Home 9 CNC Machining 9 Milling Made Simple: A Beginner’s Guide to CNC Milling

CNC technology has a significant role in the automation of the manufacturing industry. It involves using computer programs to control the movement and operation of machinery, enabling exact and consistent results.

Manufacturers use different CNC machining processes to shape the workpiece based on the material type, design specifications & Complexity. The standard CNC machining processes are CNC milling, CNC turning, CNC routing, and CNC drilling. However, this article will only cover the milling process, including its process, different operations, advantages, disadvantages, and milling services.


What is CNC Milling?

A CNC milling machine removing the material from a workpiece

CNC milling

CNC milling is a subtractive manufacturing approach that involves removing material to convert the workpiece into the desired shape using a CNC milling machine. The material removal process uses cutting tools, such as end mills and drill bits, where cutting tools are controlled by a computer program that specifies the tool path and cutting parameters, such as cutting speed and depth of cut.

CNC milling machines are used in the milling process, which is highly versatile and can perform a wide range of milling operations. They are capable of cutting a variety of materials, from plastics and composites to metals and alloys.

Typically, CNC milling technology can create parts with tolerances as tight as ± 0.001 inches to ±0.005 inches. However, the CNC milling machine must be highly accurate and precise to achieve these tolerances.


Difference between CNC milling and CNC turning

CNC milling and turning are two computer-controlled machining processes that differ significantly in their ability to create various shapes and features, the number of axes they operate in, and the types of workpieces they can handle. Therefore, understanding the differences is beneficial to choose the appropriate machining process for a particular job.

Category CNC Milling CNC Turning
Cutting tool Rotating multi-point cutting tool Single-point cutting tool
Process Material is removed from a workpiece using rotating cutting tools guided by a computer program. Material is removed from a rotating workpiece using a stationary cutting tool guided by a computer program.
Applications Producing a wide range of parts, including complex shapes and features. Producing cylindrical parts, such as shafts, bushings, and flanges, often for high-volume production.
Material Can work with various materials, including metals, plastics, composites, etc. Can work with various materials, including metals, plastics, composites, etc.
Features Capable of producing pockets, slots, holes, threads, chamfers, and complex 3D shapes. Capable of producing threads, grooves, chamfers, and other cylindrical features.
Advantages – Versatility for complex shapes and features. <br> – Precision and repeatability. <br> – Flexibility in material selection. – Efficiency for high-volume production. <br> – Simplicity in setup and operation. <br> – Cost-effective for high-volume production.
Limitations – Cost, especially for large or high-precision machines. <br> – Setup time for tool changes and workpiece alignment. <br> – Material waste during the milling process. – Limited to producing cylindrical shapes and features. <br> – Less versatility for complex parts. <br> – Lower precision for complex parts with tight tolerances.


Types of CNC Milling Operations

Various types of CNC milling operations are designed to achieve specific outcomes depending on the material type. These operations differ in the type of cutting tool used, the cut’s direction, the cut, the depth of the cut, the speed & feed rate, and other machining parameters. In addition, choosing the proper milling operation for a particular job is essential to ensure optimal efficiency, accuracy, and quality.

Let’s discuss the major CNC milling operations used in manufacturing.

  1. Face milling

Face milling operation involves cutting a flat surface perpendicular to the axis of rotation of the milling cutter. The face milling cutter contains teeth on the periphery and on the face of the cutter, which allows it to cut both axially and laterally.

It is used to create a flat surface on a workpiece or level its top. The typical applications of face milling include engine blocks, cylinder heads, and other flat surfaces on various workpieces.

  1. Peripheral milling

It is a fast and accurate machining method that offers high-quality surfaces with much less surface roughness. Peripheral milling involves cutting the outer edges of a workpiece using a cutting tool that rotates around the workpiece’s perimeter.

This operation is excellent for producing intricate contours or shapes on the workpiece’s exterior, such as gears, splines, and profiles.

  1. Slot milling

As the name suggested, Slot milling involves cutting a narrow slot or groove on the surface of a workpiece. The slot can be of varying depths and widths, depending on the design specifications. Different cutting tools, such as end mills, drill bits, and slot drills, are used in slot milling. The milling cutter rotates and engages the workpiece, removing material in a straight line to create the slot.

