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3D printing has changed the way companies think about prototyping. With the power of additive manufacturing at one’s fingertips, it is simpler than ever to turn a digital 3D design into a physical object. Startup costs are low, the learning is curve short and results, more often than not, are consistent and satisfactory. 3D printers have truly democratized the world of manufacturing.

Not everything can be 3D printed though. Certain shapes and materials remain better suited to other manufacturing processes such as CNC machining or injection molding, while many commercial 3D printers are simply unable to produce parts with the tolerances required for practical applications.

For some projects, the answer lies not with additive manufacturing or traditional machining, but somewhere in between. Combining the two processes is easier than you might think, and it can provide big advantages.

So when should you CNC machine your 3D printed parts, and how should you go about it? 3ERP, an international prototyping company with expertise in both CNC machining and additive manufacturing, knows how to combine subtractive and additive techniques and can offer manufacturing services to those who require professional-quality prototypes and products.

When should you machine your 3D printed parts?

Although 3D printing and CNC machining are often considered as diametrically opposed processes, they can actually be combined to good effect — by firstly 3D printing a part and then subjecting that part to CNC machining in order to cut down or modify certain areas.

In a time crunch

Businesses should consider CNC machining their 3D printed parts when the alternative — usually injection molding or similar — would demand too much time. Although the sequential process of 3D printing and CNC machining involves multiple steps, the combined approach is still often faster than creating and utilizing tooling for a molding process.

The combination of 3D printing and CNC machining also allows for on-the-go adjustments to the product or prototype, since it is easier to amend digital files than it is to rework an injection molding tool.

When accuracy is key

The accuracy of 3D printers improves year upon year, but many industries require critical end-use parts with tolerances that are at the moment impossible to achieve on 3D printers.

By combining 3D printing and CNC machining, the desired accuracy can be achieved while still leveraging the advantages of 3D printing, which include low costs and complex internal geometries. High-end 3D printers can generally hit tolerances of ±0.005 inches, while CNC machines can squeeze that down to ±0.002.

CNC machining the areas of a 3D printed part that demand tight tolerances can serve to transform a nearly usable object into a usable one.

Things to consider when machining 3D printed parts

Combining the processes of 3D printing and CNC machining requires expertise in both practices. It is therefore beneficial to enlist the help of an expert like 3ERP to take care of the process. But there are certain steps one can take to ensure that the manufacturing goes smoothly.


To get the best results when CNC machining 3D printed parts it is important to specify exactly what needs to be done. This should include specifying which areas require tight tolerances, allowing the machinist to carry out the work appropriately. When these tolerances are specified, the machinist may suggest certain design adjustments to the 3D printed part to make the job easier.

Size up

These suggestions may include the directive to use an excess of material. Since the CNC machining will effectively reduce the mass of the part by cutting away certain sections, it may be necessary to print extra material to allow for these adjustments. If there are insufficient layers, the machining process may not result in the correct dimensions.


The areas of the 3D printed part that need machining should be positioned appropriately so the tool can reach them.

3D printing and CNC machining with 3ERP

3ERP operates a number of 4-axis and 5-axis CNC machining centers which are ideal for adding features and tightening tolerances on 3D printed parts. And with years of expertise in both additive and subtractive manufacturing, the company knows how to handle your project in order to realize the best results.

Get in touch with 3ERP to find out how 3D printing and CNC machining can be combined to great effect.

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