Generally, screws can be divided into ordinary type, gradient type, mutant type, mixing type, separation type, shunt type and various barrier type, pin type, DIS tie-tied shunt type
and exhaust type, etc.; The number of screw heads can be single head or variable head.
For plastics that are generally not flame retardant, they can be processed using ordinary general-purpose screws, and only different diameters need to be selected according to different melt viscosities. If
It is a plastic with special performance, special products or special particle shapes, and special screws must be used. Universal screw for a certain plastic, in the plasticization and
The power consumption and other aspects are not as good as the special screw performance. The following is a special introduction to various special products and special screws manufactured for special needs.
PC screws
PC is a high-viscosity amorphous plastic, poor fluidity, easy degradation when heated for a long time, large feeding torque, difficult to melt, easy to stagnate, high material temperature, high pressure injection
Shooting, the temperature adjustment range is narrow, and the processability is not as good as 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 and non-porous
Reduce surface adhesion and degradation, fine structure treatment, storage glue effectively prevent, low shear design, small heat generation. Generally, take small and medium-sized diameter, mold PCABS+PC,
PP-R, flame retardant ABS and other effects are good. It can also be molded into general plastics and PMMA ordinary products, but the color mixing effect is poor. If the color powder is added to the plastic, it needs to be customized to strengthen the color mixing
Type screw.
With the industry's ultra-thin precision molding, it provides the screw diameter to be changed from large to small, long to short, to increase the injection pressure to more than 3000Kgf/cm, and to move the injection seat forward (change
It can be restored to its original state normally after construction).
Screws for PMMA
PMMA is a high-viscosity amorphous plastic, strong and strong feeding torque, difficult to melt, easy to stagnate, shear sensitive and easy to degrade, slightly poor fluidity, must be high material
Temperature and high pressure injection, wide range of material temperature adjustment, good processability.
The screw compression is relatively large, and the imported high-alloy steel is fully hardened, which effectively withstands high torque and high pressure impact, and the surface electroplating hard chrome reduces surface adhesion
Degradation, good plasticization uniform effect, good color mixing, low shear design, low heat generation, low degradation rate. Generally, the middle diameter is taken to form PMMA, PP-R, PC, resistance ABS, etc
It works well when adding pigment.
CP, CA acid screw components:
In view of the corrosive characteristics of acid plastics such as CP and CA, screws, glue cartridges and other plasticized parts have been specially designed in structure and surface treatment.
The screw assembly has good corrosion resistance. It is recommended to use a double alloy barrel for corrosion resistance.
PVC special screws
PVC plastics can be divided into granular and powdery forms, which are very sensitive to temperature and easy to decompose, with high viscosity and strong corrosion. The design of the screw has two characteristics: the surface must
Must be chrome-plated; There are no dispensing rings and dispensing mesons.
The screw has good plasticization, less shear heat, and is resistant to acid corrosion. Because there is no rubber ring, it cannot be used for low-viscosity plastics and injection speed pressure grading is more accurate
Product.
There are two types of screw designs: screw and glue dispensing head integrated type; The screw and dispensing head are separated. High quality requirements for products and only single plastic (PVC) rule
It is most appropriate to use a conjoined type
On the contrary, the split type can be used, but it should be noted that the separation of the screw and the separator head is easy to cause material accumulation. However, what kind of screw to choose, our company recommends that a special temperature meter must be added for accurate temperature control.
Due to the need for heat dissipation and cooling, the melt cartridge should be used with forced air cooling measures to cooperate with the screw when making PVC products. Soft PVC for beaten toys is excluded.
PU, TPU special screws
Designed for PU shear sensitivity easy to overfire, strong adhesion and characteristics, surface electroplating hard chrome, smooth feeding, high plasticizing efficiency, low temperature rise.
Soft rubber, EVA foam type special screw
Low shear, high conveying efficiency design, surface plating hard chrome.
PET special rod
PET plastic is a common raw material for general plastic bottled beverages, with low viscosity, good fluidity, large specific heat capacity, easy to stick materials, high molding temperature, but material temperature adjustment
The knots range is narrow and the processability is poor, and if the material temperature is too high, the screw shear is too large or the speed is too fast, acetaldehyde is easy to produce and acidify during PET injection molding.
For PET and PET preforms require fast plasticization and uniform plasticization, screws have good plasticization, high stability, non-sticky material, fast glue melting speed, and preform blowing
High yield at the time of bottle. It is also possible to mold general plastics. However, it should be noted that in the mainland, general manufacturers will add water inlet material when making PET preforms, in which case PET is specialized
The use of screws is not very suitable, on the contrary, ordinary screws are more suitable for chrome plating. It is necessary to attach an anti-salivation device to the nozzle.
PA6/66/46/6T special screw nails
PA is a low-viscosity crystalline plastic, high temperature, fast melting speed, good self-lubrication, good fluidity, water-based and easy to salivate, temperature-sensitive and easy to cold head, hygroscopic and easy
The screw groove of the feeding section is stuck, and the coloring is difficult.
The screw has a large compression ratio, precise anti-return, good color mixing effect, stable feeding volume, high plasticizing efficiency and good exhaust effect. Generally, take the middle diameter and form PA, PP,
LCP and other crystalline low-viscosity plastics have good effects. It is also possible to mold general plastics. For PC, PMMA flame retardant ABS and other plastics with high viscosity and poor thermal stability are not suitable (medium
Segment temperature is too high, decomposition), molding POM is necessary to electroplate hard chrome. The nozzle is best heated at constant temperature, and an anti-salivation device is necessary to be added.
PPO screws
PPO is an amorphous material, difficult to melt, easy to stagnate, sensitive to shear, easy to degrade.
It is recommended to use double alloy to improve wear resistance and corrosion resistance, grade C can be, screw feeding is smooth, and the pressure is stable.
PBT+GF special screws
PBT is a saturated resin, semi-crystalline material, high melting, rapid crystallization curing, easy decomposition, sensitive to pressure and need to add glass fiber.
Double alloy must be used to improve wear resistance, according to the amount of weaving, there are three engineering grades of C, B, A to choose from, and the pressure generated by the screw is stable. Molded PBT+GF,
Crystalline low-viscosity ordinary engineering plastics such as PA+GF have good effects.
Marbled screws
Two schemes: A: only need to replace the marbling effect screw; B: Replace the whole set of marbled screw pipe, control the computer to modify the program or add electrical plug-in.
Bakelite and urea special screw material pipe group
The material pipe is heated with a hot oil loop, and the screw is recommended C grade double alloy; Old plastic machines can also be converted into bakelite shootouts
The mixing head enhances the color mixing effect
The mixing head is another design of the dispensing head, which mainly enhances the color mixing effect, but has the following limitations when used: it will cause the back pressure to increase when melting; The melting time increases
Long; Not suitable for plastics with high viscosity, such as PMMA, PC, etc. If the customer is not satisfied with the color mixing, the back pressure of the melt can generally be increased and the screw speed can be reduced, which will be certain
The effect appears. If customers do not want to use mixing heads to add color mixing effect, chrysanthemum type glue injection mesons can also be used.
