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CNC milling is one of the most remarkable technological breakthroughs of this century. While many people know about 3D printing for creating precise physical objects, CNC milling has been around longer and is still widely used today. Its applications range from the electronics industry to manufacturing, and the technology continues to grow as more companies realize its efficiency.
In this article, you will understand what is CNC milling, how CNC milling machines work, discuss the various kinds of machines available, their advantages, and offer tips for designing parts to make the most of CNC manufacturing.
What is CNC Milling?
CNC milling is a manufacturing process that combines traditional milling with CNC (Computer Numerical Control) technology. This subtractive manufacturing process uses a rotating cutting tool to remove materials from a workpiece to manufacture parts with precision and accuracy. It operates on materials like metal, plastic, or wood. In CNC milling, the computer controls the speed of the tool, how fast it moves, the order of tool use, and the path the tool follows to cut the material.
The way the cutting tool rotates depends on the type of CNC milling machine and how advanced it is. Most CNC-milled parts are very precise, with tolerances ranging from +/- 0.001 inches to +/- 0.005 inches. Some machines can even achieve tolerances as tight as +/- 0.0005 inches.
There are also different types of milling machines based on their axes of movement. For example, 3-axis machines move in the X, Y, and Z directions, while 5-axis machines can move in X, Y, and Z, and also rotate in A and B directions. This allows 5-axis machines to create more complex and detailed parts.
How Does CNC Milling Work?
CNC milling works through coded instructions being read and input into the system to begin operations. It starts by building a 3D CAD file that pictures what the final product should look like. It’s then converted into a readable format for the milling machine. A software known as CAM (Computer-Aided Manufacturing) moves this file to the CNC machine program, which would be in a G-code format. This format acts as an instruction for the CNC milling to operate and replicate the CAD design in the material you want it to be. Ensure it’s accurate and efficient.
CNC milling also uses subtractive machining technology to manufacture both low and high volumes of complex parts. In the operations of CNC milling, materials are removed from a blank workpiece, and the machine uses a tool called a milling cutter. This tool is used to cut materials at different angles and move along various axes. Which in turn results in your desired product.
Advantages of CNC Milling
CNC milling is an important method in the production process, thereby having benefits you should be made aware of. Here are the main advantages of CNC milling:
1. Accuracy and Precision
CNC milling operations can help you minimize errors during production, which will increase the precision and accuracy of your product. This method will enable you to meet the same tolerance requirements and technical specifications of your product design.
2. Efficiency and Repeatability
CNC milling can provide you with a high volume of production due to its automation feature. It can manufacture parts in record time and give qualities and finishes that are more consistent.
3. Wide Material Compatibility
Another important advantage of CNC milling is that it can be used for several materials, some of which include plastics, wood, metals, and glass. This makes the machine more suitable for application across different industries.
4. Less Labor Intensive
The high volume of production and automating features of CNC milling machines will help you reduce the number of labor you will need for the manufacturing process. Another reason why it’s less Labor intensive is its live tooling feature, which means tools in the machine can be changed without hindering the operation. Which requires a limited number of operators.
5. Cost-Effective
Lastly, a CNC milling machine can help you manufacture products with complex designs very fast and with accuracy. This, in turn, will reduce the time you spend on production, thereby reducing the cost of errors and overtime. Also, the less labor you need to hire, the less the cost of the production process.
Applications of CNC Milling
CNC milling can be applied in several industries. This machine provides engineers and designers across different industries with a quick and reliable method of making quality products through various phases of development. Here are some of the industries that use CNC milling:
Aerospace Industry
The Aerospace industry is one sector that requires an extremely high need for precision and accuracy. This is why CNC milling machines are widely used in this sector to provide parts that ensure safety and allow the aircraft to function properly. This CNC milling process is one of the suitable methods for manufacturing parts in the aerospace industry because it can work on materials like titanium and aluminum. These materials offer durability and lightweight features, which ensure the parts needed are accurately machined. Some of these parts include landing gear parts, fuel panels, and engine parts.
