CNC turning is a subtractive manufacturing process that relies on computer numerical control (CNC) to machine parts and components. The process involves rotating a workpiece in a machine chuck at high speeds while a single-point cutting tool removes material to achieve the desired shape.
This machining process is the key to many symmetrical round parts in the manufacturing industry. It can produce cylindrical parts with high dimensional accuracy.
CNC turning operations are performed on machines called CNC lathes, previously called turning centers, and the entire turning process is controlled using computer programs and coded instructions that can control the movement of the cutting tool and the rotating workpiece. The two-way control eliminates the need for human intervention and ensures precise material removal.
CNC turning is one of the most efficient subtractive manufacturing processes and allows the transformation of raw material blanks and workpieces to highly sophisticated cylindrical parts.
Overview of CNC Turning
CNC turning is not completely operator-free and the machine is controlled using a CNC control panel that can edit CNC code, adjust cutting tool position, launch preset programs, and perform roughing cuts. The control panel is also used to input specifications from a Computer-Aided Design (CAD) file, guiding the machining process.
Computer Numerical Control itself refers to the automation of machine tools and movements through a program. The CNC machine generally interprets commands coming from a G-code, which comes from a CAD file.
In the G-code, key instructions like RPMs, spindle speed, tool movement, and feed rate are stored. CNC technology ensures accurate material removal and the correct order of machining operations.
CNC turning technology in CNC lathes and CNC turning centers is an important part of manufacturing that can facilitate rapid prototyping and low to high volume production.
The CNC Turning Process
The CNC turning process can be broken down into steps.
Start with securing the raw material in the rotating chuck of the CNC lathe machine.
Spindle speed or chuck RPM is set based on the cut, material, and desired shape.
CNC program is uploaded to the control panel
The cutting tool interacts with the rotating workpiece to remove material shaping the workpiece symmetrically.
In most CNC turning processes, single-point cutting tool moves radially to execute different types of CNC turning operations. The cutting edge is the only thing that interacts with the workpiece, not the entire tool. This part of the cutting tool is also called the insert. The small insert can produce high-dimensional accuracy and intricate circular designs.
Sometimes, the CNC turning process may involve multiple cutting tools, especially for complex parts. This is common for holes that have tight tolerances. For instance, a boring tool can enlarge an existing hole, while other tools can create internal and external threads.
CNC turning process is dynamic and the CNC lathe is capable of adjusting cutting speeds and feeds as the workpiece is machined for various machining requirements.
Types of CNC Turning Operations
There are many types of CNC turning operations to produce the desired shape on workpieces. Some of the most prominent turning operations are described below.
Straight Turning
Straight turning involves parallel movement of the cutting tool to the workpiece’s axis. Straight turning produces cylindrical parts like shafts. The principle of material removal follows a cutting tool that moves radially to remove material.
Facing
Facing is typically used for creating flat surface perpendicular to the workpiece’s axis. Facing follows further machining operations and can be used to prepare the surface. The cutting tool again moves radially across the rotating workpiece to cut a flat surface.
Threading
Threading in CNC turning forms internal and external threads, and generally, threading produces fasteners and threaded components. There are different dies that can be used to create precise thread profiles as well.
Boring
Boring is the process of enlarging an existing hole. Boring is used to improve the finish and achieve close tolerance. A boring tool can remove material from internal sections of the workpiece. Boring is commonly used for precision holes like engine cylinders.
Grooving
Grooving is the process of cutting channels into a workpiece. CNC turning can be configured to cut these narrow grooves for both functional and aesthetic reasons. The cutting tool moves radially to carve grooves onto the workpiece.
Parting
Parting is often the final process in turning. Parting separates the part from the stock. The cutting tool moves in a similar fashion as cutting narrow grooves but reaches the center of the rotating axis, completely cutting the workpiece from the stock.
Taper Turning
For conical shapes, the taper turning process can gradually reduce the workpiece diameter, and the key here is the angled movement of the cutting tool, which creates an angled tapered profile.
Knurling
Knurling is the process of creating a pattern on the workpiece to improve grip or for aesthetic reasons. Knurling involves using a special tool with a positive pattern and this knurling tool presses the pattern onto the rotating workpiece.
You can find knurled patterns on tools, railings, door knobs and handles.
CNC Turning Machines: Overview
CNC turning machines like the CNC lathes and turning centers are used for producing components with a wide variety of shapes. However, most high-volume production relies on turning centers that are optimized for specific operations.
Some turning machines feature a rotating chuck and a tool turret that holds multiple cutting tools and has the ability to switch tools quickly. Lathe machines come in different bed sizes and workholding options and are more suitable for rapid prototyping.
