A CNC router, also known as CNC Milling machine is a computerized Numerical Controlled machine that enables you to cut various materials using a 3D cutting CAD/CAM software. The CAD/CAM converts your design into a tool path so that your machine can create 3D shapes. It can cut various types of material, such as wood, foam, plastics and metals. When talking about the axis of the router we refer to the movement of the machine in which it rotates. When talking about the axis we refer to a fixed imaginary line for the measurement of the coordinates by which the router will cut.
It can rotate X, Y, and Z meaning that the machine can move right to left horizontally (X-axis), front to back horizontally (Y-axis) and vertically up and down (Z-axis), as well as around itself. The working tool also have an X-Y-Z axis motion. Adding rotation movements in other directions on top of that and you have a 4 or a 5-axis machine or more.
In simple terms, a 3-axis router involves moving the cutting tool along 3 different axis, making it suitable for parts and prototypes that are not too deep. A 4-axis router adds also a rotary axis movement called "A axis", and a 5-axis CNC router involves movement of the cutting tool along 5 different axis simultaneously (2 additional axis).
There is a conception that more complex cuts can only be made with the 5 or more axis machine, but is it a misconception or not?
We should be able to perform almost any cut using a 3-axis router, even more complex shapes. However, the 5-axis has the ability to machine on all five sides of a piece simultaneously, thus contributes to the flexibility and capabilities of the machine operator, shortening machining time. For example, trying to machine a game dice, if using a 3-axis router, the machine will only be able to cut one side of the dice in one operation. The operator will then have to turn the dice to machine the other sides, performing a new set-up, at times needing to change the tool bit. Using a 5-axis, the machine can cut all 5 sides of the dice at once, having to turn the dice only one more time for the 6th face.
Having the additional 2 axis and a larger x-axis on the 5-axis CNC router allows to shorten the project time and to be able to handle larger parts, but at the same time, having a longer x-axis can result in less stability and accuracy and calls for the full attention of the operator. So, on one hand we have machines that are able to create certain more complex shapes faster, thus might be more efficient, but at the same time, those are less affordable and more complicated machines to operate and maintain.
So, how many axis of a CNC router machine do we need? The preference depends on the particular manufacturing application needed and the end result required. Here are some instances where the 5-axis router might be used over a 3 or 4-axis:
You have an unusual out of the norm shaped piece to make
If you are in need of greater cutting speed (A 5-axis you can perform the cut in one single set-up as opposed to having to stopping and starting the tool several times with a 3-axis, turning the shape to machine it on all sides)
If you want to save on working area (One single 5-axis machine can replace several 3-axis machines running at the same time)
There are times where having a 5-axis CNC router is not enough and rather, you would need a 3-D printer or both. Sometimes, a 3-D printer is easier to use and has less limitations when producing a shape, however it is less precise than a router and is limited with the material it can use, mostly restricted to thermoplastics and resin.
The bottom line is that you get similar quality results with both 3-axis and 5-axis routers, however, if speed is of a major essence, you might want to consider the 5-axis. Bear in mind the latest requires more difficult operation, leads to more wear and tear, and is more costly.