CNC turning is a key process in modern industrial manufacturing. The technology enables precise shaping of materials by removing excess raw material from the rotating workpiece. Computer control ensures unparalleled accuracy, repeatability and efficiency. The variety of CNC turning methods available makes it possible to manufacture a wide range of parts – from simple shafts to complex parts with many complex geometric features.
The choice of the appropriate turning method depends on many factors: the type of material to be machined, the required precision, the geometric complexity of the part, the size of the production run and the available machinery. Each type of CNC turning has its own unique applications and advantages. Straight turning works well for producing cylindrical parts, while tapered turning allows for variable diameter surfaces. Advanced techniques on multi-axis machines make it possible to produce complex parts with a minimum number of fixtures.
Specialized processes like grooving and threading expand machining capabilities, allowing the creation of functional fasteners and assembly parts. Knowledge of the different types of CNC turning and their optimal applications forms the basis for effective production process planning. The right choice of method translates directly into product quality, lead time and manufacturing costs.
Basic types of CNC turning machines
CNC turning machines fall into several basic categories that differ in design, capabilities and application. Knowing these types helps in selecting the right equipment for specific production tasks.
Horizontal and vertical lathes
Horizontal lathes are characterized by the horizontal positioning of the spindle. This design is ideal for machining long workpieces, such as shafts or axles. The horizontal setting facilitates chip removal, which reduces the risk of tool damage and increases production efficiency. These machines dominate most manufacturing plants because of their versatility.
Vertical lathes have a spindle positioned vertically. This arrangement works well for machining large and heavy workpieces with complex shapes. The vertical orientation allows for easier clamping of heavy workpieces and provides better stability during machining. They are mainly used in heavy industry, where large components are machined.
Lathes by number of axes
2-axis lathes are the simplest type of CNC machines. They have an X axis (transverse movement of the tool) and a Z axis (longitudinal movement). They allow basic turning operations such as external turning, internal turning and planning. They work well for producing simple cylindrical parts.
Three-axis lathes add a Y axis, which allows milling and drilling operations to be performed off the workpiece’s axis of rotation. Expanding the capabilities with an additional axis significantly increases the functionality of the machine without having to translate the workpiece to the milling machine.
Four-axis lathes introduce a C-axis for precise angular positioning of the spindle. This allows complex machining operations, such as contour milling on a rotary surface or drilling holes at different angles.
Types of lathes by number of spindles:
- Single-spindle lathes – standard machines with one spindle
- Two-spindle lathes – have a main and opposite spindle
- Multi-spindle lathes – allow simultaneous machining of multiple workpieces
Flat-bed lathes have a horizontal guiding surface. They provide high stability and strength, which translates into the ability to machine heavy workpieces. This design works well in heavy industry and in the production of large parts.
Slant-bed lathes have guides inclined at an angle of 30-45 degrees. This design improves chip removal and visibility of the machining zone. In addition, it increases the rigidity of the machine and allows for better dimensional tolerances. These machines are suitable for producing precision parts of medium size.
Turning centers
Turning centers combine the functions of a lathe and a milling machine. They are equipped with driven rotary tools that enable milling, drilling and threading operations without having to translate the workpiece. These machines significantly reduce production time for complex parts and increase machining accuracy.
Modern turning centers often have dual spindles and multiple numerically controlled axes, allowing complex machining of the workpiece in a single fixture. This eliminates errors associated with re-mounting parts and reduces production time.
Tip: When selecting a CNC lathe, consider not only your current production needs, but also anticipated future orders. Buying a machine with more axes may seem expensive at first, but in the long run it will provide greater production flexibility and the ability to handle more complex orders.
Straight and taper turning operations in industrial production
Straight and taper turning are the basic operations performed on CNC lathes. Each has its own specific applications and manufacturing techniques that affect the efficiency of the production process.
Straight turning
Straight turning involves removing material from a rotating workpiece using a cutting tool moving parallel to the axis of rotation. The process is used to obtain cylindrical surfaces of uniform diameter throughout.
During straight turning, the tool performs a longitudinal motion, removing a layer of material of a certain depth. This operation can be performed as roughing (removing a large amount of material) or finishing (obtaining accurate dimensions and good surface quality).
Straight turning is used in the production of shafts, axles, bushings and other cylindrical parts. The process is characterized by high productivity and accuracy, especially on modern CNC lathes.
Tapered turning
Tapered turning produces surfaces with variable diameters along the axis of rotation. It creates conical surfaces that are widely used in machine and equipment components.
Methods of performing taper turning:
- Using the offset tailstock of a lathe
- Using a slide set at an angle
- With the use of a cone turning attachment
- By CNC control (the most precise method)
Taper turning using CNC control involves simultaneous control of tool movement in the X and Z axes to achieve a precise taper angle. This method provides the highest accuracy and repeatability.
