Table of Contents

CNC turning is a subtractive manufacturing process where a rotating workpiece is shaped by a stationary cutting tool which is controlled by a computer-controlled machine to fabricate CNC turned parts.

• Introduction
• Different Kinds of CNC Turning Machines
• What is the CNC Turning Process?
• What Kinds of Parts Does CNC Turning Make?
• Advantages of CNC Turning
• Common Applications of CNC Turning
• Considerations When Choosing CNC Turning
• Conclusion
• FAQs

Introduction

CNC turning is a subset of CNC machining, where a part is rotated at high speeds while a series of stationary cutting tools remove material to shape the object. The CNC refers to Computer Numerical Control which means that the lathe machine and the cutting tool are controlled by a computer algorithm while turning indicates the process where the part is rotated at high speed during machining.

Fig. 1: CNC Turned Parts

Different Kinds of CNC Turning Machines

Here are various types of CNC turning machines:

• Conventional CNC Lathes - These are the evolved form of the traditional manual lathe, equipped with computer numerical control to automate the machining process. CNC lathes bring forth enhanced accuracy, flexibility, and speed, capable of performing a wide range of turning operations, including cutting, sanding, knurling, and drilling. The strength of conventional CNC lathes lies in their versatility for both one-off projects and high-volume production, coupled with their ability to produce parts with consistent quality and precision.

Fig.2: Conventional CNC Lathes

• Swiss Lathes - Swiss lathes are specialized for precision machining of small, complex parts. The key feature of a Swiss lathe is its guide bushing, which supports the workpiece very close to the cutting action. This feature drastically reduces workpiece deflection, allowing for tighter tolerances and higher precision. Swiss lathes excel in producing parts that require intricate detailing and fine finishes, making them indispensable in industries like medical devices, electronics, and aerospace where precision is crucial.

Fig. 3: Swiss Lathes

• Turning Centers - Turning centers are essentially advanced CNC lathes equipped with additional features that extend their capability beyond simple turning. These machines might include multiple turrets, live tooling, and Y-axis movement, allowing for milling, drilling, and tapping operations to be performed in conjunction with turning. Such multitasking capabilities make turning centers highly valuable for producing complex parts in a single setup, reducing lead times and increasing efficiency in production workflows.

Fig. 4: Turning Centers

• Vertical Turning Lathes (VTLs) - Vertical turning lathes feature a vertical orientation of the workpiece, contrasting with the horizontal axis found in most traditional lathes. This vertical alignment is particularly advantageous for machining large, heavy parts, offering improved stability and support. VTLs are commonly used in the aerospace and heavy equipment industries, where their ability to handle large components with precision is very useful.

Fig. 5: Vertical Turning Lathes

• Turret Lathes - Turret lathes are equipped with a turret, or a tool holder, that houses multiple tools at once. This setup allows for quick tool changes, enhancing productivity, especially for production runs of parts requiring multiple operations. Turret lathes can be either manual or CNC-controlled, with the latter providing the added benefits of precision and automation.

Fig. 6: Turret Lathes

• Live Tooling CNC Lathes - These machines are a subset of CNC lathes that feature live tooling capabilities. Unlike standard lathes where tools are stationary while the workpiece spins, live tooling lathes have tools that can move and rotate, enabling off-center drilling, milling, and tapping operations. This capability makes them highly versatile and efficient for producing complex parts that would otherwise require additional processing steps.

Fig. 7: Live Tooling CNC Lathes

• Gang Tool Lathes - In gang tool lathes, tools are mounted on a slide in a fixed arrangement, allowing for very fast tool changes since multiple tools can be positioned very near to the workpiece simultaneously. This design is particularly effective for high-volume production of small parts, as it minimizes the non-cutting time associated with tool changes.

Fig. 8: Gang Tool Lathes

What is the CNC Turning Process?

Here is the step-by-step working process of the production of a part by CNC turning:

• Designing the Part - A detailed CAD (Computer-Aided Design) model of the part to be manufactured is created using specialized software packages.
• Converting to the CAM Program - The CAD model is translated into a CAM (Computer-Aided Manufacturing) program, which generates the machine code that controls the CNC machine.
• Programming the Machine - The operator programs the CNC machine with specific instructions for the cutting process, including the movement of the cutting tool, the speed of the lathe, and the pattern of the cuts.
• Setting Up the Machine - The CNC lathe is prepared by setting up the required tools in the turret and configuring the machine settings according to the material and part specifications and the required software program is loaded in the machine.
• Mounting the Workpiece - The raw material is secured in the chuck of the lathe, ensuring it is held firmly for precision machining.
• Machine Calibration - A calibration run is performed to confirm the setup is correct and adjust the tool positions as necessary.
• The Machining Process - The CNC turning operation is started and the machine follows the programmed path to remove material from the workpiece, shaping it according to the design automatically.
• Monitoring the Process - The machining process is supervised for any issues or adjustments needed, ensuring optimal operation.
• Quality Checking - After machining, the finished part is inspected for accuracy and quality, comparing it to the CAD model specifications.
• Post-Processing - Any necessary post-processing steps, such as cleaning, polishing, or applying surface treatments to the part are done.
• Final Inspection and Testing - A final quality control check is done, ensuring the part meets all required specifications and tolerances.

