CNC Milling Machines Axis Explained

Introduction to CNC Milling Machines Axis Types

CNC milling is a long-standing manufacturing process used in the production of industry components. CNC machines implement multi-point tools on a material via a method of rotative cutting to shape a workpiece to its desired form. Unnecessary material is removed from the workpiece during this process via computer-controlled programming performed by a machine axis, which has specifications set depending on the component required.

A&M have the extensive capabilities to utilise a range of CNC milling machines, such as 3-axis for more basic procedures, and 4 and 5 axes for more complex, intricate operations.

X, Y and Z axes represent the direction of movement during the process. Each axis holds different purposes and advantages.

VC500i Angle MAX5 Web

3 Axis CNC Milling Machine

3-axis is the simplest CNC milling machine, both in terms of set-up and what the machining operations. The workpiece is fixed in a single position, with linear X, Y and Z spindle movement possible.

These machines are generally used to machine a single side of a part, creating 2D and 2.5D geometry. This is due to the expense machining all sides could incur, as a new fixture setup would be needed for each side, which is not cost or time efficient.

Whilst many complex shapes can be manufactured by 3-axis CNC milling, it is more appropriately used for planar milled profiles, hole drilling or threading and cutting sharp edges. However, the more complex the design, the more viable a 4 or 5 axis may be, both in terms of price and the practicality.

3-axis CNC milling is suitable for most standard metal machining processes.

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4 Axis CNC Milling Machine

4-axis CNC milling incorporates a more extensive scope of materials, including aluminium, which is a metal widely used for components across various industries such as marine and automotive.

As well as the X, Y and Z axes, a further A axis is also included. This adds a rotation around the X axis. The spindle has the usual 3 linear directional movements, whilst the A axis occurs through rotation of the material. Typically, in 4 axis machines, vertical machining rotates the spindle about the Z axis. Along with the A and X axis movement, this enables 4 sides of a part to be worked for a single fixture setup.

4 axis is more a financially efficient method of machining parts which could also be machined on a 3 axis machine. Removing the need for multiple fixture changes reduces costs and decreases the chances for human error, which could lead to expensive quality assurance checks. Tighter tolerances can also be maintained on the workpiece with no requirement to change fixtures.

There are 3 types of 4 axis machining: Indexing and continuous. Indexing rotates the A axis whilst the machine is not cutting the workpiece. Once the rotation is completed, the A axis brakes, and the cutting occurs.

Continuous 4-axis machining cuts material simultaneously with A axis rotation. This type ensures complex arcs can be machined, such as the profile of cam lobes and helixes.

4-axis machining enables the manufacturing of angled features. However, all angled features must be angled around the same axes, or additional fixtures must be used.

5 Axis CNC Milling Machine

5-axis CNC milling machines boast a further 2 rotation axes on top of the A axis: the B and C axes. However, only 2 of these 3 are used dependant on the type of machine. A machine will either rotate in the A axis and C axis, or in the B-axis and C-axis.

5-axis is used for precision engineering, for instance it is the best axis for the design of aerospace parts, working at faster speeds than the other CNC milling machines and with increased functionality and capabilities.

There are various types of 5-axis CNC machines, such as 4+1, 3+2 and continuous 5 machines, with the latter 2 the most common.

In 3+2 axis machining, two rotational axes operate separately, allowing a component to be rotated to any compound angle in relation to the cutting tool. This can produce highly complex 3D shapes.

Fully continuous 5-axis machining can rotate the two-rotation axis at the same time, whilst machining is also taking place, with the cutting tool working linearly across the XYZ coordinates. This provides the opportunity to create not only complex 3D shapes, but curved surfaces which normally would not be possible without implementing a moulding process.

Image used with permission of Hurco (
Image used with permission of Hurco (

CNC X, Y, Z Axis

The X axis and Y axis are horizontal movement (side-to-side and forward-and-back), whilst the Z axis denote vertical movement (up-and-down). In more basic CNC milling machines, horizontal turning movement is possible in only two axes (X and Y). In the more advanced models, we have at A&M, there are W and Z capabilities.

For more information on our CNC milling machining axes, please get in touch with us and we’ll be happy to answer any questions you have.

7 Axis CNC Milling Machine

The most intricate and expensive form of milling is the 7-axis machine. This contains X, Y and Z, A, B and C, and an added E axis.

The E axis twists the arm during the process, allowing milling to take place around the part and turn it within its frame, making for a quicker production time and a smoother procedure.

The expense of this machining is significantly greater, due to it being more rarely required, reserved usually for highly precise components.