The Engineer guy does great videos on just about everything. Injection molding is used for just about every plastic process one way or another.
A great video from the Engineer Guy on injection molding.
An overview video.
How it’s Made on making a mold.
Making bottle caps.
How Lego bricks are made.
It all started with Ivory.
visiting Fine Molds, a small model company in Japan.
Note the mold making process.