Automotive Industry
Parts needed in the automotive sector are required to be very precise and efficient. CNC milling answers these requirements because it can help you produce drive axles, gearboxes, suspension components, exhaust parts, interior panels, and cylinder heads. You can also use the machine to repair those parts.
Medical Industry
The sensitive nature of medical and surgical tools like prostheses and custom orthopedic implants, among others, makes accuracy and precision a priority. This gives CNC milling the edge to create such components. This will make the product match the design specifications, thereby increasing productivity and efficiency. CNC milling also helps produce medical tools such as scalpels, MRI scanners, components of imaging equipment, hip replacements, knee replacements, and dental implants.
Consumer Products
CNC milling helps in producing general-purpose parts like flanges, nuts and bolts, and gears and shafts. These machines are also used to create home-based parts like cutting boards and wooden utensils, décor like coasters, wall art, and shelving.
Electronics
The level of precision of the CNC milling machine makes it ideal for the electronics sector. The industry is highly dependent on CNC milling machines. This is because it can be used to produce important parts like connectors, custom enclosures, heat sinks, circuit boards, and other parts.
Defense
CNC milling is also used for producing military parts. They are used in producing parts such as weapons, communication equipment, and vehicles. They also produce parts used for firearms such as receivers, barrels, and triggers. CNC milling machines ensure these components meet the standard required by the military.
6 Types of CNC Milling Machines
A CNC milling machine has different parts that cut through the materials used. Each type of CNC milling machine has a different setup that enables various operations. Here are the main types of CNC milling machines you can consider when carrying out your project.
1. Vertical Milling Machine
This vertical milling machine can move in three directions (axes). It has a table that works as both a work surface and a base for the spindle. As the name suggests, the spindle (the part that holds the cutting tools) is positioned vertically. The spindle also rotates the cutting tools as they work.
There are two main types of vertical CNC milling machines:
- Bed Mill: The table on a bed mill only moves side to side (perpendicular to the spindle). The spindle itself rotates along its axis.
- Turret Mill: The spindle stays in place, but the table can move side to side and forward/backward (parallel and perpendicular to the spindle). Some turret mills also have a quill, which moves the cutting tools up and down. Turret mills are more flexible and can handle a wider variety of tasks.
2. Horizontal Milling Machines
The spindle axis adjustment differentiates a vertical CNC milling machine from a horizontal CNC milling machine. In this type of CNC milling machine, the spindle axis is aligned horizontally. When you have a workpiece that is heavy and very long, it’s best to make use of horizontal milling machines. One major feature of some horizontal milling machines is that they can grind at various angles, which is enabled by the rotary table.
3. Multi-Axis CNC Milling Machine
Multi-axis CNC milling machines are special kinds of machines that can cut through materials at various angles and also move along different axes. There are different types of multi-axis milling machines:
2-Axis Milling Machines
This milling machine operates as a workpiece in the x and z axes. This means they can cut horizontally and vertically in only one direction. It makes these machines the simplest type of multi-axis milling machine.
3-axis milling machines
3-axis milling machines can move along the X, Y, and Z axes. This allows the machine to cut materials vertically in any direction. It’s one of the most common milling machines used.
4-axis milling machines
This milling machine has a spindle that can go across the three axes: side to side, back and forth, and up and down without the workpiece changing positions. It can rotate along the A-axis or X-axis. They are precise, accurate, and fast. This makes it suitable for complex operations.
5-axis CNC milling machine
The 5-axis CNC milling machine has a spindle and cutting tool that can go across three axes and enable rotation across two axes (across any of the x-axis, y-axis, or z-axis). This is the most complete multi-axis CNC milling machine amongst others.
4. Knee Type
In this type of milling machine, the work table can be adjusted vertically, and the spindle is fixed. The knee supports the work table while it rests on the saddle. The knee can either be dropped or increased. For instance, the knee-type CNC milling machine features a floor-mounted, bench-type, plain horizontal CNC milling machine.
