Difference between CNC turning and CNC milling
CNC turning and CNC milling are two common machining processes used in manufacturing industries to shape and manipulate various materials. While both processes involve the use of computer numerical control (CNC) machines, they differ in terms of the type of motion and tools used. Here's a breakdown of the main differences between CNC turning and CNC milling:
Principle of Operation:
CNC Turning: In turning, the workpiece rotates while a cutting tool remains stationary or moves along the workpiece. The cutting tool removes material from the workpiece to achieve the desired shape. This process is typically used to create cylindrical or conical shapes like shafts, rods, and pipes.
CNC Milling: In milling, the cutting tool rotates and moves along multiple axes, while the workpiece remains stationary. The cutting tool removes material from the workpiece by making various types of cutting motions, such as plunging, drilling, or side-to-side movements. Milling is suitable for creating a wide range of complex shapes, including flat surfaces, slots, and contours.
Tooling:
CNC Turning: Turning uses single-point cutting tools, such as lathe tools, which have a single cutting edge. These tools are mounted on the tool turret or tool post of the CNC lathe and can be adjusted to cut the desired shape. The cutting tools primarily remove material by shearing or scraping the workpiece.
CNC Milling: Milling involves the use of multi-point cutting tools, such as end mills, which have multiple cutting edges. These tools are typically held in a rotating tool holder or spindle and can move in various directions simultaneously. Milling tools remove material through a combination of cutting and grinding actions.
Motion and Axes:
CNC Turning: Turning machines typically have two main axes: the X-axis, which represents the radial movement of the cutting tool, and the Z-axis, which represents the axial movement along the length of the workpiece. Some advanced turning machines may have additional axes for increased flexibility.
CNC Milling: Milling machines can have multiple axes, often referred to as X, Y, and Z axes. The X-axis represents the horizontal movement of the cutting tool, the Y-axis represents the vertical movement, and the Z-axis represents the depth-wise movement. Additionally, advanced milling machines may have rotary axes (A, B, or C) for rotating the workpiece or the cutting tool.
Geometries and Applications:
CNC Turning: Turning is suitable for producing symmetrical round or cylindrical parts, such as shafts, bushings, and rings. It is also used for facing, tapering, threading, and creating features like grooves and chamfers on the workpiece.
CNC Milling: Milling is capable of producing a wide range of shapes, including flat surfaces, contours, pockets, slots, and complex 3D geometries. It is used for creating parts such as molds, dies, prototypes, and intricate components used in industries like automotive, aerospace, and electronics.
Workpiece Orientation:
CNC Turning: In turning, the workpiece is held in a chuck or collet and rotates around its axis. The cutting tool is brought into contact with the rotating workpiece to remove material and shape it. Turning is suitable for producing axisymmetric parts.
CNC Milling: In milling, the workpiece is typically secured on a worktable or fixture in a stationary position. The cutting tool moves in different directions to cut into the workpiece from various angles. Milling allows for the production of non-axisymmetric parts and complex geometries.
Material Removal Rate:
CNC Turning: Turning generally has a higher material removal rate compared to milling when it comes to cylindrical or conical workpieces. The continuous rotation of the workpiece allows for efficient and consistent material removal along the length of the part.
CNC Milling: Milling can have a higher material removal rate for flat surfaces or when removing material from multiple sides simultaneously. The multi-point cutting action and the ability to use high-speed cutting tools enable faster material removal in milling.
Set-up Time and Complexity:
CNC Turning: Setting up a turning operation is often simpler compared to milling. The workholding requirements are relatively straightforward, and the process generally involves mounting the workpiece in a chuck or collet and aligning the cutting tool. The programming for turning is also typically less complex.
CNC Milling: Milling setups can be more involved and time-consuming due to the need for precise workpiece fixturing and alignment. The workholding devices must securely hold the workpiece in place during the multi-directional cutting movements. Programming milling operations can be more complex, especially for intricate geometries and multi-axis movements.
Surface Finish:
CNC Turning: Turning tends to produce smoother surface finishes on cylindrical parts due to the continuous rotational motion of the workpiece. The cutting tool's shearing action generates less vibration, resulting in improved surface quality.
CNC Milling: Milling can produce a variety of surface finishes, ranging from rough to highly smooth, depending on factors such as the cutting tool's geometry, feed rate, and spindle speed. Achieving a desired surface finish may require additional finishing operations or the use of specific milling techniques.
Cost Considerations:
CNC Turning: Turning operations are often more cost-effective for producing cylindrical parts due to the simplicity of the setup, tooling requirements, and shorter machining times compared to milling.
CNC Milling: Milling can be cost-effective for producing complex parts with intricate features and non-axisymmetric geometries. While the setup and programming may be more involved, milling's versatility and ability to create a wide range of shapes make it suitable for various applications.
Overall, while both CNC turning and CNC milling are machining processes that utilize computer-controlled machines, they differ in terms of the workpiece and tool motions involved, as well as the types of shapes they can produce. The choice between turning and milling depends on the specific requirements of the part being produced, such as its geometry, size, material, and tolerances.
