1) Drafts (or taper) in a mold, facilitates part removal from the mold. The amount of draft angle depends on the depth of the part in the mold, and its required end use function. […]

1) Sharp corners greatly increase the stress concentration. This high amount of stress concentration can often lead to failure of plastic parts. Sharp corners can come about in non-obvious places. Examples of this are a boss attached to a surface, or a strengthening rib. These corners need to be radiused just like all other corners. [...]