Industrial applications
Straight turning is used in the production of cylindrical parts such as pins, bushings, shafts and axles. This method is the basis for the production of machine parts and equipment in almost every industry.
Tapered turning is used in the production of tapered parts, such as tapered joints, journals, valve seats and hydraulic system components. Cones are also used as centering and sealing components.
In the automotive industry, straight and taper turning are used to produce drivetrain components such as crankshafts, half-shafts and transmission components. In the aerospace industry, these methods are used to manufacture precision engine components and control systems.
Technological parameters
Key to the quality and efficiency of the turning process are properly selected technological parameters. Cutting speed, feed rate and depth of cut affect process efficiency, surface quality and tool life.
Cutting speed depends on the workpiece material and tool material. For structural steels, typical values are 60-120 m/min when using carbide tools. The feed rate determines the efficiency of the process and surface quality – a higher feed rate increases productivity, but degrades surface quality.
Tip: When taper turning, special attention should be paid to the rigidity of the machine tool-object-tool system. Insufficient rigidity can lead to vibration and deterioration of surface quality, especially with large taper lengths. The use of supports or a scope can significantly improve the stability of the process.
CNC turning services at CNC Partner
CNC Partner is a professional company specializing in CNC machining. The company offers comprehensive services in CNC turning and other metalworking methods, ensuring high quality and precision workmanship.
CNC Partner company profile
CNC Partner operates in the market as an experienced provider of machining services. The company specializes in unit and small batch production, fulfilling orders for customers in various industries. The company has a state-of-the-art machine park, which enables it to manufacture precise details in accordance with technical documentation.
CNC Partner’s team consists of qualified specialists with many years of experience in the CNC machining industry. The company focuses on the continuous development of the competence of its employees and the modernization of its machinery park, which translates into high quality services.
The company’s philosophy is based on an individual approach to each order. CNC Partner offers not only the execution of details according to the supplied documentation, but also technical advice on optimizing the structure in terms of manufacturing technology.
CNC turning service
CNC turning is one of CNC Partner’s main specialties. The service includes comprehensive execution of turned parts in accordance with the customer’s technical documentation. The company performs both simple turning operations and complex processes involving multi-axis turning.
CNC turning capabilities:
- External and internal turning
- Tapered and contoured turning
- External and internal threading
- Grooving and undercutting
- Drilling and reaming
- Turning parts with complex geometry
CNC Partner fabricates turned parts from a variety of materials, including structural steels, stainless steels, aluminum alloys, brass, bronze and plastics. The company guarantees high dimensional accuracy and surface quality in accordance with customer requirements.
Comprehensive service offering
In addition to CNC turning, the company offers a range of complementary machining services, which allows for comprehensive implementation of even complex projects.
CNC milling is a service that makes it possible to produce complex spatial shapes. CNC Partner has 3, 4 and 5-axis machining centers at its disposal, allowing it to carry out even the most demanding projects. The service includes flat milling, spatial milling and machining of parts with complex geometries.
CNC grinding ensures high dimensional accuracy and surface quality. The company offers grinding of planes, holes and external surfaces, guaranteeing precision at the micrometer level.
WEDM wire EDM is a technology that enables wire cutting of electrically conductive materials. This method allows complex shapes to be made with high accuracy, even in materials with high hardness.
Order execution process
Cooperation with CNC Partner begins with a technical consultation, during which the details of the project and feasibility are discussed. The company then prepares a price offer that takes into account the cost of materials, machining and any additional operations.
After accepting the offer, the programming team prepares CNC programs based on the provided documentation. The next stage is the execution of details in accordance with the established technological parameters. Each detail is subjected to quality control to verify compliance with the documentation.
Tip: When ordering CNC turning services, it is worthwhile to provide complete technical documentation containing not only dimensions, but also information on tolerances, surface roughness and material requirements. This will allow you to accurately determine the cost and lead time of the order.
Advanced turning techniques on multi-axis machines
The development of CNC technology has enabled the emergence of advanced turning techniques that significantly expand machining capabilities. Multi-axis machines allow complex parts to be made with a minimum number of fixtures.
Turning on 4-axis machines
4-axis machines introduce an additional C-axis that allows precise angular positioning of the spindle. This extension opens up new machining possibilities not available on standard 2-axis lathes.
The C-axis allows milling operations to be performed on the rotating surface of the workpiece. It becomes possible to mill grooves, pockets, polygons and other shapes that previously required additional clamping on the milling machine. This significantly reduces production time and increases machining accuracy.
4-axis turning also makes it possible to drill radial holes at different angular positions. Thanks to precise control of the angular position of the spindle, it is possible to produce holes distributed around the perimeter of the workpiece without having to translate the spindle.
Turning on 5-axis machines
5-axis lathes add a B-axis, which allows the tool to be tilted relative to the workpiece. This configuration allows the machining of surfaces with complex geometries that are inaccessible using conventional turning methods.
