[jonshea]

Your comparison to inject molding is correct. The press is used to hold the die mold halves together. I enjoyed this video that explained the process https://youtu.be/FUsicN-wKoY?t=234

[jameshart]

I’m confused why the machine needs to apply a ‘pressing’ force to hold the dies together. Once the die is closed, can’t you just slide rigid clamps into place to hold it in position?

[mardifoufs]

I don't think the metal is fully molten. That's why you need the huge pressures to bring it to shape

[londons_explore]

I don't understand this either.

The mould could have simple locking pins that lock it closed for the actual casting operation, and then unlock to remove the part.