Detailed introduction

30

2018

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07

Repair principle of barrel screw


 
  ScrewThe two important parts of the barrel, one is a slender threaded rod, and the other is a relatively small and long hole in diameter. Their machining and heat treatment processes are more complicated, and the accuracy is more difficult to ensure. Whether to repair or replace the new parts after the wear of these two parts must be comprehensively analyzed from an economic point of view. If the cost of repair is lower than the cost of replacing the screw, it is decided to repair. This is not necessarily the right choice. The comparison between the cost of repair and the cost of renewal is only one aspect.
Also look at the cost of repair and repair after the use of screw time and update the cost and update the screw use time ratio. It is the right choice to adopt a scheme with a small ratio to be economical.
Extruder Barrel Screw. jpg
Repair of screw:
1. The 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.
2. After the thread surface of the reduced diameter of the wear screw is treated, the wear-resistant alloy is thermally sprayed, and then ground to size. This method is generally a professional spraying plant processing repair, the cost is relatively low.
3. Weld wear-resistant alloy on the threaded part of the wear screw. According to the degree of screw wear welding 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 plant for this kind of processing cost is very high, in addition to the special requirements of the screw, generally 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 easier to fall off.
Barrel repair:
The hardness of the inner surface of the barrel is higher than that of the screw, and its damage is later than that of the screw. The obsolescence of the barrel means that the inner diameter increases due to time wear.
Its repair method is as follows:
1, due to wear to increase the diameter of the barrel, if there is a certain nitriding layer, the barrel hole can be directly boring, grinding to a new diameter size, and then according to the diameter of the preparation of new screw.
2. The inner diameter of the barrel is machined and trimmed to re-cast alloy with a thickness of 1~2mm, and then finished to size.
3. Under normal circumstances, the homogenization section of the barrel wears faster. This section (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, and stays in the normal fit clearance for processing and preparation.