CNC milling is one of the most prominent manufacturing processes. This process takes various materials and shapes them into the desired parts or products. However, a CNC milling machine can perform many different types of milling operations to handle intricate designs.
Essentially, each operation involves the removal of material from a workpiece using milling cutters attached to a moving spindle. However, the tools and spindle movement differ from one type to another.
This article discusses the different types of milling in detail, highlighting their advantages and applications. In the end, you will be able to choose the right milling process for your project.
Each type of machining involves the design of the printed part, the conversion of the design into G and M codes (instructions that the CNC machine understands), tooling and setup, and the execution of the process.
Selecting the types of CNC milling operations according to the 3D design ensures the optimum result. For example, face operations smooth surfaces, while thread operations cut threads precisely. This ensures that the most appropriate technique is used for each specific task.
This operation flattens the surface of the workpiece. As part of the vertical milling process, the cutters used in this process have an axis of rotation perpendicular to the surface, so that the face of the tool is parallel to the workpiece. As a result, the sharp teeth of the cutter remove material while the face smooths the surface.
A key advantage of this method is the high material removal rate due to the geometry of the tool. This allows rapid production of parts with a smooth finish. Face machining is particularly effective for producing flat surfaces in applications such as automotive cylinder heads and heat sinks.
This operation is specifically designed for machining flat surfaces and contours on the workpiece. Using cylindrical cutters with straight or helical teeth, it removes material to create flat or stepped surfaces, slots and recesses. The cutter axis is parallel to the workpiece surface.
Surface milling is characterised by its ability to remove material consistently across different operations. It is ideal for light machining or finishing operations. For example, it removes material from the outer layer of larger workpieces to prepare them for further machining.
As the name suggests, it refers to the machining of one side of a workpiece using side or end milling cutters. Both vertical and horizontal milling machines can perform this task. During the operation, the side edges of the rotating cutter (side teeth) remove material to create flat vertical surfaces, edges, grooves, slots, complex contours, ribs and more. The cutter has helical flutes specifically designed to target the sides of the material, as opposed to operations that focus on the top surface, such as face machining.
This technique is particularly useful in a wide range of applications, including the manufacture of automotive suspension mounts, machining channels or slots in aircraft components, the production of moulds for injection moulding or casting, the manufacture of medical implants and the construction of heat sinks for electrical and electronic equipment.
This method is characterised by its ability to simultaneously machine two parallel surfaces on the same part, while maintaining uniform distances between them.
How does straddle milling manage to machine two faces in a single set-up? It uses two or more side cutters mounted on a single arbor, which remove chips from the surface of the material as it is fed. As a result, this operation is ideal for producing parallel slots, grooves and various profiles on a workpiece.
Application examples: Jigs, fixtures, brackets, levers, gears, sprockets, gearbox & axle housings for automotive, etc.
Why is it called gang milling? Because it involves multiple cutters—such as end mills, form cutters, and slab mills—mounted together on a single arbor to create complex features and intricate details. This setup allows for various operations to be performed simultaneously on a workpiece, resulting in reduced machining time and increased efficiency.
Application examples;
Angular features in CNC machined parts are often achieved by angle milling. In this operation, the cutter axis is angled relative to the machining surface while the workpiece is held in the required orientation by an angle plate or jigs.
The cutters precisely machine the part at specific angles that can be fixed, such as 45°, 60° or 75°. This method is used to create features such as slight chamfers, bevels, T-slots, dovetails and other complex geometric profiles.
Do you know how CNC machines create irregular contours? This is achieved by form milling, which uses cutters shaped as a negative of the desired contour. For example, to machine a turbine blade, a cutter is first made with a geometry that mirrors the shape of the blade. This method allows complex designs to be shaped precisely and individually.
As the cutter rotates, it traverses over the workpiece, or the workpiece moves under the cutter. The edges of the cutter then cut away the material to create the desired geometry.
Application examples: Domed pistons, orthopaedic implants, turbine blades, mould making, guitar bodies, custom prototypes, etc.
It is one of the most popular ones among different types of milling operations. The end mills execute this operation by feeding the work into it in a perpendicular or angled direction. Meanwhile, the multiple cutting edges on the faces and periphery of the end mill remove the material while feeding the workpiece.
The end milling is extremely favorable in the machining conditions where you need: An intricate profile, precise edges, slots, and grooves with varying depths, and a smooth finish on the workpiece surface.
Saw milling is performed using a large cutter with teeth around its circumference. This method is particularly useful for making narrow slots and dividing the workpiece into two parts. The cutter moves downwards, cutting through the material with continuous feed.
However, sawing operations are generally slower than other methods due to the large size of the cutter, which can generate significant heat during rapid material removal, potentially causing thermal damage to both the work material and the cutter.
In addition, CNC sawing operations extend beyond the slots and cut-offs typical of traditional machines. They are also capable of producing other geometries, such as slight curves or profiles.
Gear milling is a specialised operation used to refine manufactured gears to precise dimensions and surface roughness, or to produce detailed tooth profiles. For example, an extruded bevel gear can be finished to a surface finish of Ra 1.2 µm. In some cases, a complete gear can be manufactured from scratch.
The tools used in gear milling include gear cutters, gear hobbers and form milling cutters. These tools allow the gear teeth to be shaped to a high degree of accuracy, surpassing the precision of other gear manufacturing techniques.
In addition, this process can handle almost any type of gear, regardless of shape or complexity, such as spur, bevel, helical and rack-and-pinion gears.
As the name suggests, it is used to cut both internal and external threads in a workpiece. For internal threads, an insert tool removes material from the surface of the existing hole to form the thread. In contrast, the desired external threads can be easily produced using the right type and size of thread milling cutters or thread mills. However, thread milling is more useful for the internal threads on the large size holes.
The thread milling parts can be found in many industries, from car engines to consumer products. Everywhere for assembly and other purposes.
The CAMS are essential components in different mechanical systems and machinery for converting linear motion into rotational or vice versa. Meanwhile, the CAM milling operation produces these components with a diving head tool. This tool facilitates the rotation of the workpiece to position it so the tool can remove the surface materials according to the designed CAM profile.
In manual operation, the operator places the workpiece and tools in the machine by hand. Milling parameters such as depth of cut, speed and feed are also set manually.
Control of the cutter movement is manual, allowing the operator to cut the workpiece in the desired direction and orientation to shape it. In addition, a handwheel can be used to make adjustments to the milling bed. Although manual operations are more time consuming and less accurate, they offer flexibility in terms of cost and customisation.
CNC milling is the most accurate and quickest operation due to the automation of the machining process. Computer control of tool movement and workpiece positioning eliminates the possibility of error and greatly reduces the time required. Almost any operation is possible with a CNC milling machine, although the correct tools or cutters are required for each specific operation.
The latest multi-axis machines (typically 3 to 6) allow intricate shapes & details on the workpiece with greater precision. As a result, the applications are wider than any other milling, from automotive and aerospace to medical components.
Are you looking for a reputable partner for your parts fabrication and machining projects? Look no further. At PROTO MFG, we specialize in CNC machining and related technologies, including sheet metal fabrication, rapid prototyping, etc. Whether it is a project with a simple design or parts with complex geometries, do not hesitate to contact us today!
