CNC lathe machines are multipurpose tools that can perform several operations intended to manufacture parts or components for several industries. Although turning is the most common process associated with lathe machines, CNC lathes are not limited to turning only but are a manufacturing process system that involves spinning. The variations that occur in turning operation are due to the variations in the geometry of the cutting tool and the interaction of the tool with the workpiece. Every operation has its way of producing the required design requirements, allowing manufacturers to develop designs specific to projects. The various categories of turning operations need to be differentiated so that the proper process can be used in production.
This article focuses on the top ten types of CNC turning operations, their uses, and how to select the proper operation for a given job. So, let’s go deeper.
Straight turning is the most straightforward operation in CNC. It involves rotating the cutting tool in a plane parallel to the axis of the workpiece to reduce its dimensions to a specific size. This operation is essential in producing parts with a constant cross-sectional thickness of symmetrical shape, such as cylinders.
Process Details:
The CNC straight-turning process employs the lathe's tool holder to move the cutting tool along the length of the workpiece. Factors such as spindle speed, feed rate, and depth of cut control coordinate the tool's movement. For instance, a depth of cut may be set at 1 mm with a feed rate of 0.2 mm/rev, which is suitable for high material cutting rates accompanied by high tool wear.
Dimensional Control:
The accuracy achieved through CNC straight turning is up to ±0.1mm, depending on the type of machine and the material being machined. The process also has high repeatability in batch production runs, an added advantage.
Applications:
This operation is standard in industries that produce parts such as axles, shafts, and fasteners because it can produce long cylindrical items of equal wall thickness for automotive and aerospace applications.
CNC Parting Operation separates the cutting tool from the rest of the workpiece material. It’s performed with high precision so that the final part is accurately separated and has the correct dimensions.
Operational Mechanics:
In CNC parting, a thin tool, which can be a blade-like tool, is inserted into the rotating workpiece. For optimal outcomes, the process must be fed at a slow feed rate and low cutting speed to break down the cutting tool and achieve the right cut. Some common parameters, such as a feed rate of 0.4 IPS and a spindle speed of 1500 RPM, may need to be accounted for. These can vary depending on the type of material being machined.
Tool Wear Management:
Tool wear highly affects CNC parting since the thin tool is used under stress. The majority of the modern CNC lathes have a feature of tool wear compensation which allows the machine to correct the tool path in operation.
Applications:
CNC parting is widely used in producing rings, collars, and other cylindrical products from bar stock. It is also used to create grooves or steps on the parts where the separation is done to a defined precision degree. Further, CNC parting is accurate to the extent that the last parts are of the correct length and only need a little finishing.
Boring is a turning operation in which the size of a hole already present in the workpiece is enlarged. CNC boring is accurate in the dimensional sense because it can produce holes of precise diameter and surface finish.
Technical Execution:
In CNC dull, a boring bar is used to cut material from the inside of a hole. The feed rate and the depth of the cut are included in the CNC program that defines the movement of the bar. Hole sizes can be made to an accuracy of up to 0.005 mm and are suitable for applications where high precision is needed.
Surface Finish Optimization:
The surface finish in boring is critical, mainly if the hole is used as a bearing surface or a guide. The surface roughness of the cut material depends on the tool's geometry and the material being cut and is in the range of Ra 2 to 8 µm.
CNC facing is a simple turning operation that provides a flat and finished surface at the extremity of a cylindrical workpiece. This helps shape the workpiece for other operations on which it has to be parallel to the axis of rotation.
Technical Overview:
In CNC facing, the cutting tool moves radially across the end surface of the workpiece, and a G-code directs the movement. Facing operation is usually done at a small depth at any one time to avoid removing excessive material at a time. The spindle speed, which is in revolutions per minute, and the feed rate, which is in millimeters per revolution, are varied to give a quality surface finish.
Surface Finish and Tolerances:
The surface finish provided in CNC facing can be of Ra 4 µm with variation depending on the material being cut and the geometry of the cutting tools. Tolerances generally are of the order of ±0. 01mm. Therefore, it is best used in accuracy-required applications.
Applications:
CNC facing is used for turning, drilling, or threading. It is used where the end face is employed as the datum face for other operations, such as manufacturing flanges, bearings, and shafts.
CNC taper turning is used in the machining of cylindrical workpieces. Taper means that one end of the workpiece has a larger diameter than the other. This operation is essential for fitting parts into different parts with a taper.
Technical Precision:
In CNC taper turning, the cutting tool is fed inclined to the workpiece’s axis of rotation. The taper angle is regulated by the CNC program, and the compound slide is controlled using a taper attachment. For example, a conventional taper angle maybe 5 degrees, with tolerance help to be ± 0.02 degrees.
Surface Finish Considerations:
Taper turning helps produce high-quality finished parts or products. The spindle speed and feed rate are critical parameters that should be set for the best results. Conventional surface roughness can range from Ra 0.8 to 1.6 µm, although this can vary depending on the tooling and processing material used to produce the microstructure.
