CNC Machining Guide:Master Techniques & Tips

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CNC machining is a method of precision manufacturing through computer-controlled machine tools. It is now widely used in aerospace, automotive, medical devices, and other fields. To achieve efficient and high-quality production in CNC machining, considerations at the design stage are critical. This guide will detail design principles and optimization methods for CNC machined parts to help designers and engineers increase productivity, reduce costs, and ensure part quality and performance.

What is CNC machining design?

CNC machining is a method of high-precision manufacturing by controlling machine tools through a computer program. It is used in a wide range of applications such as aerospace, automotive, and medical devices.CNC machining design is the process of considering and optimizing the geometry, dimensions, and materials of parts during the design phase to ensure that they can be efficiently machined by CNC machines. Good design increases productivity reduces costs, and improves part quality and performance.

But the design process requires attention to the following points:

Avoid deep holes and narrow slots: Deep holes and narrow slots can make machining more difficult and time-consuming, and it is recommended that such designs be avoided or minimized.

Use large internal radii: Increasing the size of internal corners helps to reduce stress concentrations and improve machining efficiency and quality.

Avoid sharp internal corners: CNC tools are unable to machine sharp internal corners, so rounded or “dogbone” designs are recommended.

By optimizing the design, and machining paths, machining time and material waste can be reduced, ultimately improving part productivity and quality. For example, choosing the right internal rounded corners and avoiding unnecessarily deep holes can significantly reduce machining time and costs, while increasing the durability and strength of the part.

CNC machining design -Yonglihao Machinery

Basic Principles of CNC Machining Design

By following the basic design principles provided by Yonglihao Machinery, you can dramatically improve the efficiency and quality of your CNC machining, reducing production costs and time while ensuring the durability and functionality of your parts.

Avoid deep holes and narrow slots

The presence of deep holes and narrow slots in a CNC machining design can significantly increase machining difficulty and time. Deep holes require longer tools, which are more likely to break and cause vibration. Also, deep holes require multiple cuts, which can increase machining time and cost.

The machining of narrow grooves can also be complicated by tool size limitations, and long, thin tools are prone to breakage and vibration. Therefore, deep holes and narrow grooves should be avoided as much as possible in the design. If deep holes are unavoidable, it is recommended that the hole depth be limited to three times the tool diameter.

Use of large internal radii

In CNC machining, internally rounded corners help reduce stress concentrations and increase the strength of the part. Since CNC machining tools are usually round and cannot machine sharp internal corners, the use of internal fillet designs is recommended. Increasing the size of internal fillets not only reduces cutting forces and tool wear but also improves chip removal and material flow, resulting in improved machining quality and efficiency. For example, when using a milling cutter with a radius of 10 mm, the internal corner radius should be greater than 10 mm. In addition, when designing the vertical angle, it is recommended to use an internal corner radius of not less than 1/3 cavity depth to ensure better surface quality. Machining costs can be significantly reduced and tool life can be extended by proper design of internal corners.

Avoid sharp internal corners

Since the tools in CNC machining are round, sharp internal corners cannot be machined. Sharp internal corners not only lead to premature tool wear but can also cause vibration and material deformation during machining. To avoid these problems, the design should use rounded or “dogbone” corners wherever possible. Rounded corners allow the tool to move more smoothly, reducing machining time and improving surface quality. Dog-bone corners are an effective way to avoid violent contact between the tool and the material by leaving rounded spaces in the corners.

High precision CNC machined parts-Yonglihao Machinery

Ways to Optimize Machining Paths and Reduce Costs

Through the judicious use of standard tolerances, optimizing material removal efficiencies, and selecting appropriate materials, machining paths can be effectively optimized to reduce machining time and costs while ensuring part quality and performance. This has important implications for the design and manufacturing process of CNC machining, leading to more efficient and cost-effective production.

Use of Standard Tolerances

Using standard tolerances can significantly reduce machining costs and time. Standard tolerances mean that parts do not require overly precise measurements and adjustments during the manufacturing process, thus simplifying machining steps and increasing productivity. A standard tolerance of ±0.1 mm is generally recommended to meet most design requirements without adding additional machining costs. If the design requires higher accuracy, the tolerance can be tightened to ±0.02 mm, but be aware that this will increase machining time and cost.

Choosing the right material

The choice of material has a direct impact on CNC machining design and cost. Softer materials (such as aluminum and plastics) are easier to machine than harder materials (such as steel and titanium) because they can be machined at higher cutting speeds and with less wear on the tool, resulting in increased machining speed and quality. Another advantage of soft materials is that they deform less during machining, making it easier to achieve the required tolerances and surface finish. However, it is also important to consider the end application and performance requirements when selecting a material.

