Will 3D printing replace CNC machining rapid prototyping?

[Zack00]

CNC machining is a manufacturing process where computer software controls the movement of tools and machinery. For decades, it has been a stable manufacturing process and has become one of the main manufacturing methods for precision manufacturing. But in recent years, CNC machining has been challenged by rapidly developing technology: 3D printing, which is an additive manufacturing process that builds the desired part up layer by layer.
 

But for CNC machinists who are concerned about losing their jobs, here is an opinion that might cheer you up: 3D printing is unlikely to replace CNC Machining, at least in the near future.

Accuracy

In terms of accuracy, CNC machining is superior to all 3D printing processes. Though some 3D printers promise high precision, they easily fail to deliver it from time to time. Due to the technical process of 3D printing, internal stress can be produced during the object solidification and causes the deformation. 3D printers lack the precision which is needed for mission-critical cases. Even with Selective Laser Melting (SLM) technology, the accuracy of CNC machines is hard, if not impossible, to be replicated by 3D printing.

Speed

Generally, 3D printing uses a slow process to heat the material into liquid, create layers of material, and then form the desired product, so even at the best speed, 3D printers cannot catch up with CNC machining. CNC machines can directly finish a task while the output from 3D printers usually requires separate steps, which makes the 3D printing process less efficient than the CNC process. A project that could take CNC machining less than an hour would take a 3D printer hours to get the task done.

Material

Compared to CNC machining, 3D printing has limited material options. Though both 3D printing and CNC machining are compatible with a wide range of materials, including both plastics and metals, 3D printing is more focused on thermoplastics, like PLA, ABS, or resins. On the other hand, CNC machining can work on a huge variety of materials in addition to thermoplastics: metal alloys (like aluminum, copper, steel alloys, brass), woods, acrylic, modeling foams, machining wax. The interfaces for tools necessary for different materials and the CNC machine are usually standardized, so machinists can easily exchange desired materials.

Conclusion

Overall to conclude, CNC machining has many advantages over 3D printing, which makes it will not be completely replaced by 3D printing anytime soon. But it is about which one is better than the other. As there is no perfect technique, CNC machining and 3D printing will co-exist and complement each other in the near future. Both technologies are very useful and have strengths suitable for specialized applications. If the question is “Which one is better”, it totally depends on the budget, material, manufacturing volume, and geometric complexity.