Everything You Need to Know About CNC Milling in 2024

  • Updated: June 25, 2024

About the Authors

Frank Lee

At the helm of XMAKE, Lee directs the vision with expertise honed at HIT with over 16 years in the field, including as a Lean Manufacturing System expert at General Motors and global evaluator, Frank has a proven track record of pioneering improvements across 1000 factories.
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Introduction

CNC milling, short for Computer Numerical Control Milling, is a subtractive manufacturing process that uses computer-controlled machines to shape materials by removing material from a workpiece. It’s defined by its precision, efficiency, and ability to produce complex parts with a high degree of accuracy.

The evolution of CNC milling has been marked by technological advancements that have improved machine capabilities, software integration, and material compatibility. By 2024, we expect to see even greater integration with automation, artificial intelligence, and sustainable practices.

Let’s take a deep dive into the world of CNC milling together.

Fundamentals of CNC Milling Techniques

XMAKE-CNC-Milling-Techniques

The CNC Milling Process

In the sophisticated world of CNC milling, the creation of a machine part is a journey that initiates in the digital realm. Designers expertly utilize CAD software to forge virtual models with meticulous precision, giving form to complex designs within a 3D digital space.

Once the digital blueprint is complete, it’s translated into G-code by specialized software, transforming the design into a detailed set of instructions for the milling machine. This G-code acts as the machine’s guide, dictating its every move with exacting accuracy.

The process then moves to the machine setup, where the workpiece is securely positioned on the bed, ready for the milling tools to commence their work. The correct tools are chosen and installed, readying the stage for the material removal process.

Finally, as the CNC machine comes to life, it follows the G-code script with methodical precision.    The spindle spins at high speeds, and the cutting tools glide across the workpiece, meticulously shaping the material to match the intended design, blending artistry with functionality in a seamless dance of metal and machinery.

Components of a CNC Milling Machine

Each part plays a distinct role in precision machining. Let’s discover the core components of the machine,

1. The Bed of a CNC Milling Machine

The bed of a CNC milling machine is the foundation, providing unwavering support and stability.  It’s designed to resist deflection, ensuring the workpiece remains steady during the cutting process, which is critical for maintaining precision and accuracy in every operation.

2. The Column of a CNC Milling Machine

The column is the towering structure that rises from the bed, acting as a guide for the milling machine’s vertical movements.  It houses the spindle and is responsible for the Z-axis motion, delivering the cutting tool to the workpiece with exacting precision, essential for the depth and vertical accuracy of cuts.

3. The Spindle of a CNC Milling Machine

The spindle is the heart of the CNC milling machine, where the cutting tools are mounted.  It rotates at high speeds, delivering the tool’s cutting power to the workpiece.  The spindle’s accuracy in both speed and positioning is vital for the quality and efficiency of the milling process.

4. The Tooling of a CNC Milling Machine

The tooling is the cutting edge of the operation, literally.  It includes a variety of tools that perform different operations, from roughing out the shape to finishing touches.  The selection and condition of the tooling directly affect the machine’s ability to cut a wide range of materials and achieve the desired surface finish.

CNC Milling and CNC Turning

1. Comparison with CNC Turning:

CNC turning is a rotational process ideal for creating symmetrical parts, while CNC milling offers the flexibility to handle complex and asymmetrical geometries.  Milling’s adaptability makes it suitable for a broader spectrum of part designs.

2. Distinctive Features of Each Process:

Each process has its unique features.  CNC milling’s multi-axis movement capability allows for intricate part production, whereas turning is more specialized for rotational symmetry.  Understanding these differences helps manufacturers select the appropriate process for their specific needs.

Different Types of CNC milling machines

XMAKE CNC Milling Machine

There are different types of milling machines, including vertical, horizontal, 5-axis milling machines, etc. Each type of milling has its own advantages and is used based on the specific requirements of the project.

Vertical CNC Milling Machines: 

Vertical milling machines are the most common type. They have a spindle that moves vertically and horizontally, allowing for a wide range of cutting operations.  They’re great for machining flat surfaces and are often used for prototypes and small production runs.

Horizontal CNC Milling Machines: 

With a horizontal spindle orientation, these machines are ideal for machining larger parts due to their rigidity and stability.  They’re often used for heavy-duty machining tasks.

CNC Bed Milling Machines: 

These are large-scale machines with a table that moves in all directions, while the spindle remains stationary.  They’re perfect for machining large, heavy parts with high precision.

Gantry CNC Milling Machines: 

Known for their large work areas, these machines have a moving gantry structure that carries the spindle and column, allowing for the machining of very large parts.

5-Axis Milling Machines: 

Unlike a 4-axis milling machine, the 5-axis CNC milling machine can move in five different directions, including rotation around two axes. They’re perfect for complex, three-dimensional shapes that require intricate detailing.

High-Speed CNC Milling Machines: 

Designed for rapid machining, these machines can work at high speeds and feeds, reducing production time significantly.

