1. Warping
   • Deformation of the part due to uneven cooling rates or material shrinkage, causing the part to bend or twist.
2. Sink Marks
   • Depressions or indentations on the surface of the part, usually caused by insufficient cooling time or inadequate packing pressure.
3. Short Shots
   • Incomplete filling of the mold cavity, resulting in parts that are not fully formed. This can be due to low injection pressure, insufficient material, or blocked gates.
4. Flash
   • Excess plastic material that extends from the part along the parting line of the mold. This can occur due to excessive injection pressure, worn mold components, or improper clamping force.
5. Burn Marks
   • Discolored or blackened areas on the part caused by trapped air or gas overheating during the molding process.
6. Flow Lines
   • Visible lines or streaks on the surface of the part caused by varying flow speeds of the molten plastic in the mold. This can be due to inconsistent mold temperature or improper gate location.
7. Weld Lines
   • Lines that appear where two flow fronts meet during the molding process, often leading to weak spots in the part. They can result from low melt temperature or poor mold design.
8. Voids
   • Air pockets or bubbles within the molded part, typically caused by trapped air or gas, insufficient packing pressure, or too fast an injection speed.
9. Surface Delamination
   • Thin layers on the surface of the part that peel away or separate, caused by contamination of the plastic material or improper material drying.
10. Blistering
    • Raised or bubbled areas on the surface of the part caused by trapped gas or moisture in the material or excessive mold temperature.
11. Stringing
    • Thin strands of plastic that remain attached to the part after ejection, often caused by high melt temperature, fast injection speed, or poor mold design.
12. Discoloration
    • Variations in color on the molded part, which can be due to inconsistent material mixing, contamination, or overheating.
13. Jetting
    • A defect where the molten plastic squirts into the mold cavity in a way that creates a wavy or rough surface finish, usually due to high injection speeds or improper gate design.
14. Splay Marks
    • Silver streaks or lines on the part’s surface caused by moisture in the plastic material or by volatile gases.

Material Quality and Composition

1. UV Resistance
   • Ensure the material chosen has additives that enhance UV resistance to prevent degradation when exposed to sunlight.
2. Flame Retardancy
   • Select materials with flame-retardant properties for applications requiring resistance to ignition and burning. Compliance with standards such as UL 94 can be critical.
3. Scratch Resistance
   • Use materials with higher hardness or specific coatings to improve the scratch resistance of the parts.
4. Strength
   • Choose high-quality, virgin materials for parts that require superior mechanical properties. Recycled materials can be used for less critical applications but may have reduced strength.
5. Food Safe/Medical Grade
   • Ensure materials comply with FDA regulations for food contact or ISO 10993 for medical applications. These materials should be free from contaminants and safe for use in specific environments.
6. RoHS Compliance
   • Select materials that meet the Restriction of Hazardous Substances (RoHS) directive, ensuring they are free from harmful chemicals such as lead, mercury, and cadmium.
7. Color Matching
   • Ensure consistent color matching throughout the production batch. Use masterbatches or pre-colored resins to achieve uniform color and avoid discoloration issues.

By addressing these material quality and composition factors, you can significantly enhance the performance, safety, and compliance of your plastic injection molded parts, reducing the likelihood of defects and ensuring they meet specific application requirements.