Detailed introduction

04

2022

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11

Why should the alloy screw be cooled? How to reduce its wear?


  alloy screwWhy cooling? How to reduce wear?

  

合金螺杆

 

The so-called alloy screw is made of high-quality alloy steel (38CrMOALA) or chromium-molybdenum alloy steel black cross (SACM645) by tempering, shaping, molding, fine grinding, alloy (bimetal) surface nitriding or spray welding, polishing and other processes. It has the advantages of high wear resistance and corrosion resistance. Suitable for glass fiber, plastic, PPA, PO, PPS, LCP, ABS, phenolic molding compound, magnetic powder, PC and other special engineering plastics.

When extruding materials, it is necessary to cool the alloy screw, mainly to ensure the smooth progress of production and prevent the material from decomposing due to excessive plasticizing temperature. For example, in the feed section of the screw, cooling is to prevent the temperature of the screw from being too high, and to prevent the material from sticking in the screw groove of the screw due to high temperature and rotating with the screw, thus affecting the forward movement of the material conveying, resulting in insufficient supply of the material and unable to produce normally. The homogenization section of the screw is cooled down, because the melt in this section generates more heat due to greater extrusion, friction and shear, and the temperature rises quickly, so it needs to be cooled down to prevent material decomposition.

Coolingalloy screwThe method is to introduce water or oil into the screw drilled with axial holes as a heat transfer medium for cooling. The heat conducting medium should be controlled at a constant temperature until it reaches the homogenization section of the screw. When working, the rotating screw needs a special pipe fitting to connect with the heat transfer medium pipe. This special joint is called a rotary joint.

How to reduce the wear of the injection alloy screw?

Because the screw barrel of the injection molding machine needs to be in an environment of high pressure, high temperature, high mechanical torque, and high friction when working in such an environment for a long time, the screw of the barrel will inevitably wear out. Therefore, due to the limitations of these process factors, it is difficult to reduce its wear, but a scientific and reasonable method can appropriately reduce the degree of wear. How exactly?

Generally, to improvealloy screwWear resistance, the general manufacturers will be nitrided on the surface.

In addition, we also need to understand the causes of wear in order to take targeted measures to reduce the degree of wear and improve its service life.

We will introduce the causes of alloy screw wear and the methods to reduce wear in two points:

Each plastic raw material has a suitable processing temperature, so before processing different plastic raw materials, the processing temperature needs to be adjusted to make the processing temperature as close as possible to the ideal temperature.

In the process of granular plastic entering the barrel from the hopper, the first to reach the feeding section, so that dry friction will occur in the feeding section. In this way, these plastic raw materials are prone to insufficient heating and uneven melting, which easily leads to increased wear on the screw surface and the inner wall of the barrel. Then, when the plastic raw material enters the compression section and the homogenization section, the uneven melting state of the plastic will also lead to an increase in friction.

2. The speed should be adjusted appropriately, and the speed should not be adjusted too high. At present, a large number of reinforcing agents and fillers are added to many plastic raw materials, which will cause friction between the screw and the barrel. If the speed is high, the friction will increase.