What is CNC Turning? A Complete Overview

CNC turning machine

Computer-controlled machining can take many forms. One of them is CNC turning. Below, we explain how it works and how it differs with milling. We’ll also see the parts you can produce using a CN turning machine and their uses in various industries. Continue reading to learn more.

What is CNC Turning?

CNC turning is a machining method where the workpiece rotates while the cutting tool removes material, producing the desired design and shape. The tool moves linearly, positioned against the spinning stock piece.

Turning has come a long way. Traditionally, it involved manual lathes. Today, it uses a turning center instead — and CNC control — ensuring operator safety and machining precision, among other benefits like increased versatility.


CNC means Computer Numerical Control. It refers to using computer technology to control the machining process, which results in higher accuracy than the manual method.

Parts of a computer-controlled lathe
Parts of a computer-controlled lathe
https://www.mdpi.com

Types of CNC Turning Machines

CNC turning machines are classified based on the types of turning centers. A turning center is the part that has the cutting tools. It adds more functionality to the machine than just a turning lathe, such as drilling and tapping. It’s usually either horizontal or vertical.

Horizontal Turning Center

It has a horizontally aligned spindle and tools. The workpiece mounts above it, unlike in the vertical type. A horizontal center increases efficiency and allows greater precision.

Vertical Turning Center

The center is vertically oriented. These centers allow larger or heavier workpieces. They are often used to machine heavy-duty parts for industrial applications, such as gears and flanges.

Using a turning lathe to drill holes
Using a turning lathe to drill holes
Resource: https://www.youtube.com/watch?v=1pQZgMz8RfM

How Does CNC Turning Work?

In this CNC machining method, the tool does not rotate; the workpiece does. The cutting tool or center is fed to the stock piece, removing material externally or internally. Here’s more about how that works and the expected results each operation produces.

Internal Turning Operation

This operation removes material to shape the inner diameter. The cutting tool may bore into the stock part and form tapers, chamfers, or steps. Other material removal options include drilling holes, threading, and knurling (producing serrations).

External Turning Operation

External cutting removes material to shape the part’s exterior. It can create a tapered piece or cone shape or produce chamfers and other profiles such as contours. Other external operations include facing (producing flat surfaces) and grooving.

CNC process design and programming
CNC process design and programming
Resource: https://www.youtube.com/watch?v=7sek8E0_fxU

CNC Turning Programming

Programming is an integral part of any CNC turning operation. That’s because the entire process is automatic and controlled by a computer code or program. Programming creates a set of instructions or codes.

CNC turning codes guide the machine’s motions. They determine where the tools cut the stock piece, the cutting speed and depth, feed rate, and tolerance levels. The result is a precisely shaped part.

The process involves using these software types: CAD (Computer-aided Design), CAM (Computer Aided Manufacturing), and Computer Numerical Control software.

  • The CAD program helps design the part, producing 2D or 3D digital images of the finished part.
  • The CAM software, on the other hand, helps convert the design file into a program that the cutting machine can read.
  • The CNC machine control program is the software that reads and interprets the machining codes to control the machining operations.
CNC or computer-controlled turning process
CNC or computer-controlled turning process
Resource: https://forums.tormach.com

CNC Turning Process

This manufacturing method involves several steps. After designing the part, the next step is converting the design file into a form the cutting equipment can use. Next, the operator prepares the machine, and the process can begin.

Converting Design File into CNC Code

The design file is a 2D or 3D representation of the desired part prepared. The designer later converts this file into a CAM file. This file format is what the machine will use to move the cutting tool or center against the workpiece.

Machine Preparation

The operator loads the CNC program onto the machine and positions the workpiece in the chunk. They must also select the right tools for the part and calibrate the machine to ensure every operation happens as required.

Turning Operation

The cutting process begins when the machine is calibrated and loaded with the stock piece and machining program. Various tools enable the machine to perform different operations. The tools include:

  • Grooving tools for cutting grooves in the workpiece
  • Threading tools to cut thread either internally or externally
  • Knurling tools that produce a textured surface for a firmer grip, among other functions
  • Drilling bits to create cylindrical holes and boring bars or reamers to shape holes to achieve precise diameters accurately
  • Parting blades to cut off (part) sections of material from the machined part
CNC milling vs. turning machine
CNC milling vs. turning machine
Resource: https://www.youtube.com/watch?VcYa05Qcc4o

What is The Difference Between CNC milling and Turning?

CNC milling and CNC turning are popular machining options today. But while they may seem identical, there exists a difference between them. Understanding this difference is critical when selecting the machining method for your project.

The main difference between CNC milling and CNC tuning is in their operation. You can also see it in the quality of the finished parts. In CNC turning, the stock piece spins while the cutting tool remains still or moves linearly. The process produces parts with a better surface finish than milling.


In CNC milling, the cutting tool rotates instead. A milling machine uses more complex tooling and requires more preparation. On the upside, it creates more complicated designs.

Turning produces a high-quality surface finish
Turning produces a high-quality surface finish
Resource: https://youtu.be/0iveDuysL9c?si=g9up6KswUteyyec4

CNC Turning Advantages and Disadvantages

Turning as a manufacturing process offers many benefits over other parts-making methods. However, like any other subtractive manufacturing process, it has a downside.

Advantages

  • Precision: it produces precise parts for applications where dimensional accuracy is paramount, such as aerospace products
  • Speed: you create parts more quickly than when using manual lathes and several other technologies
  • Repeatability: the process, being computer-controlled, ensures a very high degree of design consistency
  • Versatility: you can machine different materials, including metal, glass, plastic, wood, or wax, and shape them into a broad range of designs

Disadvantages

  • Design Limitation: it mainly creates cylindrical components, although square or hex parts are also possible.
  • Size Constraints: it can be challenging to machine overly large components when the workpiece rotates instead of the cutting tool
CNC turned parts
CNC turned parts
Resource: https://www.researchgate.net

CNC Turning Parts

CNC lathes and tool centers produce various parts for different industries, including small and large or heavy-duty components. Here is a collection of these parts and where they find valuable applications.

  • Electrical – it produces various electrical parts like enclosures and connectors
  • Consumer Goods – it makes various parts of computers, mobile phones, and various other devices
  • Tools – many tools in use today contain parts made using computer-controlled lathes and cutting centers
  • Healthcare – in healthcare, the process helps create medical implants or diagnostic tools and equipment
  • Automotive – used to manufacture engine parts, suspension systems, gearbox components, etc.
  • Industrial Machinery – machine parts like those used to make press parts are usually turned
  • Marine Applications – used to create parts for shipbuilding like engine components and other marine applications
  • Energy Industry – the parts of wind turbines are commonly machined by this method or those used in oil and gas and similar sectors
  • Defense and Aerospace – the method produces high-precision and complex parts, such as landing gear components, turbine blades, and other intricate products for defense and aerospace needs

CNC companies can turn workpieces to create functional parts or produce prototypes for other manufacturing methods.

Conclusion

CNC turning is a popular way of producing parts. It involves moving a cutting tool linearly against a spinning workpiece. The process offers various advantages, from accuracy to repeatability and speed.

When choosing a turning service for your project, consider the provider’s expertise and experience. Other important considerations include the quality control measures in place and the estimated turn-around time.

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