Similarly, larger turning machines have powered rotary tools that expand machining capabilities to milling, drilling, and tapping. CNC technology allows you to pre-select these machines and tools to generate tool paths that ensure exact control over the cutting process.
Key Components of CNC Turning Machine
Spindle and rotating chuck: the rotating chuck holds the workpiece and sort of acts as a jig or fixture, naturally built into the machine. You can adjust the spindle’s rotation speed for the right material.
Tool and turret holders: In CNC turning, the tool turret holds multiple cutting tools (up to 12 tools). The tool holders secure the cutting tool and minimize vibration for the cutting process. The tool and turret setup enables CNC turning operations within a single setup by minimizing tool changes.
CNC control panel: The CNC control panel allows the CNC operator to interact with the CNC turning machines via an interface. The CNC control panel can adjust material and part specifications, interpret CAD files, and control the spindle speed, tool movement, and other parameters.
Cross Slide: The cutting tool movement is controlled by the cross slide. It allows the single-point cutting tool to engage with the rotating workpiece radially. The cross slide is important for many turning operations like facing, straight turning, tapers, and many other CNC machining processes.
CNC Turning Centers
CNC turning centers are turning machines that combine many machining processes and capabilities. CNC turning centers usually have a tool turret that houses many cutting tools for complex CNC turning operations.
CNC turning centers are ideally useful for producing components with intricate geometries, with different turning operations.
CNC Lathes
CNC lathes are advanced and specialized turning centers catering for machining of cylindrical parts. These CNC turning lathe machines use a single-point cutting tool that moves on the cross slide described earlier to shape the rotating workpiece in the chuck.
CNC lathes are widely used for rapid prototyping and low to high-volume production.
Horizontal Turning Center
Horizontal turning centers are a solution specifically for vibration-prone machining operations. They are capable of machining long workpieces. The CNC turning principle is still identical, and the workpiece is rotated in the chuck where the cutting tool moves radially.
Horizontal turning centers are capable of producing components with long axles and extended lengths.
Vertical Turning Center
Vertical turning centers hold the workpiece vertically in the rotating chuck. This reduces the load on the spindle and improves stability. Vertical turning centers are ideal for machining large diameter parts like turbines and rotors with high dimensional accuracy.
Materials Used in CNC Turning
CNC turning is compatible with many materials, including raw materials, casts, and composites.
Metals
Aluminum
Steel
Titanium
Copper alloys like brass
Stainless steel, etc.
Aluminum, steel, and titanium are common CNC machining materials due to their strength, weight, and machinability. Aluminum is lightweight with great machinability, and titanium is a hard and tough material to machine compared to steel and brass. All these metals are commonly used in CNC turning to produce parts of high-strength for medical and aerospace applications.
Plastics
Nylon
ABS
PTFE
Polycarbonate
Acrylic
These plastics are machined for their use in automobiles and for biocompatibility in medical applications. Plastics have a higher machinability and allow for rapid prototyping and production.
Composites
Composite machining is slightly technical because of the layering of fiberglass and requires a specialized cutting tool. The composite turning process has the risk of delamination, but it offers high strength-to-weight ratios.
Tooling In CNC Turning
CNC turning involves rotating the cutting tool to remove material with precision and accuracy. Cutting tools in CNC turning are commonly made from carbide or high-speed steel, which can withstand the demands of the cutting process.
| Tool Type | Description | Applications |
| Turning Tool | A single-point cutting tool is used for general material removal. | Straight turning, facing, and taper turning for cylindrical parts like shafts. |
| Boring Tool | A tool designed to enlarge and refine existing holes. | Boring operations for precise holes in engine cylinders or bearing housings. |
| Threading Tool | A specialized tool for cutting internal and external threads. | Threading for fasteners, bolts, and fittings requiring secure connections. |
| Grooving Tool | A narrow tool for cutting channels or grooves into the workpiece. | Grooving for seals, O-rings, or aesthetic features on external surfaces. |
| Parting Tool | A thin tool used to separate the finished part from the raw material. | Parting operations are used to complete the machining of components like bushings. |
| Knurling Tool | A tool that presses patterns into the workpiece for textured surfaces. | Knurling for handles, knobs, or components requiring enhanced grip. |
| Nylon 6 | 230-290℃ | 70-120℃ |
CNC turning tool life can be extended using correct lubricants, cutting fluids, as the cutting tool engages various materials to reduce friction and remove chips.
Applications of CNC Turning
CNC turning services are employed in many different industries because of the modular nature of the cutting tool and the requirements of these industries.
