The part looks acceptable after molding, but cracks appear around screw bosses, corners or weld lines later. Where should the investigation begin?
Do not assume the resin alone is responsible. Residual stress, moisture, sharp geometry, chemical contact and an unsuitable PC/ABS balance can produce similar symptoms. Separate processing, design and material variables before changing grades.
Information that changes the recommendation
- Drying record, actual dew point and time between drying and molding
- Melt temperature, mold temperature, packing pressure and cooling balance
- Crack location relative to gates, weld lines, corners and screw bosses
- Contact with cleaners, oils, adhesives, paints or other chemicals
- Required impact level, heat resistance and stress-crack resistance
Start with a controlled molding trial using verified drying conditions and a documented process window. Compare parts at equal wall thickness and conditioning time.
If cracks remain concentrated around high-stress geometry, review radii, boss design and assembly torque before increasing impact modification.
When chemical exposure is involved, test the actual finished part under load. A room-temperature pellet data sheet cannot predict every molded-part interaction.