What is CNC Turning?
CNC Turning is a manufacturing process in which bars of material are held in a chuck and rotated while a tool is fed to the piece to remove material to create the desired shape.
A turret, with tooling attached is programmed to move to the bar of raw material and remove material to create the programmed result.
This is also called “subtraction machining” since it involves material removal. If the center has both tuning and milling capabilities, such as the one above, the rotation can be stopped to allow for milling out of other shapes.
The starting material, though usual round, can be other shapes such as squares or hexagons.
Depending on the bar feeder, the bar length can vary. This affects how much handling is required for volume jobs.
CNC lathes or turning centers have tooling mounted on a turret which is computer-controlled. The more tools that the turret can hold, the more options are available for complexities on the part.
CNC’s with “live” tooling options, can stop the bar rotation and add additional features such as drilled holes, slots and milled surfaces.
Some CNC turning centers have one spindle, allowing work to be done all from one side, while other turning centers, have two spindles, a main and sub-spindle.
A part can be partially machined on the main spindle, moved to the sub-spindle and have additional work done to the other side this configuration.
There are many different kinds of CNC turning centers with various types of tooling options, spindle options, outer diameter limitations as well as power and speed capabilities that affect the types of parts that can be economically made on it.
CNC Turning Machine Components
A CNC turning machine, a marvel in the realm of precision machining, comprises various essential components, each integral to its efficient and accurate functioning. These components work in unison to transform raw materials into finished products with precision and intricacy.
1. CNC Control Panel.
The CNC control panel is the command center of the turning machine. It is where operators input and manage the machine’s computer programs, which guide the machining process.
This panel enables the precise control of the machine’s movements, speed, and turning operations, ensuring accuracy and repeatability in the manufacturing process.
2. Spindles.
The spindle is a critical component that holds and rotates the workpiece or the cutting tool. In CNC turning, the spindle’s rotation speed can be precisely controlled, allowing for the machining of materials at the optimal cutting speed.
This component is essential for ensuring the workpiece is machined accurately and to the desired specifications.
3. Headstocks and Tailstocks.
These components provide crucial support to the workpiece during the turning process.
The headstock holds one end of the workpiece, while the tailstock can be moved and locked in position to accommodate various lengths of material.
This setup ensures stability and precision in machining operations.
4. Tool Turret.
The tool turret is a revolving unit that holds multiple cutting tools. It allows for quick tool changes during the machining process, enhancing efficiency and productivity.
The turret’s ability to hold various tools enables the machine to perform a wide range of operations like cutting, drilling, and threading without needing manual tool changes.
5. Chuck and Collet.
These components are used to hold the workpiece in place during the turning process.
The chuck is a clamping device that can be adjusted to hold various sizes and shapes of materials, while collets provide a more precise and secure grip, especially for smaller or delicate workpieces.
6. Lathe Bed.
The lathe bed forms the base of the machine and is a foundation for the other components. It supports the headstock, tailstock, and carriage, ensuring alignment and smooth movement.
The rigidity and construction of the lathe bed are crucial for maintaining precision during machining.
7. Carriage.
The carriage moves along the lathe bed, carrying the cutting tool. It consists of components like the saddle, cross-slide, and tool post, which together provide precise control over the tool’s movement and positioning.
This component is vital for shaping the workpiece as per the programmed instructions.
How Does CNC Turning Work?
The CNC turning process can be quite complex. However, we will give you a simplified, stepwise breakdown of the process, from design to manufacturing.
The general steps of CNC turning are:
#1. Convert the CAD Design File to CNC Program.
The first step involves preparing a CAD file for translation into CNC turning machine language. This does not involve advanced programming.
You must already have some 2D drawings of your design. In that case, you need to capture these designs electronically using software such as AutoCAD or SolidWorks.
Once there is an electronic design in the CAD file format, you can then convert it to a CAM program.
You can also use the same software tools mentioned above to export the drawing in CAM format.
The manufacturing engineer can then use the software to test the manufacturability of the component.
#2. Prepare the CNC Turning Machine.
The next step is the machine setup. Although most of the processes are automated, there is still a need for an operator. To effectively prepare the CNC turning lathe, you should follow these steps:
- Make sure you put the power off. The CNC machining process can get pretty dangerous. So, you should take extra care and check the power switches.
- Secure the part onto the chunk. The chuck is responsible for holding the part in place during the turning process. Not properly loading it can be dangerous and could result in components with the wrong dimensions.
- Load the tool turret. Several tools are involved in the turning operation, so you must ensure you’re picking the right tool for your specific finish. The turret will help hold as many tools as possible at once to give you a seamless operation.
- Ensure proper calibration. You must set the tool and the workpiece in the right way to ensure that the result meets the demands.
