Two crucial machining techniques, CNC milling and CNC turning, are powerful in their own regard in the world of CNC machining. Both processes use computer-controlled tools to sculpt raw materials into precise parts.
But the real problem arises when people have to choose between the two techniques. Both techniques provide excellent precision and top-notch output in the machining process.
Fortunately, we are here to make your life easier with this detailed comparison guide of CNC Milling vs CNC Turning. We will dive deep into their functionalities, strengths, and weaknesses to help you choose the best solution for your projects and needs. Let’s get started.
CNC Milling vs CNC Tuning
While CNC milling and turning in CNC machining fulfil the same purpose of creating precise machine parts, they excel in different areas. Knowing where these techniques excel, or their differences can help you choose the right process for your needs. Go through the factors we are about to discuss here that differentiate these two techniques.
Working Principle
What makes the two processes different is how each functions. This is where the major difference between CNC milling and turning comes in. Both techniques use a different process of removing material to create a desired shape.
CNC Milling
In CNC milling, the workpiece stays fixed while a multi-axis tool moves around it. The magic unfolds with the multi-axis cutting tool. This versatile tool whirs and manoeuvres along various directions (X, Y, and Z axes, with some machines offering additional rotary axes), meticulously removing material to bring your design to life. Milling machines create intricate features on flat, angled, or curved surfaces.
CNC Turning
On the other hand, in CNC turning, the workpiece rotates on a lathe, and a single-point cutting tool shapes it. The cutting tools are strategically positioned to shape the rotating material precisely. It’s the perfect method for crafting parts with cylindrical or conical features, like shafts, gears, and bushings.
Cost
Another factor that significantly differs between the two mechanisms is cost. The cost can greatly vary between these two techniques depending on different factors. Here’s how they differ in terms of cost.
CNC Milling
The cost of CNC milling can be quite high compared to CNC turning. Several factors play into play in the excessive cost of this technique. The factors include –
- Complex Setups: Milling machines often require more complex setups due to the multi-axis nature of the process and the need to secure workpieces at various angles. This can be time-consuming and labour-intensive, impacting overall production costs.
- Multi-Axis Machines: Milling machines with more axes, such as 5-axis CNC machines, offer greater flexibility but are more expensive than simpler 3-axis machines.
- Machining Time: Intricate parts with numerous features can take longer to machine using CNC milling than simpler, symmetrical parts on a lathe. This extended machining time translates to higher operational costs.
CNC Turning:
In contrast, CNC turning has always been more of a budget option. The factors below contribute greatly to making this such a cost-effective solution over CNC milling.
- Simpler Setups: Lathes typically require less complex setups compared to milling machines. The workpiece is secured on the rotating spindle, and the toolpath is often more straightforward for symmetrical parts.
- Fewer Axes: Lathes typically have fewer axes (usually 2 or 3) than milling machines, leading to lower initial investment costs.
- Production Speed: Turning can be significantly faster than milling for high-volume production of symmetrical parts. The continuous cutting action and efficient use of a single tool contribute to faster production times and lower overall costs per unit.
Productivity
The next factor that differentiates the two techniques is productivity. This means the speed and efficiency of producing parts are different for the two techniques. While one is faster, the other is a bit slow. Take a look at how each of them performs in terms of productivity.
CNC Milling:
Production speed in CNC milling can vary significantly depending on the complexity of the part being machined. For simpler designs with minimal features, milling can surpass turning in speed.
However, as part complexity increases, machining times can also extend. Intricate features with multiple toolpaths and tight tolerances can take considerably longer to mill than turning a simple cylindrical shape.
CNC Turning:
CNC turning reigns supreme when it comes to high-volume production of symmetrical parts. The continuous cutting nature of turning, where the tool is constantly engaged with the material, translates to faster production times.
Additionally, using a single-point cutting tool minimises tool changes, further streamlining the process. This combination of factors makes turning the ideal choice for mass-producing parts like fasteners, bushings, and other components with consistent rotational geometries.
