CNC milling is an essential process in the production of complex components. As one of the extensive functions of CNC precision machining, this process helps to manufacture precision parts for many industries. Due to its widespread application, this technology continues to develop and grow.
CNC milling is a computer-controlled process that involves using cutting tools to remove a portion of the workpiece. Its basic setup includes a workbench and cutting tools attached to the spindle. The workpiece is placed on the workbench of the machine, while the cutting tool rotates to shape the workpiece.
The rotation of the cutting tool will depend on the type and complexity of the CNC milling machine. Most CNC milling parts can achieve high tolerances between+/-0.001 inches and+/-0.005 inches. Some machines can even achieve tolerances of up to+/-0.0005 inches.
Therefore, this process has a wide range of applications and can be used for various materials, including metal, plastic, wood, and glass. It can also help create various customized products to meet unique needs.
CNC milling process
Usually, CNC milling operations are carried out in three stages:
1. Design CAD files
The first stage involves using CAD software to create a virtual representative of your expected product. You can use different CAD-CAM programs to develop the G code required for machining. Transforming CAD design into CNC programming language is very important because it is a language that machines can understand. You can check and modify the code to meet the functionality of the machine. This software also enables manufacturing engineers to simulate the entire milling process. Therefore, they can check for design errors and avoid creating complex models that are difficult to machine.
The operator also needs a technical engineering drawing that includes the following information:
- Dimensions and Key Features of Parts
- tolerance
- Construction line
- Indication of threads
- Organize preferences
2. Set up milling machine
Although CNC milling machines can automatically cut workpieces, certain aspects of the process still require machine operators. For example, the operator must fix the workpiece to the workbench and adjust the tool of the spindle.
Modern milling machines have the ability to process with electricity. Therefore, they have the ability to replace tools during the milling process. This reduces the number of pauses during the operation. However, initial setup and program checks are still required before starting the process.
3. Production Components
As mentioned earlier, CNC milling uses a rotating tool that cuts chips when in contact with the workpiece. The continuous rotation of the tool gives the desired shape. Depending on the type of raw material and the required shape of the final product, this process may include different operations.
The previous operations used larger tools to carve the material and obtain a rough shape. Then, changing tools will help create more precise machined parts. Precision CNC milling is achieved in the final stage, involving unparalleled surface roughness and engineering tolerance levels.
Multiple CNC milling operations
CNC milling centers can generate multiple complex features with high accuracy. These features include threads, chamfers, grooves, etc. However, creating these features requires various milling operations, such as:
1. Flat milling
It is also known as surface milling, which uses a horizontal milling machine. Therefore, the tool has a rotation axis parallel to the workbench. Plane milling uses different shapes and directions of cutting tools based on the desired results. The combination of wide cutting tools (fast feed speed) and finer cutting teeth (faster cutting speed) is an excellent cost-effective choice. It also ensures better surface finish and high-quality final products.
2. Face milling
This type of milling uses cutting tools with teeth on the side and end. The side teeth perform the main cutting work, while the other teeth on the tip contribute to surface smoothness. Face milling is usually performed after face milling, as it can create complex contours and leave high-quality finishes.
3. Angle milling
This is one of the best milling operations for creating grooves, chamfers, grooves, and other complex features. Traditional 3-axis milling cutters use different types of tools – dovetail groove cutters for bevel grooves or conical cutting heads for chamfering. The axis of the tool is usually perpendicular or in a straight line with the cutting surface.
4. Forming milling
This milling operation uses special tools to create more complex contours. Concave and convex cutting tools are the most common here. They help create surface contours, circular edges, and circular grooves in a single cut.
5. Other milling operations
In addition to the milling operations mentioned above, CNC milling machines can also perform other types of specialized milling operations, such as:
Profile milling:
Here, the tool creates a cutting path along an inclined or vertical surface on the blank. This process uses a profile milling cutter that may be parallel or perpendicular to the surface of the workpiece.
Linkage milling:
This is a subcategory of forming milling that uses multiple tools to create patterns simultaneously. Tools usually have different shapes, sizes, or widths. They may perform similar or different operations to create more complex features or parts in a shorter amount of time.
Cross milling:
This milling operation allows the machine tool to process two or more parallel workpieces in one cut. Two cutting tools are arranged on both sides of the workpiece to mill both sides on the same machine tool spindle.
Advantages and Disadvantages of CNC Milling in Part Manufacturing
Due to its advantages, CNC milling technology is crucial for various industrial processes. Nevertheless, there are still some drawbacks that need to be noted. Here are some advantages and disadvantages of this manufacturing technology.
Advantages of CNC milling
Precision and accuracy
The nature of CNC milling operations minimizes the margin of error, ensuring higher accuracy and precision. This technology can produce parts that meet precise technical specifications and tolerance requirements.
Most CNC milling parts can achieve high tolerances between+/-0.001 inches and+/-0.005 inches, while some can achieve+/-0.0005 inches. The automation of this process also limits human error. Even if you require surface treatment, micro milling allows for the removal of some thickness to prevent affecting the size of the part.
Efficiency and Repeatability
Due to the involvement of automation, CNC milling centers can provide high output. Advanced milling machines can produce parts with more consistent quality and finish faster.
Wide material compatibility
This process is suitable for various materials, including metal, plastic, glass, and wood. This further increases its versatility, making it very suitable for various applications.
Reduce labor-intensive
The automation and high production of CNC milling machines significantly reduce the labor force used in this process. These machines also allow the use of live tools to ensure tool replacement without stopping operation. This process only requires a few operators.
Cost effectiveness
CNC milling machines can produce complex products faster, more accurately, and efficiently. This reduces the time spent in the production phase. In addition, the lower demand for labor further reduces process costs.
Disadvantages of CNC milling
High machine costs
The initial investment cost of CNC milling machines is higher than that of traditional manual equipment. This may push up overall manufacturing costs.
Enhanced training is required for operators
Not everyone can operate CNC milling machines. From designers to programmers and machine operators, they all need to receive sufficient training to achieve the best results from the process.
High level maintenance
It is necessary to regularly maintain milling machines to ensure their normal operation and extend tool life. This increases the downtime of using milling machines.