In the world of manufacturing, precision, efficiency, and quality are key. CNC turning, a popular subtractive manufacturing method, is one tool in an engineer’s toolkit that checks all these boxes.
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Whether you’re new to the concept or just need a quick refresher, this guide will walk you through the ins and outs of CNC turning, its advantages, and its many applications.
CNC turning is a manufacturing process where a rod of material is held in a chuck and rotated while a cutting tool is fed into the rotating workpiece, removing material and shaping it into a desired part. CNC stands for Computer Numerical Control, which means the cutting processes are controlled by a computer and software.
The operation begins by securing a piece of raw material, often cylindrical, into the CNC machine’s chuck. The chuck spins the material at high speeds. A cutting tool, controlled by the CNC system, then moves along the rotating workpiece, cutting away material to form the desired shape. The precision of the CNC system ensures the cuts are accurate, consistent, and can be repeated many times over.
How does the machine know where to cut? This is part of the data fed into the CNC machine from the CAD or CAM file that your team creates and sends to us. Either our machinists will tell the turning machine what to do, or we’ll feed the CAM file directly into the turning machine.
There are a number of benefits associated with CNC turning a part. Here are some of the bigger reasons why you might want to use a CNC turning machine for your next project.
CNC turning is a highly versatile process, used across a broad range of industries and applications. Its ability to efficiently produce round or cylindrical parts makes it an invaluable tool for various engineering projects. Here are some specific examples of when an engineer might opt for CNC turning:
There are various operations that a machinist can perform on a CNC turning machine, since it’s such a highly versatile machine. Here are some common types of CNC turning operations:
Turning is the basic operation where the cutting tool moves parallel to the axis of rotation of the workpiece, cutting and shaping the outer surface.
A narrow cut is made on the workpiece to create a groove. This is useful for parts that need to fit into each other.
The cutting tool moves perpendicular to the workpiece’s axis, reducing the overall length of the part.
The tool cuts deep into the workpiece, separating it into two pieces. This is often the last step in the turning process.
This process is used to cut hardened materials. It can replace grinding in many cases, offering a more efficient method of shaping hard surfaces.
A hole that has already been drilled is enlarged or improved by boring the hole.
Knurling is when a pattern is rolled onto the surface of the part for grip, aesthetics, or other functional purposes.
The tool cuts a helical groove on the surface of the part, creating threads for screws or bolts.
This operation is used to slightly enlarge a pre-drilled hole to achieve a more accurate diameter or finish.
This operation creates a round hole in the workpiece. It’s often done before operations like boring or reaming.
While both CNC turning and milling are subtractive manufacturing processes controlled by a computer, they have their differences. CNC turning is typically used to create round or tubular shapes from larger workpieces, whereas CNC milling is generally used to create more complex shapes and features like slots, holes, and even intricate surface contours.
In CNC milling, the workpiece is stationary, and the cutting tool moves around it, which is the opposite of CNC turning. The decision between turning and milling will depend on the specific requirements of your design.
CNC turning is a subtractive manufacturing technology widely used to creat cylindrical and circular components across numerous industries. This versatile technology creates high-quality components from a wide range of materials. So, what exactly is CNC turning, how does it work, and is it the right solution for your specific manufacturing needs?
This guide thoroughly examines CNC turning, how it works, and the working principles of CNC turning machines. The guide also explores different CNC turning operations and their diverse applications, advantages, and limitations.
What is CNC Turning?
CNC Turning vs CNC Milling
How Does CNC Turning Work?
How Does a CNC Turning Machine Work?
CNC Turning Operations
Applications of CNC Turning
CNC Turning Materials
What are the Advantages and Limitations of CNC Turning?
Conclusion
Why Choose Geomiq?
CNC turning is a form of CNC machining, a subtractive manufacturing process that creates parts by progressively removing portions of a solid workpiece until the final desired geometry forms. In CNC turning, the workpiece rotates along a stationary axis. A cutting tool selectively moves into the workpiece, shearing away bits of material on contact. This process is carried out by CNC turning machines, also known as CNC lathe machines or CNC lathes. In most CNC turning configurations, the workpiece does not undergo linear motion, only rotation along a fixed axis. The cutting tool, on the other hand, moves towards and away from the workpiece, up and down, and left to right, completing two to three axes of motion. Advanced machines may be capable of additional axes of motion.
Manual lathes exist in which an operator manually controls the movement of the cutting tool. These machines are still quite popular but are mainly used in non-industrial applications as they are significantly less capable and more error-prone than their CNC counterparts. In CNC lathes, a machinist programs a computer using G-Code generated from a digital 3D model of the required part. Using the G-Code, the computer precisely controls the speed, direction, movement, and orientation of the workpiece and cutting tooling, continually adjusting these parameters until the finished object materialises.
