CNC Milling: Everything You Need to Know

What are your manufacturing goals?

CNC milling is your solution if those goals involve the high-precision creation of complex three-dimensional shapes. CNC milling can handle everything, from single prototypes to high-volume production, providing consistent, high-quality results.

This guide explains everything you need to know to start or improve your CNC milling projects. You’ll see how CNC milling works, popular industry applications, how to design for this process, and more.

What is CNC Milling?

CNC milling is a computer-controlled machining process that uses a rotating cutting tool to remove material from a workpiece. This subtractive manufacturing process creates the desired shape by systematically removing material from a solid metal, plastic, or other material block.

CNC milling’s precision and accuracy make it a popular choice in various industries, including aerospace, automotive, and medical. By leveraging computer numerical control (CNC) technology, this machining process ensures high repeatability and consistency, making it ideal for producing complex and intricate parts.

How Does the CNC Milling Process Work?

CNC milling is a subtractive manufacturing process that uses computer-controlled, multi-point, rotary cutters to remove material from a workpiece and produce a custom-designed part or product. This includes various multi-axis CNC milling machines, which can move along different axes and cut at multiple angles.

The process begins with a 3D CAD model converted into a series of commands through CAM software. These commands guide the machine’s movements with high precision. A CNC machine utilizes these commands to operate its components, such as tool holders and spindles, ensuring precise parts production.

The workpiece is secured to the milling machine’s table, and the rotating tool is cut. This versatile process can produce a variety of shapes and features, including holes, slots, pockets, and even complex surface contours. The operator initiates a machining program to start milling after attaching cutting tools and placing the workpiece on the table.

The CNC Milling Process

The CNC milling process involves several critical steps to transform a digital design into a physical part. It begins with creating a computer-aided design (CAD) model, which is then converted into a CNC program using computer-aided manufacturing (CAM) software. This program dictates the movement of the cutting tool in multiple axes, ensuring precise material removal according to the defined tool paths.

The next step is to set up the milling machine, where the workpiece is securely fixed and the appropriate cutting tools are selected. The machine can be equipped with various cutting tools, such as end mills, face mills, and ball nose mills, each designed for specific milling operations. The CNC milling process then performs the programmed operations, meticulously removing material to achieve the desired shape. Finally, finishing operations may be performed to enhance the surface quality and meet the required specifications.

Types of CNC Milling Operations

CNC milling encompasses various operations, each suited to different machining needs. Face milling involves machining a flat surface perpendicular to the cutter’s axis, creating a smooth finish. On the other hand, plain milling machines a flat surface parallel to the cutter’s axis, often used to create large, flat areas.

Angular milling is used to machine flat surfaces at an angle, providing versatility in creating angled features. Form milling is ideal for machining irregular surfaces, such as curved or complex shapes, using specialized milling cutters. Other notable CNC milling operations include end milling, which uses an end mill to create pockets and contours; slab milling, for machining large, flat surfaces; thread milling, for cutting threads; and gear milling, for producing gear teeth.

CNC Milling Machines

CNC milling machines are classified based on their configuration and the number of axes in motion. The main types include vertical, horizontal, and universal milling machines. Vertical milling machines feature a vertically oriented spindle, making them suitable for tasks that require precision and detail. Horizontal milling machines, with their horizontally oriented spindle, are ideal for heavy-duty milling operations and material removal.

Universal milling machines combine the capabilities of both vertical and horizontal milling machines, offering flexibility for various milling tasks. These machines can perform multiple operations, making them versatile for many machining processes. Understanding each type’s specific characteristics and applications helps select the right CNC milling machine for a given project.

CNC Milling Machine Components

A CNC milling machine comprises several essential components that work together to perform precise milling operations. The spindle is the rotating part that holds the cutting tool, providing the necessary speed and torque for material removal. The tool holder secures the cutting tool, ensuring stability and accuracy during the cutting process.

The workpiece fixture holds the workpiece firmly, preventing any movement affecting the machining accuracy. The control system, often a computer, manages the movement of the cutting tool based on the CNC program, ensuring precise execution of the milling operations. The power supply provides the necessary energy to operate the machine. These components enable the CNC milling machine to perform complex and precise machining tasks, transforming digital designs into high-quality physical parts.

Benefits of CNC Milling

CNC milling is notable for its precision. It can produce complex parts with tight tolerances, making it an excellent choice for intricate designs that require a high level of detail.

Another advantage of CNC milling is its versatility. It can work with various materials, from metals to plastics, and produce many shapes and features.

