Focus on extrusion screw manufacturing for 30 years
Screw classification and type
Screw classification and type
Usually the screw can be divided into ordinary type, gradual type, mutation type, mixing type, separation type, diversion type and various barrier type, pin type, DIS opening diversion type and exhaust type; The number of screw heads can be single head or variable head.
For the general plastic without flame retardant, the use of common screw can be processed, only need to choose different diameter according to different melting viscosity. If it is a special performance of plastic, special products or special particle shape of plastic, must use special screw. General screw for a certain kind of plastic, in plasticizing and consumption of power and other aspects than the performance of special screw. The following is a variety of special products, special needs and manufacture of special screw for one by one introduction.
PC special screw, PC for high viscosity non-crystalline plastic, poor mobility, long time heat degradation, feeding torque is big, difficult to melt, easy to stagnation plug, need high material temperature, high pressure injection, material temperature adjustment range is narrow, technology as PMMA. The screw adopts imported high alloy steel full hardening treatment, effectively bear high torsion, high pressure impact, wear resistance, surface electroplating, corrosion resistance, smooth and non-porous to reduce surface adhesion and degradation, the details of the structure carefully processed, the effective prevention of glue, low shear design, small heat. Generally take small and medium diameter, forming PCABS+PC, PP-R, flame retardant ABS effect is good. Can also form general plastic and PMMA common products, but the color mixing effect is poor. If adding toner to plastic, you need to customize the screw to strengthen the mixing color. In line with the ultra-thin precision molding in the industry, the diameter of the screw is changed from large to small, from long to short, and the injection pressure is increased to more than 3000Kgf/cm. The injector seat is moved forward for modification (it can be restored to its original state normally after modification).
PMMA special screw, PMMA for high viscosity non-crystalline plastic, quality of strong and tough feeding torque, difficult to melt, easy to plug, shear sensitive to degradation, slightly poor liquidity, must be high material temperature, high pressure injection, material temperature adjustment range is wide, technology is good. Sscrew compression is relatively large, using imported high alloy steel full hardening treatment, effectively bear high torsion, high pressure impact, surface plating hard chromium to reduce surface adhesion and degradation, good plasticizing uniformity, good color mixing, low shear design, low heat, low degradation rate. Generally take the middle diameter, forming PMMA, PP-R, PC, ABS and other resistance toner when the effect is good.
PVC special screw, PVC plastic can be divided into granular and powdery, temperature reaction is very sensitive to decomposition, high viscosity, strong corrosive. The screw design has two characteristics: the surface must be chrome plated; No rubber ring and rubber meson. Good plasticizing, less shear heat, acid corrosion resistance. Because there is no apron, can not be used for low viscosity plastics and injection speed and pressure classification of more accurate products. There are two kinds of screw design: screw and glue head integrated; Separate screw and glue head. The high quality of the product and only make a single plastic (PVC) is the most appropriate to use the connecting type, on the contrary, can choose the split type, but it should be noted that the screw and glue head separate easy to cause the product. But what kind of screw to choose our company suggests that we must add a special thermometer for accurate temperature control, because of the need to heat and cool down, PVC products to melt plastic tube to adopt forced air cooling measures and screw use. Soft PVC toys are excluded.
Special screw for PU and TPU, designed for PU shear sensitive, easy to overfire, strong adhesion and characteristics, hard chrome plating surface, smooth feeding, high plasticizing efficiency, low temperature rise. Soft glue, EVA foaming type special screw low shear, high transmission efficiency design, surface plating hard chromium.
PET special rod, PET plastic for the general plastic bottled drinks commonly used raw materials, low viscosity, good liquidity, large specific heat capacity, easy to stick material, molding temperature is high, but the material temperature adjustment range is narrow, poor technology, PET injection molding if the material temperature is too high, the screw shear is too large or speed is too fast are easy to produce acetaldehyde and lead to acidification. For PET and PET preform plasticizing fast, uniform plasticizing characteristics, screw plasticizing good, high stability, non-stick material, melt fast, the preform blowing rate is high. It can also be molded into general plastics. But it should be noted that in the mainland general manufacturers in making PET preform will add water inlet material, in this case, PET special screw is not very suitable, on the contrary, ordinary screw plating is more appropriate. It is necessary to add an anti-salivation device to the nozzle.
PA6/66/46/6T special screw, PA for low viscosity crystalline plastic, high temperature, melting speed, good self-lubrication, good liquidity is water easy to salivate, temperature sensitive easy cold head, hygroscopic big easy to stick feeding section screw slot, coloring difficult. The screw compression ratio is large, the reverse stop is precise, the color mixing effect is good, the feeding quantity is stable, the plasticizing efficiency is high, the exhaust effect is good. Generally take the middle diameter, forming PA, PP, LCP and other crystalline low viscosity plastic effect is good. It can also be molded into general plastics. For PC, PMMA flame retardant ABS and other high viscosity and poor thermal stability of the plastic is not applicable (high temperature in the middle, decomposition), forming POM is necessary to electroplate hard chromium. The nozzle constant temperature heating is the best, and it is necessary to add anti-salivation device.
PPO special screw, PPO is an amorphous material, difficult to melt, easy to block, sensitive to shear, easy to degrade. Recommended use of double alloy to improve wear resistance, corrosion resistance, grade C, screw feeding smooth, stable pressure.
PBT+GF special screw, PBT is a saturated resin, semi-crystalline material, high melting degree, rapid crystallization fast curing, easy to decompose, sensitive to pressure and need to add glass fiber. Dual alloy must be used to improve the wear resistance. According to the amount of weaving, there are three engineering grades C, B and A available. The pressure generated by the screw is stable. Molded PBT+GF, PA+GF crystal low viscosity common engineering plastics effect is good.