When considering CNC machining vs. 3D printing for prototyping, it's essential to compare all factors relevant to your project. Both methods are standard today, but each one has its own advantages and limitations. Learn more about each technique to determine the right path for your prototype.

An Overview of CNC Machining and 3D Printing

The primary difference between CNC machining and 3D printing is how they form parts and products. CNC machining is a subtractive manufacturing process, in which materials are cut or removed from a blank workpiece to shape the finished product. In contrast, 3D printing is an additive manufacturing process, in which only the exact amount of materials are used—added layer by layer—to produce the final part.

The following is an overview of the various factors project managers must consider when deciding on a production method for their prototype.

Materials 

Both 3D printing and CNC machining can process metals and plastics but not to an equal extent. CNC equipment is capable of supporting a wider range of materials, including:

• Aluminum

• Stainless steel

• Brass

• Titanium

• Zinc alloys

• Magnesium alloys

• ABS

• Polypropylene (PP)

• Nylon (PA66)

• Polycarbonate (PC)

• PEEK

• POM

• Acrylic (PMMA)

• Wood

• Wax

In contrast, 3D printers are more restricted to plastics and composites, such as PLA, nylon, ABS, TPU, and Ultem. Some specialized 3D printers can accommodate metals, including aluminum, titanium, stainless steel, and Inconel.

Cost

The cost advantages of using a CNC machine vs. a 3D printer are usually a matter of scale. For large production runs, CNC machining provides a lower cost per unit. 3D printing is usually cheaper on smaller runs, however, because the per-unit costs are the same regardless of production volume.

Cost also depends on part complexity. While CNC machining expenses increase in proportion to complexity, this is generally a non-issue with 3D printing, where the cost is the same regardless of complexity.

Speed & Turnaround Time

Compared to CNC machining, 3D printing is much faster, and Empire Group can 3D print orders overnight and have them delivered the next day. 

CNC machining is about 1.5 times slower than 3D printing, but machining is preferable in applications that require real materials with origin traceability. Most 3D printing consists of simulated compounds, whereas CNC machining uses raw materials. The defense industry, for example, needs to have origin traceability so that organizations can trace any issues in the supply chain. 3D printing is not regulated as much, but it does not have origin traceability.  

Precision & Quality

3D printing has a more consistent output, but CNC machining provides superior accuracy and precision. However, there are other variables in machining that come down to the actual operator. Furthermore, end-of-tooling parts are virtually impossible to be machined. 

3D printing, particularly multi-jet fusion (MJF) printing, unlocks much more potential that otherwise wouldn’t be possible with CNC machining. In some cases, choosing 3D printing over machining means you only need to print one part instead of producing and assembling five separate parts. 

Complex Parts & Customization

CNC machines have various mechanical limitations, including:

• Restricted tool clearance and access

• Limitations around hold and mount points

• Size and shape restrictions, mostly due to tool geometry (even in 5-axis systems)

• Repeated part reorientation, which is often a workaround to the other limitations

These hurdles can also result in greater labor costs. By contrast, 3D printers can add raw materials wherever the design requires, with far fewer extra labor steps. By overcoming the inherent mechanical limitations of CNC, 3D printing also supports greater customization.

Contact Our Experts for Premium Prototyping/Part Production Solutions

Empire Group's ISO- and ITAR-certified manufacturing services ensure our customers receive the most effective solutions for even their most challenging product designs. For every prototyping and production-run project, we weigh the pros and cons of CNC vs. 3D printing according to what will accommodate clients’ needs and unique requirements. 

For help determining whether CNC machining or 3D printing is the optimal choice for your part design, contact us or request a quote today.