1. Screw Design
Screw Diameter: Choose the appropriate screw diameter based on the size of the injection molding machine and application requirements.
Length-to-Diameter Ratio (L/D): Common L/D ratios range from 20:1 to 30:1 to ensure the plastic is sufficiently plasticized.
Screw Groove Depth: Design different groove depths based on the characteristics of the plastic to ensure uniform melting on the screw.
2. Screw Structure
Feed Section: The front end of the screw, used for receiving and preheating plastic pellets.
Compression Section: The middle part, which further compresses and heats the plastic, causing it to melt.
Metering Section: The final part of the screw, ensuring uniform melted plastic and controlling the injection amount.
3. Material Selection
Alloy Steel: PS screws are typically made from high-strength alloy steel, providing excellent wear and corrosion resistance.
Surface Treatment: To extend the screw's lifespan, surface nitriding or chrome plating can be performed.
4. Processing Parameters
Temperature Control: The melting point of polystyrene is relatively low, generally between 180°C and 230°C, requiring precise temperature control.
Rotational Speed and Back Pressure: Appropriate screw rotational speed and back pressure help ensure uniform plasticization and improve injection quality.
5. Maintenance and Care
Regular Cleaning: Prevent residue buildup that can affect screw performance.
Wear Inspection: Regularly check for screw wear and replace or repair as necessary.