CNC or 3D printer have different use cases. CNCs are best used for subtractive manufacturing and 3d printing is best used for additive manufacturing.
An advanced manufacturer may even combine both.
It depends on the source material being used.
It’s easier to cnc a slab of rock, because it’s impossible to 3d print a rock. It would also be better to cnc fine wood pieces instead of 3d printing them or using pressboard techniques, because the wood would retain the grain pattern and structural integrity that a fused wooden object would not have.
However cnc machining cannot make objects with enclosed cavities. To make such an object would require 2 parts, in addition to lots of drilling and fasteners to match what 3d printing can make.
When it comes to metal, DMLS (full melt, unlike SLS or binderjetting) has a fully fused piece of metal and can outperform CNC machining in the ability to make any part or complex geometry. In fact 3d printing titanium is more cost efficient than cnc machining it with the same or better performance for most applications.
However CNCs can also be used to help end finishing and polishing of even 3d printed parts.
To sum up, CNC or 3D printer depends on your preference.
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