CNC machining has become an integral part of manufacturing in today’s world. With its ability to produce complex parts with high precision, it has revolutionized the manufacturing industry. However, designing parts for CNC machining can be a challenging task, and if not done correctly, it can lead to suboptimal results. In this comprehensive guide, we will walk you through the process of how to design CNC machining parts, step-by-step.

How to Design CNC Machining Parts

How to Design CNC Machining Parts – Guidelines

#1 Understanding the Basics of CNC Machining

CNC machining is a process that uses computer-controlled tools to remove material from a workpiece to create a part. The process involves several steps, including CAD design, CAM programming, tool selection, material selection, and machine setup. Understanding these basics is essential before moving on to designing parts for CNC machining.

#2 Designing for CNC Machining

Designing for CNC machining requires a different approach than traditional manufacturing methods. In this section, we will discuss the key design considerations that you should keep in mind when designing parts for CNC machining. These considerations include material selection, part orientation, feature size and complexity, and tolerances.

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2.1: Material Selection

The selection of material plays a crucial role in the success of CNC machining. Materials with high strength and stiffness, such as aluminum, titanium, and steel, are ideal. They allow for precise cuts and can withstand the forces exerted during machining. In contrast, materials with low strength and stiffness, such as plastics, can be challenging to machine.

2.2: Part Orientation

The orientation of the part during machining can affect its accuracy and surface finish. Designing parts with flat surfaces parallel to the machine’s X-Y plane can improve accuracy and reduce the need for additional operations. Parts with complex geometries may require multiple setups or 5-axis machining.

2.3: Feature Size and Complexity

The size and complexity of features on a part can impact machining time, cost, and accuracy. Designing parts with simple and easy-to-machine features can reduce machining time and cost. Complex features, such as undercuts, internal threads, and blind holes, require additional operations, increasing machining time and cost.

2.4: Tolerances

Tolerances refer to the allowable deviation from the design specifications. Tighter tolerances require more precise machining and can increase the cost of production. Designing parts with appropriate tolerances is essential for ensuring a good fit and function.

#3 Creating the CAD Model

Creating the CAD Model

Creating a 3D CAD model is the first step in designing parts. In this section, we will discuss the key steps involved in creating a CAD model.

3.1: Choosing the Right CAD Software

Choosing the right CAD software is crucial for creating an accurate and efficient 3D model. Software such as SolidWorks, AutoCAD, and Fusion 360 are popular choices for creating CNC machined parts.

3.2: Designing for Manufacturability

Designing for manufacturability is the process of creating a CAD model that considers the manufacturing process. It involves ensuring that the model can be machined without difficulty and that it meets the design requirements.

#4 Creating the CAM Program

Creating the CAM Program

Creating a CAM program is the next step in designing parts for CNC machining. Here are some steps of creating the CAM program.

4.1: CAM Software Selection

Choosing the right CAM software is essential for creating an efficient and accurate program for machining the part. Software such as Mastercam, GibbsCAM, and Fusion 360 are popular choices for creating CAM programs.

4.2: Programming the Toolpath

Programming the toolpath involves selecting the appropriate cutting tools, speeds, feeds, and cutting strategies to machine the part. The toolpath should be optimized for efficiency and accuracy while taking into consideration the design specifications and tolerances.

#5 Machining the Part

Once the CAD model and CAM program are created, the part can be machined. In this section, we will discuss the key steps involved in machining the part.

5.1: Material Selection and Setup

Selecting the appropriate material and setting up the machine are crucial for successful machining. The machine should be calibrated and checked for accuracy before beginning the machining process.

5.2: Machining the Part

Machining the part involves running the CAM program on the CNC machine to remove material and create the part. It is essential to monitor the machining process and make adjustments as needed to ensure accuracy and quality.

#6 Post-Machining Processes

Post-machining processes may be required to finish the part, such as deburring, polishing, and coating. In this section, we will discuss the key post-machining processes and considerations.

6.1: Deburring

Deburring is the process of removing sharp edges and burrs from the machined part. It is essential for safety and improving the part’s aesthetics.

6.2: Polishing

Polishing is the process of smoothing the surface of the part to improve its aesthetics and functionality. You can achieve it through various methods, such as sanding, buffing, and chemical treatments.

6.3: Coating

Coating the part can improve its durability, corrosion resistance, and aesthetics. There are several coating options available, such as anodizing, plating, and painting.

Importance of CNC Design for Manufacturability

Computer Numerical Control, has revolutionized the manufacturing industry by allowing for high precision, consistency, and efficiency in producing complex parts and components.

