can be directly bored to a new diameter, and then a new screw can be prepared according to this diameter.
2. The inner diameter of the barrel is machined and trimmed, and the alloy is re-cast to a thickness of 1~2mm, and then finished to size.
3.Under normal circumstances, the homogenization section of the barrel wears quickly. This section (take 5~7D long) can be trimmed by boring, and then equipped with a nitriding alloy steel bushing. The diameter of the inner hole refers to the diameter of the screw. Normally match the gap, and carry out processing and preparation.
It is emphasized here that the screw and the barrel are two important parts, one is a slender threaded rod, and the other is a relatively small diameter and long hole. Their machining and heat treatment processes are relatively complicated, and the guarantee of accuracy will be relatively high. difficulty. Therefore, whether to repair or replace these two parts with new ones after wear and tear must be comprehensively analyzed from an economic perspective. If the repair cost is lower than the cost of replacing the new screw, it is decided to repair, which is not necessarily the right choice, because the comparison of repair cost and update cost is only one aspect. In addition, it also depends on the ratio of the repair cost and the screw usage time after repair to the replacement cost and the screw usage time after the repair. The most economical and correct choice is to adopt a plan with a smaller cost ratio.
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With nearly 20 years in the intelligent extrusion equipment industry, he has held key roles at Jwell Machinery, including General Manager and Rotating Chairman. Since 2024, he has managed multiple subsidiaries, driving business expansion and industrial upgrades, while leading innovation in intelligent manufacturing and global growth.
