CNC fabrication involves the use of Computer Numerical Control (CNC) machines to shape and resize a block of material (known as a workpiece) by automatically removing bits of the material. Typically, the materials used are plastic or metal, and when the removal is completed a finished part or product has been produced.
This process is also referred to as subtractive manufacturing. To carry out CNC fabrication, a computer application is used to control the movement of a machine that has changeable machine tools.
Common types of CNC machine tools
CNC machining processes include the two most common – milling and turning, as well as grinding, routing and electrical discharge machining (EDM).
Milling applies rotary cutting tools to the workpiece surface, moving along 3, 4 or 5 axes. Milling basically means cutting or trimming the workpiece, and can rapidly produce complex geometries and precision parts from metals or thermoplastics.
Turning applies a lathe to fabricate parts that contain cylindrical features. The workpiece is rotated on a rod against precision turning tools to create rounded edges, radial and axial holes, slots and grooves.
Advantages of CNC fabrication
CNC machining is a much faster process than traditional machining by hand. As long as the computer code is correct and tallies with the design, the resulting part will be highly accurate and precise to very tight tolerances.
CNC fabrication is ideal for rapid prototyping due to the speed and convenience of the process. It can also be used to manufacture end-use products and components but is usually only cost-effective for low-volume short production runs. This makes it ideal for specialist, low-use or low-replacement parts and components.
The speed of CNC machining is the biggest advantage. In the time it takes to wait for a quote from a traditional machine shop, you can send your design directly to a CNC fabrication company, get the parts made and sent back to you.
Multiple-axis CNC machining
CNC milling involves removing material using rotary cutting tools. Either the workpiece remains still and the cutting tools move into it or the workpiece is fed into the machine at a predetermined angle to the tool axis. The more axes of movement a machine has, the more intricate and complex shaping can take place and speedier results are obtained. To find out more about the axes of movement, check out this informative video.
3-axis CNC machining
3 axis CNC milling is still one of the most popular and widely used machining processes. In 3-axis machining, the workpiece is held in place while the rotary cutting tool cuts along three axes, x, y and z. 3-axis CNC is most often used for drilling holes, milling slots and cutting around sharp edges. It’s a relatively simple form of CNC machining that yields simple results. It isn’t ideal for complex geometry or parts for complex assemblies.
As it only cuts on three axes, the process may also be slower than 4 or 5-axis CNC, as the workpiece may need to be manually repositioned to attain the required shape.
4-axis CNC machining
In 4-axis CNC milling, a fourth axis is added to the movement of the cutting tool, which allows rotation around the x-axis. So, now there are four axes – x, y, z and A-axis (rotation around the x-axis). Most 4-axis CNC machines also allow the workpiece to be rotated too, which is known as the B-axis, effectively allowing the machine to act as both a mill and lathe.
4-axis CNC machining is ideal if you need holes and cut-out sections in the side surface of a piece or around the curved surface of a cylinder. It speeds up the process considerably and offers highly precise results.
5-axis CNC machining
5-axis CNC milling includes an extra rotational axis compared to 4-axis CNC. The fifth axis is a rotation around the y-axis, which is also known as the B-axis. The workpiece may also be rotated on some machines and is sometimes referred to as the B-axis or the C-axis.
Due to the high versatility of 5-axis CNC machining, it is used to create precision parts that are complex or intricate. This includes medical parts for artificial prosthetics or bones, aerospace parts, titanium parts, oil and gas machinery parts, military products and parts, etc. Using five axes allows for intricate cuts and undercuts, slot and groove milling in awkward places and highly precise shaping of complex geometries.
It also enables single-step machining, i.e. no requirement for manual repositioning of the workpiece or adjustment of tools. This significantly reduces the lead time, reduces tool wear and makes the entire process much more efficient as ideal cutting positions can be achieved quickly and seamlessly.