5. Planer Type
The planer type bears a resemblance to the bed-type CNC milling machine in some aspects. The work table of a planer-type milling machine is set up along the Y and Z axes. The spindle of this machine can move in 3 axes (X, Y, and Z axes). But planer-type milling machines can support a wide range of machine tools.
6. Bed Type
The bed-type milling machine work table is joined directly to the bed of the milling machine. This machine is classified based on the number of spindles it uses. There are simplex, duplex, and triplex. Simplex uses one spindle that moves either in the X or Y direction, duplex uses two, and triplex uses three spindles.
CNC Milling Process Steps
There are several key steps to follow when using a CNC milling machine to manufacture a product:
1. Designing the CAD Model
The first step in the CNC milling process is creating a CAD model design for your desired product. As the name implies, CAD (Computer Aided Design) software assists you in creating a 2D or 3D model for any design you want to produce. You can use software such as Autodesk or SolidWorks to create the design for your final product.
While some software can convert 2D drawings into 3D CAD files, some software will allow you to trace a 2D image to convert it into a 3D file. Note that your design should contain information such as the dimension of the part, tolerance, indication of thread, construction lines, and finishing preferences.
2. Converting CAD to G-code
CAD models are not recognized by CNC milling machines directly. However, you can convert the CAD model into G-code, a code the milling machine will understand. It is important to export your CAD model into a format that is CNC-compatible with the CAD/CAM software you have used. Examples of a CNC-compatible file format are STL and STEP.
In case the software you used cannot convert the design into a CNC-compatible format, you can use online services such as Convert.emachineshop.com and Cadexchanger. When you have converted, the file will instruct the milling machine on the rotational and linear movement, toolpath, workpiece speed, and cutting sequence associated with the production process.
3. Setting Up the Machine
Before starting production, the operator will set up the workpiece and the machine. This involves attaching the cutting tools to the spindle and placing the workpiece on the table. This will help enable smooth production, thereby reducing machine breakdowns and pauses in the production process.
4. Executing the Milling Process
Once the setup is complete, the operator reviews the program one last time before starting the machine for production. The production process is automated, so it will continue running until it has reached its mark. You can adjust the process to ensure you get the best result.
5. Post-Processing and Finishing
Once the CNC milling machine has concluded production, the result might need additional post-processing, which may include polishing, deburring or surface treatment to get a high-quality product.
FAQs
What materials does CNC milling use?
There is a wide variety of available materials to use in a CNC milling, not knowing them can pose a challenge. This is the classification of materials used in CNC milling:
Metal: Aluminum, stainless steel, tool steel, copper, mild steel, and copper
Plastics: Nylon, ABS, and Polycarbonate
Others: wood, zinc, ceramics, stones, and plywood.
What is the difference between CNC milling and turning?
CNC milling and turning are different machining processes that offer specific purposes in manufacturing. CNC milling operates by holding the workpiece in position as the cutting tool rotates, which allows for pockets, complex cuts, and contours on various materials. While CNC turning uses a rotating workpiece and a stationary cutting tool, which makes it ideal for cylindrical components like bushings and shafts. Both manufacturing processes increase precision and efficiency, but they offer distinct services to several manufacturing needs.
What products can you make with CNC milling machines?
The list of product CNC milling machines can produce is endless, some of them include: custom signage, candle holders, cutting boards, bookends, coasters, furniture, toys and games, wooden serving trays, jewelry, aerospace, engraving, custom furniture components, machine components, wood, computer parts, intricate sculptures. As long as it can be designed. The CNC milling machine can manufacture it. You can get a wide range of custom parts no matter the complexity.
Conclusion
CNC milling is an incredible machining technique that is useful for a wide range of projects. But, to take advantage of the benefits listed in this article, you must take the time to find a reliable company to work with.
At Richconn we offer expert CNC milling services that prioritize creating high-tolerance precision of plastic and metal parts at a favorable cost. Our access to top-tier multi-axis CNC milling machines can assist you in producing quality parts on time. Contact us now to get your project accomplished without any hinge.
