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CNC machining vs 3D printing for production: explained & compared

overhead view of cnc machines on a production floorStratasys Direct Manufacturing offers a range of manufacturing solutions to help you achieve efficient production and perfect parts you need. When pursuing low-volume production projects, two manufacturing methods may rise to the top: 3D printing and CNC machining. Both offering plastic and metal materials, and it may be difficult to know which solution is best suited for your project. In the following, we addressed the advantages of each to help you navigate your next production order.

CNC machining and 3D printing defined

CNC machining is a subtractive manufacturing method that uses cutting tools to remove material from a block of raw material following a computerized path to form the part. Stratasys Direct uses 3-axis and 5-axis CNC machines that move a tool along three or five different axes to mill the material into the specified geometry. CNC machining is generally used for rapid production of prototypes, master patterns and low volumes of production parts in both metal and plastic materials.

3D printing is an additive manufacturing method that joins material layer by layer from 3D model data, usually through the deposition of material through a nozzle, UV cure and/or thermal energy. Stratasys Direct offers four 3D printing technologies for production manufacturing: FDM®, Laser Sintering (LS), Multi Jet Fusion (MJF) and Direct Metal Laser Melting (DMLM). 3D printing is used for rapid prototyping and fabrication of low volume production parts in both metal and plastic.

At a high-level, CNC machining and 3D printing address similar manufacturing challenges. Below, we dive into the inherent differences to help you navigate when to use each process based on application, specifications and your budget.

CNC machining and 3D printing materials compared

an engineer inspects a stratasys fdm printerWhen choosing a manufacturing method, you may be focused on the best material for your application, whether it's related to cost or product requirements. While you can generally CNC machine most commercial plastics and metals, materials available in 3D printing are tied to 3D printing technologies.

For example, plastics commonly used in injection molding and CNC machining have been developed to work with thermoplastic 3D printing technologies like FDM and LS. Traditionally machined metals, such as stainless steel and titanium, have been developed for powder metal manufacturing with Direct Metal Laser Melting (DMLM).

3D printing material achievements have skyrocketed over the past five to ten years. Today, the 3D printing processes available are substantial for creating production parts in a wide range of plastic and metal materials. The advancements in additive manufacturing technology coupled with corresponding advancements in material evolutions have hugely impacted the way 3D printing is viewed and relied upon by engineers, designers and manufacturers during product development and production.

For the most part, both manufacturing methods offer commercial plastics and alloys utilized in typical applications, with access to specialty materials found in industries like aerospace and medical. With your material needs met by both options, what other factors might influence your manufacturing choices?

CNC machining and 3D printing design comparisons

Part size - At Stratasys Direct the build volume on our CNC machines with single cut envelopes reaches up to 84 in. x 40 in. x 36 in. The largest 3D printing build volume at Stratasys Direct is on an FDM printer at 36 in. x 24 in. x 36 in. For both manufacturing methods, we can build larger parts by splitting the design into multiple components and assembling or welding the components together.

a lathe cnc machines a fuel tank

Tolerance - One of CNC machining’s greatest strengths is its ability to achieve very tight tolerances – often +/- 0.005” or 0.001”/”, whichever is greater. For well-designed parts, tolerances +/- 0.0035 in. or +/-.0015 in., whichever is greater, are possible with FDM technology. If tolerance is a priority, CNC machining is the best manufacturing option. Stratasys Direct Manufacturing also offers to-tolerance machining for 3D printed parts after the build.

Speed - 3D printing excels when it comes to fast production. Depending on part geometry and size, 3D printing jobs with technologies like MJF and FDM takes hours to complete. CNC machining may be a faster operation if the part is a simple geometry with limited passes. CNC machining can require more of an operator than a 3D printer; often a machinist must manually reposition fixture or parts during the build, lengthening the machining time.

Design complexity - 3D printing gives you the freedom to design complex master patterns with holes, organic shapes and channels not possible with CNC machining. It also opens the door to part consolidation in which multiple components can be combined into one-part design to cut down on the number of molds. CNC machined patterns can achieve involved geometries, but the more complicated the design the more dependent it becomes on manual fabrication and post-finishing.

Even though both methods are competent for low-volume production parts, the most appropriate processes address your material needs, part geometry and project timeline.