Applications:
Taper turning is used primarily to manufacture parts such as Morse tapers, which hold tools to machine spindles, pipe threads, and tapered pins. CNC machines produce highly precise tapers requiring sensitive application standards and specifications.
CNC tapping is a process of cutting internal threads in a workpiece. This operation helps get the proper size of the holes required to make mechanical fasteners and joints. CNC tapping uses a tool that is expected to create threads through holes with great precision and within a short time.
Tapping Parameters:
CNC machines also accurately regulate the tapping process’s speed, feed rate, and depth. Thread tolerances are generally within the range of ± 0.01mm, so the internal threads are of a very high standard. These are programmed into the machine so the threading is done appropriately and equally.
Surface Integrity:
The threaded surface must always be clean and free from any kind of damage simultaneously. Incorrect threading, formation of burrs, and defects are eliminated by proper orientation of the tapping tool and proper cutting conditions. The material used in making tapping tools and lubrication also determines the smoothness and the quality of the thread that has been produced.
Applications:
CNC tapping is widely used in the automobile, aerospace, electronics, and other industries. It produces parts such as machine frames, support plates, gear cases, and more.
Another CNC turning operation is Contouring, which produces different curved shapes on the workpiece. It entails using tool paths programmed to mimic geometric shapes to cut materials. This technique is particularly relevant where sharp changes in gradient and curvature are needed for improved aesthetic and functional characteristics.
Contouring Parameters:
The CNC machine is susceptible to tool path, curvature, and depth of cut. This precision is essential to creating suitable hard-to-mold shapes. Traditionally, contouring tolerances are of the order of ±0.05 mm, which enables one to achieve a high level of conformance to the design.
Surface Integrity:
Quality tools and the highest cutting speed are required for countering work to avoid problems such as tool marks and the non-uniformity of the curved surface.
Applications:
CNC contouring is applied where curves are needed to make shapes, such as aerospace, automobile, and medical sectors.
The cnc threading operation is one in which threads are produced using helical grooves made on a workpiece's cylindrical surface. This process is helpful in the manufacturing of threaded parts with close tolerances and a high degree of accuracy.
Precision Threading:
CNC machines can also produce internal and external threads depending on the size and shape required. The CNC program regulates the threads' pitch, depth, and profile; the tolerance can be as low as plus/minus 0.01 mm. For instance, an ordinary thread size of M10×1.5 (metric thread) can be produced with the same quality, whether the first, second or any other cycle.
Tooling and Cycle Time:
CNC threading involves threading tools and cycle time, which are very important. Carbide inserts are preferred due to their wear resistance and the retention of their cutting-edge features, allowing for efficient, fast cutting and smooth threads.
Applications:
They were used in considerable measure for the manufacture of screws, bolts, and nuts. It is also used in making internal threads in parts such as pipe fittings and valve bodies, where the geometry of the thread is significant in assembly and sealing.
A grooving operation involves cutting a narrow channel or groove in a job material with a carbide-tipped or HSS tool. CNC grooving helps cut special features in the material and is suitable for parts with slots.
Grooving Parameters:
The CNC machine regulates the width, depth, and position of the groove to a very high degree of precision. Depending on the device's use, groove widths are expected to range from 5mm to a few millimeters. Depth control in subsea operations is also precise, as is often the case, to plus or minus 0.2mm. The width of the groove is 0.2 mm, and the groove is as per the design.
Surface Integrity:
While grooving, the surface of the workpiece has to be shielded so as not to be spoiled in any way. Thus, to prevent the formation of a burr and to obtain a smooth surface of the groove, the cutting tool should be kept sharp, and the cutting speed and feed rate should be appropriately selected.
Applications:
CNC Grooving manufactures O-ring seats, snap ring grooves, and other countersunk parts. It is also used to create parts for other CNC operations, such as threading or welding; grooves are necessary for a proper fit.
Knurling is a turning operation in which a pattern is produced on the surface of the workpiece. CNC knurling is crucial in cases where the grip or appearance of the part is an issue since it provides precision.
Pattern Creation:
CNC knurling entails rotating the imprint tool against the workpiece to create several knurls. The CNC program developed for this purpose controls the depth and pitch of the knurling pattern, which is usually between 0.5 mm and 2.0 mm so that the knurl pattern on the handle surface is symmetrical.
Material Considerations:
The material being knurled is also essential in this process. For example, aluminum needs to control tool pressure so that it does not bend, while steel needs slow feed rates to prevent rapid tool wear.
Applications:
CNC knurling is applied in the production of tool handles, fasteners, and knobs, which need a better grip. It is also used in aesthetic functions where the appearance of the knurled pattern is of value in the product. The other advantage of CNC knurling is that it is very accurate and the knurled surface of each part will be like the other.
CNC turning is a versatile process in CNC machining with several benefits. As a pioneer of change and improvement in precision engineering, CNC Yangsen uses the latest advanced technology. With state-of-the-art CNC machines, CNC Yangsen offers accuracy and consistency in a variety of turning processes. Their technology ranges from the simplest facing and straight turning to complex operations such as threading and grooving, enabling the production of components with high-dimensional precision and accuracy.
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