CNC Turning VS CNC Milling Processes: 7 Key Differences

In one previous article, I discussed CNC milling and lathe machines. Both of them are essential in any machining process. But in the world of modern manufacturing, CNC turning and the CNC milling process stands out. Although they use the same technology, what sets them apart? The answer is possible with the debate over CNC turning VS CNC milling processes.

 

These two processes vary in many terms. Knowing the difference helps you choose the proper process for your project. A wrongly chosen manufacturing process wastes time and ultimately leads to failure. Are you confused between CNC milling and CNC turning operations? Worry not! This article will make everything clear, simple, and easy to grasp. So let’s get started! 

 

Overview of CNC Turning and CNC Milling

CNC turning and milling are two modern manufacturing procedures. Both create complex geometry parts with accuracy. However, a CNC turning process cuts and shapes the material using a rotating worktable. On the flip side, CNC milling creates shapes with stationary worktables and rotating cutting tools. 

 

In simple words, the CNC turning process cuts and shape a rotating workpiece. Actually, the workpiece is clamped with a rotating worktable. This table moves in a linear direction with the help of spindles. However, the cutting tools remain stationary during the whole procedure. When the rotating workpiece moves around the cutting tools, they remove material to create the desired shape.

 

Now if we look at the milling procedure, it uses rotating cutting tools. These tools are clamped with rotating arms connected with spindles. During milling, the workpiece remains on the stationary worktable. However, cutting tools rotate in different directions to remove material from the workpiece. What is common between these two processes is the CNC system. 

 

These two processes use CNC machines that work with computer instructions. HOW? Operators prepare model designs using CAD software. This model is converted into readable G-code language using CAM software. CAM software directs the tools to create complex and precise shapes. 

 

CNC Turning vs CNC Milling: Key Differences

 

I hope you have grasped the basic concept of turning and milling operations from the overview. Right? At first glance, CNC turning and milling machines look alike. However, these two processes shape the material in different ways. So, let’s explore the key differences in a head-to-head comparison. 

 

1- Shape and Geometry Produced

It is one of the most significant differences between CNC milling and turning. The turning process produces only round and conical shapes. The limitation to round shapes is due to the spin movement of the workpiece. The only rotation of the worktable naturally creates round shapes. The Common geometries a CNC turning process creates are cylindrical, conical, grooves, and rings.

 

Conversely, the CNC milling process is not confined to fewer shapes. It can create several types of geometries due to rotating cutting tools. As you know, cutting tool rotation is more straightforward than with a worktable. So you can easily rotate the tools and cut the material from different sides. The standard shapes you can obtain by milling are square, angular, and 3D complex geometries. 

 

2- Cutting Tools Used

 

Due to the difference in main motion, both processes use different tools. The nature of tools changes with the requirement of cutting action. For example, in the turning process, only the work table rotates. So, it requires tools that work better in a stationary position and have cutting edges in a single direction. These tools are commonly called single-pint tools.

 

The list of tools that turning operations uses is :

 

• Turning tools: These tools remove material from the surface of the workpiece.
• Grooving tools: Such tools create pockets and deep grooves
• Parting tools: Separate the final part after machining
• Boring tools: Enlarge the already drilled holes
• Threading tools: create threads for bolts and screws

 

On the reverse side, in milling operations, the worktable remains fixed. However, cutting tools rotate in several directions. So, this procedure needs those tools that have cutting edges all around. In simple words, the milling procedure uses multi-pint cutting machines. The list of cutting tools includes:

 

• End mills: These tools cut and contour the workpiece.
• Chamfer mills: They create inclined edges.
• Face mills: With large cutting edges, these tools cut flat and large surfaces.
• Ball nose cutters: These tools create 3D contoured shapes.
• Drill bits: Drill bits create holes of various sizes.

 

3- Axes of Movement

Axes of movement refer to the direction in which cutting tools or workpieces move. Simply put, it indicates how many directions you can take to cut a material. Both the milling and turning processes vary in the axes of movement. For instance, the turning procedure involves only the X and Z axes. These two axes provide linear motion to the rotating workpiece. 

 

Along the X-axis, the workpiece moves perpendicular to the cutting tools. However, along the Z axis, the workpiece rotates parallel to the cutting tools. In other words, you can cut and shape your material in two directions. However, some advanced turning procedures also involve a C axis. This axis provides rotational movement to the workpiece. 

 

Now, if we discuss the milling procedure, it commonly involves five axes of movement. The three axes involve X, Y, and Z. These axes provide linear motion to the cutting tools. The two additional axes are A and B. These axes provide a rotational movement to the cutting tools. This means you can cut the workpiece from several directions and create more complex shapes. 

 

4- Machining Speed

 

Machining speed is another main factor that differentiates CNC milling from turning. Basically, CNC turning is faster. The first reason is the worktable’s movement in just two directions. The workpiece remains in continuous touch with cutting tools in this linear movement. Thus, the material removal rate is fast in this process.

