Introduction：CNC turning is a common subtractive process for machining rotational parts and is widely used across industries. It enables operations such as facing, step turning, drilling, reaming, and threading, delivering high precision and smooth surface finishes. This guide introduces the essentials of CNC turning to help you better understand the process and make informed machining choices.
What is CNC Turning?
CNC turning is a common subtractive manufacturing process, typically used to produce parts with rotational features. It operates by rotating the workpiece around a spindle while the cutting tool performs reciprocating motions to remove material, ultimately forming the finished product.
How does CNC Turning Work?
CNC turning is typically performed using CNC lathes or CNC turning centers. Standard CNC lathes are sufficient for most conventional parts, while live-spindle machines specialize in slender, high-precision components. Turning centers offer greater machining capabilities, enabling the production of more complex parts such as eccentric shafts or components with multi-process features. The CNC turning process generally follows these steps:
- Workpiece Clamping: Design and select appropriate fixtures based on part geometry and machining requirements, then secure the workpiece.
- Program Input: Develop the program (G-code) in CAM software, to confirm tool paths, feed rates, spindle speeds, and other parameters.
- Machining the workpiece: As the spindle rotates the workpiece, the cutting tool moves along the X and Z axes according to programmed instructions. This allows the tool to perform operations such as external turning and threading. Through continuous machining, the part is gradually shaped to its final form.
- Part Inspection and Finished Product: After machining, parts are usually inspected for dimensions and accuracy to ensure they meet the required specifications and deliver the best results.
What Operations Can CNC Turning Perform?
CNC turning possesses diverse machining capabilities, enabling the creation of various part features through different operations.
External Turning
Cutting the workpiece’s outer diameter using a radially moving tool to produce cylindrical surfaces.
Facing
Use a tool with axial movement to cut the end face of the workpiece, producing a flat surface.
Step urning
A machining process that uses a cutting tool to produce a cylindrical surface with stepped features of varying diameters on the workpiece.
Drilling
Using a drill bit to process specific locations on a workpiece, creating initial holes.
Boring
The process of finishing an already machined hole to improve its accuracy or surface finish.
Thread urning
Using a thread turning tool to cut threads on the inner and outer surfaces of a workpiece.
Grooving / Parting
To use cutting tools to machine grooves on the surface of a workpiece or to directly sever the workpiece.
Rolling
Using a knurling tool with hardened teeth to press into the surface of a rotating workpiece, creating a raised and recessed pattern.
Chamfering
CNC turning efficiently performs chamfering operations on workpieces.
What Parts are Suitable for CNC Turning?
Shaft Components: Shaft parts are characterized by a large length-to-diameter ratio and are the most common components produced by CNC turning. With CNC turning, it is possible to efficiently machine features such as external diameters, steps, and threads with high precision.
Disc, sleeve, and ring-shaped parts: These components have a relatively small length-to-diameter ratio and are typically machined on CNC turning equipment to produce features such as internal and external diameters, end faces, and grooves.
Threaded components: CNC turning also frequently processes threaded items like bolts, nuts, and lead screws.
Spherical components: CNC turning is the preferred process for machining spherical surfaces (especially external spheres), offering significant efficiency and cost advantages over multi-axis milling.
Complex Rotational Parts: Beyond the above components, CNC turning (especially on turning-milling centers) can also process complex rotational parts, such as those with eccentric or irregular structures, camshafts, crankshafts, and similar components.
What Materials can CNC Turning Process?
CNC turning can process a variety of metals and plastics, particularly excelling in machining aluminum alloys, low-carbon steel, and brass. Processing other metals typically requires specific tooling and cutting parameters. Below are the machining characteristics and difficulty levels for materials commonly processed via CNC turning.
| Metal Name | Characteristics | Processing Difficulty |
|---|---|---|
|
Aluminum Alloys |
One of the most common turning materials. Aluminum is lightweight, allows high machining speeds, causes minimal tool wear, and delivers excellent surface finishes. |
Very Easy
|
|
Low-Carbon Steel |
Relatively low in cost with high strength and stable cutting performance, making it ideal for a wide range of structural components.
|
Easy |
|
Brass |
Requires low cutting force, causes almost no tool wear, and produces excellent surface finishes. |
Easy |
|
Cast Iron
|
High hardness and good wear resistance, but tends to produce brittle chips that can affect both the environment and tool life. |
Easy |
|
Stainless Steel |
Excellent corrosion resistance, but prone to work hardening during machining. Requires stricter tool quality and cutting parameters. |
Difficult |
|
Titanium Alloys |
High strength and corrosion resistance, but poor thermal conductivity makes them prone to tool sticking. Requires specialized tooling and processes. |
Very Difficult |
|
Engineering Plastics |
Low cutting force and relatively easy to machine, but prone to thermal deformation if heat dissipation is not well managed. |
Easy, |
Is CNC Turning Suitable for Your Project?
