Since its first development in the 1940s, Computer Numerical Control (CNC) machining has been a significant milestone in manufacturing and machining.
CNC technology has undoubtedly advanced over time. Now, with various machines available, it delivers an efficient alternative to traditional manufacturing methods. These machines can create precise and repeatable components and parts without the inaccuracies and mistakes of manual machining.
CNC machining also offers various cutting styles, from milling and drilling to grinding and knurling, each suited to multiple applications. However, one of the most popular cutting styles has to be CNC turning because of its flexibility, accuracy and suitability for a range of uses.
So, what is CNC turning? How does it work?
What is CNC turning?
CNC turning is a type of CNC machining.
CNC machining is a subtractive manufacturing process involving computer-automated machines. The machines are programmed to chip away at raw blocks or rods of material to create a specific shape.
When it comes to turning, specific turning machines are programmed. These machines include chucks that rotate the workpiece at high speeds while a cutting tool trims the excess material. Unlike traditional machinery, turning machines offer exact results and are ideal for conical, cylindrical and tubular components with axial symmetry.
Two things that need to be kept in mind during the turning process are turning speed — the velocity of workpiece rotation — and feed rate — the velocity at which the cutting tool moves along the workpiece. If cutting speed and feed rate aren’t accurately determined or aren’t exactly right before manufacturing, you risk damaging the material.
Generally, lower turning speeds and higher feed rates are appropriate for ‘roughing’ out the shape. Smooth finishes can be obtained with a high turning speed and a lower feed rate, and the same goes for precise tolerance requirements.
What is a CNC turning machine?
The most common CNC turning machine is a lathe. CNC lathes are perfect for precisely cutting and shaping materials. They offer higher accuracy and take less effort to operate than regular lathes, manufacturing components in shorter time frames and tighter tolerances.
CNC lathes are also ideal for volume manufacturing due to automation benefits, like running 3m bars and measuring multiple parts per load and cycle times in seconds, not minutes.
How does a CNC lathe work?
Once the component’s design has been converted into a suitable format, instructions are programmed into the lathe using a Computer-Aided Design (CAD) file. This file uses G-code to tell the machine how to move and dictates the cutting tool’s path, speed and depth, allowing the lathe to get to work.
What types of CNC lathes are there?
There are two main types of lathes: vertical and horizontal.
The main difference between them is their orientation and preferred applications. For instance, horizontal lathes have a horizontally positioned spindle and are perfect for longer, cylindrical components. Vertical lathes, on the other hand, are better suited to heavy, large-diameter and short workpieces as their spindle is vertically positioned.
What is a CNC turning centre?
A CNC turning centre operates like a lathe. However, a turning centre often provides more advanced technology when it comes to tool changing.
Turning centres are capable of various cutting methods, including facing, threading, knurling and drilling. Lathes, on the other hand, tend to stick to straightforward turning. Lathes are usually 2-axis machines, whereas turning centres can be 3-axis, 4-axis, or 5-axis.
There are plenty of turning centres out there, all with different tooling and spindle options, outer diameter limitations, power and speed. Like lathes, there are vertical and horizontal turning centres. Both allow for detailed and intricate machining without the need for multiple machines. While horizontal turning centres are more common, vertical turning centres have an edge regarding heavy and short parts.
Applications
So, what is CNC turning used for?
Due to its versatility, it’s a fantastic process for various industries and applications. CNC turning services are available for manufacturing automotive parts such as gears and shafts and for the aerospace industry, where accuracy and precision are necessary.
CNC turning services are also excellent for electrical components. This includes connectors, circuit boards and conductors, medical tools, implants and other parts that must meet adequate standards and specifications.
Advantages
CNC turning has many advantages, making it an excellent option for your projects.
Not only is it accurate and precise, thanks to its computer-automated operation, which prevents human error, but it’s also flexible. It delivers a wide variety of parts and shapes and produces them quickly, efficiently, and safely.
Manual machining methods can make it hard to repeatedly achieve the same shape or geometry, but CNC turning also provides repeatability. This allows you to create the same product in large batches with consistent dimensions.
It’s versatile, too, ensuring compatibility with multiple materials. Materials affect the properties of machined parts, changing factors such as functionality and surface finish, so it’s essential to pick the right one for optimal results.
Common materials for CNC turning parts are steel and aluminium, both known for their strength and resilience and brass and copper, which are perfect for electrical applications and aesthetic purposes. If metal isn’t appropriate, different plastics and woods offer cost-effective alternatives that suit various turning projects.
What is the difference between CNC milling and turning?
The most evident difference between CNC milling and CNC turning is the machinery. While CNC turning uses lathes and turning centres, CNC milling requires CNC mills.
CNC mills are similar to lathes in terms of programming and operation, but their working methods can differ. While CNC milling holds the workpiece in place or moves it linearly, CNC turning rotates the workpiece.
They also offer differences in their uses, tooling, and cutting. Turning is best for cylindrical and conical parts, while milling suits flat and irregular surfaces better. Milling can involve complex and multi-point cutting tools, whereas turning includes single-point cutting tools.
Other differences include surface finish and set-up. While both options offer good surface finishes, turning provides smoother and more polished results. Milling is more likely to leave tool marks, but this relies on strategy, methods and cutting tools. As for set-up, turning typically requires fewer tools, making it a quicker and often more cost-effective process.
Should you use CNC milling or turning for your project?
When deciding which best suits your needs, you should consider a few factors:
- The desired part
- Its shape and size
- Materials
- Volume
- Finish
You should also consider your budget, as costs may differ between processes, batch sizes, and appropriate materials.
Summing up CNC turning
Our overview covered the basics of CNC turning, the machines used and their capabilities, and how CNC turning differs from CNC milling.
CNC turning is a CNC machining process that involves rotating a workpiece and using a cutting tool to chip away specific parts to create a desired product.
These come in a variety of machining types, including CNC lathes and CNC turning centres. Perhaps the main way that these differ from CNC milling is that milling does not rotate the material, making turning machines better suited for cylindrical and conical parts and a more reliable option for a smoother finish.
CNC turning is great for a huge number of industries — especially those where precision and polish go hand in hand, such as automotive and aerospace. As CNC turning evolves with new technology, software, and machinery, it will only become more popular.
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