Usually the screw can be divided into common type, gradual type, abrupt type, mixed type, separate type, split type and various types of barrier, pin type, DIS open and split type and exhaust type; the number of screw heads can be single Or change head and wait.
For plastics that are not normally fire-retardant, they can be processed using common general-purpose screws. Different diameters can be selected depending on the melt viscosity. If it is a special plastic, special product or special particle shape plastic, a special screw must be used. For a certain plastic, the general-purpose screw has superior performance in terms of plasticizing and power consumption than a special screw. The following is a special screw made by special products and special needs.
Pc is a highly viscous amorphous plastic with poor fluidity, prone to degradation by heat for a long time, large feeding torque, difficult to melt, and easy to stagnate, requires high material temperature, high pressure injection, narrow material temperature adjustment range, and is not as good as PMMA.
The screw adopts imported high-alloy steel full hardening treatment, effectively withstands high torque, high pressure impact, wear resistance, surface plating, corrosion resistance, smooth and non-porous to reduce the surface adhesion and degradation, careful handling of detailed structures, and effective prevention of hidden glue. Low shear design, low heat. Generally take small and medium diameter, molding PCABS + PC, PP-R, flame retardant ABS and other effects. General plastics and PMMA general products can also be molded, but the color mixing effect is poor. Such as plastic plus color powder, need to order enhanced mixing screw.
With the industry's ultra-thin precision molding, provide screw diameter large change, long change, raise the injection pressure to 3000Kgf/cm or more, the injection seat forward transformation (reform can be restored to the original state).
PMMA special screw
PMMA is a highly viscous non-crystalline plastic, which is characterized by high toughness, strong torque, difficult to melt, easy to stagnate, sensitive to shear, easy to degrade, less fluidity, high material temperature, high pressure injection, wide material temperature adjustment range, Better craftsmanship.
Screw compression is relatively large, the use of imported high-alloy steel full hardening treatment, effectively withstand high torque, high pressure impact, hard chromium plating surface to reduce surface adhesion and degradation, good plasticization effect, good color mixing, low shear design low heat, The degradation rate is low. Generally take the middle diameter, forming PMMA, PP-R, PC, blocking ABS and other color powder when the effect is good.
CP, CA acid screw components:
For the corrosive nature of CP, CA and other acidic plastics, screw, melt tube and other plastic parts have been specially designed in the structure and surface treatment.
The screw assembly has good corrosion resistance. It is recommended to use dual alloy barrels for corrosion resistance.
PVC special screw
PVC plastic can be divided into granular and powdery, very sensitive to the temperature of the reaction is easy to decompose, high viscosity, strong corrosion. The design of the screw has two characteristics: the surface must be chrome-plated; there is no aprons and splitting mesons.
Screw plasticization, less shear heat, acid corrosion. Because there is no apron, it cannot be used for low-viscosity plastics and injection pressures.
There are two kinds of screw design: screw and rubber head integrated; screw and dispensing head split type. High quality requirements for the product and the use of a single piece of plastic (PVC) are best suited for conjoined styles. Otherwise, separate styles may be used. However, attention should be paid to the fact that the screw and dispensing head can easily cause build-up. But what kind of screw is recommended, we must add a special temperature meter for precise temperature control. Because of the need for cooling and cooling, when using PVC as a product, the forced-air cooling measures must be used in conjunction with the screw. Except for soft PVC used in toys, PU and TPU special screws are designed for PU shear sensitive and over-fired, with strong adhesive force and characteristics, hard chromium plated on the surface, smooth feeding, high plasticization efficiency, and low temperature rise.
Soft rubber, EVA foaming special screw
Low shear, high delivery efficiency design, hard chromium plated surface.
PET plastic is a common raw material for ordinary plastic bottled beverages. It has low viscosity, good fluidity, high specific heat capacity, and easy to stick materials. It has a high molding temperature, but its temperature adjustment range is narrow, and its processability is poor. If the material is too hot during PET injection molding, it is too high. When the screw shear is too large or the rotational speed is too fast, it is easy to produce acetaldehyde and cause acidification.
For PET and PET preforms, they require fast plasticization and uniform plasticization. The plasticization of the screw is good, the stability is high, the non-stick material, the speed of the melt glue are fast, and the preforming rate when the preform is blown is high. General plastics can also be molded. However, it should be noted that general manufacturers in the mainland will add feed material to the PET preforms. In this case, the PET special screw is not very suitable, whereas ordinary screw chrome plating is more appropriate. It is necessary to attach an anti-fluid device to the nozzle.
PA6/66/46/6T special screw
PA is a low-viscosity crystalline plastic, high temperature, fast melting speed, good self-lubrication, good fluidity is easy to flow, temperature-sensitive and easy to cold head, moisture-absorbing large and easy to stick feeding section screw groove, difficult to color.
Screw compression ratio, anti-precision precision, color mixing effect, stable feed, high plasticization efficiency, good exhaust effect. Generally take the middle diameter, molding PA, PP, LCP and other crystal-type low-viscosity plastic effect is good. General plastic can also be molded. For PC, PMMA flame-retardant ABS and other high viscosity and poor thermal stability of the plastic is not suitable (middle temperature is too high, decomposition), forming POM is necessary to plate hard chrome. The nozzle thermostatic heating is best, and additional anti-fluid devices are necessary.
PPO special screw
PPO is a non-crystalline 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 used, smooth screw feeding and stable pressure.
PBT+GF special screw
PBT is a saturated resin, semi-crystalline material, high melting degree, rapid solidification of crystallization, easy to decompose, sensitive to pressure and need to add glass fiber.
Double alloy must be used to improve the wear resistance. According to the amount of fiber added, there are three engineering grades: C, B and A. The screw produces stable pressure. Forming PBT+GF, PA+GF and other low-viscosity ordinary engineering plastics are effective.
Marble special screw
Two options: A: Only need to replace the marble effect screw; B: Replace the marble screw material tube set, control the computer to modify the program or add electrical plug.
Bakelite, urea special screw material group
The material pipe is heated with hot oil and the coil is recommended. The screw is recommended to use the C-grade double alloy; the old plastic machine can also be modified into a bakelite injection mixing head to enhance the color mixing effect.
Mixing head is another design of dispensing head, mainly to enhance the effect of color mixing, but it has the following limitations when it is used: It will cause back pressure increase when melted; Melting time increases; Not suitable for plastics with high viscosity, such as PMMA, PC and so on. If the customer is not satisfied with the color mixing, the back pressure of the melted rubber can be increased and the screw speed can be reduced. There will be a certain effect. If the customer is not willing to use the mixing head to add color mixing effect, chrysanthemum-type injection mesons can also be used.