What Kinds of Parts Does CNC Turning Make?

CNC turning is adept at producing a variety of cylindrical and round-shaped parts with high precision. The rotating workpiece in CNC turning enables the efficient production of cylindrical or round shapes. This method is particularly suited for creating parts with symmetrical features around their axis, such as shafts, pins, and bushings.

Specific Examples of CNC-Turned Parts

• Axle Shafts for Automobiles - A car’s gear shaft is a prime example of a part made using CNC turning. It is crucial for transmitting torque in vehicles and must be made with high precision to fit perfectly within the transmission system. The process ensures that these shafts have the necessary durability and performance characteristics required for long-term use in varying conditions.

Fig. 9: Axle Shaft

• Bone Screws in Medical Sector - Another example is bone screws. These are highly specialized screws used during orthopedic surgeries to hold bones in place. The precision of CNC turning is vital for creating the intricate threads and specific dimensions needed for these screws to be effective in medical procedures.

Fig. 10: Bone Screws

• Hydraulic Components for Aircraft - In the aerospace industry, hydraulic components such as engine turbine blades, pistons, and valves are often produced through CNC turning. These parts must adhere to strict aerospace standards for precision and reliability, given their critical role in controlling aircraft systems. The capability to work with a variety of materials, including high-strength alloys, makes CNC turning ideal for these applications.

Advantages of CNC Turning

Precision Production

CNC turning ensures that each cut is made exactly according to the specifications, allowing for the production of parts with very tight tolerances.

For standard CNC turning operations, tolerances within the range of ±0.005 inches (±0.127 mm) are commonly attainable. The exact tolerance that can be achieved depends on the type of machine, the cutting tool used, the speed and the accuracy of the fixturing.

Advanced CNC turning centers equipped with high-precision tooling and capabilities such as live tooling, Y-axis movement, and sub-spindle operations, can achieve tolerances of ±0.001 inches (±0.025 mm) commonly and even up to ±0.0005 inches (±0.0127 mm) for certain materials and parts.

Swiss-type CNC lathes can push these boundaries even further, to achieve tolerances within the range of ±0.0002 inches (±0.00508 mm) or better.

Table 1: Precision Tolerances Achieved by Different CNC Turning Operations

Superior Finishes

CNC turning ensures the production of parts with superior surface finishes, critical for many industrial applications. High-quality surface finishes are critical for engine parts. transmission gears, and bearing surfaces to reduce friction, and wear, and to improve efficiency. CNC turning can produce everything from a rough, milled finish to a highly polished surface suitable for bearing surfaces and axles.

Table 2: Surface Roughness Standards for CNC Milling Across Various Materials

Versatility of Material

CNC turning's adaptability in handling a diverse range of materials, from metals to plastics and composites, enables manufacturers to choose the optimal material for each specific application based on properties such as tolerance, strength, weight, surface, and corrosion resistance.

Table 3: Material Selection Guide

Repeatability

Repeatability stands out as another key benefit. CNC turning ensures that each part produced is virtually identical to the other, a crucial factor in high-volume production runs. This consistency is vital in maintaining quality control and operational efficiency across batches, making CNC turning an ideal solution for mass production.

Speed

CNC turning machines operate at a pace far surpassing that of manual machining, reducing production times and increasing throughput.

CNC turning machines operate at high speeds when machining softer materials, such as aluminum and brass often ranging from 600 to 3,000 RPM. For hard materials such as mild steel, and stainless steel the typical spindle speeds might range from 300 to 1,200 RPM. Harder materials such as titanium or hardened steel may necessitate slower speeds to reduce tool wear and manage heat, typically ranging from 100 to 800 RPM.

Rate of Material Removal

The rate of material removal varies based on the specific project. For soft materials, the rates of material removal can be quite high, easily reaching several cubic inches per minute, but for medium and hard materials, the material removal rates are generally lower and range from less than 1 in³/min to several in³/min, depending on the cutting conditions.

Cost Competitiveness

CNC turning can produce parts economically. This is especially true for small parts produced in high volumes, such as screws, bushings, and rings. The process's efficiency, combined with the reduction in labor costs due to automation, makes it possible to produce components cost-effectively.

Common Applications of CNC Turning

The versatility and precision of CNC turning make it indispensable for producing parts that require exact tolerances and smooth finishes, making it a valuable manufacturing process utilized across a wide range of industries.