- Upload the CNC program. The last step before starting the operation is to upload the CNC code into the machine.
You need to keep two variables in mind at this stage. The first one is the turning speed (the speed at which the workpiece rotates).
The second variable is the feed rate (the speed of the cutting tool as it moves along a rotating workpiece).
A Professional machinist must determine these values because wrong estimations will affect end results.
In addition, improper estimations in some materials could lead to uneven finishes or irreparable damage to the workpiece.
That said, you can stick to a low turning speed and a high feed rate to “rough out” the shape. On the other hand, a high turning speed plus a lower feed rate is ideal for smooth finishes and parts with precise tolerance requirements.
#3. Manufacture the CNC Turned Parts.
The final step is to manufacture your desired part. There are different turning operations you can choose, depending on the result you wish to get.
Also, the part’s complexity will determine how many cycles you will have. The cycle time calculation will help you know the final time spent on the component, which is crucial for cost calculation.
Typically, the turning cycle time will comprise:
- Loading time. Although this is part of the setup, a cycle may require another means of loading the workpiece onto the machinery.
- Cutting time. This is the time it takes to cut the workpiece. Feed rate and cutting depth are factors that affect cutting time.
- Idle time. Any operation that does not involve cutting is an idle operation. For example, changing the settings of the turning center, the movement of the tool, etc.
The result of the manufacturing process will depend on the raw material used. A component obtained from plastic will differ in functionality and surface roughness from a metal component.
Types of CNC Turning Operations
There are various types of lathe tools for CNC turning. As a result, you can perform several operations on a workpiece.
These operations are categorized as external and internal operations. External operations help change the outer diameter of the component. On the other hand, internal operations change the inner diameter.
The individual operation is defined by the cutting tool used and the path it takes to remove the materials. Let’s check them out.
Turning Specific Operations (External)
#1. Turning.
In this process, a single-point turning tool moves along the workpiece side to remove materials and form different features.
The features it can create include tapers, chamfers, steps, and contours. The machining of these features typically occurs at small radial depths of cut, with multiple passes being made to reach the end diameter.
Tapered turning involves the production of conical surfaces by gradually reducing or increasing the diameter of a cylindrical workpiece.
#2. Hard Turning.
This type of turning is performed on materials with Rockwell C hardness that is greater than 45. Heat treatment on the material is crucial before carrying out this process.
Hard turning aims to limit or replace traditional grinding operations. It favorably competes with rough grinding when used for stock removal purposes.
However, it may not be suitable for operations where dimension and form are critical.
#3. Facing.
During this process, the single-point turning tool radiates along the material’s end. This way, it removes thin layers of material, providing smooth flat surfaces. The depths of a face are typically very small, and the machining can occur in a single pass.
#4. Grooving.
This operation also involves a radial movement of a single-point turning tool into the workpiece’s side.
Thus, it cuts a groove that has equal width to the cutting tool. It is also possible to make multiple cuts to form larger grooves than the width of the tool.
Likewise, some manufacturers use special tools to create grooves with varying geometries.
#5. Parting.
Like grooving, the cutting tool moves radially into the workpiece’s side. The single-point tool continues until it reaches the inner diameter or center of the workpiece. Therefore, it parts or cuts off a section of the raw material.
Non-Specific Operations (Internal)
#1. Boring.
Boring tools enter the workpiece actually to cut along the internal surface and form features like tapers, chamfers, steps, and contours.
You can set the boring tool to cut the desired diameter with an adjustable boring head.
It may be beneficial to perform boring operations after drilling a hole in the workpiece. This will help get more precise dimensions.
#2. Drilling.
Drilling removes materials from the internal parts of a workpiece using standard drill bits. These drill bits are stationary in the tool turret or tailstock of the turning center.
#3. Threading.
This operation uses a single-point threading tool having a 60-degree pointed nose. This tool moves axially along the workpiece side to cut threads into the component’s outer surface. Machinists can cut threads to specified lengths, while some threads may require multiple passes.
#4. Knurling.
This process involves cutting serrated patterns onto the workpiece’s surface using a special-purpose knurling tool. This pattern serves as a visual enhancement or a hand grip.
#5. Reaming.
This sizing operation removes small amounts of metal from an already drilled hole. It helps to make internal holes with exact diameters. For instance, when you make a 6mm hole with a 5.98mm drill bit, you can easily read it to the accurate dimension.
Types of CNC Turning Machines
А CNC lathe is the most important components for the CNC turning process. The world of CNC turning machines is diverse, with each type tailored for specific needs.
Understanding these differences is crucial for selecting the appropriate machine for a project.
