Basic theoretical questions for mold design

Hı everyone,

I work as Tool Designer Intern in Mold Department - automotive company and I have some questions for mold design.

Generally I know to use NX for mold Design plastic part (for very complicate plastic parts) but some theoretical answers I need . In my department they don't know my questions explain as they don't speak english.

90 % I learned alone about Mold Design from internet, youtube and also how to use NX and Catia for mold design.

My question is : Where I need to put Air Valves on cavity /core
1. I know why they use for but I don't where do I put them on core /cavity side. Only I know there are on Lieder pin but where else I should put them.

2. when I need to use cooling channel in sliders. I saw some mold ,their sliders are with cooling channel, why ?


That is basic questions what I need to find answer


Thank you in advance