What is CNC Milling?
CNC milling is a specific type of CNC machining. This article will introduce CNC milling from multiple aspects, including how milling works, common milling equipment, and milling advantages.
What is CNC Milling?
CNC milling is a milling processing method based on computer numerical control (CNC) technology. Through precise control of the movement of the cutting tool and the workpiece, it can process various raw materials into three-dimensional parts and components with extremely high precision.
Advanced CNC milling machines are equipped with 5 or even more independent motion axes. These multi-axis simultaneous milling machines greatly expand the processing capabilities. They can not only efficiently manufacture more complex geometric shapes but also avoid the possible loss of precision and waste of time caused by transferring the workpiece to different machines, significantly improving production efficiency and processing precision.
How Does a CNC Milling Machine Work?
A CNC milling machine controls the cutting movement of the cutting tool on the workpiece through a computer program.
- The operator uses computer-aided design (CAD) software to create a three-dimensional model of the workpiece.
- The model is then converted into a numerical control program through computer-aided manufacturing (CAM) software. This program includes processing parameters such as the tool path, cutting speed, and feed rate.
- The machine tool precisely controls the movement of the cutting tool according to these instructions and performs milling processing on the workpiece, thus processing the raw material into the required shape and size.
What are 3-Axis, 4-Axis, and 5-Axis Milling Machines?
3-axis, 4-axis, and 5-axis milling machines are classified according to the number of machine tool coordinate axes and their simultaneous movement capabilities. The more the number of coordinate axes, the stronger the processing capabilities and flexibility of the machine tool.
3-Axis Milling Machine
A 3-axis milling machine usually has three linear coordinate axes, namely the X, Y, and Z axes. The X-axis and Y-axis define the planar movement of the machine tool worktable, while the Z-axis controls the vertical up-and-down movement of the cutting tool.
A 3-axis milling machine can machine two-dimensional planar graphics and simple three-dimensional shapes with a certain height, such as planar milling, drilling, boring, slotting, and other processing operations.
4-Axis Milling Machine
A 4-axis milling machine adds a rotational axis, usually the A-axis, on the basis of the 3-axis. The A-axis generally rotates around the X-axis or Y-axis, enabling the workpiece to perform linear movements in the other three directions while rotating, achieving four-axis simultaneous movement processing.
In addition to the processing capabilities of a 3-axis milling machine, a 4-axis milling machine can also machine parts with features such as inclined surfaces, cylindrical surfaces, and conical surfaces. It can more conveniently achieve the processing of some complex shapes, reduce the number of workpiece clamping times, and improve processing precision and efficiency.
5-Axis Milling Machine
A 5-axis milling machine adds two rotational axes, usually the A-axis and the C-axis, on the basis of the 3-axis. The A-axis can rotate around the X-axis, and the C-axis can rotate around the Z-axis. In this way, the cutting tool or the workpiece can perform simultaneous linkage movements in the directions of five coordinate axes, achieving more complex spatial attitude adjustment and processing path control.
A 5-axis milling machine has powerful processing capabilities and can machine various complex three-dimensional curved surfaces and irregularly shaped parts, such as the blades and impellers of aero engines, complex sculpture models, artificial joints in medical devices, and so on.
What are the Advantages of CNC Milling?
In modern manufacturing, CNC milling has several advantages, and the following are its main advantages:
High Precision
CNC milling machines precisely control the movement trajectory of the cutting tool through a computer, enabling extremely high machining precision, generally reaching ±0.01mm or even higher.
It can machine parts with strict requirements for dimensional accuracy and geometric tolerances, meeting the needs of industries with extremely high precision requirements such as aerospace, medical devices, and precision molds.
High Flexibility
Just by modifying the numerical control program, it is easy to change the shape and size of the machined parts without the need for large-scale adjustments to the machine tool or the replacement of a large number of tooling fixtures.
This makes CNC milling particularly suitable for single-piece and small-batch production as well as rapid prototyping of products. It can quickly respond to changes in market demand, reducing production costs and shortening the production cycle.
Strong Capability for Machining Complex Shapes
Through multi-axis simultaneous movement control, it can machine various complex three-dimensional curved surfaces and contours. Whether it is the complex curved surfaces of impellers and blades or various irregular cavities in molds, CNC milling can precisely machine them, which is difficult to achieve with traditional processing methods.
High Degree of Automation
The CNC milling process is controlled by a computer program, and the machine tool can automatically complete multiple machining steps without human intervention. This not only improves production efficiency but also reduces the impact of human factors on machining quality and ensures the stability of machining quality.
High Production Efficiency
Parameters such as the cutting speed, feed rate, and cutting depth of the machine tool can be optimized and adjusted according to the performance of the machining material and the cutting tool to achieve efficient cutting. At the same time, multiple surfaces and multiple processes can be machined in one clamping, reducing the number of workpiece clamping times and auxiliary time, and further improving production efficiency.
Good Surface Quality
By reasonably selecting the cutting tool, cutting parameters, and machining process, CNC milling can obtain a good surface finish, generally reaching Ra0.8 – Ra3.2μm, meeting the surface quality requirements of most parts and reducing subsequent surface treatment processes.
