I enjoyed MIT's Fundamentals of Manufacturing course, on edx [0]. The team talk about casting, injection molding, 3D printing, and a couple of other ways.

[0] https://www.edx.org/learn/manufacturing/massachusetts-instit... the course bills itself at 14 weeks of 4-6 hours, that would be right if I did the homework to the fullest, but I consumed the course material in half that during a given week.