How To Improve The Use Of Screw Barrel

The injection-molded screw works in high temperature, high pressure, high mechanical torque and high friction environment for a long time. The first few factors are required by the process conditions, while the loss caused by friction is inevitable. Generally screw has been surface nitriding treatment, in order to improve the surface hardness, that is, improve the ability to resist wear. However, if the causes of wear are ignored and the wear is not reduced as much as possible, the working life of the screw will be greatly reduced.

The causes of screw wear and ways to reduce wear are described below:

1, each plastic, there is an ideal plasticizing processing temperature range, should control the barrel processing temperature, make it close to this temperature range. Granular plastics from the hopper into the barrel, the first will reach the feeding section, in the feeding section will inevitably appear dry friction, when these plastics are not heated enough, uneven melting, it is easy to cause the inner wall of the barrel and screw surface wear increased. Similarly, in the compression section and the homogenization section, if the plastic melting state is disordered and uneven, it will also cause increased wear.

2, the speed should be properly adjusted. Because part of the plastic with strengthening agents, such as glass fiber, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastic. In the injection molding of these plastics, if a high speed is used, it will increase the shear force of the plastic at the same time, it will also strengthen the corresponding production of more torn fibers, torn fibers contain sharp ends, so that the wear force is greatly increased. When inorganic minerals glide on metal surface at high speed, their scraping effect is not small. So the speed should not be adjusted too high.

3, to check the debris in the plastic. Generally speaking, the original purchase of fresh plastic and no debris, but after transportation, weighing, drying, mixing color, especially adding recycled material, it is possible to mix debris. As small as metal scrap, as large as heating ring nut paper clip, and even a string of warehouse keys, mixed into the barrel have occurred, the damage to the screw is self-evident (the barrel will also be damaged at the same time), so it is necessary to install the magnet frame, strict feeding management and monitoring.

4, the moisture contained in the plastic has a certain impact on the wear of the screw surface. If the plastic does not remove all the water before injection molding, the residual water will enter the compression section of the screw, and the “steam particles” with high temperature pressure will be formed before melting in the molten plastic. With the advance of the screw in the injection process, from the homogenization section to the screw head, these “steam particles” will release pressure and expand in the injection process, like fine impurities and hard particles. Friction damage to the wall. In addition, under high temperature and pressure, moisture may act as a catalyst for the cracking of certain types of plastics, producing harmful impurities that can erode metal surfaces. Therefore, the drying work before plastic injection molding is not only directly related to the quality of the workpiece, but also affects the working life of the screw.