Due to the rotational movement of the workpiece, CNC turning produces cylindrical, helical, circular, and conical geometries. This machining process is optimised to produce these specific geometries seamlessly, which are challenging to create via other machining processes. CNC turning produces features that are relatively symmetrical around a central axis.
Image of turned components
CNC turning is carried out by dedicated machines called CNC lathes or CNC turning machines. This machining process is compatible with various rigid materials, including plastics, metals, wood, wax, glass, ceramic, and stone.
CNC turning and CNC milling are the two main forms of CNC machining. The primary difference between them is the type of geometries they produce, resulting from differences in their machine configurations, machining operation, and cutting tools. In the CNC milling process, the cutting tool, usually cylindrical, rotates along its axis and moves linearly, typically in three axes, into a non-rotating workpiece. In 5-axis milling machines, the cutting tool, workpiece, or both provide additional rotational axes to provide the cutting tool with better access to different areas of the workpiece. CNC milling produces parametric, cubic, and flat geometries. It can also create curves and contours.
*Image of 5-axis milling?
Conversely, in CNC turning, the workpiece rotates on a fixed axis and remains stationary. The cutting tool, typically straight and cubic shaped, does rotate but moves in various linear directions to selectively remove portions of the workpiece while it rotates. CNC turning produces cylindrical, helical, circular, and conical geometries, many of which are challenging to machine via CNC milling due to tool and workpiece movement restrictions.
*Image CNC turning
Advanced Mill turning centres that combine elements and capabilities of CNC milling and CNC turning exist. Also known as CNC turning centres, these multi-axis machines are capable of fully rotating the workpiece while also moving the cutting tool in multiple linear and rotational axes. They may also feature a tool turret head with multiple specialised rotating and non-rotating tools. Turning centres can create more complex geometries faster than CNC turning and CNC milling combined.
Image of CNC turning centre
The CNC turning process, from idea to final product, usually consists of five main steps.
The first step in creating a component via CNC turning is creating a 3D model of the component using CAD (Computer-Aided Software). The 3D model contains details, such as dimensions, scale, and material.
After creating the model, the designer uses CAM (Computer-Aided Manufacturing) to convert the model into G-code, a CNC programming language that CNC turning machines can read. The CAM software analyses the 3D model and creates a set of instructions on how the CNC turning machine must operate to replicate the part in a workpiece. The G-code dictates the movement, orientation, speed, and feed of the cutting tool and workpiece, progressively controlling these parameters until the object forms.
The machinist programs the CNC lathe’s computer with the generated G-code. Next, they load the workpiece into the machine, install the appropriate cutting tools, and set up any required additional tools, fixtures, and systems, such as a cooling system.
After setting up the CNC turning machine and securing the workpiece, the operator begins the operation. Depending on the project and the geometry being machined, human intervention may be optional from this point. The machine executes consecutive lines of code, progressively cutting out pieces of the workpiece until the desired object materialises.
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Post-processing refers to the operations and processes carried out on a finished part to give it specific properties or capabilities. Post-processing may be functional or aesthetic and is often optional, as CNC turning machines can produce parts with excellent finishing.
Anodised type II - Red
CNC turning post-processing options include:
See our CNC surface finishes gallery for more details on CNC turning finishing options.
CNC turning operations are performed by dedicated, specialised machines known as CNC turning machines or CNC lathes. There are various types and configurations of CNC lathes. However, they all follow the same working principle - a clamping device holds and rotates the workpiece. At the same time, the machine feeds various cutting tools into the workpiece along specific paths in the X, Y, and Z axes, progressively removing material and creating the desired shape.
To fully understand how CNC lathes work. It is imperative to know these machines' different components and their functions. The image below is a labelled diagram of a CNC of a CNC lathe.
**Image of machine
Headstock: The headstock provides the necessary power to drive the workpiece rotation. Positioned at one end of the machine bed, this area of the CNC lathe contains the driving motor, connecting it to the spindle and chuck.
Chuck: The chuck is a clamping that holds the workpiece in place, using jaws that can expand or contract to accommodate various sizes. This component is mounted on the spindle, and as the spindle rotates, it spins the workpiece, allowing for consistent material removal and symmetrical shaping. Chucks can be hydraulic, pneumatic, or manual.
