Common Problems and Solutions for Injection Molding Machine Screws

FAQ 1: Screw Slippage

Problem: During pre-molding, the screw rotates but doesn't push material forward, creating slippage.

Causes:

Insufficient material feeding due to short barrel length or poor material adhesion.

Low material melt temperature caused by short residence time in the barrel.

Uneven material mixing leading to black spots, light streaks, or marble patterns in molded products.

Solutions:

Material and Temperature: Add a small amount of material to improve packing at the barrel end. Simultaneously, verify the melting temperature against the set barrel temperature. A short residence time can lead to insufficient melting.

Mixing Inspection: Analyze molded parts for signs of poor mixing. Black spots, light streaks, or marble patterns indicate inadequate material blending within the barrel.

FAQ 2: Screw Not Discharging Material

Problem: The screw rotates but doesn't discharge material, hindering production.

Causes:

Blockage in the discharge port by solidified plastic.

Inaccurate temperature control, particularly high temperatures at the rear of the barrel.

Plastic adhering to the screw, causing it to rotate without material transport.

Excessive lubricant on the plastic, leading to screw slippage.

High content of recycled material affecting material flow.

Worn screw, barrel, or check ring, causing leakage and hindering material movement.

Large plastic particles causing bridging in the feeding section.

Design incompatibility between the new screw and the existing barrel's discharge port or feeding section's screw groove depth.

Solutions:

Blockage Check: Inspect the discharge port for obstructions caused by solidified plastic.

Temperature Control: Verify the temperature settings and ensure proper cooling water circulation, especially at the rear of the barrel.

Screw Cleaning: Remove any plastic adhering to the screw surface.

Lubricant Optimization: Adjust lubricant quantity to prevent excessive slippage.

Recycled Material Management: Control the amount of recycled material used to maintain optimal flow properties.

Screw and Barrel Maintenance: Regularly inspect and replace worn screws, barrels, and check rings to prevent leakage and material transport issues.

Material Size Management: Ensure plastic particles are small enough to avoid bridging in the feeding section.

Design Compatibility Review: If a new screw is not discharging material, verify compatibility between the screw design (feeding section groove depth) and the existing barrel's discharge port design.

Pro Tips:

Implement preventive maintenance practices to minimize screw and barrel wear.

Regularly clean the screw and barrel to remove material residue and prevent degradation.

Choose the appropriate screw design for the specific plastic material being processed.

Invest in high-quality screws and barrels manufactured from wear-resistant materials.

Consult your screw and barrel manufacturer for material-specific recommendations and troubleshooting assistance.