During Cooling the injection molded part shrinks onto the mold components.
For ejection of the part draft angles are used.
If they are missing, it might lead to no ejection of the part, or visible scratches or scoring arise during ejection.
Dependent on material and surface different draft angles are chosen:
Amorphous materials need bigger draft angles, than semi-crystalline materials.
The higher shrinkage of semi-crystalline materials is the reason for this.