The B-axis allows the tool to be positioned at an optimal angle to the work surface, improving cutting conditions and surface quality. This is particularly useful when machining curved surfaces and parts with variable geometries.
Benefits of 5-axis turning:
- Ability to machine complex shapes in a single fixture
- Optimization of the tool application angle
- Reduction in the number of tools needed to machine a part
- Reduction in production time
- Increased dimensional accuracy
Modern turning centers are often equipped with a counter-spindle, which allows the workpiece to take over and continue machining the other side of the workpiece without manual repositioning. This technology significantly increases production efficiency and machining accuracy.
The turning process with a counter-spindle begins by machining one side of the workpiece in the main spindle. The workpiece is then taken over by the counter-spindle, allowing the other side to be machined. The entire process takes place automatically, without operator intervention.
Turning with a counter-spindle eliminates errors associated with re-mounting the workpiece, which is particularly important in the production of precision parts. In addition, it significantly reduces production time by eliminating downtime associated with repositioning the workpiece.
Turning-Milling
Advanced machining centers combine turning and milling capabilities, allowing complex machining of a workpiece in a single fixture. These machines are equipped with driven rotary tools and additional CNC-controlled axes.
Turning-milling makes it possible to perform milling operations, drilling, threading and other machining processes without having to transfer the workpiece to another machine. This technology is used in the production of complex parts that require both turning and milling operations.
Tip: When planning the machining process on multi-axis machines, consider combining several operations in a single fixture. Analyzing the machine’s capabilities in terms of available axes and tools can lead to significant optimization of the production process, reduced machining time and improved dimensional accuracy of the workpiece.
Specialized CNC turning processes from grooving to threading
CNC turning encompasses a number of specialized processes that produce a variety of geometric features on a workpiece. Each of these processes requires appropriate preparation of the machine, tools and machining parameters.
Grooving
Grooving is the process of creating narrow channels or recesses on the surface of a workpiece. This operation is performed using special grooving knives, which are shaped to match the required geometry of the groove.
External grooving involves making a groove on the outer cylindrical surface of the workpiece. This process is used when creating places for sealing rings, circlips or when cutting off the finished part from the starting material.
Internal grooving is performed on the inner cylindrical surface, most often in holes. It requires special tools with a long overhang, which can lead to problems with system stiffness and machining accuracy.
Types of grooving by shape:
- Straight grooving – making rectangular channels
- Shape grooving – making grooves with a special profile
- Face grooving – creating grooves on the face of the workpiece
- Undercutting – a special type of grooving used to create undercuts
Threading
Threading on CNC lathes can be performed by various methods, depending on the requirements for accuracy, performance and type of thread.
Threading with a lathe knife involves making a thread using a special knife with a profile adapted to the thread parameters. The process requires precise synchronization of the tool feed with the spindle rotation. This method makes it possible to produce threads of various profiles and pitches, both external and internal.
Die head tapping uses a special tool equipped with cutting inserts with a thread profile. The head rotates synchronously with the workpiece, which allows for fast and accurate threading. This method is particularly effective for large diameter threads.
Rotary tooling threading uses driven rotary tools, such as taps or thread mills. This method is mainly used on turning centers equipped with driven tools.
Shape turning
Shape turning makes it possible to produce surfaces with complex geometries, such as curves, spheres or irregular profiles. This process requires special tools or advanced CNC control.
Shape turning with profile knives involves using a tool whose cutting edge is shaped to match the profile of the surface to be machined. This method is simple to implement, but limited to relatively simple shapes.
Shape turning with axis interpolation uses the capabilities of CNC control to simultaneously control the movement of the tool in several axes. This allows complex shapes to be made without the need for special profile tools.
Drilling and reaming
Modern CNC lathes allow drilling and reaming operations to be performed directly on the machine, without having to translate the workpiece. These operations can be performed both in and out of the spindle axis (using driven tools).
Drilling in the spindle axis is carried out using drills mounted in the lathe’s tool holder. This process allows holes to be made coaxial with the turned workpiece.
Reaming is used to increase the dimensional accuracy and surface quality of a hole previously made by drilling or internal turning. This operation is performed with reamers that provide high dimensional accuracy and low surface roughness.
Note: When planning the grooving process, special attention should be paid to chip evacuation from the cutting zone. Chips trapped in the groove can lead to tool damage or surface deterioration. The use of high-pressure coolant directed directly at the cutting zone can significantly improve the efficiency of the process.
Selecting the right CNC turning method for specific materials and projects
The selection of the optimal CNC turning method depends on many factors, including the type of material to be machined, workpiece geometry, quality requirements and economic aspects. The right choice translates directly into quality, time and production cost.
