Complete List of Special Materials for Injection Molding Machine Screws

For plastics without flame retardants, ordinary universal screws can be used for processing, and different diameters need to be selected based on different melting viscosities. For plastics with special performance (PC, PMMA, PA, LCP, PES, PET, PVC, CA, CP, thermosetting plastics, etc.), special products (transparent optical lenses, LCD light-emitting plates - light guide plates, bottle blanks, gears, connectors, etc.), or specific granule shaped (powder, sheet) plastics, halogen-free products, special metal ocean screws must be used. Universal screws are not superior in terms of plasticization and power consumption compared to specialized screws for a certain type of plastic. Below is an introduction to various special products and specialized screws manufactured for special needs.
PC dedicated screw
PC is a high viscosity non crystalline plastic with poor flowability, easy degradation when heated for a long time, high feeding torque, difficulty in melting, and easy blockage. It requires high material temperature and high pressure injection, with a narrow range of material temperature adjustment and inferior processability compared to PMMA. The screw adopts imported powder alloy full hardening (full alloy) or imported high alloy steel full hardening treatment, effectively withstanding high temperature, high torque, high pressure impact, wear resistance, corrosion resistance, smooth and no pores to reduce surface adhesion and degradation. The detailed structure is carefully treated, and the adhesive is effectively prevented. The low shear design, small and medium-sized diameter heating, forming PC, ABS+PC, PP-R, flame retardant ABS, and other materials have good effects. It can also be used to shape general plastics and PMMA ordinary products.
Jinyang Company cooperates with the industry in ultra-thin precision molding, and the transparent lens type requires design optimization of screw parameters. At the same time, it provides screw diameter changes from large to small, length changes from short, and increases the injection pressure to over 3000Kgf/cm. The injection seat is moved forward for modification (after modification, it can be restored to its original state normally) Jinyang screw rod.
Shenzhen Jinyang Injection Molding Machine Screw
PMMA dedicated screw
PMMA is a high viscosity non crystalline plastic with strong toughness and high feeding torque. It is difficult to melt, easy to block, sensitive to shear and easy to degrade, and has slightly poor flowability. It must be injected at high material temperature and pressure, with a wide range of material temperature adjustment and good processability.
The screw has a large compression ratio and is fully hardened with imported high alloy steel, effectively withstanding high torque and high pressure impacts. The surface is electroplated with hard chromium to reduce surface adhesion and degradation, with good plasticization uniformity, good color mixing, low shear design, low heat generation, and low degradation rate. Generally, the middle diameter is used to form PMMA, PP-R, PC, and ABS with good results.
Jinyang injection molding machine screw barrel
PA6/66/46/6T special screw
PA is a low viscosity crystalline plastic with high temperature, fast melting speed, good self-lubrication, and good flowability. It belongs to water-based and easy to salivate, temperature sensitive and easy to cool, and has high moisture absorption, which is easy to get stuck in the screw groove of the feeding section, making coloring difficult.
After optimizing the parameter design of the PA specialized screw, it has high compression ratio, precise backstop, good color mixing effect, stable feed rate, high plasticization efficiency, and good exhaust effect. Generally, taking the middle diameter and molding PA, PP, LCP and other crystalline low viscosity plastics have good effects It can also be molded into general plastics. It is not suitable for high viscosity and poor thermal stability plastics such as PC and PMMA flame-retardant ABS (with high intermediate temperature and decomposition), and it is necessary to electroplate hard chromium for forming POM. The nozzle is best heated at a constant temperature, and it is necessary to add an anti salivation device.
PPO dedicated screw
PPO is an amorphous material that is difficult to melt, easy to block, sensitive to shear, and easy to degrade. It is recommended to use dual alloys to improve wear and corrosion resistance. Grade C is sufficient, with smooth screw feeding and stable pressure generation.
PBT+GF dedicated screw
PBT is a saturated resin, a semi crystalline material with high melting degree, rapid solidification of crystallization, easy decomposition, pressure sensitivity, and the need to add glass fiber. JY dual alloy or full alloy must be used to improve wear resistance. There are three engineering grades available depending on the amount of fiber added, and the pressure generated by the screw is stable. Forming PBT+GF, PA+GF and other crystalline low viscosity ordinary engineering plastics has good effects.
PVC special screw
PVC plastic can be divided into granular and powdered forms, which are very sensitive to temperature reactions and easy to decompose. It has high viscosity and strong corrosiveness. The design of screws has two characteristics: the surface must be corrosion-resistant; There are no separation rings or separation 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 products with more accurate injection speed and pressure grading.
There are two types of screw designs: the screw and the glue separating head are integrated; Screw and dispensing head are separated. If the product has high quality requirements and only produces a single plastic (PVC), the use of a connected type is the most suitable. If not, a split type can be used. However, it should be noted that separating the screw and the dividing head can easily cause material accumulation. But our company suggests adding a dedicated temperature gauge for precise temperature control when selecting the screw. Due to the need for heat dissipation and cooling, when making PVC products, the melt tube should be used with forced air cooling measures in conjunction with the screw. Excluding soft PVC for making toys.
PET special screw
PET plastic is the common raw material for ordinary plastic bottled drinks at present. It has low viscosity, good fluidity, large specific heat capacity, and is easy to stick. It has high molding temperature, but narrow material temperature adjustment range and poor processability. If the material temperature is too high, the screw shear is too large, or the rotation speed is too fast, PET plastic is easy to produce acetaldehyde during injection molding, which will lead to acidification. For PET and PET bottle preforms, the characteristics of fast and uniform plasticization are required. The screw has good plasticization, high stability, non sticking material, fast melting speed, and high yield during bottle blowing. It can also be molded into general plastics.