CNC Milling Operations

XMAKE CNC Milling Machine

Toolpaths and Cutting Strategies

1. Toolpaths

Toolpaths are meticulously planned routes that dictate the tool’s journey across the workpiece, ensuring both efficiency and precision.  They’re the roadmap for the machine, optimizing the milling process to achieve the desired outcome with minimal waste and maximum accuracy.

2. Cutting Strategies

Cutting strategies are tailored to the task at hand, employing zig-zag patterns for swift material evacuation in roughing processes, and contouring techniques for a smooth, refined finish.  Each strategy is selected to balance speed with the need for a precise cut, adapting to the material and the part’s specifications.

CNC Milling Methods: Angular, Face, Plain, and Form Milling

1. Angular Milling

Angular milling is characterized by its ability to create angled surfaces and features.  It’s defined by the tool’s axis of rotation being set at a specific angle to the workpiece, allowing for the production of complex geometric shapes and efficient material removal in areas with tight tolerances.

2. Face Milling

Face milling is all about creating flat, planar surfaces with precision.  The tool’s axis of rotation is perpendicular to the workpiece’s surface, ensuring a clean, even cut.  It’s ideal for large surface areas and is often the first step in achieving a part’s required dimensions.

3. Plain Milling

Plain milling is a straightforward process where the cutting tool’s axis is parallel to the workpiece’s surface.  It’s used for a variety of applications, from slotting and profiling to obtaining a smooth finish on wide surfaces.  The simplicity of the process makes it versatile and accessible for many milling tasks.

4. Form Milling

Form milling is the art of creating complex, irregular surfaces.  It requires specialized tools and careful planning to achieve the desired contour or shape.  This technique is particularly useful for producing parts with unique geometries that cannot be manufactured through standard milling processes.

Finishing Techniques in CNC Milling

1. Surface Finishes and Their Applications

Surface finishes in CNC milling are as diverse as the parts they adorn.  They’re applied to meet the specific functional requirements or aesthetic standards of a part.  From matte to glossy, each finish serves a purpose, whether it’s to improve wear resistance, reduce friction, or simply to look good.

2. Part Marking Techniques

Part marking techniques such as laser engraving and silk screening elevate a part’s identity.  They’re used for clear part identification, branding, or purely decorative purposes.  These methods offer a permanent and precise way to add textual details to the part, enhancing its value and functionality.

Common Materials Used in CNC Milling

1. Plastics Used in CNC Milling:

Plastics are favored in CNC milling for their lightweight and ease of machining. They are versatile materials, suitable for a range of applications from prototyping to functional parts, due to their moldability and resistance to corrosion.

2. Aluminum Used in CNC Milling:

Aluminum stands out for its excellent strength-to-weight ratio. It’s a go-to material for industries like aerospace and automotive, where parts need to be both strong and lightweight. CNC milling aluminum is efficient, thanks to its softness and non-ferrous nature, which reduces tool wear.

3. Steel Used in CNC Milling:

Steel is prized for its durability and strength, making it ideal for heavy-duty applications. It poses a greater challenge in CNC milling due to its hardness, requiring robust tools and careful heat management. Yet, the end result justifies the effort, with steel components finding use in construction, machinery, and tools.

Benefits of CNC Milling

XMAKE CNC milling produces complex shapes

Precision and accuracy

CNC milling offers unparalleled precision and accuracy in machining operations, ensuring consistent and reliable results with tight tolerances. This level of precision is crucial for industries that require high-quality components.

With CNC milling, manufacturers can achieve complex geometries and intricate designs with the utmost accuracy, reducing the margin of error and improving overall product quality.

Efficiency and speed

One of the key benefits of CNC milling is its efficiency and speed in producing parts compared to traditional machining methods. The automated nature of CNC milling machines allows for quick and precise production of components.

By streamlining the manufacturing process and minimizing manual intervention, CNC milling enhances productivity and reduces lead times, making it an ideal choice for mass production and prototyping.

Cost-effectiveness

Another benefit of CNC milling is the cost-effectiveness it offers. Because the milling tools can be easily changed and controlled using cam software, there is less wastage of materials and time. This leads to a more cost-effective CNC milling work process. Additionally, the CNC milling process can be customized to fit the specific needs of each project, making it an ideal choice for custom manufacturing services.

By optimizing cutting strategies and toolpaths, CNC milling minimizes material wastage and ensures higher utilization rates, leading to cost savings in the manufacturing process.

Ability to produce complex shapes and designs

CNC milling also has the ability to produce complex shapes and designs, thanks to the use of different tools and machining centers. Whether you are using a 3-axis milling machine or a more advanced 5-axis milling machine, you can create a wide range of CNC milling projects. This makes CNC milling a versatile and valuable tool in the world of CNC manufacturing.

CNC milling machines can work with a wide range of materials and produce intricate details with high precision, enabling the production of customized components and parts for diverse applications across various industries.

Overall, CNC milling brings a lot to the table when it comes to manufacturing. From its accuracy and precision to its efficiency and speed, it is a valuable tool for any manufacturer. With its cost-effectiveness and ability to produce complex shapes and designs, CNC milling is worth considering for your next project.