1. Horizontal CNC Lathes.
Horizontal CNC lathes, characterized by their horizontally aligned spindle, stand as a testament to the advancement in CNC technology and machining processes.
These lathes are designed for optimum efficiency, facilitating a wide array of machining operations.
With the integration of advanced computer numerical control systems, these machines offer precision and flexibility in machining various parts.
Applications:
- Aerospace Components: Crafting intricate components like turbine blades, engine mounts, and landing gear parts.
- Automotive Parts: Manufacturing engine components, gearboxes, and suspension systems.
- Electrical Fittings: Creating connectors, housings, and various electrical circuit components.
- Medical Equipment: Producing surgical tools, implants, and diagnostic devices.
- Consumer Electronics: Machining parts for smartphones, laptops, and other personal devices.
Advantages:
- High Precision: Achieving tight tolerances and intricate details with consistency.
- Versatility: Capable of machining a diverse range of materials, including metals, plastics, and composites.
- Large Volume Production: Ideal for high-volume manufacturing, ensuring speed and repeatability.
- Reduced Waste: Efficient material usage, minimizing scrap and optimizing raw material utilization.
- Customization Flexibility: Adaptable for bespoke manufacturing, catering to specific industry needs.
2. Vertical CNC Lathes.
Vertical CNC lathes, distinguished by their vertically oriented spindle, are pivotal in machining heavy and large-diameter workpieces.
These lathes offer a unique advantage in handling cumbersome materials, supported by their robust construction and advanced CNC control systems.
Applications:
- Large Gears and Flanges: Crafting components for industrial machinery and automotive applications.
- Heavy-duty Flywheels: Manufacturing essential parts for mechanical power transmission.
- Industrial Machinery Parts: Producing parts for manufacturing equipment, including presses and pumps.
- Wind Turbine Components: Machining large and heavy parts used in renewable energy sectors.
- Marine Equipment: Creating components for ship engines and propulsion systems.
Advantages:
- Heavy Part Handling: Specifically designed to manage heavy and large components.
- Operator Ergonomics: Reducing physical strain on operators, enhancing safety and comfort.
- Improved Chip Management: Effective removal of chips, maintaining clean operational conditions.
- Stability and Rigidity: Ensuring accuracy in machining, even with substantial workpieces.
- High Load Capacity: Capable of supporting and machining heavier materials efficiently.
3. Horizontal Turning Centers.
Horizontal turning centers represent a leap in CNC machining, offering not just turning but also milling, drilling, and tapping capabilities.
These centers embody the fusion of versatility and precision, making them ideal for complex parts production.
Applications:
- Multifaceted Industrial Components: Producing parts for industrial automation and robotics.
- Complex Mechanical Assemblies: Crafting components for aerospace and defense applications.
- Precision Tools: Manufacturing high-precision cutting tools and fixtures.
- Custom Automotive Parts: Creating bespoke components for specialized automotive applications.
- Energy Sector Components: Machining parts for oil and gas, and renewable energy industries.
Advantages:
- Multitasking Capabilities: Combining various machining processes in one setup.
- Reduced Setup Times: Minimizing downtime between operations, enhancing productivity.
- High Productivity: Efficiently producing complex parts with fewer machine setups.
- Flexibility in Design Changes: Adapting quickly to design modifications.
- Cost-Effectiveness: Reducing the need for multiple specialized machines.
4. Vertical Turning Centers.
Vertical turning centers, akin to vertical lathes, elevate the CNC turning process by incorporating additional milling and drilling functions.
These centers are tailored for intricate geometries and complex machining tasks, harnessing the power of CNC technology.
Applications:
- Precision Bearings: Manufacturing high-precision bearings for various industrial applications.
- Aerospace Engine Components: Producing critical parts for aircraft engines and systems.
- Complex Industrial Machinery: Crafting components for heavy machinery and equipment.
- Large-Scale Architectural Elements: Machining parts for structural and architectural applications.
- Research and Development Prototyping: Creating prototypes for experimental and innovative projects.
Advantages:
- Suitable for Complex Geometries: Excelling in producing parts with intricate designs.
- High Precision and Accuracy: Maintaining tight tolerances and high-quality finishes.
- Operator Visibility and Access: Facilitating easier inspection and maintenance.
- Enhanced Customization: Adaptable to a wide range of complex machining tasks.
- Reduced Floor Space Requirement: Optimizing workspace utilization with its vertical design.
Materials That are Best Suited for CNC Turning
Choosing the right material for CNC turning is pivotal in achieving desired results. The suitability of a material is influenced by its properties and the intended application of the finished part.
- Steel: Known for its strength and durability, steel is commonly used in CNC turning for parts that require resilience.