Selecting the method by material
The properties of the material being machined have a key impact on the choice of turning method and machining parameters. Different materials require specific approaches due to their hardness, strength and machinability.
Structural steel lends itself well to turning operations using standard carbide tools. For medium hardness steels, medium cutting speeds and feeds are recommended. For finish machining, it is worth using inserts with antiwear coatings to increase tool life.
Stainless steel has poorer machinability and a tendency to strengthen during machining. When turning stainless steel, it is recommended to use lower cutting speeds, higher feed rates and intensive cooling. Tools should have a sharp cutting edge and a positive rake angle.
Recommendations for different materials:
- Aluminum and its alloys – high cutting speeds, high feeds, tools with a large rake angle
- Cast iron – medium cutting speeds, dry machining capability, carbide tools
- Titanium and its alloys – low cutting speeds, intensive cooling, tools with high wear resistance
- Plastics – high cutting speeds, tools with sharp cutting edge, minimal cooling
Selecting the method according to the geometry of the workpiece
The geometry of the workpiece is a key factor in selecting a CNC turning method. Complex shapes may require advanced machining techniques and specialized machinery.
Cylindrical workpieces with simple geometries can be made on standard 2-axis lathes. The process is efficient and economical for parts such as shafts, bushings and simple axes.
Workpieces with complex geometries that include non-rotating features (e.g., grooves, pockets, radial holes) require multi-axis lathes with driven tools. Lathe-milling centers allow complex machining of such workpieces in a single fixture.
Workpieces requiring machining on both sides are most effectively performed on lathes with a counter-spindle. This technology eliminates the need to manually translate the workpiece, which increases accuracy and production efficiency.
Economic aspects of selection
When choosing a CNC turning method, it is important to consider not only technical aspects, but also economic ones. Optimizing the process in terms of cost can significantly affect the competitiveness of production.
The size of the production run has a significant impact on the choice of turning method. For unit and small batch production, machine flexibility and versatility are key. For high-volume production, it is worth considering dedicated solutions that maximize productivity.
Tooling costs represent a significant portion of production costs. Choosing the right tools and optimizing their use can result in significant savings. For hard-to-machine materials, it is worth considering premium tools, which, despite their higher price, provide longer life and better machining quality.
Quality criteria
Requirements for dimensional accuracy and surface quality have a key impact on the choice of CNC turning method. Different machining techniques allow for different levels of accuracy.
Standard turning achieves dimensional accuracy in the IT7-IT9 range and surface roughness Ra 1.6-6.3 μm. For most industrial applications, these parameters are sufficient.
Precision turning, performed on high-stiffness machines using specialized tools, makes it possible to achieve dimensional accuracy IT5-IT6 and surface roughness Ra 0.4-1.6 μm. This method is used in the production of components with higher quality requirements.
Finishing turning, often combined with micro-cutting, makes it possible to achieve the highest dimensional accuracy (IT4-IT5) and very low surface roughness (Ra 0.1-0.4 μm). This technique requires specialized machinery, tools and experienced personnel.
Tip: When selecting a CNC turning method for a specific project, it is worthwhile to conduct an analysis of the technological possibilities of various machining variants. A comparison of machining time, tooling costs and the quality achieved will allow you to choose the optimal solution. In the case of complex workpieces, it is often more cost-effective to use advanced technology that allows the entire workpiece to be machined in a single fixture, rather than dividing the process into several simpler operations.
Summary
CNC turning is a core technology in modern industrial manufacturing, offering a wide range of machining options. The variety of turning methods available allows the process to be optimally adapted to the specific requirements of each project. Basic machine types, from simple 2-axis lathes to advanced 5-axis machining centers, provide flexibility for a wide variety of production tasks.
Straight and tapered turning are used in the production of cylindrical and tapered parts, which are the basic components of machines and equipment. Advanced turning techniques on multi-axis machines extend machining capabilities to complex shapes that previously required multiple operations on different machines. Specialized processes, such as grooving and threading, complement basic turning methods to produce functional features of a workpiece.
The choice of the right CNC turning method depends on many factors: the type of material, the geometry of the workpiece, quality requirements and economic aspects. The right choice translates directly into product quality, lead time and production costs. Knowledge of different types of CNC turning and their optimal applications is the foundation for effective planning of the production process.
Companies specializing in CNC turning services, such as CNC Partner, offer comprehensive machining solutions, combining different technologies to realize even the most demanding projects. The continuous development of CNC technology is opening up new opportunities for precision, productivity and automation of turning processes, resulting in increasingly higher quality end products.
Sources:
- https://en.wikipedia.org/wiki/Grinding_(abrasive_cutting)
- https://journal.eu-jr.eu/engineering/article/download/1832/1840/
- https://uhv.cheme.cmu.edu/procedures/machining/ch5.pdf
- https://sciencebring.com/index.php/ijasr/article/view/795