Renovation and repair technology of old screw and barrel


The combined working quality of the two parts of the sc […]

The combined working quality of the two parts of the screw and the barrel has an important influence 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 and barrel are severely worn and the output of plastic machinery decreases, maintenance of the screw and barrel should be arranged.

 In response to the needs of various plastic products, Hachide Plastic Machinery Factory currently uses super engineering plastics mostly containing additives such as fire retardant, glass fiber, stone powder, modifier, etc., which causes rapid corrosion, wear and shorten life of the barrel and screw. In addition to the remarkable achievements in the manufacture of double alloy screws and barrels, our company's engineering and technical personnel have combined with traditional Chinese technology to research and develop the repair of old screws with double alloy spraying, which ensures the sprayed alloy The layer will never fall off, no cracks, no pores, and strictly control the deformation of the workpiece. The old barrel uses boring or inner hole inserts. After repair, the plasticization parameters in the whole machine do not need to be modified, and its service life is much longer than that of the conventional material parts you purchase, which brings to the rubber and plastics industry. Greater wealth. Dongguan injection molding machine screw manufacturers analyzed the renovation and repair technology of old screws and barrels.

First, Screw repair technology
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 manufactured according to the normal gap with the barrel.
2. After the thread surface of the abrasion screw diameter is reduced, the wear-resistant tungsten carbide alloy is thermally sprayed, and then processed to the size by grinding.
3. The wear-resistant tungsten carbide alloy is welded on the threaded part of the wear screw. According to the degree of screw wear, surfacing 1 ~ 2mm thick, and then grinding the screw to size. This wear-resistant tungsten carbide 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.
4. Repair the bottom diameter of the screw as the treatment method of electroplating hard chromium. Chromium is also a wear-resistant and corrosion-resistant metal, but the hard chromium layer is easier to fall off.

Second, the repair technology of the barrel

The hardness of the inner surface of the barrel is higher than the screw, and its damage is later than the screw. The scrapping of the barrel is the increase of the inner diameter due to time wear. Its repair method is as follows:

1. If the barrel increases in diameter due to wear, if there is a certain nitriding layer, the inner bore of the barrel can be directly bored and smoothed to a new diameter size, and then a new screw is prepared according to this diameter.
2. The inner diameter of the barrel is machined and trimmed to re-cast the tungsten carbide alloy with a thickness of 1 ~ 2mm, and then finished to the diameter.
3. Under normal circumstances, the homogenization section of the barrel wears faster. You can insert this section (take 5 ~ 7D long) through the reaming sleeve, and then equip with a nitriding alloy steel bushing. Process and prepare within the normal fit gap. Note: It is emphasized here that the two important parts of the screw and the barrel, one is a slender threaded rod, and the other is a hole with a small diameter and a long hole. Their machining and heat treatment processes are more complicated, and the accuracy is guaranteed. more difficult. Therefore, whether the two parts are worn or repaired or replaced with new ones, Dongguan Huahong reminds you to make a comprehensive analysis from an economic perspective. If the repair cost is lower than the cost of replacing the new screw, you decide to repair it, which is not necessarily correct. The choice of repair cost and the cost of renewal are only one aspect. In addition, it depends on the ratio of the repair cost and the time of using the screw after repair to the cost of renewal and the time of using the renewed screw. It is economical to adopt a scheme with a small ratio, which is the right choice.
4. Materials for screw and barrel manufacturing High-strength alloys 45, 40Cr and 38CrMoAlA are commonly used as the manufacturing materials for screw and barrel of Haichide Plastic Machinery Factory. The yield strength of this material is about 900MPa. After nitriding treatment, the hardness is above 950HV, which is both wear-resistant and has good corrosion resistance.