  1. Plain milling

Plain milling is a type of milling operation that creates a flat surface parallel to the axis of rotation of the milling cutter. During the operation, the milling cutter rotates and engages the workpiece, removing material in a flat plane. It can be used to create a flat surface on a workpiece, to level the top of a workpiece, or to cut a groove or slot.

  1. Pocket milling

Pocket milling is suitable for creating a closed pocket or cavity on the surface of a workpiece. Different cutting tools like end mills, ball nose mills, and slot drills can be used to create a pocket with various shapes, including rectangular, circular, or irregular, and can be of varying depths and widths.

  1. Form milling

Form milling is commonly used in manufacturing components with complex shapes because it allows cutting a workpiece into a specific condition or contour. The operation uses a tool that matches the desired contour, allowing the device to create a detailed profile or pattern on the workpiece’s surface.

  1. Other milling operations

Numerous other milling operations exist, such as drilling, profiling, thread milling, plunge milling, angular milling, and slide milling.


Material Selection for CNC Milling

You need to select the suitable material for a specific job to obtain the desired product’s desired quality and performance. Choosing the suitable material for milling requires several considerations milling operations, design complexity, material properties, cost, and testing.

Here’s a step-wise guide to help you make the best choice:

  1. Determine the end use: Determine the purpose and application of the final product will dictate the kind of material you should use based on required strength, durability, temperature resistance, and chemical resistance.
  2. Consider the milling operations: Different materials have varying properties that demand suitable milling tools & operations. For instance, some materials are harder to cut and may require specialized tools or milling techniques.
  3. Determine the required precision: Your design’s size and Complexity of your design will determine the precision and accuracy needed in your milling process. Some materials are more straightforward to mill than others, and the level of precision required may affect your material selection.
  4. List the material options: There are several materials to choose from, such as aluminum, brass, steel, and plastics. Make a list of possible options with the properties and characteristics of each material.
  5. Compare the cost: Before comparing the cost, shortlist the materials by comparing them against your requirements. Now, select the best option by considering the cost of the raw material, tooling, and labor required for milling.

Summary of the important considerations in material selection for CNC milling

Consideration Factors to Consider
End Use – Purpose and application of the final product <br> – Required strength, durability, temperature resistance, and chemical resistance
Milling Operations – Material properties and their effect on milling <br> – Need for specialized tools or milling techniques
Required Precision – Size and complexity of the design <br> – level of precision and accuracy needed
Material Options – Aluminum, brass, steel, plastics, etc. <br> – Properties and characteristics of each material
Cost Comparison – Shortlisted materials based on requirements <br> – Cost of raw material, tooling, and labor for milling

Finalize your material: Once you’ve selected a material, testing and refining your milling process to ensure optimal results is essential. So, try the material with adjustments to the milling parameters and tooling. If all results are okay, finalize the material.


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Advantages and Disadvantages of CNC Milling Parts

Steel automotive components created with CNC milling

Mill parts

CNC milling is an efficient manufacturing technique with many benefits, including improved accuracy, repeatability, and efficiency compared to conventional milling. However, it has a few drawbacks, such as high installation costs and part size restrictions.


  • CNC milling machines can create exact components with tolerances as small as 0.001 inches.
  • Milling operations can create identical parts with the same level of precision and accuracy, even in high-volume production runs.
  • CNC milling machines can work constantly and independently, cutting down on the labor and time needed for production.
  • It allows creating the part with complex shapes and contours
  • CNC milling machines can work with a range of materials, providing greater product design flexibility. Common materials are steel, copper, titanium, aluminum, plastics, ceramics, and more.


  • High initial costs for equipment and training
  • Limitations on part size and Complexity
  • Lack of flexibility for small-scale production runs
  • Requires skilled operators and programmers
  • Maintenance and repair costs can be high


How CNC Milling Services Works?

Tool movement and feed direction in the CNC milling process

Working CNC milling

The CNC milling services start with design creation and involve other stages throughout the process.

