A taper applied to the faces of the part that prevent them from being parallel to the motion of the mold opening is called draft. This keeps the part from being damaged due to scraping as the part is ejected out of the mold. Recommended draft:
0.5 degrees on all vertical faces is strongly advised.
2 degrees works very well in most situations.
3 degrees is minimum for a shutoff (metal sliding on metal).
3 degrees is required for light texture.
5 or more degrees is required for heavy texture .