While manufacturers use both computer numerical control (CNC) machining and 3D printing to produce prototypes and production parts, the two methods work in completely different ways.
Despite being an older technique, continued innovations – such as 5 axis machining – have kept CNC machining the dominant force in the machining industry.
The opposite approaches of CNC machining and 3D printing
CNC is subtractive. It starts with a solid block of material, which is then cut away to yield the required configuration. Materials to which CNC machining is applied include:
- Steel alloys
3D printing is additive. The printer lays down layers of material until it produces the finished form. A smaller number of materials are usable in printers, predominantly thermoplastics, such as:
- Polylactic acid (PLA)
- Acrylonitrile butadiene styrene (ABS)
Some 3D printers work with resins as binders for metals or wood. Printers used for thermoplastics will not work for resins nor will resin printers work with thermoplastics.
While both methods are computer controlled, you will find that there are advantages and disadvantages to both CNC machining and 3D printing.
CNC machining can achieve finer tolerances than 3D printing. Moreover, the heat of a printer may deform thermoplastic and other softer materials, leading to dimensional variations not seen with CNC machining.
Often, CNC machining requires several operations and the creation of fixtures to hold the material in place. Although this takes time, the total production time for 3D printing is usually slower!
Modern machines, software and cutters allow swift removal of material while the gradual building of layers by a printer is slower, in part due to material setting taking some time.
When a prototype requires multiple iterations, a 3D printer may be the better choice as you can use software to make revisions and print different versions of the same part on the same machine at the same time!
However, these 3D prototypes are not robust enough for production. The output of a 3-D printer will be anisotropic, with characteristics such as tensile strength, varying by direction throughout the piece. As CNC machining does not have this type of variability, it is better suited to turning out parts that can go straight to the manufacturing line.
While the use of 3-D printing continues to grow, it is clear that subtractive CNC machining still dominates.
What is 5 axis CNC machining capable of?
In the right hands, 5 axis machines can make components more complex than was once imaginable. The important part is the right hands!
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