Applications of CNC Milling

XMAKE CNC milling produces complex shapes

Aerospace industry

In the aerospace industry, CNC milling is widely used for manufacturing precision components such as aircraft parts, engine components, and structural elements. The high precision and quality of CNC milling make it essential for aerospace applications.

From prototyping new designs to producing complex aerospace components, CNC milling plays a crucial role in ensuring the safety and reliability of aircraft systems and structures.

Automotive industry

The automotive industry utilizes CNC milling for producing engine parts, chassis components, and custom automotive accessories with high precision and accuracy. CNC milling machines aid in the mass production and customization of automotive parts.

By leveraging CNC milling technology, automotive manufacturers can streamline production processes, improve product quality, and meet the stringent industry standards for safety and performance.

Medical device manufacturing

In the medical device manufacturing sector, CNC milling is essential for creating intricate components for medical devices, implants, and prosthetics. The precision and consistency offered by CNC milling ensure the quality and reliability of medical products.

CNC milling enables the production of custom orthopedic implants, surgical instruments, and dental prosthetics with precise dimensions and complex geometries, meeting the unique requirements of the medical industry.

Prototyping and rapid manufacturing

CNC milling is commonly used for prototyping new products and rapid manufacturing of parts due to its ability to quickly produce prototypes and functional components. It accelerates the product development cycle and allows for the rapid iteration of designs. By using CNC milling for prototyping and rapid manufacturing, designers and engineers can test and validate their concepts in a cost-effective and time-efficient manner, leading to faster product launches and innovation.

CNC Milling Cost Factors

XMAKE Selection of various metal materials

1. Influence of Part Design and Complexity

Complex designs may increase costs due to longer machining times and more complex tool paths.

2. Material Costs

The type of material used can significantly affect the cost of CNC milling.

3. Tooling and Machine Utilization

The cost of tools and the efficiency of machine use are critical factors in the overall cost.

4. Environmental Impact and Sustainability

Modern CNC milling considers the environmental footprint, with a focus on sustainable practices and materials.

5. Customization and Personalization in CNC Milling

CNC milling allows for high levels of customization, which can increase costs due to unique tooling and programming.

6. Integration with Other Manufacturing Processes

The cost of integrating CNC milling with other manufacturing processes, such as additive manufacturing, is considered.

7. Comparative Cost Analysis

A comparison of CNC milling costs with other manufacturing methods provides insight into its economic viability.

Conclusion

So, in conclusion, CNC milling is one of the most common types of CNC machining processes, and a mill is used to create a flat surface using basic CNC milling tools. CNC milling and machining can offer high accuracy and precision, thanks to the CAD and cam software used to program the machine tool interface. With CNC milling becoming more affordable, it’s a great option for various projects. Whether you need to create prototypes or mass-produce parts, CNC milling services can help meet your needs.

For those looking to get started with CNC milling work, it’s important to understand the different tools and techniques involved in the process. By exploring the benefits and applications of CNC milling, you can see how this type of machining can benefit your own projects. If you’re interested in learning more about CNC milling, don’t hesitate to reach out to a professional who can guide you through the process.

FAQs About CNC Milling Work

1.    Can I use a standard drill bit in a milling machine?

Yes, you can use a standard drill bit in a milling machine, but ensure it’s securely mounted in the spindle and the machine is programmed to perform drilling operations, not milling.

2.    Can I replace a drill press with a milling machine?

A milling machine can replace a drill press for more complex tasks, offering versatility beyond simple hole-making.   However, it’s not a direct substitute due to differences in design and functionality.

3.    What are the milling defects in stainless steel?

Milling defects in stainless steel can include tool wear, chatter marks, and heat-affected zones, which occur due to the material’s hardness and tendency to work-harden.

4.    What is the best way to cut through a thick stainless steel plate?

The best way to cut through a thick stainless steel plate is with a slow feed rate, using a carbide-tipped tool designed for hard materials, and ensuring adequate coolant supply to manage heat.

5.    How to choose the right CNC machining company in China?

Choose the right CNC machining company in China by evaluating their technical capabilities, quality certifications, customer reviews, and lead times, and by requesting samples to assess their workmanship and reliability.

References

1. Leo, G. (2022a, July 5). What is CNC Milling? The Ultimate Guide 2022 | Madridia. Aria | Online Manufacturing for On-Demand Custom Services. https://www.madearia.com/zh-CN/blog/what-is-cnc-milling-ultimate-guide-2022/

2. Leo, G. (2024b, January 24). CNC milling explained: processes, types, and benefits. aria | Online Manufacturing for On-Demand Customized Services. https://www.madearia.com/zh-CN/blog/cnc-milling-explained-process-types-and-benefits/.

3. Acharya, D. (2024b, January 12). Six CNC milling technologies: an in-depth exploration. Proleantech | Custom Parts On-Demand Manufacturing. https://proleantech.com/zh-CN/six-major-cnc-milling-techniques/.

4. Acharya, D. (2024f, June 14). CNC milling vs. CNC turning: what’s the difference? Proleantech | Custom Parts On-Demand Manufacturing. https://proleantech.com/zh-CN/cnc-milling-vs-cnc-turning/.

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