The subtractive manufacturing process known as CNC machining transforms a stock piece of material into a finished product. With the assistance of computer programming inputs, pieces of the plastic, metal, or wood are removed until the part is created.

Processes like CNC milling use computerized controls and rotating cutters to clear out material from a workpiece. Another CNC, or computer numerical control, method known as turning combines both lathe and mill capabilities to slice material into desired shapes – forms that may feature holes, flats, or grooves.

So, when is a part a good fit for CNC processes? And when is 3D printing the better manufacturing option?

In a Tech Briefs webinar this month titled CNC Machining: How to Reduce Costs and Accelerate Production, a reader asked our machining pro from the manufacturing company Proto Labs:

"When can 3D printing be a viable alternative to CNC machining?

Read Gus Breiland’s edited response below.

Gus Breiland, Technical Sales Engineer, Proto Labs (Maple Plain, MN): 3D printing is thankfully a viable resource these days. It’s becoming more and more capable as a manufacturing process. What I would encourage folks to understand, in my humble opinion, is that 3D printing has a purpose for difficult geometry, or a geometry that may not be possible in other manufacturing processes. 3D printing also has a place with small components at higher volumes.

If a part is a machined part or a molded part, and it really does conform to those traditional manufacturing processes, I still often find that a machined part is [best as] a machined part.

But if you add a significant amount of complexity, or you want to reduce the quantity of parts by having un-manufacturable geometries, such as curved internal channels or pockets inside a sealed vessel, those are opportunities to really utilize the capabilities of 3D printing.

Do you agree? Share your comments and questions below.