Classification of screws

Generally, the screw can be divided into ordinary type, gradual type, mutant type, mixing type, separation type, split type and various barrier type, pin type, DIS split type and exhaust type; the number of screw heads can be single head Or change the head and so on.

For plastics that are generally free of flame retardants, they can be processed using ordinary general-purpose screws, and only different diameters may be selected according to different melt viscosities.

If it is a special plastic, special product or special particle shape plastic, a special screw must be used.

Special screw introduction

The general-purpose screw is superior to a special screw in terms of plasticization and power consumption for a certain type of plastic. The following are the special screws manufactured by various special products and special needs.

PC special screw:

PC is a high-viscosity non-crystalline plastic with poor fluidity. It is easily degraded by heat for a long time. It has large feeding torque, is difficult to melt, and is easy to stagnate. It requires high temperature and high pressure injection. The temperature adjustment range is narrow and the process is not as good as PMMA.

The screw is fully hardened by imported high-alloy steel, which can withstand high torque, high pressure impact, wear resistance, surface plating, corrosion resistance, smooth and non-porous to reduce surface adhesion and degradation, careful treatment of fine structure, and effective prevention of hiding glue. Low shear design, low heat. Generally take small and medium diameter, molding PCABS + PC, PP-R, flame retardant ABS and other effects. It can also form general plastics and PMMA common products, but the color mixing effect is poor. If the color powder is added to the plastic, it is necessary to order the enhanced color mixing screw.

Cooperate with the industry's ultra-thin precision molding, provide large and small screw diameter, long and short, increase the injection pressure to 3000Kgf/cm or more, and move the seat forward and transform it (it can be restored to its original state after transformation).

PMMA special screw:

PMMA is a high-viscosity non-crystalline plastic. The toughness of the material is strong, it is difficult to melt, easy to stagnate, shear sensitive and easy to degrade, and the fluidity is slightly poor. It must be injected with high temperature and high pressure, and the temperature adjustment range is wide. Good process. The screw compression is relatively large, and it is fully hardened by imported high-alloy steel. It can withstand high torque and high pressure impact. The surface is plated with hard chrome to reduce surface adhesion and degradation. The plasticization uniform effect is good, the color mixing is good, and the low shear design has low heat. The degradation rate is low. Generally, the intermediate diameter is taken, and the effect is good when forming PMMA, PP-R, PC, and ABS.

CP, CA acid screw assembly:

For the corrosive properties of acidic plastics such as CP and CA, screws, melt cylinders and other plasticized parts have been specially designed in terms of structure and surface treatment. The screw assembly has good corrosion resistance. It is recommended to use a dual alloy barrel for corrosion resistance.

PVC special screw:

PVC plastic can be divided into granular and powdery, very sensitive to temperature and easy to decompose, high viscosity and strong corrosive. The design of the screw has two characteristics: the surface must be chrome-plated; there is no rubberized ring and rubberized meson. The screw plasticization is good, the shear heat is less, and the acid corrosion is resistant. Because there is no apron, it can not be used for low viscosity plastics and injection speeds with more accurate pressure classification.

There are two types of screw design: the screw and the rubber head are integrated; the screw and the rubber head are separated. It is most suitable for the quality of the product and only the one-piece type is used for the single-plastic (PVC). Otherwise, the split type can be used, but it should be noted that the screw and the separation head are easy to cause the accumulation. But what kind of screw is used? We recommend that a special temperature gauge must be added for precise temperature control. Because of the need to dissipate heat and cool down, the molten rubber cylinder should be used with the screw when the PVC product is used. Except for soft PVC for making toys.

PU, TPU special screw:

Designed for PU shear sensitive overheating, strong adhesion and characteristics, the surface is plated with hard chrome, the feeding is smooth, the plasticizing efficiency is high, and the temperature rise is low.

Soft rubber, EVA foam type special screw:

Low shear, high transport efficiency design, hard chrome plating on the surface.

PET special rod:

PET plastic is a common raw material for general plastic bottled beverages. It has low viscosity, good fluidity, large specific heat capacity, easy sticking, and high molding temperature. However, the temperature adjustment range is narrow and the processability is poor. If the material temperature is too high during PET injection molding. When the screw shear is too large or the rotation speed is too fast, acetaldehyde is easily generated to cause acidification.

For PET and PET preforms, the plasticizing speed is fast and the plasticizing is uniform. The screw plasticizing is good, the stability is high, the non-sticking material, the melting speed is fast, and the preforming rate is high when the preform is blown. It can also be molded into general plastics. However, it should be noted that the general manufacturer in the mainland will add the nozzle material when making the PET preform. In this case, the PET special screw is not very suitable. On the contrary, the ordinary screw chrome plating is more suitable. It is necessary to attach an anti-rogue device to the nozzle.

PA6/66/46/6T special screw:

PA is a low-viscosity crystalline plastic with high temperature, fast melting speed, good self-lubricating property, good fluidity and easy flow of water. The temperature is sensitive and easy to cool, and the hygroscopicity is easy to get stuck in the feeding section screw groove.

The screw compression ratio is large, the anti-reverse precision, the color mixing effect is good, the feed amount is stable, the plasticization efficiency is high, and the exhaust effect is good. Generally, the intermediate diameter is taken, and the crystalline low-viscosity plastics such as PA, PP, and LCP are formed to have good effects, and general plastics can also be formed. It is not suitable for plastics with high viscosity and poor thermal stability such as PC and PMMA flame retardant ABS (the middle temperature is too high and decomposed), and it is necessary to form hard chromium for forming POM. It is best to heat the nozzle at a constant temperature, and it is necessary to add an anti-flow device.

PPO special screw:

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

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

PBT+GF special screw:

PBT is a saturated resin, semi-crystalline material with high degree of melting, rapid solidification of crystals, easy decomposition, pressure sensitivity and the addition of glass fiber.

Double alloys must be used to improve wear resistance. According to the amount of weaving, there are three engineering grades of C, B and A, and the screw produces stable pressure. Forming PBT+GF,

Crystalline low viscosity general engineering plastics such as PA+GF have good effects.

Marble thread special screw:

Two options: A: only need to replace the marble effect screw; B: replace the marble spiral screw tube set, control the computer to modify the program or add electrical plug.

Bakelite and urea special screw material tube set:

The material pipe is heated by hot oil loop type, and the screw is recommended to be C grade double alloy; the old plastic machine can also be converted into bakelite injection mixing head to enhance the color mixing effect; the mixing head is another design of the rubberized head, mainly to enhance the color mixing effect. However, the following restrictions are imposed: the back pressure will increase when the glue is melted; the glue time will increase; it is not suitable for plastics with high viscosity, such as PMMA, PC, etc. If the customer is not satisfied with the color mixing, the melt back pressure and the screw speed can be increased, and a certain effect will appear. If the customer does not want to use the mixing head to add color effects, you can also use chrysanthemum-type rubber meson.

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