- Part Geometry: If your part features cylindrical, annular, or other symmetrical structures centered around an axis, CNC turning is often the ideal choice.However, if the design involves complex surfaces, irregular structures, or large flat areas, CNC milling or other machining processes may be more suitable.
- Machining Features: Parts with features such as external circles, internal bores, threads, and chamfers.
- Precision Requirements: CNC turning is the ideal choice for components demanding high coaxiality, roundness, and surface finish.
- Production Volume: Since CNC turning does not require tooling, it offers a cost advantage for small-batch or custom parts. For large-scale production, however, processes such as forging or stamping may be more efficient. The final choice of manufacturing method should be made by weighing factors such as cost, precision, and efficiency.
- Processable Materials: CNC turning works with many metals and plastics, and is especially cost-effective for aluminum alloys, low-carbon steel, and brass. Harder materials like stainless steel and titanium require special tooling, which raises costs. Always consider the material when evaluating the feasibility and economics of CNC turning.
In summary, the selection of a machining process is not determined by a single factor but rather the result of balancing multiple considerations. If you remain uncertain about the optimal machining approach for your part, feel free to contact Xmake. Our team will provide professional evaluation and recommend the most suitable solution.
CNC Turning Costs
Cost is one factor in selecting a manufacturing process. CNC turning costs are typically determined by factors such as equipment labor rates, part complexity, precision requirements, material type, and production batch size. The following prices serve as industry references only (may vary by manufacturer). For an accurate quote, please provide part drawings and specifications. Xmake offers rapid assessments and customized quotes to help you execute projects more efficiently.
Machine Tooling Costs: CNC machining fees are typically calculated based on machine operating hours. For standard lathes, costs usually range from $4 to $17 per hour. More advanced equipment, such as turn-mill hybrid machines, may come at higher rates.
Machining Complexity: The complexity and precision requirements of a part are key factors influencing machining costs. More intricate components demand longer processing times and often require higher-grade equipment, resulting in higher overall costs. Simple parts like flanges, with low machining complexity, typically incur lower costs. However, parts requiring features such as threads or deep holes significantly increase the cost.
Batch Production: Unit costs for small-batch production are often higher than those for large-scale production. Operating CNC lathe equipment involves fixed costs like setup and programming. When these costs are distributed across fewer parts, the per-unit cost rises, potentially exceeding large-batch production costs by 30%-50%.
Material Costs: The cost of machining materials depends on both the type and the quantity required. For example, aluminum alloys are relatively affordable at around $3.5/kg, while stainless steel is higher at $4–7/kg, and titanium alloys are much more expensive at about $28/kg. Material utilization is also an important factor — higher yield rates help reduce overall material expenses.
Other Calculation Factors: Beyond the aforementioned costs, actual machining processes also involve tool wear and replacement expenses, fixture design and maintenance costs, as well as expenditures for quality inspection. These collectively constitute the overall cost of CNC turning.
Advantages of CNC Turning
High Precision: CNC turning delivers exceptional accuracy, meeting the machining requirements for most components.
High Consistency: Leveraging CNC systems, CNC turning consistently produces parts with identical dimensions and shapes, making it ideal for high-volume production.
Superior Surface Finish: By controlling various parameters and utilizing coolant, CNC turning can directly produce parts with high surface finish quality, eliminating the need for additional finishing operations.
Efficiency: CNC turning does not require high-speed rotating workpieces. Instead, it employs continuously moving cutting tools to rapidly remove material, enabling efficient part completion.
Disadvantages of CNC Turning
Limited Shape Capabilities: CNC turning is generally suited for machining parts with rotational symmetry. It struggles with complex curved surfaces or asymmetrical structures.
High Initial Costs: CNC turning requires pre-processing tasks like code programming, fixture design, and setup. For small production runs, these costs are spread thin, resulting in a high unit price.
How Can Xmake Help?
To effectively execute CNC turning, thorough preparation is essential before machining—covering design optimization, material selection, process parameter setup, fixture solutions, and more. Equally crucial is choosing the right supplier, as this directly impacts machining efficiency and final quality.
As a professional CNC machining manufacturer, Xmake delivers expert CNC turning services. Contact us today for your customized solution!