Material Compatibility
While the other three factors are the most crucial differences, you can also notice differences in material compatibility. This might not be as significant as the others, but some materials are more compatible with milling, while some go along better with turning.
CNC Milling
With its multi-axis capabilities and diverse range of cutting tools, CNC milling offers greater flexibility regarding material compatibility. Specialised tools can be employed for challenging materials like titanium or hardened steel, ensuring clean cuts and minimal tool wear.
For instance, a ball-end mill can create intricate contours in hard materials, whereas a drill bit attachment allows for the creation of holes.
CNC Turning
While CNC turning also works with a wide range of materials, its reliance on single-point cutting tools can limit its effectiveness with certain materials. Ductile materials like soft aluminium or brass might cause the tool to clog or wear down faster than milling.
However, advancements in tool coatings and insert materials continuously improve the turning capacity for various materials.
Surface finishes
Although the surface finish may not matter in every project, it’s better to be informed. The techniques here excel at different surface finishes based on different factors.
CNC Milling:
The multidirectional movement of the cutting tool in CNC milling can leave slight tool path marks on the material surface, especially on intricate features.
That’s why, depending on the application’s requirements, additional finishing steps like polishing or sanding become necessary to achieve a smooth surface finish on the part.
CNC Turning:
As for CNC turning, the continuous cutting action of the tool on a rotating workpiece often results in a smoother surface finish, particularly on cylindrical shapes. This is because the tool constantly engages with the material, creating a more uniform texture. So, achieving a smooth finish doesn’t require any extra process.
Part complexity
The detail and variety each technique can put in the part’s designs vary significantly. In fact, considering this factor alone can help you decide whether CNC milling would be a better choice for you or whether you should lean toward CNC turning.
CNC Milling
When it comes to complexity, CNC milling reigns supreme. Its ability to move along multiple axes allows for the creation of highly intricate features like pockets, slots, undercuts, and 3D geometries. This makes milling the go-to choice for parts with intricate details and multiple surfaces that require precise shaping.
CNC Turning
CNC turning is limited to rotational geometries. While it can create features like threads, grooves, and tapers on cylindrical parts, it cannot replicate the level of detail achievable with milling on multi-planar surfaces.
However, some CNC turning centres offer additional capabilities like live tooling, which incorporates rotating tools on the lathe. This allows for some limited milling operations to be performed on the rotating workpiece, expanding the design possibilities for certain parts.
Is CNC Milling Better than CNC Turning?
There’s no definitive answer to whether CNC milling is “better” than CNC turning. Both are exceptional machining processes, but each excels in different areas. The ideal choice depends on the specific requirements of your project. Here’s a comparison table to help you visualise the key differences.
| Factor | CNC Milling | CNC Turning |
| Mechanism | Fixed workpiece, moving multi-axis tool | Rotating workpiece, stationary single-point tool |
| Pricing | Generally more expensive | Typically less expensive |
| Productivity | Varies based on complexity | Often faster for symmetrical parts |
| Compatibility | Broader range | Good for various materials |
| Surface Finish | It may require additional finishing | Doesn’t require on cylindrical surfaces |
| Part Complexity | Ideal for complex shapes | Limited to rotational geometries |
| Features | Great for pockets, slots, and undercuts | suited for threads, grooves, and tapers on cylindrical parts. |
| Material Properties | offers more flexibility for challenging materials | less efficient for ductile materials |
| Production Volume | suitable for low to medium-volume production | shines in the high-volume production of symmetrical parts |
Conclusion
To conclude, the choice between CNC Milling and CNC turning is not definitive, and there is no single “better” process here. It will heavily depend on things like part geometry, production volume, budget, and desired surface finish, and always affect which is better for you.
In some cases, combining both techniques might be the most efficient approach for intricate parts with rotational and non-rotational features. So, the key here is to “Consider Your Project.” For the best solution, you can consult special services like Zintilon, who guide you through these techniques and give you a clear answer.