Wide Range of Machinable Materials
It can machine almost all kinds of metal materials and non-metal materials, such as steel, aluminum, copper, titanium alloy, plastic, composite materials, etc. Different materials can achieve efficient machining by selecting appropriate cutting tools and cutting parameters.
What is the Difference between CNC Milling and CNC Turning?
CNC milling and CNC turning are two common numerical control machining processes, and their main differences are as follows:
Machining Principle
CNC Milling: Remove materials through the rotation of the milling cutter and the relative movement of the workpiece. The milling cutter can have multiple cutting edges and can cut in multiple directions, enabling the machining of various complex shapes such as planes, curved surfaces, grooves, and cavities.
CNC Turning: Mainly carry out cutting through the rotation of the workpiece and the movement of the cutting tool along the axis or in the radial direction of the workpiece. Turning is mainly used for machining rotary parts, such as cylindrical, conical, and threaded shapes.
Machining Equipment
CNC Milling Machine: The structure is relatively complex, usually having three or more coordinate axes, such as the X, Y, and Z axes, and some also have rotational axes (A, B, C axes) to achieve multi-axis simultaneous movement machining. Common types include vertical milling machines, horizontal milling machines, and gantry milling machines.
CNC Turning Machine: Generally has two main coordinate axes, namely the X-axis and the Z-axis, which control the radial and axial movements of the cutting tool respectively. The spindle of the lathe drives the workpiece to rotate, and the cutting tool is installed on the tool holder for cutting.
Cutting Tool
CNC Milling: There are a wide variety of cutting tools, including end mills, end mills, ball nose mills, keyway mills, form mills, etc., and the appropriate cutting tool can be selected according to different machining requirements.
CNC Turning: The cutting tools are relatively simple, mainly including external turning tools, internal turning tools, threading tools, parting tools, etc., and the shape and size of the cutting tools are selected according to the type of the machined parts and the process requirements.
Machining Objects
CNC Milling: Suitable for machining various parts with complex shapes, such as molds, boxes, brackets, impellers, blades, etc., capable of achieving high-precision plane and curved surface machining, as well as the machining of various features such as holes, grooves, and cavities.
CNC Turning: Mainly used for machining rotary parts, such as shaft parts, disc parts, and sleeve parts, and can complete the machining of surfaces such as the outer circle, inner hole, end face, and thread. It has high machining efficiency and good precision for parts with a rotationally symmetric shape.
Machining Precision
CNC Milling: Can achieve relatively high machining precision, generally controlled between ±0.01mm – ±0.05mm. For some high-precision milling machines, through precise programming and cutting tool path control, parts with even higher precision can be machined.
CNC Turning: The machining precision can usually also reach a relatively high level. The machining precision of the outer circle and inner hole can be controlled at about ±0.01mm – ±0.02mm, and the machining precision of the thread can reach ±0.05mm – ±0.1mm.
In actual product production, we usually combine the two machining methods to complete the machining of more complex parts.
What Types of Parts Can Be Manufactured Using a CNC Milling Machine?
Thanks to its high precision, high flexibility, and powerful machining capabilities, a CNC milling machine can be used to manufacture various types of parts and is widely applied in multiple industries. Here are some common examples:
Mechanical Manufacturing Industry
Box-type Parts: Such as engine blocks, gearbox housings, etc. These parts usually have multiple hole systems, planes, and complex internal cavity structures.
Shaft-type Parts: In addition to turning processing, for some shafts with keyways, planes, or special shapes, a CNC milling machine is also required for auxiliary processing.
Mechanical Parts with Complex Shapes: Such as cams, eccentric wheels, etc. The contour curves of cams are usually quite complex and require precise machining to ensure their motion accuracy.
Mold Manufacturing Industry
Injection Molds: Molds used for producing plastic products, and the shapes of their cavities and cores are often very complex and require high-precision machining.
Die-casting Molds: Molds used for die-casting metal parts, which need to withstand high temperatures and high pressures.
Stamping Molds: By using a CNC milling machine to machine the cutting edges, contours, and positioning structures of the molds, the precision and service life of the stamping molds can be ensured, and stamping parts with accurate dimensions and complex shapes can be produced, such as automobile body panel molds, stamping molds for electronic device casings, etc.
Electronic Equipment Manufacturing Industry
Mobile Phone Casings: Modern mobile phone casings usually feature thinness, lightness, and high precision, and various holes, grooves, button positions, and decorative textures need to be machined.
Computer Chassis: The frames and panels of the chassis need to be machined with various mounting holes, cooling holes, and card slots, etc. Fixtures and Jigs for Electronic Components: Used to fix and position the electronic components during the production process, which require high precision and good repeatability.
Aerospace Industry
Aircraft Structural Parts: Such as the beams, ribs, and skin panels of the wings, etc. These parts usually have the requirements of large size, complex shape, and high precision.
Engine Components: Such as impellers, blades, etc. The impellers and blades of aircraft engines need to withstand high temperatures, high pressures, and high-speed airflow, and have extremely high requirements for their shape precision and surface quality.
English