These industries include, but are not limited to:

• Automotive - Components like axles, gearbox shafts, and engine parts, which require high precision and durability are manufactured by CNC turning.
• Aerospace - CNC turning is used for manufacturing critical aircraft components such as landing gear parts, hydraulic fittings, and airframe pieces, where precision and strength are paramount.
• Medical - CNC turning is used to manufacture surgical instruments, implants, screws, and components demanding exceptional accuracy and biocompatibility.
• Consumer Electronics - Many parts used in household goods need CNC-turned parts for casings, knobs, and connectors, where precision and aesthetics are important.
• Defense Hardware - A lot of defense-related equipment needs CNC turning for components of military equipment and vehicles, requiring high reliability and adherence to strict standards.
• Energy - In sectors like oil and gas or renewable energy, CNC turning is used to produce components for pumps, valves, and fittings, which must withstand harsh conditions and high stress.
• Construction - CNC-turned parts are used in machinery and structural components that require robustness and durability. These include building hardware such as locks, hinges valves, faucets, and connectors. And electrical fittings such as connectors, junction boxes, switchgear parts, and structural components such as bolts, nuts, and custom fasteners.
• Maritime - CNC turning is used for manufacturing parts used in ships and submarines, such as shafts, propellers, and fittings, which must resist corrosion and high pressure.

Considerations When Choosing CNC Turning

When considering CNC turning for manufacturing parts, several key factors come into play to ensure the process aligns with the project's requirements. Understanding these considerations can guide decision-making and optimize outcomes in terms of efficiency, cost, and quality.

• Part Complexity - CNC turning is exceptionally well-suited for parts with cylindrical features, including complex geometries that can be difficult to achieve with other manufacturing processes. Its precision and control make it ideal for producing components with intricate details, such as threads, tapers, and grooves. For parts that demand high precision and specific shapes along their rotational axis, CNC turning offers an ideal solution.
• Production Volume - The decision between CNC turning and manual machining often hinges on the volume of parts needed. For small production runs, manual machining might be more cost-effective due to lower initial setup costs. However, as the quantity increases, CNC turning becomes increasingly advantageous.
• Material Factors - The choice of material has a significant impact on the machining process. Some materials are inherently easier to machine than others, affecting the speed, tool wear, and finish quality of the parts produced.

Metals like aluminum and brass are generally more conducive to CNC turning, allowing for faster production times and longer tool life. In contrast, harder materials such as stainless steel or exotic alloys may require more time and specialized tooling, impacting the overall cost and feasibility of the project.

Conclusion

CNC turning stands as a vital manufacturing process that combines precision, versatility, and efficiency to produce cylindrical and complex parts. Characterized by its ability to shape materials with a rotating movement of the workpiece against a stationary cutting tool, CNC turning excels in creating CNC-turned parts with intricate geometries and tight tolerances. This process offers significant benefits, including unparalleled accuracy, consistency in high-volume production, and the capability to work with a diverse range of materials.

Choose Komacut

If you are looking to leverage the advantages of CNC turning for your manufacturing needs, then explore the services of Komacut which offers a promising path. Komacut is an innovative platform that provides access to precision CNC machining services, including CNC turning, making it easier for businesses and individuals to bring their engineering projects to life with high-quality parts.

Check out the Komacut website and learn how it can streamline your manufacturing process, offering a seamless, efficient, and cost-effective solution to meet your CNC machining requirements.  By utilizing Komacut manufacturing services you can capitalize on the latest in parts production technology, ensuring your projects benefit from the precision and reliability that their CNC turning facilities have to offer.

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FAQs

What is CNC turning?

CNC turning is a manufacturing process where material bars are held in a chuck and rotated while a tool removes material to create a desired shape and size, offering high precision and efficiency using computer-controlled equipment.

What are the major benefits of CNC turning?

The major benefits include the ability to produce intricate and complex parts with tight tolerances, high repeatability for large production volumes, versatility in machining different materials, increased speed compared to manual machining, and cost-effectiveness for high-volume production of small parts.

What industries benefit from CNC turning?

Industries such as automotive, aerospace, medical, consumer goods, and defense benefit from the precision and versatility of CNC turning for manufacturing various components.

Can CNC turning handle complex part geometries?

Yes, CNC turning is particularly suitable for parts with cylindrical features and can handle complex geometries with precision.

Is CNC turning cost-effective for small production runs?

For very small production runs, manual machining might be more cost-effective due to lower setup costs. However, CNC turning becomes more economical as production volume increases due to its automation and repeatability.

What materials can be machined using CNC turning?

CNC turning can machine a wide range of materials, including metals like steel, aluminum, and brass, as well as plastics and composites. See the materials table here.

How does CNC turning differ from CNC milling?

In CNC turning, the workpiece rotates, and the cutting tool moves in a linear motion. In contrast, CNC milling involves the cutting tool moving and rotating while the workpiece remains stationary.

What is the precision capability of CNC turning?

CNC turning can achieve tolerances within micrometers, ensuring parts are produced with high accuracy and quality surface finishes. See the turning tolerance table here.

How can I get started with CNC turning for my manufacturing needs?

Online quotation platforms like Komacut can provide access to precision CNC turning services, quick quotes and easy ordering, streamlining the process of obtaining high-quality machined parts for your projects.

What should I consider when choosing CNC turning for a project?

The primary issue to consider is the part geometry: is the part’s shape suitable for the process? What is the part diameter? Can the part be slightly larger or smaller to meet a standard material size?