Automotive
CNC turning is widely used in the vehicle and truck industry. The most common automobile parts are made using CNC turning like transmission parts, suspension rods. CNC turning has the ability to produce components in high volumes with good precision and consistent quality.
Aerospace
The aerospace industry uses CNC turning for precision parts like turbine blades, landing gear, and fittings. Aerospace requires machining of high-strength-to-weight ratio materials like titanium with strict aerospace standards.
Medical
CNC turning is also used to produce ball sockets, surgical instruments, and other types of equipment. CNC turning has the ability to machine biocompatible materials at fairly low costs for high-volume productions.
CNC turning services also support rapid prototyping via CNC turning and ensure the accuracy of custom part manufacturing process.
Advantages of CNC Turning
In the manufacturing industry, CNC turning is a preferable machining process due to many distinct benefits it offers.
Dimensional accuracy:
CNC turning produces parts that meet stringent dimensional standards and precise measurement requirements. The computer programs reduce the errors related to human intervention.
Versatility:
CNC turning machines are of many types and can conduct many operations. In addition, CNC turning uses tools whose inserts can be changed or replaced to accommodate different materials. Multiple cutting tools and powered rotary tools can create complex round geometry.
Scale production:
The Turning process reduces production time and costs. CNC turning is ideal for rapid prototyping and large-scale production runs, which increases productivity. This is useful for manufacturing effectiveness.
Material choices:
CNC turning is suitable for many types of metals and non-metals like acrylic and ceramics. The material flexibility ensures a broader applicability of CNC turning.
CNC Milling VS CNC Turning: Which One To Choose?
CNC milling and CNC turning are both highly precise and efficient machining processes. Unlike CNC turning, which rotates the workpiece and uses a stationary cutting tool to shape it, CNC milling uses a moving cutting tool with motion in 3 axes or more to remove material.
This allows CNC milling to produce rectangular parts and features like pockets, chamfers, fillets and flat surfaces. Both processes use CNC machines and computer-aided design tech, but the bottom line in most cases is the shape of the workpiece and final part.
CNC milling is more versatile for multi-axis machining, and CNC turning is suitable for cylindrical or round parts.
Common CNC Turning Challenges
To completely understand CNC turning, you need to learn about the common limitations of the CNC turning machine.
Tool Wear
CNC turning uses sharp-edged tools, and even though the entire tool is shaped like a small bar stick, only the front edge is useful for chipping away material at high RPMs. The cutting edge can deteriorate quickly with unoptimized cutting parameters like wrong removal rate, tougher material or wrong choice of inserts.
Material Properties
Material properties change as the material changes. Aluminum, brass and stainless steel all have different machinability, strength and applications. Before starting CNC operations, it is better to test materials in a rough pass for process optimisation.
Errors and Tolerances
Even though CNC lathes are automated, they are still prone to programming errors. In fact, the high reliance of CNC machines on CAD-supported files and programs means quality checks start at the design stage.
CNC turning centers and CNC lathes are limited by their bed size, tool radius, and tolerances.A CNC lathe machine cannot achieve tolerances with prismatic shapes and irregular curves.
Conclusion
CNC turning is critical to many industries, part production, manufacturing and sometimes is the starting point for many other types of machining. Using CNC lathes and turning centers, you can achieve tolerances of up to 0.001″ or sometimes even smaller in highly precise turning centers.
It is widely used in industries like aerospace, rapid prototyping, and medical devices. On top of this, the CNC technology requires minimal human intervention, and parts can be produced from anywhere by simply uploading a design to the CNC. Modern CNCs are capable of network machining and monitoring, which offers reliable solutions for complex components and precision machining operations.
FAQs
Q: What is CNC turning?
A: CNC turning is a subtractive (material removing) manufacturing process where a workpiece rotates in a metal chuck and a cutting tool moves towards the workpiece, removing material gradually.
Q: What is a CNC turning job?
A: A CNC turning job usually involves managing the CNC machine and operating the computer control of the CNC to remove material from rotating workpiece.
Q: What is the difference between CNC milling and CNC turning?
A: The main difference between CNC turning and CNC milling, is that turning uses a rotating workpiece and a stationary cutting tool, but milling uses a rotating and traveling cutting tool that feeds into the workpiece.
Q: What is CNC turning for dummies?
A: CNC turning uses a computer-controlled lathe to remove material from a rotating piece, shaping it into precise cylindrical parts.
Q: What is turning in a CNC machine?
A: Turning is the actual operation where a workpiece rotates and a stationary tool moves in to cut the material.
Q: What does a CNC turner do?
A: A CNC turner operates a computer-controlled lathe to manufacture precise cylindrical components by removing material from rotating workpieces.