Troubleshooting Common PC/ABS Injection Molding Defects

  Injection molding PC/ABS blends can present specific challenges. Silver streaks or silver marks, appearing as silver-white lines along the flow direction, are primarily caused by trapped gases—often from moisture in the material, entrapped air, or pyrolysis gases from overheating. Solutions begin with thorough material drying, followed by process adjustments and ensuring adequate mold venting.

Flow marks, surface patterns from a cooling melt front, are addressed by increasing melt temperature to improve fluidity, alongside adjustments to mold temperature and injection speed. Shrinkage and voids (sinks or dents) result from insufficient packing or cooling issues. Corrective measures include raising mold and melt temperatures, increasing holding pressure and time, and optimizing gate design. Warpage and deformation stem from internal stress or uneven cooling/shrinkage, remedied by process adjustments like longer cycles and lower melt temps, as well as design modifications such as adding ribs and uniform wall thickness.

Jetting, caused by a fast-moving melt stream "shooting" into the cavity, is solved by increasing melt/nozzle temperature, reducing injection speed, raising mold temperature, or modifying gate design. Pitting or surface defects from poor additive dispersion require checking material batches, ensuring proper drying, and potentially adding a dispersant or back pressure. Delamination or peeling is often related to high shear stress causing flow separation, potentially exacerbated by compatibility issues between PC and ABS. Solutions involve verifying material formulation (compatibilizer use), increasing melt and mold temperatures to reduce shear, and avoiding restrictive gates or high-friction mold surfaces.