Modern CNC milling machines are amazing tools for prototyping and producing parts quickly and reliably. To do this, they must be able to move along multiple axes of travel while maintaining dimensional accuracy. For this reason, CNC milling machines are categorized according to the number of axes they operate on, with the most common being 3-, 4- and 5-axis milling machines. These movements determine the characteristics of the parts that can be manufactured and also affect productivity and accuracy. In general, the more degrees of freedom available, the more complex the geometry that can be produced. To find out if CNC machining is right for your next project, let’s explore the benefits and uses of these different types.
1. How does a CNC machine move?
Obviously, we’re not talking about starting and walking away from the machine itself. Rather, it’s the movement of the cutting tool relative to the workpiece that’s important here.
First, how do we determine which axis is which? Imagine that you are facing a typical 3-axis CNC milling machine. From your point of reference, the X-axis will be parallel to the front of your body, moving from left to right. the Y-axis is perpendicular to your direction, moving forward and backward, while the Z-axis is perpendicular.
In a typical milling machine, the table moves in the X/Y plane. The spindle, which holds the cutting tool, moves in the Z-axis. Note also that the cutting tool rotates in the spindle, but this rotational motion is not considered an axis of motion.
Overall, the range of these movements defines a three-dimensional space, i.e. a cube, in which the machine performs cutting operations.
2. What is a 3-axis milling machine used for?
We use 3-axis machines every day for a variety of milling operations. They are ideally suited to removing material quickly and efficiently and producing flat or planar surfaces. These geometries are calledprismatic, which is basically a rectilinear shape rather than a more organic shape. Yes, a 3-axis milling machine can make round contours, but it is not suited for this task.
3-axis milling machines are commonly used for drilling and tapping, but only along the Z-axis. This is because the spindle moves up and down and cannot access the workpiece from the side. This is a limitation for many parts that require holes or grooves to be machined on multiple surfaces, which are often inaccessible on a 3-axis machine.
Of course, this limitation can be overcome if the part is removed from the table and then repositioned. This is acceptable if there is no other option, but the part must be re-indexed. This means using a contact probe to establish a new reference point before restarting machining.
This is a slow process and is highly likely to produce dimensional errors. Therefore, if possible, always avoid removing parts from the fixture and repositioning them during the work process.
3-Axis milling machines can produce circular features, but only in the X/Y plane. Nonetheless, the relative simplicity of the motion is good for many projects that do not require complexity and can benefit from maximum part throughput and process efficiency.
What are the advantages of 3.4-axis CNC milling machines?
Adding a fourth axis of motion opens up many new machining possibilities. This is usually accomplished by adding a rotational motion along the X-axis. This additional rotation along the X-axis is called the A-axis.
The rotary table allows the machinist to mount the part at one end and then rotate it to access the remaining sides of the workpiece. This avoids the problems of re-mounting and re-indexing on a 3-axis milling machine. With the part partially suspended – i.e. not touching the table surface – it is now possible to drill holes or completely penetrate other features of the part.
Most importantly, the workpiece rotates during machining, allowing for more complex curves and contours to be created. It is even possible to rotate the part as if it were on a lathe, creating cylindrical and spherical contours. However, 4-axis milling machines are not optimized for this type of operation and can be slower than dedicated lathes.
4. What are the advantages of 5-axis CNC milling machine?
Another degree of freedom can be added, this time along the Y-axis. The rotation around the Y-axis is called the B-axis.
To achieve five axes of freedom, a 3-axis milling machine can be modified with arotary disk headThis is an auxiliary attachment that provides motion on the A and B axes. This is an auxiliary attachment that provides movement in the A and B axes. Combined with the other features of the 3 Axis milling machine, it is now possible to create more complex shapes, such as helical rotors. These rotors have complex compound curves in multiple directions and can only be accomplished on a 5-axis machine.
However, 3-axis machines with milling heads have limitations. First, a dedicated 5-axis machine is usually more rigid. This is because it must maintain accuracy, even when moving in multiple directions at once. This precision means that even for relatively simple parts, the tolerances are smaller.
5. How many other axes?
To create more complex parts quickly and minimally, CNC machining centers are greatly expanding their capacity.9-axis machines combine lathe and milling capabilities with advanced robotics to provide an all-in-one solution. However, they are often large and costly to operate. These machines are typically used in aerospace, military or scientific applications.
For most products, 5 axes are enough to create feature-rich parts to tight tolerances. When you contact SANHUNG for your next CNC Rapid Prototyping or Low Volume Manufacturing project, please contact us.You can expect this when you get a free quote.
