What are the classification and types of screws

Update:10 Nov 2021

Usually the screw can be divided into ordinary type, gradual type, mutation type, mixing type, separation type, split type and various barrier type, pin type, DIS open split type and exhaust type, etc.; the number of screw heads can be single. Or become first class.
For plastics without flame retardants, they can be processed using ordinary general-purpose screws, and only need to select different diameters according to different melt viscosities. If it is a plastic with a special performance, a special product or a plastic with a special particle shape, a special screw must be used. For a certain kind of plastic, the general purpose screw is not as superior as the special screw in terms of plasticization and power consumption. The following is an introduction to various special products and special screws manufactured for special needs.
PC special screw
Pc is a high-viscosity non-crystalline plastic with poor fluidity, long-term heating and easy degradation, large feeding torque, difficult to melt, easy to block, high material temperature, high pressure injection, material temperature adjustment range is narrow, and the manufacturability is not as good as PMMA.
The screw adopts imported high-alloy steel fully hardened treatment, which can effectively withstand high torque, high pressure impact, wear resistance, surface electroplating, corrosion resistance, smooth and non-porous to reduce surface adhesion and degradation. The detailed structure is carefully treated, and the hidden glue is effectively prevented. Low shear design, low heat generation. Generally, small and medium diameters are used to form PCABS+PC, PP-R, flame-retardant ABS, etc. The effect is good. It can also form general plastics and PMMA general products, but the color mixing effect is poor. If you add toner to the plastic, you need to customize the enhanced color mixing screw.
With the industry's ultra-thin precision molding, the screw diameter can be changed from large to small, and the length is changed to short. The injection pressure can be increased to more than 3000Kgf/cm.
PMMA special screw
PMMA is a high-viscosity non-crystalline plastic. It is strong and tough. It has a large feeding torque, is difficult to melt, easy to block, shear sensitive and easy to degrade, and has poor fluidity. It must be injected with high material temperature and high pressure, and has a wide range of material temperature adjustment. The manufacturability is better.
The screw has a relatively large compression and adopts imported high-alloy steel fully hardened treatment, which can effectively withstand high torque and high pressure impact. The surface is electroplated with hard chromium to reduce surface adhesion and degradation. The plasticization effect is good, the color mixing is good, and the low-shear design has low heat generation. The degradation rate is low. Generally, the middle diameter is used to form PMMA, PP-R, PC, resistive ABS, etc. when adding toner, the effect is good.
CP, CA acid screw components:
In view of the strong corrosive characteristics of acidic plastics such as CP and CA, the screw, melt barrel 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 dual alloy barrel for corrosion resistance.
PVC special screw
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 corrosiveness. The design of the screw has two characteristics: the surface must be chrome-plated; there is no rubber ring and glue meson.
The screw has good plasticization, low shear heating, and acid corrosion resistance. Because there is no rubber ring, it cannot be used for low-viscosity plastics and products with more precise injection speed and pressure classification.
There are two types of screw designs: screw and dispensing head are integrated; screw and dispensing head are separated. For products with high quality requirements and only single plastic (PVC), the conjoined type is most suitable. Otherwise, the split type can be used. However, it should be noted that the separation of the screw and the glue head may cause material accumulation. But what kind of screw to choose, our company recommends that you must add a special thermometer for precise temperature control. Because of the need for heat dissipation and cooling, when making PVC products, the melt cylinder should be used with forced air cooling and the screw. Except soft PVC for making toys