Though 3D printing took the world by storm when it debuted, the technology has yet to revolutionise the manufacturing industry; while 3D printers offer hobbyists and tinkerers a range of exciting possibilities, when it comes to creating parts professionally, CNC still reigns supreme. CNC machined parts are different from their 3D printed counterparts in the following ways:
CNC machined parts are much stronger. 3D printing relies on a “layer by layer” manufacturing technique, so 3D printed parts cannot easily be made from durable materials like metal. Likewise, this “layer by layer” method means that the parts have inherent structural weaknesses as the layers of the material cannot be 100 per cent fused together. In the words of professional 3D printer Nick Allen, a 3D printed object is “comparable to a Lego wall — you place all the bricks on top of each other, and press down: feels strong, but push the wall from the side and it breaks really easily.”
CNC machining, on the other hand, relies on the use of a block of solid material which is then cut, sanded, and/or milled into shape; parts made in this way retain the structural integrity of the material they are created from.
CNC parts are far more diverse. Because CNC machines can work with a wider range of materials than 3D printers can (CNC machines can create parts from metal, plastic, or wood), CNC machined parts are able to fulfil a wider variety of purposes and functions. A 3D printer cannot, for example, manufacture everything from automobile parts to parts for wooden musical instruments.
CNC parts require less “post processing”. Though the internet is full of images of glossy plastic 3D printed parts, in reality, though 3D printers can indeed create plastic parts, they typically leave the printer in a very rough, matte state that demands hours of hand finishing. CNC parts, on the other hand, are often ready to use from the moment they leave the machine—and in the demanding, fast-paced world of manufacturing, this efficiency is paramount.
CNC machines work more quickly. Building something from scratch layer by layer is a much slower process than refining it from an existing body of material. Likewise, the only way to speed up 3D printing relies on making the layers of material used thicker, which greatly reduces the quality of the finished part and therefore adds more time in the form of post-processing. If you want a quality finish on a 3D printed part, you can expect to wait hours or even days for the item to be manufactured.
CNC machined parts are far more precise. Nothing beats CNC for sheer accuracy when manufacturing parts; because of the inferior surface finish and structural weaknesses that result from the 3D printing process, 3D printed parts simply cannot be produced with the kind of accuracy required to make, for example, a plastic lens cap for a camera lens. Not only would the lens cap likely be a poor fit prior to post-processing if made by a 3D printer, the weakness of the layered ABS plastic would mean that the clips of the cap would quickly break with repeated use.
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