Computer numerical control (CNC) machining is a common subtractive manufacturing technology. Unlike 3D printing, the process typically begins with a solid block of material (blank) and removes material to achieve the required final shape, using a variety of sharp rotating tools or cutters.
CNC is one of the most popular methods of manufacturing for both small one-off jobs and medium to high volume production. It offers excellent repeatability, high accuracy and a wide range of materials and surface finishes.
Additive Manufacturing (AM or 3D printing) processes build parts by adding material one layer at a time. AM processes require no special tooling or fixtures.
It only makes sense to use 3D printing in the following cases:
When traditional methods are not able to produce the part, for example for highly complex, topology-optimized geometries.
When volumes is small like 1 or 2 pieces.
When tolerance control is not so important.
5 Reasons Why To Choose CNC Machining:
CNC mills usually handle a wide variety of materials such as metal, plastic, wood, or just about any other type of material you want to use. With 3D printing, on the other hand, you can only work with a few materials such as ABS or PLA plastic. Although metal 3D printing is currently possible, achieving the same finish and strength that is obtainable with CNC machining is virtually impossible with mainstream 3D printers.
CNC machining offers tight tolerance and excellent repeatability. Very large to very small parts can be CNC machined accurately.
When production volume is big like more than 100pcs, CNC machining and much more competitive over 3D printing regarding cost and delivery time.
CNC machining is faster than 3D printing, because it works by reduction instead of addition. Where 3D printing works by building up layer upon layer of the chosen material to make the product, machining works by cutting away material to make the desired shape. It is faster to start with something and cut away than it is to start with nothing and build up. To give you a simplistic example, if you want to make a rectangle, you take a square piece of metal and cut it in half. You simply take the raw material and cut away what you don’t need, quickly.
Sometimes, a quick copy of part is required to use as a test. With CNC machining, you can trade quality for speed and make a quick part for testing. With 3D printing, on the other hand, there are limited options to customize quality settings. Each time you need a product to do a test, you have to wait for a part that is meticulously built up, layer upon layer. When testing, this can become quite time consuming and costly. By using machining instead of 3D printing, you can speed up the development phase of your project. It will even allow you to select different quality levels for different parts of your overall project.