What is the Difference between a 3 Axis and a 4 Axis CNC Router Machine?

The primary difference between a 3-axis and a 4-axis CNC router machining is the level of complexity of movement that the cutting tool and the workpiece can relatively move through each other. Higher the complexity of motion of these two parts, higher is the geometric complexity of the machined end product.

Let’s understand these 3-axis and 4-axis CNC routers more deeply to establish the differences between them.

3-Axis CNC Router 

In this case, the CNC router follows the simplest machining mechanism where the workpiece is fitted to one position. Then the router spindle is made available to move in all three linear directions, i.e., X, Y and Z axes.

3-axis CNC router machines are especially used to machine 2 dimensional and 2.5 dimensional geometry. You can machine all the 6 sides of a workpiece. But, for that, you have to integrate a new equipment setup (for each side of the workpiece) to the router. This could be an expensive addition to your 3-axis machine. With a single fixture installation, only one side can be machined.

Also read about the Best Beginner CNC 3 axis Controllers in 2022 .

You can manufacture many practical and complicated shapes with a 3-axis CNC milling device, typically when utilized under an avid CNC routing facility. Drillings, planar milled profiles, and in-line threaded holes along an axis can be best produced by a 3-axis CNC router. You can use Dovetail milling and T-slot cutters to implement the undercut features in a workpiece.

However, any features angular to the X-Y-Z coordinate system (despite being planar) are not possible with a 3-axis machining device. Both the angled and compound angled features are not fit to be machined by a 3-axis CNC router machine.

Interesting read: How to Design a 5-axis CNC Router?

4-Axis CNC Router

In this case, the rotation is made along the A-axis (it is about X-axis). The router spindle includes 3 linear X-Y-Z axes of movement, similar to the 3-axis CNC machine, plus an extra A-axis along which the workpiece is rotated. A couple of arrangements are there for the 4-axis CNC router. However, they are typically of vertical CNC machining type, where the router spindle is rotated about the Z-axis. The material to be machined is fitted in the X-axis and can rotate in the A-axis with the fixture. You can machine four sides of the workpiece with a single equipment installation.

Also read the complete review of DDCSV1 4Axis CNC Controller

A 4-axis router machine is economically more workable to machine such designs which are only theoretically possible in 3-axis CNC routers. For instance, if you require two different fixtures costing £1000 and £800 respectively to machine a part with a 3-axis machine, only a single fixture costing  £1000 will be required to machine a workpiece by using the A-axis capability of a 4-axis router machine. So, you save £800 in the second type of machining. Also, you won’t have to do fixture change-overs, which further limits your expense. 

Interesting read: 4 Best 5-Axis CNC Controllers: Reviews and Buying Guide


All in all, with a 4-axis machining device, you can expect to create high-quality parts free from manual error without any need for costly QA(Quality Assurance) checks. Plus, it reduces accuracy loss that is normally caused due to equipment  setup and re-setup installation.

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