The real answer is it depends. There will always be trade-offs with whichever choice you make. In general, with simple parts, either additive or CNC can make it. Here, the decision will often rest on cost—which approach will do it for the least cost?

Can an additive system produce the same part that a CNC can? Additive service providers will tell you that if you are trying to match additive to milling and turning capabilities, what might stop you is the surface finish available today. Today’s additive systems produce parts that typically require post-process finishing. CNCs often do not need that step. In several years, surface finish may cease to be a drawback for additive systems.

But today, parts are being additively made for combustion engines. And internal combustion engines are being manufactured with additive technologies.

A question to consider, using an engine block as an example, is, is it more cost effective to cast the engine and perform secondary machining or do you have enough benefit from the geometry constraints or material needs to handle a part additively?

Additive is a third option for producing parts; CNC machining and injection molding are the other two options. For now, additive is best used for parts with complex geometries that would be too expensive to build with either CNCs or injection molding. Additive can also replace molding for short run items as the cost to produce a mold is often less than that of a mold for injection molding. Casting is another area where additive can be more cost effective.