Detailed introduction

07

2023

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02

What is the important role of alloy screw in plastic machinery?


  alloy screwWhat is the important role in plastics machinery?

  

合金螺杆


The mechanical structure of the injection molding machine is mainly divided into injection molding part and clamping part. The function of the injection part is to melt the plastic and inject it into the mold cavity, while the function of the mold locking part is to control the opening and closing of the mold, the ejection of the product, and other actions.

The injection part mainly has two forms: piston type and reciprocating alloy screw type. At present, there are few piston injection molding machines. The reciprocating alloy screw injection molding machine melts and mixes solid plastic particles or powder through the rotation of the alloy screw in the heated barrel, extrudes it into the cavity at the front of the barrel, and then moves forward along the axisalloy screw, Melt the plastic in the cavity into the mold cavity. During the plasticizing process, the plastic is compacted in the alloy screw groove driven by the edge of the alloy screw and receives the heat transferred by the cylinder wall. In addition, due to the friction between the plastic and the plastic, the plastic and the cylinder and the screw surface, the temperature gradually increases to the melting temperature.

The molten plastic is stirred and further mixed by Luo Xuan, following the spiral groove into the front of the barrel and pushing the spiral back. Injection parts and plasticizing related parts mainly include: barrel, screw, stop ring, shuttle, nozzle, flange, hopper, etc.

The screw is an important part of the injection molding machine. Its function is to transport, melt, compact, mix and pressurize plastics. All this is achieved by rotating the screw in the tube. When the screw rotates, the plastic will produce friction and mutual movement between the inner wall of the barrel, the bottom of the screw groove, the screw edge advancing surface, and the plastic and the plastic. The progress of plastics is the result of this combination of movements, and the heat generated by friction is also absorbed to raise the temperature of the plastic and make it melt. The structure of the screw will directly affect the extent of these effects.

At the same time, the rotation of the screw shears the molten film between the solid bed and the inner wall of the barrel, thereby melting the solids between the molten film and the solid bed interface. As the spiral shape of the solid bed moves forward, the volume of the solid bed gradually decreases, while the volume of the molten bath gradually increases. If the rate at which the thickness of the solid bed decreases is lower than the rate at which the depth of the spiral groove becomes shallow, the sensitivity of viscosity to temperature and shear rate, the corrosiveness of pyrolysis gases, and the coefficient of friction between plastic particles. Generally speaking, when processing some plastics with outstanding melt characteristics, the shear heat of a certain section will be too high for ordinary general-purpose screws, which can usually be eliminated by reducing the screw speed. But this is bound to affect productivity.