Computer Numerical Control (CNC) milling machines have changed substantially over the last few decades. They have increased production speed, part accuracy, and helped manufactures become more efficient. CNC milling machines are available in several configurations, including 3-axis, 4-axis, and 5-axis CNC milling machines. We’ve previously discussed the different types of CNC milling machines, including vertical machining vs horizontal. Today we are discussing the intricacies of machines with differing numbers of axes.
Do you really need all 3 machines? Probably not, but the answer depends on your specific needs. Each machine has a list of unique features, benefits, and limitations. In this article, we compare and contrast three-axis, four-axis, and five-axis CNC milling machines, including their advantages and disadvantages.
3-Axis CNC Milling Machines
Invented all the way back in the 1800’s, modern 3-axis CNC milling machines have come a long way from its earliest form. Due to cost and other factors, the three-axis CNC milling machine is the most common type of milling machine in use today. Put simply, it has three axes of motion, including the X, Y, and Z axis. The X-axis moves left to right, the Y-axis moves front to back, and the Z-axis moves up and down. While it’s the most simple of the machines on our list, it is ideal for cutting flat surfaces and producing simple 2D and 2.5D shapes.
Advantages of 3-Axis Machines
- Easy to use: By far these machines are the easiest to operate. Making them suitable for all experience levels including beginners.
- Cost-effective: Overall these machines are less expensive when compared to both 4-axis and 5-axis CNC milling machines.
- Simple programming: Programming on a three-axis milling machine is easier than the other machines on our list. This can save time for programming simple yet specific tasks.
Disadvantages of 3-Axis Machines
- Limited versatility: Unfortunately, three-axis milling machines cannot perform complex tasks such as cutting curved surfaces. If your project has complex shapes or surfaces, or you’re looking for a machine that can do everything, you’ll need to look at the other machines. Alternatively you could look at purchasing a trunnion table or rotary table to increase the capabilities of a 3-axis machine.
- Limited precision: While the machines themselves can be high quality, the three-axis CNC milling machine is limited in terms of precision. Making it unsuitable for many for tasks and parts that have strict tolerances.
- Limited productivity: Because of their setup three-axis machines are typically slow and therefore is typically not the best choice for high-volume production.
4-Axis CNC Milling Machines
The four-axis CNC milling machine was developed as an improvement over three-axis machines. It has all the features, plus an additional rotary axis, called the A-axis. The rotary axis allows the spindle to rotate around the X-axis while the machine is not cutting material. This enables the machine to cut curved surfaces and make more complex shapes often times with less fixtures.
Advantages of 4-Axis Machines
- Increased versatility: 4-axis CNC machining is far more versatile than the three-axis. It can produce more complex parts 3-axis machines simply can’t, in less time, and with less setup. Making them more suitable for parts with complex shapes and curves.
- Better precision: These machines can produce far more accurate and precise results than the three-axis CNC milling machines simply because of the addition of the A-axis. More control over the cutting process means more flexibility.
- Higher productivity: The four-axis CNC milling machine is suitable for high-volume production. The addition of the 4th axis allows the machine to cut areas that a 3-axis might require another fixture or different setup. Saving you setup time means you can produce more complex parts a lot quicker.
Disadvantages of 4-Axis Machines
- Higher cost: When compared to 3-axis machines these are typically more expensive. Though if you’re buying on the second hand market you may find a deal. Added cost means it may not be suitable for small businesses or individuals.
- More complex programming: With an additional axis comes additional programming requirements. This means your operator needs to have more experience and training.
- Limited rotation: Four-axis CNC milling machines can only rotate around the X-axis and only when the machine is not cutting. This creates limitations if your part requires cutting where rotation would have to occur around another axis.
5-Axis CNC Milling Machine
For the sake of our article, the 5-axis CNC milling machine is the most advanced type of CNC milling machine we’ll discuss. However, you can buy 7, 9, and even 12-axis milling machines these days. The five-axis machine has all the features of the 3-axis and 4-axis machines, plus two additional rotary axes, which are the B-axis and C-axis. The two additional rotary axes allow the spindle to rotate around the Y-axis and Z-axis, which allows this machine to cut 5 sides of a part from a various compound angles. If you’re looking to produce parts with complex geometries, look no further.
Advantages of 5-Axis Machines
- Highest versatility: These machines are the most versatile on our list. It can cut curved surfaces and make complex shapes from different angles, which allows for more intricate designs and increased efficiency.
- Improved precision: It’s no surprise 5 axis CNC machines are the most precise CNC milling machine. They are so precise you can produce parts that typically require a molding process. All tasks are performed with high precision, making it ideal for high-quality production.
- Highest productivity: For all the reasons 4-axis machines beat 3, the 5-axis CNC milling machines beat out 4-axis machines in terms of volume. If you are looking for a machine to produce the most parts in the least time, this is the machine for you.
- Reduced setup and production time: Simply set your part up once and then the machine will perform multiple operations from various compound angles. Saving your operator from having to stop production and reposition the part.
Disadvantages of 5-Axis Machines
- Highest cost: With all it’s additional features comes an increased cost. The 5-axis CNC milling machine is the most expensive on our list. These machines can cost anywhere from $200k – $500k+. This often makes them cost prohibitive for smaller shops and businesses.
- Most complex programming: Utilizing a 5-axis machine will require a high-level understanding of your programming software. Meaning more time learning and training or the need to higher a far more experienced operator.
- Larger space requirements: Something not often discussed is the sheer size of these machines. They are larger than their 3-axis and 4-axis counterparts. This can cause issues for shops with less overall space.
WRAPPING IT ALL UP
By now you have a solid understanding of the various CNC milling machines that are available on the market today. 3-axis, 4-axis, and 5-axis milling machines offer varying levels of precision, versatility, and production for today’s manufacturing processes. While 3-axis machines are suitable for simple operations, 4-axis machines offer additional rotational movement for greater flexibility. 5-axis machines provide the most advanced capabilities, allowing for complex geometries and intricate designs.
However, with increased capabilities also come higher costs and more complicated operation. Ultimately, the choice between these machines depends on your specific needs and project requirements. By carefully considering your design, materials, and level of precision needed, you can choose the milling machine that best suits your needs to achieve optimal results.
