In daily injection molding production, discoloration, scorching and raw material degradation of injection-molded products are common process abnormalities, which affect product quality, increase costs and even damage equipment. Such problems are related to raw material handling, process parameters and equipment structure. The core causes and practical countermeasures are summarized below to help troubleshoot and solve problems quickly.

        1. Main Causes

        A.  The core issue is physical and chemical changes during raw material processing, or mismatches among process, equipment and material properties. Specific causes are as follows:

        B.  Poor drying of materials, excessive volatiles, which vaporize at high temperatures and cause abnormalities;

Insufficient heat resistance of colorants and additives, leading to degradation under high-temperature shear;

        C. Raw material contamination (mixed with impurities, oil, etc.), causing discoloration and scorching at high temperatures;

        D. Uneven melting of materials, local overheating of unmelted particles under high pressure and temperature;

        E. Excessively low melt temperature, insufficient melting, easy to generate shear overheating and result in degradation;

        F.Excessively low screw back pressure, poor exhaust and mixing effect, producing bubbles and unmelted materials;

       G.Excessively high screw speed, excessive shear heat generation, leading to raw material degradation and scorching;

       H.Excessively high injection weight ratio, abnormal melt residence or improper injection parameters, causing overheating;

       I. Overly short residence time of melt in the barrel, insufficient melting, local overheating of unmelted materials;

      J. Overly low length-to-diameter ratio of the barrel, insufficient melting and mixing time of raw materials;

      K.Overly low screw compression ratio, poor plasticizing and exhaust effect, unsatisfactory melting quality;

      L. Lack of shear and mixing sections on the screw, uneven melting of raw materials, easy local overheating.

     2. Corresponding Solutions

     A. Based on practical operation, targeted adjustments are made as follows to quickly restore normal production:

     B. Poor material drying: Re-dry according to the process to remove volatiles and avoid secondary moisture absorption;

     C. Additive degradation: Replace colorants and additives with suitable heat resistance, and control the addition ratio;

     D. Raw material contamination: Replace qualified raw materials, clean the equipment, and standardize raw material storage and feeding procedures;

     E. Uneven melting: Reduce screw speed and properly increase melt temperature to ensure sufficient melting;

     F. Excessively low melt temperature: Reduce barrel temperature, adjust speed and back pressure accordingly to avoid shear overheating;

    G. Low back pressure: Increase screw back pressure to enhance exhaust and plasticizing effects;

    H. Excessively high speed: Reduce screw speed, optimize injection parameters, and reduce local overheating;

     I. Excessively high injection weight: Adjust the weight to match the equipment and mold, optimize injection pressure and speed;

     J. Low barrel length-to-diameter ratio: Replace the barrel with a larger diameter and higher length-to-diameter ratio to improve melting and mixing effects;

     K. Low screw compression ratio: Replace the screw with a higher compression ratio to enhance plasticizing and exhaust capacity;

    L. Lack of shear and mixing sections on the screw: Modify or replace the screw to add shear and mixing structures.

    3. Summary
     In general, the core of such problems lies in the coordinated matching of raw materials, process and equipment.

     Prioritize troubleshooting raw material handling and process parameters (easy to adjust and quick to take effect), then check the equipment structure.
     Daily standardized raw material management, equipment maintenance and parameter recording can effectively reduce abnormalities and ensure stable production.