CNC Turning Services
CNC turning is a popular manufacturing technique for creating cylinder-shaped components out of a variety of materials In contrast to CNC milling, which includes rotating the workpiece while keeping the cutting tool stationary, CNC turning requires rotating the workpiece. The development of advanced turning centers, which go beyond conventional turning operations by including milling capabilities, has been facilitated by the progress of CNC turning. These centers enable the production of complex and sophisticated parts.
An introduction to CNC lathe machines will be provided. We will examine common nomenclature, the workings of CNC turning, the variety of operations that may be performed, and the many parts that make up a CNC turning machine.
What is CNC Turning
CNC turning is a subtractive manufacturing technique that involves the removal of material from a typically cylindrical stock piece, although it can also be applied to various stock shapes like hex or square bars. In this process, the workpiece rotates while a cutting tool engages with it, steadily eliminating material until the desired shape is achieved.
Turning machines come in both vertical and horizontal configurations, as illustrated in the diagram above (depicting 6 axes, though the number of axes can vary). Vertical CNC turning is commonly employed for machining large and heavy components since it aligns the material’s center of gravity with the rotational axis.
However, horizontal CNC turning involves mounting the workpiece in a way that creates a cantilever effect. This setup can lead to vibrations in sizeable, weighty pieces, potentially affecting machining quality and causing damage to the turning machine and tooling.
Despite its advantages, vertical turning has its own drawbacks. One significant issue is chip evacuation: if cutting chips are not efficiently removed after being cut, it can result in problems like chip recutting and surface scratching. Consequently, horizontal CNC turning is the more prevalent choice for most applications.
CNC Lathes vs. CNC Turning Centers
Distinguishing between a CNC lathe and a CNC turning center essentially boils down to their respective capabilities. Typically, a turning center exhibits a broader range of functionalities, whereas a lathe primarily focuses on turning operations. A lathe is a machine designed specifically for cutting materials via the rotational process, while turning is a more general term that encompasses various rotational cutting methods.
In the pre-CNC era, identifying and categorizing lathe machines was relatively straightforward. However, as technology has advanced, numerous new features have been incorporated. Consequently, it has become necessary to differentiate between simpler CNC machines, which perform operations akin to traditional lathes, and more advanced machines, often referred to as CNC turning centers, capable of executing turning cuts in diverse ways.
Some companies draw distinctions based on the number of toolpath axes a machine can maneuver. CNC toolpaths are categorized as 2D, 3D, 4-axis, or 5-axis (applicable to both milling and turning processes). Lathes typically fall into the 2-axis category, while turning centers are typically equipped with 3-axis, 4-axis, or 5-axis capabilities. Conversely, some enterprises categorize machines as turning centers if they can perform turning cuts alongside milling and drilling operations.
Components of CNC Turning Machines
CNC turning machines comprise essential components that work in tandem to shape workpieces. These components include a spindle, connected to the machine’s drive system at one end, and equipped with a chuck at the other end to secure the workpiece for cutting. The chuck typically features three or four jaws, with three being the most common. Four-jaw chucks can accommodate square bars and facilitate off-center turning.
Cutting tools are often crafted from carbide inserts, which are affixed to tool holders. These holders are then bolted onto the turret, with the choice of holder depending on the specific tool type. Before machining commences, tools are indexed as part of the pre-machining setup.
Materials for CNC Turning Tooling
Numerous companies invest substantial research efforts into enhancing tooling materials, inserts, coatings, and alloys to boost tool longevity and performance. The selection of the appropriate insert is critical, as insert designs vary, and choosing the wrong one for a particular material can lead to tool breakage or workpiece damage, especially when using identical speed and feed settings.
An essential aspect of materials engineering concerning CNC turning tool inserts revolves around crystal orientation. Microscopic examinations reveal the individual crystalline areas, or grains, within the material. These grain characteristics, such as size, structure, and orientation, result from the material’s composition (alloy) and the specific heat treatments and other processes applied to it. The grain properties play a pivotal role in determining mechanical performance.
The figure below showcases a comparison between the microstructure of a typical alumina coating for CNC turning inserts and the microstructure achieved using Sandvik’s Inveio® technology. In the typical coating, a random crystal structure is observed, whereas Sandvik’s innovation yields a unidirectional crystal arrangement. This transformation in microstructure enhances resistance to crater wear and flank wear while facilitating superior heat dissipation during machining. Consequently, a unidirectional crystal structure prolongs cutting edge sharpness, improves wear resistance, extends tool lifespan, and substantially reduces machining expenses.
Types of CNC Turning Operations
Turning, in the context of CNC machining, encompasses a diverse set of operations that can be carried out on a turning center. Below, we outline some of the more common types of turning operations.
Facing involves cutting a flat surface perpendicular to the rotational axis of the workpiece. The tool is affixed to a tool holder situated on the lathe’s carriage. During the operation, the facing tool traverses across the rotational axis of the part, creating a flat surface. Face turning can serve as either a preliminary roughing cut or a final finishing pass.
CNC turning operations entail the removal of material from the outer diameter of the workpiece. Turning can be executed parallel to the rotational axis for cylindrical shaping or at an angle to achieve tapered geometries.
When a hole is required along the rotational axis of the part, a drilling operation is performed. Advanced turning centers allow for hole drilling in various orientations, not solely limited to the central axis.
After drilling, it may be necessary to expand the hole’s diameter. Boring operations involve feeding a cutting tool into an existing hole, effectively enlarging the inner wall of the cavity.
Threading encompasses the process of cutting threads, either into a hole or along the outer diameter of a workpiece, creating screw-like grooves for fastening or assembly purposes.
Grooving or Parting
Grooving is typically employed to shape features such as O-ring or circlip grooves, as well as for contouring operations. A grooving tool, sometimes referred to as a parting-off tool, is used to separate the finished part from the original workpiece stock.
Knurling imparts a diamond-pattern texture onto the outer diameter of a part. This pattern is not achieved through cutting but rather by compressing the material into the desired pattern using a knurling tool. Knurling is often employed to enhance grip or provide a tactile surface on a component.
Benefits of CNC Turning
CNC turning offers numerous advantages, some of which are outlined below:
CNC turning consistently delivers highly accurate parts, thanks to its automated process that eliminates human error.
CNC turning is a versatile manufacturing technology capable of producing a wide variety of intricate components. CNC turning centers enhance this versatility by incorporating both milling and turning functions.
CNC turning ensures operator safety by conducting all cutting operations behind machine guards, eliminating the risks associated with manual turning machines.
CNC turning machines operate swiftly and efficiently, adhering to precise instructions without interruption. Quick tool changes further expedite the production process when necessary.
CNC Turning at Sungplastic
At Sungplastic, we provide:
Advanced CNC turning machines
Advanced CNC centre equipped with 3-aixs, 4-aixs, 5-aixs capacities and more axis
Skilled workers, professional designers, strong production lines
Various CNC machining process
Low volume manufacturing
High volume production
Small parts or large parts manufacturing
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