When dealing with complex 3D geometry, you need a system to work out and communicate exactly how to move in that 3D space.

Many CNC machines do this with a 3-axis system of points, but some use more. This is not to say a 3-axis CNC machine can’t still interpret and carry out complex instructions, and we’ll take a look at what these machines do and how they’re used.

What is 3-axis machining?

A 3-axis CNC machine is one that moves its spindle in any combination of three directions across the XYZ axis. These represent the three-dimensional movement that the tool can take. If you visualise a cube, any point within that cube can be defined in terms of the XYZ axes.

A 3-axis machine keeps its workpiece stationary as it works. In other words, the movement doesn’t apply to the piece actually being cut; only the tool, which moves and operates as necessary to cut away material.

3-axis machines differentiate themselves from 4 and 5-axis machines by only moving their spindle along the three planes. Other machines offer different ways for the tool and workpiece to move and interact.

What are the different types of 3 axis machines?

3-axis machines can come in various configurations that change their capabilities and how they carry out a job.

3-axis milling machines, for instance, come as horizontal, vertical, or bridge mills. Horizontal mills have their spindle axis aligned horizontally, using shorter and thicker tools that can make heavier cuts and remove great amounts of material from the workpiece.

Vertical mills have their spindle axis positioned vertically, and they tend to use thinner and longer tools capable of cutting deep into the workpiece. Vertical tools can’t cut as much surface detail as horizontal machines but they are highly accurate.

A bridge mill makes use of a gantry that enables reaching other sides of the workpiece, thereby increasing the detail that can be cut into the material. The extra travel also means longer and larger parts can be machined with more ease.

Other types of CNC machines use different tools and approaches along 3 axes, such as CNC lathes or routers.

How do you use a 3-axis CNC machine?

A 3-axis CNC machine is programmed using G-code, which tells the machine how to make the necessary movements to create the desired part. Often, the part is coded in with the help of a CAD model.

In order to cut away material, the machine will either move its tool around the workpiece, move the workpiece around the stationary tool, or combine both approaches as necessary. Generally, a moving table means a more rigid spindle.

What are the benefits of 3 axis machining?

3-axis machines have a degree of relative simplicity that makes them an ideal choice for producing precision components. All three axes can move at once, allowing complex movements to take place despite being seen as more ‘traditional’ compared to machines that offer extra axes.

3-axis CNC machines can make many different cuts and take different approaches to a workpiece, making them versatile and suitable for parts with tight tolerances.

What alternatives are there to 3 axis machining?

4 and 5-axis CNC machines are now commonplace, which use one or two additional rotary axes. These can manoeuvre the workpiece in different ways to increase the overall precision and dexterity of the machine.

However, for some parts these extra axes are not necessary, and use rotary beds means that the CNC machine is consuming more power than if only moving the spindle and/or work bed.

Alternatively, there is the option of not using computerised numerical control at all, and opting more manual machines or other methods such as casting to make parts. However, there are different factors to consider with these other approaches, such as differences in speed of work, cost, accuracy, and ability to create complex geometries in parts.

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