Moreover, CNC milling allows for the production of parts in low or high volumes efficiently. While the initial setup costs can be high compared to additive manufacturing, particularly for complex parts, these costs are offset by the process’s speed, repeatability, and precision when manufacturing larger quantities.

Types of CNC Milling Applications

Many industries appreciate CNC milling’s ability to produce highly accurate and complex parts. Here are a few notable ones:

Automotive: The automotive industry is one of the original adopters of the earliest form of CNC machining. Today, everything from engine parts to intricate chassis components can be manufactured with exceptional precision and consistency, ensuring every vehicle component functions flawlessly.

Aerospace: The aerospace industry has stringent precision, durability, and performance requirements. Therefore, it heavily relies on CNC milling. This versatile manufacturing process produces turbine components, structural elements, intricate control systems, and other vital parts. CNC milling can handle the high-strength alloys often used in this industry, contributing to the production of reliable and efficient aircraft components.

Want to see how other industries use CNC machining? 

Consumer Electronics: CNC milling plays a significant role in consumer electronics manufacturing. It aids in creating everything from circuit boards to enclosures and various internal components. Given modern electronic devices’ shrinking sizes and increasing complexity, CNC milling’s precision and adaptability are vital for producing intricate components.

Industrial Machinery: CNC milling is also a key player in producing industrial machinery and heavy equipment. This includes manufacturing significant, heavy-duty components and creating smaller, high-precision parts used in various machinery systems.

How Much Does CNC Milling Cost?

The cost of CNC milling varies widely, depending on the complexity of the part, the type of material used, and the volume of parts needed.

While the upfront cost can be relatively high due to the need for tooling setup and programming, this cost is quickly diluted when producing more significant quantities, making CNC milling a cost-effective choice for high-volume production.

However, alternative methods like 3D printing might be more economical for low-volume production or prototyping.

Popular CNC Milling Machines and Materials

CNC milling is compatible with various materials, each with unique properties that make them suitable for different applications. Some of the most commonly used materials in CNC milling:

Aluminum: Lightweight, strong, and easy to machine, aluminum is a preferred choice for many industries, including aerospace and automotive. Its excellent thermal and electrical conductivity adds to its wide range of uses.

Stainless Steel: Known for its strength and resistance to corrosion, stainless steel is famous for applications that demand durability and longevity.

Brass: Brass offers a good balance of strength, corrosion resistance, and machinability, making it ideal for components like gears, valves, and fittings. Its decorative appearance also makes it popular in jewellery and artistic applications.

ABS Plastic: ABS is a rigid, impact-resistant plastic that machines well, making it a good choice for durable parts and prototypes. It’s commonly used in the automotive industry, consumer products, and electronic enclosures.

Nylon: This versatile plastic offers excellent wear resistance, high strength, and good machinability. It’s often used for gears, bushings, and other wear-resistant parts in industrial applications.

Design Considerations for CNC Milling

When designing parts for CNC milling, various factors come into play:

Tool Accessibility: All features should be accessible by the milling tool. Complex interior features or deep cavities may require specialized tools or multi-axis milling machines. Our expert team at MakerVerse can work with you to ensure the efficiency of your design.

Part Orientation: The part’s positioning during the machining process affects the ease of manufacturing and final quality. It can influence tool access, machining time, and surface finish.

Tolerances: The level of precision necessary in the final part impacts the machining process and cost. Tighter tolerances often require slower machining speeds and more complex equipment, increasing production costs.

Feature Size and Type: The size and type of features in your design can affect the final part’s machinability and strength. Small features may require specialized tools, and thin walls or sharp internal corners can weaken the part or be difficult to machine.

Surface Finish: The desired surface finish can influence the machining process. Rough finishes are quicker and cheaper to produce. Find out more about the different finishing options.

Comparing CNC Milling, Laser Cutting, and 3D Printing

The correct manufacturing method depends on production volume, part complexity, material requirements, and budget.

Due to its precision and versatility, CNC milling is often the best choice for high-volume production of complex parts.

Laser cutting, on the other hand, is faster and more cost-effective for 2D parts. It’s also better suited for specific materials.

At the MakerVerse office, the benefits of 3D printing vs. CNC machining are widely debated. In short, 3D printing is ideal for low-volume production and prototyping, particularly for complex geometries that would be difficult to machine. For a more in-depth comparison, we wrote an article comparing these two methods.

Getting Started with CNC Milling

CNC milling is a versatile and precise manufacturing method that can bring your ideas to life.

Ready to start? With MakerVerse, it’s easy. Just upload your design for a quote. Our experts can guide you through the manufacturing process, ensuring the industrial-grade quality of your parts. Discover the possibilities of CNC milling with MakerVerse today.