Increase material removal efficiency

Optimizing the design to use standard tool sizes and reducing the number of tool changes is key to increasing material removal efficiency. Standard-sized tools should be used wherever possible, as they are not only more readily available but also less costly. In addition, the design should consider reducing the number of machining steps, for example by reducing the use of tooling and optimizing machining paths to improve efficiency. Designs can try to standardize the diameters of holes and slots so that multiple machining steps can be done with the same tool, thus reducing the number of tool changes and adjustment time.

CNC machining with high economic value

Design Implications of Complex Geometries and Material Selection

To effectively improve the design and machining efficiency of complex geometries and to ensure the quality and functionality of your parts, Yonglihao Machinery has compiled a list of best practices and considerations to help you make better decisions. 

Best Practices for Designing Complex Geometries

When designing parts with complex geometries, there are a few key things to keep in mind. First, avoid overly complex internal features, such as deep holes, narrow slots, and sharp internal corners, which can make machining more difficult and costly. Second, try to use larger internal fillets to minimize stress concentrations and increase part strength. Additionally, tool accessibility should be considered during design to ensure that all features can be machined with standard tools.

Recommended design tools include CAD and CAM software such as AutoCAD and SolidWorks, which help designers accurately create complex geometries and generate optimized machining paths. Using these tools reduces trial and error time and improves the accuracy and manufacturability of the design.


When machining parts with complex geometries, you may encounter some common problems.

Deep holes and narrow grooves tend to cause tool breakage and machining errors. To avoid these problems, reduce the depth of each feed by cutting in stages and use specially designed tools to improve machining stability. Secondly, complex internal features may prevent the tool from fully accessing the machined surface, and special machining methods such as multi-axis CNC machines or electric discharge machining (EDM) can be considered.

Different materials behave differently in CNC machining, with harder materials such as titanium and stainless steel being more difficult and costly to machine, while softer materials such as aluminum and plastics are easier to machine. The design should be based on the application requirements of the part and consider the machining characteristics of the material. For example, aluminum is easy to machine and less expensive, but may not be suitable for applications requiring high strength.

CNC Machining Guide-Yonglihao Machinery

Material selection and its design implications

By understanding the machining characteristics and design requirements of different materials, designers can optimize the design of CNC-machined parts to ensure optimal performance and cost-effectiveness.

Performance of different materials in CNC machining

The machining characteristics of different materials vary greatly in CNC machining. Commonly machined materials include aluminum, steel, titanium, and plastic. When selecting a material, comprehensive consideration should be given to the environment in which the part will be used and the functional requirements. Select the best machining material.

Aluminum: Aluminum is one of the most commonly used CNC machining materials. It is characterized by lightweight, moderate strength, and easy cutting. Aluminum also has a high thermal conductivity, which helps to dissipate heat quickly, thus reducing tool wear.

Steel: Steel has high strength and wear resistance, but is more difficult to machine. Machining steel requires stronger tools and lower cutting speeds, which increases machining time and costs.

Titanium: Titanium has very high strength and corrosion resistance, but is very difficult to machine. Titanium’s high hardness and low thermal conductivity cause rapid tool wear, so special tools and coolants are required.

Plastics: Plastic materials such as ABS and polycarbonate are easy and inexpensive to machine. However, plastics are less thermally stable and require temperature control during machining to prevent distortion.

Impact of Material Properties on Design

Material properties have a direct impact on the design of a part. Aluminum’s high thermal conductivity and ease of machining allow for more complex geometries, while the high hardness of steel and titanium limit design complexity. The flexibility and low strength of plastics require the addition of support structures during design to ensure part stability and durability. By understanding these material properties, designers can optimize their designs to maximize processing efficiency and part performance.

Design and manufacture of complex geometric parts


In this paper, we focus on the basic design principles, optimized machining paths, and rational material selection in the CNC machining design guide. A detailed explanation is given. Avoiding the design of deep holes, narrow slots, and sharp internal angles can help reduce machining difficulty and cost. Using large internal radii and standard tool sizes can improve material removal efficiency and reduce machining time. Choosing the right materials, such as aluminum, steel, titanium, and plastics, can meet the needs of different applications and improve part quality.

Following these design principles and optimization methods not only improves the efficiency and quality of CNC machining but also significantly reduces production costs. By properly designing and optimizing machining paths, you can ensure the durability and functionality of your parts.

If you have any CNC machining design needs or require further technical support, please contact Yonglihao Machinery, we provide professional CNC machining services and will provide you with the best solution to ensure the successful completion of your project!


Common problems include deep holes and narrow slots that make machining difficult and costly, sharp internal corners that are difficult to machine, and poor material selection that affects machining efficiency and quality.

Material selection should be based on a combination of application and performance requirements. Aluminum is for lightweight requirements, steel for high-strength needs, titanium for high-performance parts, and plastics for low-cost applications.

Optimizing paths includes using standard tool sizes to reduce the number of tool changes, reducing the use of tooling to optimize the design, and using CAD/CAM software to generate optimized machining paths to improve efficiency.

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