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General introduction to common screw of bottle blowing machine

Issuing time:2019-10-08 00:00

Generally, the screw can be divided into ordinary type, gradual change type, mutation type, mixing type, separation type, shunt type, as well as various barrier type, pin type, dis open tie shunt type and exhaust type, etc.; the number of screw heads can be single head or variable head, etc. For the general plastics without flame retardant, the general screw can be used for processing, and only different diameters need to be selected according to different melting viscosity. If it is a plastic with special properties, special products or special particle shape, special screw must be used. For a certain kind of plastic, the performance of general screw is not superior to that of special screw in terms of plasticization and power consumption. The following is a variety of special products, special needs and the production of special screws for one by one.




PC special screw




PC is a high viscosity non crystalline plastic with poor fluidity, easy degradation after long-time heating, large feeding torque, difficult melting and easy stagnation. It needs high material temperature and high pressure injection. The range of material temperature regulation is narrow, and the processability is inferior to PMMA.




The screw adopts imported high alloy steel full hardening treatment, which can effectively withstand high torque, high pressure impact, wear resistance, surface plating, corrosion resistance, smooth without pores to reduce surface adhesion and degradation. The detailed structure is carefully treated, and the rubber is effectively prevented, with low shear design and small heat. Generally, small and medium diameter is adopted, and the effect of forming pcabs + PC, PP-R and flame-retardant ABS is good. It can also form general plastics and PMMA general products, but the color mixing effect is poor. For example, adding color powder to plastics, it is necessary to order reinforced color mixing screw.




With the industry's ultra-thin precision molding, the screw diameter is changed from large to small, from long to short, the injection pressure is increased to more than 3000kgf / cm, and the injection seat is moved forward for transformation (after transformation, it can be normally restored to the original state).




PMMA special screw




PMMA is a high viscosity non crystalline plastic, with strong toughness, high feeding torque, difficult to melt, easy to jam, shear sensitive and easy to degrade, slightly poor fluidity. It must be injected with high material temperature and pressure, with wide range of material temperature adjustment and good processability.




The screw has a large compression ratio. It adopts the imported high alloy steel full hardening treatment to effectively withstand the impact of high torque and pressure. The hard chromium plating on the surface reduces the surface adhesion and degradation. It has good plasticizing effect, good color mixing, low shear design heat and low degradation rate. Generally, the middle diameter is used to form PMMA, PP-R, PC, ABS and other additive powder with good effect. CP, CA acid screw assembly: in view of the corrosive characteristics of CP, Ca and other acid plastics, the screw, melt cartridge and other plastic parts are specially designed in structure and surface treatment.




The screw assembly has good corrosion resistance. It is recommended to use double alloy barrel for corrosion resistance.




PVC special screw




PVC plastic can be divided into granular and powdery. It is very sensitive to temperature and easy to decompose. It has high viscosity and strong corrosiveness. The screw design has two characteristics: the surface must be chrome plated; there is no separating ring and separating meson.




The screw has good plasticization, less shear heating and acid corrosion resistance. Because there is no rubber ring, it can not be used for low viscosity plastics and products with lower injection speed and pressure classification.




There are two types of screw design: screw and rubber head integrated; screw and rubber head separated. For products with high quality requirements and only single plastic (PVC), the use of the conjoined type * is appropriate. Otherwise, the split type can be selected. However, it should be noted that the separation of the screw and the rubber head is easy to cause material accumulation. However, we suggest to add a special thermometer to control the temperature of which screw is selected. Because of the need of heat dissipation and temperature reduction, when making PVC products, the glue melting cylinder should adopt the forced air cooling measures to cooperate with the screw. Except for soft PVC toys.




Pu, TPU special screw




Designed for PU shear sensitive, easy to over fire, strong adhesion and characteristics, hard chrome plating on the surface, smooth feeding, high plasticizing efficiency, low temperature rise.




Soft rubber, EVA foaming special screw low shear, high delivery efficiency design, surface plating hard chromium.




PET special pole




PET plastic is the common raw material of plastic bottled drinks at present. It has low viscosity, good fluidity, large specific heat capacity and easy to stick material. The molding temperature is high, but the range of material temperature adjustment is narrow and the processability is poor. If the material temperature is too high, the screw shear is too large or the rotation speed is too fast, the pet injection molding will easily produce acetaldehyde, which will lead to acidification.




According to the requirements of pet and PET Preforms for fast and even plasticization, the screw has good plasticization, high stability, non stick material, fast melting speed and high rate of bottle blowing. It can also form general plastics. However, it should be noted that the general producers in mainland China will add water inlet material when making pet bottle blanks. In this case, the special screw for pet is not very suitable. On the contrary, the common screw is more suitable for chromium plating. It is necessary to add anti salivation device in the nozzle.




Special screw




PA is a low viscosity crystalline plastic, with high temperature, fast melting speed, good self-lubricating property, good fluidity, easy to salivate, temperature sensitive, easy to cool head, high moisture absorption, easy to block the screw slot in the feeding section, and difficult to dye.




The screw has large compression ratio, precise check, good color mixing effect, stable feeding volume, high plasticizing efficiency and good exhaust effect. Generally take the middle diameter, forming PA, PP, LCP and other crystalline low viscosity plastics with good effect. It can also form general plastics. For PC, PMMA flame retardant ABS and other plastics with high viscosity and poor thermal stability, it is not applicable (too high temperature in the middle section, decomposition), so it is necessary to electroplate hard chromium for forming POM. The constant temperature heating of the nozzle is good, and it is necessary to add anti salivation device.




PPO special screw




PPO is an amorphous material, which is difficult to melt, easy to jam, sensitive to shear and easy to degrade.




It is recommended to use double alloy to improve wear resistance and corrosion resistance, grade C is enough, screw feeding is smooth and pressure is stable.




PBT + GF special screw




PBT saturated resin


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