Here is an overview of how the CNC milling services work;

  1. Design Creation: The first step is to design the part to be manufactured using CAD (Computer-Aided design) software. The design can also be created from a 3D scan of an existing part.
  2. Conversion to CNC Code: The CAD software converts the design into a set of instructions called CNC code. This code contains the precise coordinates and movements the milling machine will use to shape the part.
  3. Machine Setup: The operator sets up the CNC milling machine by loading the workpiece into the machine and securing it. The operator also loads the CNC code into the machine’s computer.
  4. Milling Process: The milling process begins once the machine is set up. According to the CNC code, the machine uses a cutting tool, typically a rotating end mill, to remove material from the workpiece. The cutting tool moves along multiple axes, such as X, Y, and Z, to create the desired shape.
  5. Surface finishing: After the component has been milled, it could still need to be finished with sanding, polishing, or painting. Before being used or sent to the customer, the finished product is checked for accuracy and quality.
  6. Shipment and delivery: After quality inspection, manufacturers ship the parts (or products) to the clients with proper packaging


Prolean’s CNC Milling Services with Competitive Pricing

Creating precise parts with CNC milling operations could be challenging without experienced engineers and advanced mill machines. If you want to outsource the milling parts or products, Prolean can become a trusted partner. ProleanTech is a leading on-demand manufacturing company based in China with years of experience in CNC milling services for different industries.

Our CNC milling services are tailored to meet each client’s specific needs. We use advanced technology and equipment to ensure the highest standards of accuracy and precision. Additionally, our engineers work closely with clients to provide personalized solutions for unique needs and specifications.

Whether you need CNC milling services for prototyping, low-volume production runs, or high-volume production runs, Prolean has the expertise and resources to deliver top-quality results. Our competitive pricing ensures that you get the best value for your money without compromising quality or service. Please send us your design to start the project.


Types of Milling Machines

Schematic diagram of horizontal and vertical CNC milling machines

CNC milling machines

CNC milling machines come in different types, each designed for specific machining tasks and applications. Following are some common types of CNC milling machines:

  • Vertical milling machines: These machines feature a spindle that moves up and down, allowing for the creation of complex parts with intricate shapes and features.
  • Horizontal milling machines: These machines have a horizontal spindle and are ideal for cutting long or large parts. They are often used in mass-production settings.
  • 5-axis milling machines: These machines have five axes of movement, enabling the creation of complex geometries and shapes. They are commonly used in the aerospace and automotive industries.
  • Bed-type milling machines: These machines move along the X and Y axes while a fixed bed supports the workpiece. These are suitable for They are suitable for
  • Gantry milling machines: CNC milling machines with a bridge-like structure spanning the work area’s length. These are used in machining large parts with high precision.


What is the Small CNC Mills?

Small size four-axis CNC milling machine

Small CNC mills

A small CNC mill is a type of milling machine smaller than traditional CNC mills. It makes small CNC mills more suitable for home workshops or small businesses. Furthermore, they can work with metal, plastic, and wood to create precise cuts, holes, and shapes with high accuracy.

The followings are some examples that can be made with a small CNC mill

  • Custom parts for machinery or equipment
  • Prototypes for new products
  • Decorative objects, such as signs or sculptures
  • Jewelry and other small items
  • Parts for model airplanes or other hobby projects
  • Overall, a small CNC mill can be a versatile tool for anyone who needs to create precision parts or objects with complex shapes.

A small CNC mill can be a versatile tool for anyone creating small parts or objects with complex shapes. Moreover, it could be excellent equipment for your workshop to learn and understand how CNC milling operations work.


Summing Up

This article is a beginner’s guide to CNC milling, one of the most versatile subtractive manufacturing approaches. It has discussed different types of milling operations, material selection, advantages, and more. If you still found difficult to understand the milling process, please don’t hesitate to contact us.


What is CNC milling?

It is a machining process that uses computer-controlled rotating cutting tools to remove material from a workpiece. The cutting tool moves in multiple axes to create complex shapes and features, where the computer program dictates the tool’s movement. 

What are the different types of CNC milling operations used in manufacturing?

Some common types of CNC milling operations used in manufacturing include face milling, end milling, drilling, and tapping.

What factors should be considered when choosing a milling operation for a specific job?

Different factors should be considered, including the material being machined, the required tolerances, the desired surface finish, and the available cutting tools and equipment,

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