- Aluminum: Lightweight yet strong, aluminum is preferred for parts that need to be both sturdy and light.
- Brass: With its low friction and non-sparking properties, brass is ideal for components in electrical applications.
- Copper: Highly conductive, copper is often used in electrical components.
- Plastics: Various plastics are used in CNC turning for their versatility and lower cost, suitable for a wide range of applications.
Each of these materials has its own set of properties that make them suitable for different types of CNC turning projects.
Advantages Of CNC Turning
CNC turning has several benefits, including the following:
Accuracy
The CNC turning machine can execute exact measurements and eliminate human mistakes using CAD or CAM files.
Experts can deliver incredibly high accuracy using cutting-edge machinery, whether for the production of prototypes or the completion of the entire production cycle.
Every cut is precise since the machine being used is programmed. In other words, the final piece in the production run is identical to the first piece.
Flexibility
Turning centers come in various sizes to accommodate your applications’ flexibility. The adjustment is rather easy because this machine’s tasks are preprogrammed.
The operator can finish your component by making the necessary programming adjustments to your CAM program or even build something entirely different.
Therefore, you can rely on the same precision CNC machining services company if you need many unique parts.
Safety
Manufacturing firms adhere to strict safety rules and regulations to guarantee complete safety. Since the turning machine is automatic, less labor is required because the operator is only there to monitor the machine.
Likewise, the lathe body employs fully enclosed or semi-enclosed protective devices to avoid flying particles from the processed item and lessen harm to the crew.
Faster Results
There is a lower chance of error when tasks specified by programming are carried out on CNC lathes or turning centers.
As a result, this machine can finish production more quickly without sacrificing the final output quality. Finally, you can receive the necessary components faster than with other options.
Disadvantages Of CNC Turning
- Initial Cost: The upfront cost of CNC machinery and setup can be high.
- Limitation on Shapes: While versatile, CNC turning is primarily used for round or cylindrical parts.
- Skill Requirement: Operating and programming CNC machines require skilled personnel.
Applications of CNC Turning
CNC turning and machining processes are highly beneficial to different manufacturing sectors. Below we will take a brief look at the applications of turning operations.
Automotive Industry
CNC turning operations are pretty common in the manufacture of components of automobiles that help improve the functioning of the vehicle.
The process is compatible with manufacturing metal components like cylinder blocks and plastic components like dashboard components.
Electrical Industry
CNC turning is suitable for creating circuit boards, among other electrical components. Since it’s an extremely precise machining process, products are electronically efficient, meeting all requirements and specifications.
Aerospace Industry
The aviation industry requires a process like CNC turning and machining because of its high dimensional accuracy.
They are suitable for designing steel parts for the shuttle and aircraft fasteners and internal components.
CNC Turning vs. CNC Milling
When it comes to choosing the right CNC machining process for your project, understanding the differences between CNC turning and CNC milling is essential.
Both processes offer unique advantages and capabilities that can significantly impact the final outcome of your machined part.
Let’s dive deeper into the key differences between CNC turning and CNC milling and provide a guideline to help you determine the right process for your part.
Workpiece Motion: The Core Difference
The main difference between CNC turning and CNC milling lies in the workpiece motion. In CNC turning, the workpiece rotates while the cutting tool remains stationary.
This process allows for the creation of axially symmetric parts with incredible precision and smooth finishes.
CNC milling involves a stationary workpiece while the cutting tool moves in multiple axes. This process enables the production of parts with complex geometries and intricate details that would be impossible to achieve with turning alone.
Versatility in Part Geometry
The versatility of CNC turning and CNC milling differs significantly, particularly when it comes to part geometry.
While CNC turning excels at creating parts with axial symmetry, such as cylinders, cones, and disks, CNC milling offers a broader range of possibilities.
With the ability to produce complex shapes, pockets, slots, and intricate 3D features, CNC milling is the go-to option for parts requiring more elaborate designs.
Achieving the Perfect Surface Finish
Both CNC turning and CNC milling can achieve high-quality surface finishes, but the nature of these finishes can vary.
The continuous rotation of the workpiece in CNC turning typically results in a smoother, more polished finish.
In contrast, CNC milling may leave a pattern of tool marks, depending on the milling strategy and cutting tool used.
However, with the right tooling and parameters, CNC milling can also achieve excellent surface finishes.
Tooling and Setup: Time and Cost Considerations
When it comes to tooling and setup, CNC turning generally has the upper hand. Fewer tools are required, and the setup process is often quicker and more straightforward.
In comparison, CNC milling may necessitate multiple tools to achieve the desired complex geometries, which can increase both setup time and cost.
This is an important consideration when evaluating the most efficient and cost-effective manufacturing process for your part.