Date：2018-07-18
The combined work quality of the two parts of the barrel screw has an important impact on the plasticization of the material, the quality of the product and the production efficiency. Their working quality is related to the manufacturing precision and assembly clearance of the barrel screw. When the screw barrel is seriously worn and the output of the plastic machine is reduced, the maintenance of the screw and the barrel should be arranged.
Most of the ultra-engineering plastics currently used contain additives such as fire retardant, glass fiber, stone powder and modifier, which cause the barrel and screw to corrode, wear and shorten the life. In addition to the remarkable achievements in the manufacture of twin-alloy screws and barrels, our company's engineers and technicians have combined research and development to develop double-alloy spraying repairing technology to ensure the alloys spray-welded. The layer never falls off, no cracks, no pores, and we strictly controls the deformation of the workpiece. The old barrel is equipped with a boring or inner hole insert. After repairing, the plasticizing parameters in the whole machine do not need to be modified. The service life is much higher than the conventional material parts you purchase.
First, the screw repair technology
1 It should be considered according to the actual inner diameter of the barrel, and the outer diameter deviation of the new screw is decided according to the normal gap of the barrel.
2 After the surface treatment, spray the tungsten carbide alloy is thermally and then grinding.
3 Surfacing the wear-resistant tungsten carbide alloy on the threaded portion of the wear screw. Build 1 to 2 mm thick according to the degree of screw wear, and then grind the screw. The wear-resistant tungsten carbide alloy is composed of materials such as C, Cr, Vi, Co, W and B, which increases the anti-wear and corrosion resistance of the screw.
4 repairing the screw bottom diameter by electroplating hard chrome treatment, chromium is also wear-resistant and corrosion-resistant metal, but the hard chrome layer is easier to fall off.
Second, the repair technology of the barrel
The inner surface of the barrel is harder than screw, and its damage is later than the screw. The inner diameter increases due to time wear causes scrapping of the barrel. The repair method is as follows:
1 The barrel with increased diameter due to wear. If there is a little layer of nitriding, the inner hole of the barrel can be directly honed and smoothed to a new diameter size, and then you need a new screw according to the diameter.
2 The inner diameter of the barrel is machined and trimmed to recast the tungsten carbide alloy, the thickness is between 1 and 2 mm, and then finished to the required diameter.
3 Under normal circumstances, the homogenization section of the barrel wears faster. This section (take 5~7D long) can be inserted through the reaming hole, and then prepare a nitriding alloy steel bushing. The diameter of the inner hole is referenced to the screw diameter to make a new one.
Notice: Their machining and heat treatment processes are complicated and the precision is guaranteed. Therefore, no matter repair or replace with new ones, remind you to be fully analyzed from economic view. Though the repair cost is lower than the cost of replacing the new screw, the comparison between repair costs and renewal costs is only one aspect. You also need to consider the ratio of use time and renewal costs. It is economical to adopt a scheme with a small ratio.
4 screw and barrel manufacturing materials
The manufacturing materials of the screw and barrel are usually high-quality alloys such as 45, 40Cr and 38CrMoAlA. The yield strength of this material is about 900MPa. After nitriding treatment, the hardness is above 950 HV, which is both wear-resistant and has good corrosion resistance.
