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A Balance Between CNC Machining and 3D Printing For Metal Parts

Additive and Subtractive Manufacturing

Manufacturing can be broken into two main technologies – additive manufacturing and subtractive manufacturing. The additive manufacturing process builds a part from scratch, layer by layer, until the part is complete. Using only the material that is needed to create the part (with minimal support structures), this process results in little to no waste. 3D printing is the most common form of additive manufacturing.


This process typically starts with a 3D model of the part that is generated utilizing computer-aided drafting (CAD) software.  The CAD model is processed by slicing software that will give the 3D printer the instructions needed to produce the part layer by layer. Metal 3d printing service providers are often used to help incorporate this technology into companies’ manufacturing workflows.

Traditional subtractive manufacturing process produces parts by removing unneeded material from a larger solid piece of stock. This process inherently results in a good deal of waste.

While some subtractive manufacturing processes are done manually, many are semiautomated using computer numerical control (CNC) machining. This process results in a high level of accuracy and allows for repeatability.

Similar to additive manufacturing, the subtractive process when utilizing CNC starts with a 3D model of the part generated with CAD software. The CAD software is then used to export CNC files that will be used to manipulate the tools within the CNC machines to produce the final part.

Balancing Both Technologies When Producing Metal Parts

When it comes to producing metal parts, additive and subtractive technologies both have advantages and disadvantages. While certain types of parts or circumstances may call for one process over another, many times a balance between the two can provide greater flexibility and increased proficiency.

For example, metal 3D printing can produce very complex geometric parts, but at times, it can be a fairly slow process. In contrast, CNC machining can offer a less time-consuming process but is much more limited when it comes to complex part geometry.

As stated above, material waste is also a consideration for both technologies. This is an important factor to consider in terms of total material costs.

In terms of manufacturing runs of multiple differing parts, some parts may better lend themselves to one process over another.  However, some parts may require the use of both processes.

For example, some parts produced via metal 3D printing may need a secondary CNC process to apply reams, bores, tapped threads, or milled surfaces. Also, many metal 3D printed parts require secondary processes to remove support material or apply the desired final surface finish utilizing subtractive manufacturing processes.  These additional steps are referred to as post processing.

Careful planning is a must when considering whether to utilize one process over another, or a combination of the two should be used. Required accuracy, precision, tolerances, surface finish, as well as weight reduction, topographical optimization, and part complexity are all important factors that need to be considered when choosing the appropriate method. Material preferences, availability, and cost are additional factors to consider. Metal 3D printing service providers are well versed in helping clients through this decision process.


The design flexibility of 3D metal printing, along with the ability to produce highly complex geometry, make additive manufacturing a perfect technology to pair with the increased accuracy and superior surface finish abilities of subtractive manufacturing’s CNC process.

The metal 3d printing service providers at GPI Prototype and Manufacturing Services are here to help you decide how to balance these two processes for your next metal 3d printing project. Give us a call (847-615-8900) or LiveChat us to discuss your metal manufacturing questions and challenges.  

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940 North Shore Drive
Lake Bluff, IL 60044
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