3-axis VS 4-axis VS 5-axis CNC Machining-Which is the Best?

Mar. 26, 2022

5 Axis CNC Machining Parts

 

The number of axes on a CNC machine determines the type of work it can do, the level of detail it can cut, and the workpiece locations it can manipulate. The main difference between 3-axis, 4-axis and 5-axis machining is the complexity of the movement both the workpiece and the cutting tool can move through, relative to each other. The more complex the motion of the two parts, the more complex the geometry of the final machined part can be. So what does this all mean? The following provides a better explanation of the differences between 3 axis, 4 axis, and 5 axis CNC machines. This will include introducing their basic principles, their differences, and how to choose one in your machining project?

 

What is 3-Axis CNC Machining?

3-axis machining is the most widely used form of CNC machining today. A typical 3-axis CNC machining process involves three mechanisms in part creation. One is the spindle up and down movement, while the others are by moving it side to side and back and forth.

The most simple type of machining, where the workpiece is fixed in a single position. Movement of the spindle is available in the X, Y and Z linear directions.

3-axis machines are typically used for machining of 2D and 2.5D geometry. Machining of all 6 sides of a part is possible in 3 axis machining but a new fixturing set-up is required for each side, which could be expensive (more on that below). For a single fixture setup, only one side of the part can be machined.

Many complex and practical shapes can be manufactured by 3 axis CNC milling, especially when in the hands of a world class CNC machining facility. 3-axis machining is best suited to manufacture of planar milled profiles, drillings & threaded holes in-line with an axis. Undercut features are possible with the use of T-slot cutters and Dovetail milling cutters.

However, sometimes the designed feature physically cannot be manufactured by a 3-axis machine, or the feature might be more economically viable to machine with a 4 or 5 axis machine.

Features not possible in 3 axis milling include any features on an angle to the X-Y-Z co-ordinate system, even if the feature itself is planar. There are two types of angled features you can design, and understanding the distinction between them is important when designing parts for CNC milling.

Angled feature

This is a feature machined on an angle to one of the X, Y or Z axes. For example, the planar milled surface below is at 45° to the X-axis e.g. a rotation of the A-axis.

Compound angle feature

This is a feature machined on an angle to two axes. For example the planar milled surface below is machined at a 45° angle to the X-axis, and a 30° angle to the Z axis.

Both angled and compound angle features cannot be machined by 3-axis CNC machines.

3 axis machining implies that the workpiece remains in the same position while the cutting tool operates along the XYZ plane to trim away material. This is suitable for parts that don’t require a lot of depth and detail. 3 axis machining is most commonly used to produce mechanical components and is best suited for:

 Automatic/interactive operation

 Milling slots

 Drilling holes

 Cutting sharp edges

 

What is 4-Axis CNC Machining?

Generally, 4-axis CNC machining is preferred to 3-axis CNC machining as it speeds up and improves the accuracy of the production process. The 4-axis CNC machining process encompasses the same mechanism of action. However, from its name, there is an additional axis included.

In a 4-axis CNC machine, the spindle travels along three axes: up and down, side to side, and back and forth, while the workpiece remains stationary on the machine table. The 4-axis CNC machining further rotates along the X-axis, also known as the A-axis. This extra axis allows the 4-axis CNC machining to function in situations that involve hole drilling or cut-outs.

This adds a rotation about the X-axis, called the A-axis. The spindle has 3 linear axes of movement (X-Y-Z), like in 3-axis machining, plus the A-axis occurs by rotation of the workpiece. There are a few different arrangements for 4 axis machines, but typically they are of the ‘vertical machining’ type, where the spindle rotates about the Z axis. The workpiece is mounted in the X-axis and can rotate with the fixture in the A-axis. For a single fixture setup, 4 sides of the part can be machined.

4-axis machining can be used as a more economically viable way of machining parts theoretically possible on a 3-axis machine. As an example, for a part we recently machined we found that using a 3-axis machine would have required two unique fixtures at a cost of £1000 and £800 respectively. By utilising the A-axis capability of 4-axis machining, only one fixture was required at a cost of £1000. This also eliminated the need for fixture change-overs, reducing costs even further. Eliminating the risk of human error meant we machined the part to a high quality with no need for expensive Quality Assurance investigations. Removing the need to change fixtures has the additional benefit that tighter tolerances can be held between features on different sides of the part. Loss of accuracy due to fixturing and re-setup has been removed.

