Repair of extruder screw and barrel

Repair of rubber extruder screw

1. The twisted screw shall be considered according to the actual inner diameter of the barrel and manufactured according to the normal clearance with the barrel and the outer diameter deviation of the new screw.

2. After the thread surface with reduced diameter of the wear screw is treated, the wear-resistant alloy is thermally sprayed and then ground to the size. This method is generally processed and repaired by professional spraying plants, and the cost is relatively low.

3. The wear-resistant alloy is overlaid on the thread part of the worn screw. According to the wear degree of the screw, the thickness of the weld bead is 1 ~ 2mm, and then the screw is ground to the 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. The cost of this kind of processing is very high in professional surfacing plants. Except for the screw with special requirements, it is rarely used.

4. The repair screw can also be plated with hard chromium on the surface. Chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easy to fall off.

Repair of rubber extruder barrel

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 scrapping of the barrel means that the inner diameter increases due to time wear. Its repair method is as follows:

1. For the barrel with increased diameter due to wear, if there is a certain nitriding layer, the inner hole of the barrel can be directly bored, ground to a new diameter, and then a new screw can be prepared according to this diameter.

2. The inner diameter of the barrel shall be re cast with alloy after machining and trimming, and the thickness shall be between 1 and 2mm, and then it shall be finished to the size.

3. In general, the homogenizing section of the barrel wears quickly. This section (5-7d long) can be bored and trimmed, and then a nitrided alloy steel bushing can be equipped. The diameter of the inner hole refers to the diameter of the screw, and it can be processed and prepared in the normal matching gap.

It is emphasized here that the screw and barrel are two important parts, one is a slender threaded rod, and the other is a small and long hole. Their machining and heat treatment processes are complex, and it is difficult to guarantee the accuracy. Therefore, whether to repair or replace these two parts after wear 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. This is not necessarily the correct choice. The comparison between the repair cost and the renewal cost is only one aspect. In addition, the ratio of the repair cost to the use time of the screw after repair to the renewal cost and the use time of the screw after renewal should also be considered. It is economical and correct to adopt the scheme with small ratio.