However, the success of CNC milling or machining depends heavily on the design of the product itself. In order to ensure manufacturability, it is important to consider the limitations and capabilities of CNC machines during the design phase. This means taking into account factors such as material selection, tolerances, and geometries that are compatible with processes.

A well-designed product that optimizes CNC machining can improve production efficiency, lead to higher quality end products, and reduce costs. Therefore, investing time and effort into CNC design for manufacturability is crucial for any company that wants to remain competitive in today’s fast-paced manufacturing industry.

CNC machining Undercuts

There are certain design features, such as undercuts, that can pose challenges for CNC machining. Undercuts are indentations or recesses in a part that the cutting tool cannot access directly. This can make it difficult to machine these areas without causing damage to the part or the tool itself.

Fortunately, you can employ several strategies to machine undercuts effectively. One approach is to use a multi-axis CNC machine that is capable of tilting and rotating the cutting tool to access the undercut. Another approach is to use specialized tools, such as end mills with long reach or tapered designs, that can reach into tight spaces.

To make machining undercuts easier, you can optimize the design of the part itself in addition to using specialized tools and machines. For example, adding draft angles to the part can make it easier to remove from the mold or machine, while also reducing the need for complex tool paths. Similarly, modifying the geometry of the part to reduce the number of undercuts or simplify their shape can also make machining easier.

Machining undercuts with CNC requires a combination of specialized tools, machines, and optimized part design. With the right approach, however, it is possible to produce highly complex and precise parts that feature undercuts and other challenging design features.

Importance of Drafting a technical drawing

The importance of drafting a technical drawing cannot be overstated. Technical drawings serve as the blueprint for CNC machined parts and provide essential information for the machining process. A well-drafted technical drawing will specify the exact dimensions, tolerances, and material specifications required for the part, ensuring that it is manufactured to the correct specifications. Without a technical drawing, it can be difficult to communicate design intent and ensure that the final product meets the desired specifications.

Technical drawings help to identify potential issues with the design before production begins. This can save time and money by preventing costly mistakes and rework. By providing a clear representation of the design, technical drawings also help to ensure that all stakeholders are on the same page and understand the expectations for the final product.

Another benefit of drafting a technical drawing is that it can be used as a reference for future production runs or modifications. By maintaining accurate and detailed technical drawings, manufacturers can ensure consistency in their products and easily make modifications as needed.

Drafting a technical drawing is a critical step in the process. It helps to ensure that the final product is manufactured to the desired specifications, identifies potential issues early on, and provides a reference for future production runs or modifications. By taking the time to draft a high-quality technical drawing, manufacturers can improve the efficiency and quality of their CNC machining operations.

Frequently Asked Questions

What is the CNC machining process?

CNC machining is a process in which computer-controlled machines shape and cut materials into specific shapes and sizes. It is a modern technology that has revolutionized the manufacturing industry by enabling faster production, increased precision, and lower labor costs. It stands for “computer numerical control” and it involves the use of computers to control machine tools like lathes, mills, drills, routers, etc. The process begins with a CAD (Computer-aided Design) file of the item to be produced. This file is uploaded to a CAM (Computer Aided Manufacturing) software that allows the user to define the parameters such as speed, cutting depth, feed rate and other details necessary for machining.

What are the main restrictions of CNC design?

CNC design also comes with its own set of restrictions that could become an obstacle for those who are creating designs. The main restrictions of CNC design include the type and size of material available, the number of axes used in the machining process, as well as the complexity and accuracy of each component.

The type and size of material that is available for CNC design can be limited because some materials may not be compatible with certain machines or require more expensive tools to work properly. Additionally, CNC machines have a limited number of axes which can limit how complex a component can be designed since components need multiple sides to be created accurately. Finally, precision is key for any component design and this means that the level of accuracy needs to meet certain criteria in order for components to fit together properly when assembled.

What is 5-axis CNC machining?

5-axis CNC machining is a process of creating parts and components with precise measurements by using computer numerical control (CNC) machines. The five axes refer to the various linear directions in which the cutting tool can move, each of which is labeled as an axis. This allows for more precise parts and components to be produced compared to traditional 3-axis CNC machining.

The 5-axis CNC process involves a machine that moves along five different axes at once while cutting materials such as aluminum, brass, plastic, or steel. It can cut complex shapes and intricate details with accuracy and repeatability while reducing production time significantly. It also allows for multi-sided operations, making it ideal for producing complex 3D geometries on hard materials efficiently and quickly.


Designing parts for CNC machining requires careful consideration of several factors, including material selection, part orientation, feature size and complexity, and tolerances. Creating an accurate CAD model and CAM program is crucial for successful machining, and post-machining processes may be required to finish the part. By following the steps outlined in this comprehensive guide, you can design and machine high-quality parts that meet your design specifications and requirements.