Spindle: The spindle is a motor-driven component that powers the rotation of the chuck and the workpiece. A computer precisely controls the spindle’s speed during the CNC turning operation, which is critical for achieving tight tolerances and smooth finishes on the turned parts.
Tailstock: Positioned opposite the chuck, the tailstock supports the free end of longer workpieces, ensuring they remain stable during machining. It often includes a centre or a quill that holds the workpiece, preventing deflection or wobbling, which is particularly helpful when working with long, thin parts.
Tool Turret: A rotating platform that holds multiple cutting tools, including turning, boring, and threading tools. The turret can index or rotate to bring a specific tool into position for cutting. This multi-tool setup allows for rapid tool changes, enhancing efficiency by minimising downtime between CNC turning operations.
Bed: Also known as the lathe bed, this is the heavy base structure of the CNC turning machine, which provides rigidity and stability. It supports all other components, including the turret and tailstock, and absorbs vibrations during machining, helping maintain precision. The bed also typically houses the guideways, which allow for smooth, accurate movement of the turret along the X and Z axes.
Carriage: The carriage in a CNC turning machine is a critical component that moves the cutting tools along the X and Z axes to control the cutting position and depth. It supports and guides the tool turret or tool post along the length of the workpiece, enabling the machine to perform operations like turning, facing, and threading.
Control Panel: The control panel is the CNC turning machine operator’s interface with the machine, typically featuring a display screen, a keypad, and various controls. The control panel allows the operator to input programs (G-code), adjust settings, and monitor real-time machine status. Advanced CNC controls can simulate tool paths, track tool wear, and provide error alerts.
CNC turning produces a variety of features and shapes, using different turning operations that differ by specific motions, cutting tools, and cutting techniques. A combination of several operations is usually required to produce a part. The most common CNC turning operations are as follows.
Turning is the primary operation in CNC turning. This operation involves removing material from the outer area of the workpiece. The cutting tool moves in and out of the workpiece, varying depth to create contours or steps. Turning is done parallel to the workpiece's rotational axis (straight turning) to create straight cylindrical features or at an angle to the surface (tapered turning), creating tapered conical features.
This CNC turning operation involves removing material on one end of the workpiece to create a flat surface. In facing, the cutting tool is positioned parallel to the workpiece rotational axis at one end and moves into the workpiece by a predetermined depth.
Grooving creates a recess or groove around the circumference of the workpiece. In this CNC turning operation, the tool is positioned at a specific point perpendicular to the workpiece. As the workpiece rotates, the cutting tool gradually moves into it, up to the desired depth. The cutting tool may also move sideways to increase the groove’s width. Practical examples of grooves are O ring grooves on pistons.
The parting CNC turning operation is very similar to grooving, except that in parting, the cutting tool continues to move deeper into the workpiece until it cuts off a section.
In CNC turning, drilling involves creating a hole on one end of the workpiece using a drilling cutting tool. The tool is placed along the central axis of the workpiece, creating a centralised hole as the workpiece rotates. Advanced turning centres can drill holes in different axes and orientations of the workpiece.
As the name implies, threading in CNC turning creates threads around the external circumference of the workpiece. In this operation, the cutting tool starts at the beginning of the thread and moves sideways as the workpiece rotates. The CNC machine precisely controls the speed and movement of the cutting tool to achieve accurate thread depth and pitch. Special threading tools can also thread preformed holes using the same technique.
Knurling in CNC turning involves etching a pattern onto the surface of a part. This operation uses specialised knurling tools that feature the desired pattern on their surface.
CNC turning is an indispensable manufacturing process with countless applications across various industries. Its widespread usage is a result of its accuracy, speed, versatility, and compatibility with various materials. This CNC machining service is used for custom one-off parts as well as batch production.
Manufacturing applications of CNC turning can be broadly classified into three categories. These categories, which vary by the number of parts produced and the function of the parts, are as follows:
CNC turning plays a crucial role in rapid prototyping, allowing manufacturers to create functional prototypes quickly and cost-effectively. Since CNC turning efficiently produces complex components fast, it’s ideal for testing product fit, form, and function. CNC turning enables quick iterations and real-world testing to refine designs.
Custom, one-off parts are a core application of CNC turning, especially when replacement parts or highly specific custom parts are needed. For example, if a pump shaft or bushing in machinery needs a replacement, CNC turning allows engineers to rapidly manufacture a replacement without waiting for an OEM supplier.
Additionally, CNC turning allows manufacturers to innovate and create unique parts for specific one-off purposes. Examples include medical and dental custom implants or specialised surgical tools tailored to individual patient needs. Another example is custom baseball bats made to fit the grip and preferences of specific professional athletes.