CP, CA acidic screw components
Due to the strong corrosiveness of acidic plastics such as CP and CA, special designs have been made for the structure and surface treatment of screws, barrels, and other plasticized parts. The screw components have good corrosion resistance. It is recommended to use a dual alloy cylinder for corrosion resistance. Jinyang screw
PU, TPU dedicated screws
Designed for the characteristics of PU shear sensitivity, easy overheating, strong adhesion, and surface alloy, smooth feeding, high plasticization efficiency, and low temperature rise.
Soft rubber, EVA foaming special screw
Low shear, high conveying efficiency design, surface corrosion resistance.
Marble pattern special screw
Two options:
A: Just replace the marble effect screw;
B: Replace the complete set of marble pattern screw material pipes, control the computer to modify programs or add electrical peripherals.
Special screw barrel group for bakelite and urea
The barrel is heated by hot oil loop heating, and the screw is recommended to be made of medium grade double alloy; Old plastic machines can also be converted into bakelite for firing.
Mixing head enhances color mixing effect
The mixing head is another design of the screw head, which mainly enhances the color mixing effect. However, there are the following limitations when using it: it can cause an increase in back pressure during adhesive melting; The melting time increases; Not suitable for high viscosity plastics such as PMMA, PC, etc. If the customer is not satisfied with the color mixing, they can generally increase the melt back pressure and reduce the screw speed, which will have a certain effect. If users are unwilling to use a mixing head to add color mixing effects, they can also use chrysanthemum shaped glue injection mesons. Connected material pipe head, extended nozzle, catapult nozzle, and other gold screws.
Introduction to Injection Molding Screw
The plasticized screw is divided into three sections based on its geometric appearance
1. Feed zone
This section is the depth of the fixed screw groove, where solid plastic particles are tightly compressed to form a solid bed. Due to the shear effect of the melt tube, in addition to gradually increasing the plastic temperature, the plastic is also transported forward. It is necessary to ensure that the plastic begins to melt at the end of the feeding section (that is, it needs to be preheated to the melting point). The length of this section is divided into crystallinity (PA, POM, PE, PP, CA, etc.), non crystallinity (AS, PS, PU, ABS, etc.), thermal sensitivity (PVC, etc.), glass addition, etc. Generally, solid specific heat ↑, melting point ↑, and latent heat ↑ require more heat to heat up to the melting point, and the feeding section should be long; Solid state thermal conductivity ↓, slow heat transfer, slow temperature rise in the plastic center, and long feeding section; Preheat ↑, the feeding section can be short. Crystalline materials are the longest, followed by amorphous materials, and thermal sensitivity is the shortest. Jinyang screw
2. Compression zone
This section is a gradually decreasing screw groove with deep teeth, and its functions include plastic raw material melting, mixing, shear compression, and pressurized exhaust. Plastic will completely dissolve at this stage and its volume will decrease, so the design of compression degree (compression ratio) is important. For amorphous plastics, the compression section should be longer, otherwise if the volume of the screw groove decreases quickly and the material volume does not decrease, blockage may occur. Crystalline plastics are actually not fully crystalline (such as PE: 40-90% crystallinity, LDPE: 65% crystallinity), so there is currently a trend of lengthening the compression section. Thermal sensitivity, high viscosity, fire resistance, low conductivity, and high additives all require special consideration.
3. Measuring zone
This section is the fixed groove depth of the screw screw groove. Its main functions include mixing, glue output and feeding, and metering. In addition, it must also provide sufficient pressure to maintain a uniform temperature of the glue and stabilize the flow rate of the molten plastic. A longer metering section results in better mixing effect; If the measuring section is too long, it is easy for the melt to stay for too long and cause thermal decomposition; If it is too short, it can cause uneven temperature.
Main factors affecting plasticization quality
Length to diameter ratio=working length of screw (mm) ÷ screw diameter (mm)
If the aspect ratio is large, the food is easy to eat evenly, but it is easy to go overboard. Plastics with better thermal stability can use longer screws to improve mixing performance without worrying about burning; Plastic with poor thermal stability can be used with shorter screws or without threads at the end of the screw. Compression ratio=feed tooth depth (mm) ÷ metering tooth depth (mm) Considering the compressibility of material, filling degree, reflux, compactness of products, heat transfer and exhaust. An appropriate compression ratio can increase the density of plastic, making the bonding between molecules more tight, helping to reduce air intake, reduce temperature rise caused by pressure, and affect the difference in output. Inappropriate compression ratios will damage the physical properties of plastic. The higher the compression ratio, the higher the temperature rise generated during the plasticization process of plastic in the material pipe, and the better the mixing uniformity of the plastic in the process of cementation, The relative discharge volume is greatly reduced. When the tooth depth of the feeding section is deeper, the conveying capacity is greater, but the torque required for the screw is greater; The tooth depth of the feeding section is too shallow, the conveying capacity is insufficient, and the compression ratio is insufficient. When the tooth depth of the measuring section is too deep and the compression ratio is insufficient, a larger feeding force is required; When it is too shallow, it is easy to overheat and burn. High compression ratio is suitable for non fusible plastics, especially for plastics with low melting viscosity and thermal stability. Low compression ratio is suitable for fusible plastics, especially for high melting viscosity and heat sensitive plastics.