1. Short Shot / Incomplete Filling
1 Insufficient injection pressure 
2 Too slow injection speed 
3 Poor mold cavity ventilation 
4 Blocked gate 
5 Too short injection time 
6 Nozzle leakage 
2. Flash / Burr
1 Excessive injection pressure 
2 Insufficient mold clamping force, loose mold clamping 
3 Poor sealing of mold joint surface, foreign matters on mold or deformed template 
4 Damaged mold joint position 
3. Air Bubbles / Moist Plastic Raw Material
1 Decomposition of plastic raw material 
2 Too low molding temperature 
3 Poor weld line 
4 Plastic raw material mixed with impurities 
5 Insufficient plastic thickness around inserts 
6 Too low mold temperature 
7 Unreasonable gate position design 
8 Moist plastic raw material 
4. Weld Line
1 Too low temperature 
2 Too low melt temperature 
3 Poor mold cavity ventilation 
5. Silver Streaks
1 Plastic raw material contains moisture and volatiles 
2 Too low drying temperature 
3 Excessively large gate size 
6. Black Spots (Color Mixing)
1 Decomposition of plastic raw material 
2 Plastic raw material debris stuck between plunger and barrel 
3 Plastic raw material contaminated or mixed with impurities 
4 Uneven plastic raw material particles 
5 Poor mold cavity ventilation 
7. Deformation
    1 Too high mold temperature, insufficient cooling time 
    2 Significant difference in product wall thickness 
    3 Improper ejector pin position, uneven force on products 
    4 Uneven mold cavity, unsmooth demolding, excessive friction