 

Moreover, the cutting tools used in this process are single-point tools. These tools do not require repositioning, which saves time. On the other hand, the milling operation is a comparatively complex and slow procedure. The movement of cutting tools in several directions slows down the overall process. Moreover, the frequent repositioning of the tools also takes time. 

 

5- Production Volume

 

Production volume indicates how many parts a process can create in a given time. It is directly related to the machining speed. The higher the machining speed, the higher the production volume. So, if we talk about the production volume of the turning process, it is higher. It means you can create more parts in less time.

 

The reason lies in the continuous cutting of material in two directions. It enhances the feed rate and reduces the time taken. Moreover, using single-point tools that do not require repositioning further reduces the downtime. On the other hand, the milling process has a low production volume.

 

This process creates fewer parts in more time. The first reason is the movement of cutting tools in multiple directions, which increases the cycle time. Moreover, changing the tool after every cycle reduces the feed rate. Hence, the milling operation is effective for medium—to low-scale production volume. 

 

6- Applications

 

Both processes stand out in precision. However, they serve different industries due to the creation of various geometric shapes. Let’s first understand the typical application of the turning process:

 

• Automotive Industry: This process creates vehicle shafts and axles. Moreover, the higher production process is handy for producing brakes and steering systems.

• Aerospace Industry: This process can effectively handle lightweight material. So, in aerospace industries, it creates ultra-precise parts such as gears and engine shafts.

• Oil & Gas Industry: CNC turning creates cylindrical parts such as pipes and valves. It also ensures tight tolerances, so bushing and bearing parts are made using this procedure.

• Medical Industry: In the medical industry, CNC turning creates bone screws and rods. Other components, such as Scalpels, clamps, and forceps, are also designed using this process.

 

CNC milling is known for producing more intricate geometries. Thus, several industries benefit from this process. Some of those include:

 

1. Electronics Industry: CNC milling can handle a variety of materials. Thus, it is used in making casing of laptops and phones. Moreover, it also produces heat skins and circuit boards.
2. Robotics Industry: The higher precision level of this process is helpful in the robotic industry. It is used to create robotic arms, brackets, and sensor housing.
3. Defense and Military Industry: CNC milling is used to design weapons for defense. Moreover, military vehicle parts such as armor planting and navigation systems use CNC milling.
4. Tool and Die Making: Several tools, such as die and punches, require high precision. These tools are significant parts of critical machines and include complex shapes. All those complex design molds and dies are created using CNC milling. 

 

7- Cost and Affordability 

 

Last but not least, cost is another factor that differentiates CNC milling from turning. CNC turning is a cost-effective option in terms of cost. WHY? The first reason is its higher production volume. As I said above, CNC turning produces more parts in less time, which increases sales costs. Moreover, this process is automated and reduces labor costs.

 

On the flip side, CNC milling is an expensive operation overall. The main reason is the contribution of heavy, complex, and costly tools. All these tools require frequent repositioning, which requires skillful operators. So, the cost of labor also increases. Lastly, the lower production volume of CNC milling also justifies its higher price. 

 

Is the CNC Lathe & Turning the Same?

 

NO! CNC lathe and turning are not the same terms. Many people mix these terms due to the same origin. Let me eliminate the confusion with a simple explanation. A CNC lathe is a machine that performs turning operations. This machine has a rotating worktable that moves in linear directions. The workpiece you want to machine is securely clamped to this table.  

 

When rotating, the workpiece moves along the X and Z axes against the cutting tools, obtaining the desired shape. On the other hand, CNC turning is a process that uses a CNC lathe to create complex shapes. This process creates grooves, threads, slots, and pockets on a flat surface. 

 

Choosing Between CNC Turning and CNC Milling

 

Both CNC turning and CNC milling are powerful machining methods. However, it is crucial to know which method is more reliable. In the section below, I will discuss key considerations to help you choose the right option. So, let’s jump right in!

 

• First, understand the complexity of the shape you want to create. CNC turning is a good option if your project involves round and simple geometry products. However, go for the CNC milling process to produce intricate design products.
• Production volume is another factor you must consider. For simple and higher volume products, you should choose CNC turning. Conversely, CNC milling is the best choice for complex and less-volume products.
• The type of material matters a lot when selecting a manufacturing process. So, if your project concerns soft to medium materials such as plastic and aluminum, go for CNC turning. On the other hand, CNC milling is suitable for handling stiffer and rigid materials.
• Lastly, keep your budget in mind. CNC turning is a cost-friendly option due to the large production volume. It is best suited for simple and small large-scale projects. However, CNC milling is an expensive process due to the use of costly tools. So, if you prefer complex shapes with a high budget, CNC milling is your go-to option.

 

Conclusion 

 

CNC milling and CNC turning are two modern manufacturing methods. In this article, I have discussed how these techniques vary. For example, CNC turning creates simple and round shapes. Moreover, the cutting tools in this process are simple and move along two axes.

 

Last, but not the least, CNC turning is very fast, and cost-effective method. On the other hand, CNC milling produces complex-shaped products. This process uses advanced cutting tools that move in several directions, so it is slower and has less production volume. So, first, understand the nature of your project and choose the method that suits you better.