CNC turning is primarily employed for manufacturing circular components and is the preferred choice for cylindrical and conical shapes. While not as common as CNC milling, it stands as the second most widely used process for manufacturing mechanical parts.
This article focuses on the CNC turning process, providing an overview of its fundamental principles, the various types of CNC turning machines, and delves into the range of turning operations and their applications.
What is CNC Turning?
CNC turning is a manufacturing process primarily involving lathes and/or CNC turning centers, where the workpiece is rapidly rotated in a chuck for machining instead of moving the cutting tool. For this reason, CNC turning is not suited for workpieces requiring intricate details, although it is much faster when performing relatively simple cuts. Specialization and advanced technology in modern lathes allow them to process multiple workpieces on a single lathe. Workpieces can be held in place using collets, and multiple tools can be set up for operations. Through turning, operations involving cutting material from the exterior of the workpiece and drilling holes within it can be relatively easily accomplished.
What is the Difference Between CNC Turning and CNC Milling?
CNC turning involves a rotating chuck or spindle where the workpiece is typically fixed. A set of cutting tools enters the spinning metal blank, removing material, and creating a cylindrical element.
In contrast, CNC milling involves securing the workpiece on a movable worktable. In this case, the cutter rotates and moves into the piece, removing material and forming flat surfaces.
Computer numerical control (CNC) turning and CNC milling also share many similarities. For instance, both deal with geometries, tolerances, surface area smoothness, and CNC control. Specific software adjusts the motions of CNC mills and CNC lathes, so skilled and technically proficient workers are required at some stage of the machining process.
Advantages of CNC Turning
CNC turning achieves faster speeds when performing tasks such as boring, drilling, and shaping. This allows industries to meet deadlines and boost production capabilities on the go. However, complex designs can be challenging and may take longer to complete.
CNC turning offers high precision and can execute operations with exacting machining. It is trusted for many critical parts with cylindrical surfaces, such as rollers, bullets, gears, and drill bits.
CNC turning is highly adaptable and can interface with CNC milling to meet industrial demands. It can also produce components for other mechanical parts, ranging from bolts and nuts to torque and turbines. However, backward compatibility and asymmetrical designs are crucial for this beneficial interconnection.
Complex Product Shapes
Producing parts with circular designs using milling and machining processes can be very challenging, not to mention they often do not meet size requirements and require trimming.
On the other hand, CNC turning excels in handling these tasks perfectly. Thus, it can be used to manufacture some of the most critical industrial parts, such as:
- Nuts and bolts
- Bullets and firearms
- Beams and pipes
- Ball joints
- Circular turbines
CNC Turning Operations
Taper turning creates a cylindrical shape that gradually decreases in diameter from one end to the other. This can be achieved through a) compound slide, b) taper turning attachment, c) hydraulic copying attachment, d) C.N.C. lathe, e) form tool, f) by offsetting the tailstock. this method is more suitable for shallow tapers.
Hard turning is a turning operation performed on materials with a Rockwell C hardness greater than 45. It is typically carried out after the workpiece has undergone heat treatment. This process aims to replace or limit traditional grinding operations. Hard turning, when applied for pure cutting purposes, offers advantages over rough grinding. However, for precision finishing where shape and size are critical, grinding yields superior results. Grinding produces higher roundness and cylindrical dimension precision. Moreover, achieving a polished surface finish with Rz=0.3-0.8z is not possible with hard turning alone. Hard turning is suitable for parts requiring roundness accuracy of 0.5-12 micrometers and/or surface roughness of 0.8-7.0 micrometers. It is used in applications like gears, injection pump components, and hydraulic parts.
Facing in turning operations involves moving the cutting tool perpendicular to the rotational axis of the workpiece. This can be executed through the operation of a cross slide, distinct from longitudinal feed (turning). It is typically the first and often the last operation performed during workpiece production, hence called “finishing.”
This process, also known as cutoff or slitting, is used to create deep grooves and remove an entire or partially complete component from its parent material.
Grooving is similar to parting, but it involves cutting grooves to a specific depth rather than completely separating a component from the stock. Grooving can be done on internal and external surfaces, as well as on the surface of a part (face grooving or face turning).
Thread machining is another CNC turning process that involves moving a cutting tool along the side of the material to cut threads onto the external components of a workpiece. Threads are spiral-shaped grooves with specific lengths and pitches.
Used to remove material from within the workpiece. This process utilizes standard drills fixed on the lathe tailstock or tool turret. It can also be accomplished using a standalone drilling machine.
Types of CNC Lathes
In fact, lathes are typical machines used for turning operations. However, these devices come in different types, each more suitable for specific turning tasks. There are four distinct types of CNC lathes available for your machining projects.
Horizontal CNC Lathe
Horizontal CNC lathes are categorized into horizontal guide rail CNC lathes and inclined guide rail CNC lathes. The inclined guide rail structure enhances the lathe’s rigidity and chip removal efficiency.
Vertical CNC Lathe
Vertical CNC lathes, commonly known as vertical lathes, have their lathe spindle oriented vertically to the horizontal plane. They feature a large-diameter circular worktable for clamping workpieces. This type of machine is primarily used for machining large, complex parts with significant radial dimensions and relatively smaller axial dimensions.
Horizontal Turning Center
A horizontal turning center is an enclosed machine with drilling and milling capabilities. As the name suggests, it operates horizontally, with the tool mounted on top, gradually rotating and cutting into the workpiece while relying on gravity for chip removal.
Vertical Turning Center
Combining elements of a horizontal turning center and a CNC milling machine, its design positions the rotary chuck closer to the ground, making it easier to handle larger workpieces.
Applications of CNC Turning:
CNC turning and machining processes offer versatile solutions across various manufacturing sectors. Explore the diverse applications of turning operations:
Automotive Industry: CNC turning is extensively employed in manufacturing automobile components, enhancing vehicle performance. It’s compatible with both metal components like cylinder blocks and plastic parts such as dashboard components.
Electrical Industry: NC turning is ideal for crafting precise electrical components, including circuit boards. Its high precision ensures electronically efficient products, meeting rigorous specifications.
Aerospace Industry: The aerospace sector relies on CNC turning and machining due to its exceptional dimensional accuracy. It’s crucial for producing steel parts for shuttles, aircraft fasteners, and intricate internal components.
Medical Industry: CNC turning plays a critical role in manufacturing medical devices and components. It ensures the precision needed for surgical instruments, implants, and diagnostic equipment.
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CNC turning is a versatile and precise manufacturing technique, ideal for various industries and large-scale production. This article has provided you with a comprehensive understanding of the process, enabling informed decisions for your fabrication needs.
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