Detailed introduction





How does the alloy screw prevent it from slipping?

When the alloy screw is difficult to compact the material at the feed inlet, or when there is not enough adhesion to convey the material along the length of the barrel, the alloy screw will slip. In the pre-forming stage of the alloy screw, when the alloy screw rotates in the barrel to convey the material in the direction of the screw and retreat to accumulate the material for the next injection, the screw will also slip. If the screw starts to slide during the preforming stage, whenalloy screwWhen the rotation is continued, the axial movement of the alloy screw will stop. Usually, the screw slip will lead to the degradation of the material before injection molding, and there will also be product quality problems such as short injection and prolonged processing cycle.



The reasons for the slippage of the alloy screw include excessive back pressure, overheating or overcooling of the rear half of the cylinder, wear of the cylinder or screw, too shallow spiral groove of the screw feed section, improper design of the hopper, shortage or blockage of materials in the hopper, wet resin, The lubricant content in the resin is too high, the particle size of the material is too fine, and the cutting shape of the resin or recycled material is poor.

The low temperature at the back of the barrel is usuallyalloy screwThe main cause of slippage. The barrel of the injection molding machine is divided into three parts. At the rear of the feed section, a thin layer of molten polymer is formed during heating and compression. The molten film layer adheres to the barrel. Without this thin layer, the granular material is difficult to transport forward.

The material in the feed section must be heated to a critical temperature to create a critical molten film layer. However, usually the residence time of the material in the barrel is too short to allow the polymer to reach this temperature. This situation may be due to the small scale of the equipment and the corresponding small barrel and screw. If the residence time is too short, the polymer will easily melt or be insufficiently mixed, which will cause the screw to slip or stall.

Now, introduce two simple ways to deal with this problem. Add a small amount of material from the end of the barrel for cleaning and check the melting temperature. If the residence time is short, the melt temperature will be lower than the set point of the barrel temperature. The second method is to observe the molded product. If marble markings, black spots or light stripes are found, the materials in the barrel are not well mixed.

One of the ways to solve the slip of the alloy screw is to gradually increase the temperature of the feed section until the rotation and retreat of the screw are coordinated. Sometimes the barrel temperature must be raised above the recommended set point to achieve this range.

Setting too high a back pressure can also cause the screw to stall or slip. Increasing the set point of the back pressure also increases the energy entering the material. If the back pressure is set too high, the screw may not generate enough pressure,alloy screwIt will rotate at a certain position without retreating, which will do more work for the melt and significantly increase the melt temperature, which will adversely affect product quality and cycle time. The back pressure exerted on the melt can be adjusted by means of a control valve on the injection cylinder.