How to choose a correct manufacturing process among CNC machining, die casting, forging, Molding and 3D printing?

There are many manufacturing processes, CNC machining, die casting, injection molding (plastics), forging, EDM (Electrical discharge machining), wire EDM, 3D printing and etc., maybe for one of your project there are two or more processes can be used to produce it, then how to choose the most cost effective or most reasonable option? Below is a chart for your reference,

However that is not always absolute, sometimes we can choose more than two options for a single part, but we have to choose one due to limitation of manufacturing processes, for example if we want to get a part with strength of extension and shearing, then we cannot choose 3D printing even that is more cost effective, one another example we can use both CNC machining and forging to make non standard hexagon socket bolts, you still have to choose CNC machining while you want very good surface and precision dimensions.

On the other hand, sometimes we cannot choose only one process due to limitation, such as for some aluminum alloy parts applied in engines and drive systems, total CNC machining will be very expensive or unavailable, so final option is die casting, but the tolerances of die casting beyond our requirement, so we only use die casting to produce rough casting pieces and CNC machining should be used as a second-finishing process.