Manufacturers use CNC turning to produce bulk quantities of end-use parts and parts for final assemblies or as components in larger systems. Industries like automotive, electronics, construction, etc. leverage CNC turning to produce high volumes of threaded fasteners, pins, bearing sleeves, and countless other components with tight tolerances, ensuring each part meets stringent quality standards.
CNC turning batch production
CNC turning is an efficient, cost-effective manufacturing process for creating a plethora of high-quality components, ranging from mission-critical, mechanical aerospace components to DIY furniture. Some commonly CNC turned components used in countless industrial and domestic applications are as follows.
Mechanical components are parts used in various mechanical systems and engines to maintain alignment, connect parts, transmit motion, reduce friction, prevent leakage, and fasten assemblies. CNC turned mechanical components include shafts, bearings, couplings, pistons, bushings, hubs, axles, and spacers. These components are used in numerous mechanical systems, such as combustion engines, industrial equipment, and production lines.
Audio connector pins, control knobs and dials, cylindrical enclosures, electrical connector pins, electric motor components (shaft, rotor, bearing, stator, etc.), antennae, socket contacts, and other cylindrical and circular electrical components can be manufactured via CNC turning. While they are typically mass-produced on assembly lines, custom or large versions of these components require CNC turning.
CNC turning’s accuracy and compatibility with various materials make it ideal for manufacturing fluid control components such as nozzles, hydraulic rods, pistons, fittings, pipe connectors, Archimedes screws, heat sinks, and couplings. These components are typically manufactured from metals and plastics.
CNC turning is ideal for both custom and mass-produced medical devices, such as implants, prosthetics, orthotics, bone screws, surgical instruments, and components in medical equipment. This CNC manufacturing technique’s high accuracy and material versatility make it suitable for these devices. Note that when ordering custom or generic medical devices, it is vital to work with a custom manufacturer with the necessary accreditation to manufacture parts for the medical industry. Geomiq is a proud owner of ISO medical device manufacturing accreditations that officially certify our rigorous dedication to international high-quality standards and our expertise in medical device manufacturing.
CNC turning facilitates the creation of countless consumer products we use daily. These products include watch bezels, lamp holders, lighting fixtures, door handles, appliance and tool handles, jewellery, key chains, furniture, toys, rolling pins, decor, and countless other items.
Sports equipment such as bats, clubs, poles, handles, wheels, and rollers need to be of precise form and weight to ensure athletic performance. CNC turning provides a highly accurate means of manufacturing these sports equipment to specific requirements. It is common for professional athletes to create custom bats, clubs, handles (for bikes, ski poles, etc.), arrow shafts, and other personal sports equipment to meet their preferences.
Manufacturers use CNC turning to produce custom fasteners such as screws, pins, dowels, bolts, nuts, spacers, tension rods, and washers.
The requirement for a material to be compatible with CNC turning and CNC machining technologies, in general, is rigidity. The material must be rigid enough to be formed into a solid blank that the CNC lathe can conveniently hold. Rigidity is also required to withstand the force and vibrations of the tool against the workpiece during machining. Based on these requirements, CNC turning is compatible with various materials, including metals, plastics, wood, ceramic, concrete, and wax. However, metals and plastics are the most ubiquitous CNC-turning manufacturing materials for industrial applications.
Metals are the most used engineering materials, so it is no surprise that they are the most machined. Various types of metals and metal alloys have different properties and applications. The table below details the most common CNC machining metals.
CNC turning metals: alloys, properties, and applications
CNC turning can also manufacture products from various rigid plastics. See our CNC plastics machining article to learn more about the processes, applications, benefits, and limitations of machining these unique materials. The table below shows the properties and applications of some of the most common CNC turning plastics.
CNC machining plastics: properties and applications
While CNC turning is indispensable in manufacturing due to its capabilities and benefits, this manufacturing process also has inherent limitations. On one hand, the CNC turning process offers exceptional accuracy, repeatability, and material versatility. However, limitations such as geometry restrictions and material wastage exist. Some benefits and limitations of CNC turning are explored below.
The following are some of the benefits of CNC turning
The following are some of the disadvantages of CNC turning:
CNC turning is a versatile and precise manufacturing method, essential in producing components across various industries. Its ability to work with a wide range of materials, from metals to plastics, allows for flexibility in design and functionality, whether for small batches or large-scale production. While there are some limitations, such as tooling costs and material constraints, advancements in CNC technology continue to enhance its capabilities. By understanding its strengths and limitations, manufacturers can effectively use CNC turning to achieve high-quality, efficient production results.
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