There are two types of 4-axis CNC machining: indexing and continuous.

Index 4-axis CNC machining is when the 4th axis (A-axis) rotates whilst the machine is not cutting material. Once the correct rotation is selected, a brake is applied and the machine resumes cutting.

In continuous 4-axis machining, the machine can cut material at the same time as the A-axis rotation, simultaneously. This allows complex arcs to be machined, such as the profile of cam lobes, and helixes.

4-axis machining gives us the ability to machine angled features, otherwise not possible with a 3-axis machine. Bear in mind that 4-axis machining allows a single axis of rotation per fixture setup, so all angled features must be angled about the same axes, or additional fixtures put in place.

This rotation allows the workpiece to be cut around the B axis. This method is beneficial when holes or cuts need to be made on the sides of a workpiece. The addition of a fourth axis (A axis) allows a workpiece to be automatically flipped over, so the machine can remove material from both sides. 4 axis machining is multifunctional and can be used for:

 Intermittent cutting

 

Continuous cutting

 

Engraving curved surfaces

 

What is 5-Axis CNC Machining?

A 5-axis CNC machining process is also a lot like a 3-axis CNC machining process. However, it comes with some very important features that provide those two extra axes and a great deal more cutting flexibility.

On a 5-axis CNC machining, the spindle and cutting tool move along three axes. However, there are other rotations about the X-axis (called the A-axis), Y-axis (called the B-axis), and the Z-axis (called the C-axis). 5-axis machines can utilize any two of these rotational axes, depending on their configuration. The A, B, and C axes perform a 180° rotation around the X, Y, and Z axes, correspondingly.

These CNC milling machines utilise 2 of the 3 possible rotation axis, depending on the type of machine. A machine will either utilise a rotation in the A-axis and C-axis, or a rotation in the B-axis and C-axis. The rotation either occurs by the workpiece, or by the spindle.

There are two main types of 5-axis CNC machines, 3+2 machines, and fully continuous 5-axis machines.

In 3+2 axis machining two rotational axes operate independently to each other, meaning that the workpiece can be rotated to any compound angle in relation to the cutting tool for features to be machined. However, two axes rotation at the same time as machining is not possible. 3+2 machining can produce highly complex 3D shapes. Fully continuous 5-axis machining can simultaneously rotate the two rotation axis, at the same time as machining and the cutting tool moving linearly in XYZ co-ordinates.

Continuous 5-axis machining can produce highly complex 3D shapes, not only planar compound angled features but complex curved 3D surfaces, giving us the ability to produce parts normally reserved for moulding processes.

5-axis machining gives designers a huge level of flexibility to design very complex 3D geometry. Understanding the possibilities of each type of CNC machining is essential in design of CNC machined parts.

5-axis CNC machining is employed in different capacities based on this feature. It can perform milling, turning, etc. Therefore, you only need a single machine to work on several parts.

This type of machining is used in the automobile, aerospace, and boating industries. Application is commonly favored for extremely complex components that are solid and would otherwise have to be cast. 5 axis machining requires greater CNC programming preparation time to accommodate complex rotatory movement but allows one workpiece to be worked on all five sides during one operation. 5 axis machining is beneficial when components require a great deal of intricacy and quick precision. This includes:

 Feature accuracy

 Increased productivity

 Higher quality finishes

 Cutting intricate details

 Machining complex shapes


The conclusion

Regardless of their particular configurations, all 4-axis and 5-axis machines can move their cutting tools in more varied ways, and from a greater number of angles, than 3-axis machines. This allows for more complex machining operations and increased accuracy and can eliminate the need for multiple setups. As a seasoned and specialist machine shop focused on CNC manufacturing for several years, XYT can provide precision 5 axis CNC machining services and 5 axis milling. Our engineers and machinists can perform accurate five-axis machining services and create five-axis machining to eliminate simplicity. No matter exactly how complicated the CNC machining parts are, each step will indeed be implemented with a strenuous attitude to supply extraordinary 5 axis machining components that demonstrate the most refined requirements. If you need 5 Axis CNC Machining Services, please feel free to contact us!

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