What is a Turning? An Overview of Turning Operations in CNC Machining(the melting point Dunn)

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Turning is one of the most common and important machining processes used in manufacturing. It involves rotating a workpiece while a single-point cutting tool is fed linearly against it to cut away material. This produces cylindrical shapes and often round-shaped geometries. Turning can create various external and internal features on parts like cylinders, cones, grooves, shoulders, and holes. It is an efficient method for machining axi-symmetric parts that require rotational symmetry.
Turning operations are primarily performed on lathes or turning centers, which are essential machine tools found in any machine shop. Lathes hold the workpiece on a spindle that rotates. As the spindle turns, the cutting tool is fed slowly across the part along its axis of rotation. The linear and rotational movements are precisely controlled to remove material and leave the desired shape, size, and finish. Modern CNC lathes automate the turning process for high precision parts.
Here are some key things to know about turning in CNC machining:
Types of Turning
There are several different types of turning operations:
- Outside diameter (OD) turning - The most common type, this involves turning the external surface of a cylindrical or conical workpiece. The cutting tool shapes the outside diameter (OD).
- Inside diameter (ID) turning - Also called boring, this turns internal surfaces to create bores, holes, grooves, and other ID features. A boring bar is used for ID turning.
- Facing - Machining the end face of a cylindrical part perpendicular to its axis. This creates a flat surface and establishes part length.
- Taper turning - Produces conical or tapered shapes by turning at an angle to the workpiece axis. The cutting tool is set at an angle to the rotational axis.
- Threading - Cutting helical grooves on inner or outer diameters to create screw threads for bolts, nuts, etc. Threading tools have a 60 degree tip angle.
- Grooving/parting - Cutting narrow, groove-like features into the part. Also used to cut complete inner/outer diameters to part off finished parts.
- Form turning - Complex turning operations that use specially shaped cutting tools to produce intricate contours, curves, and non-cylindrical geometries.
Turning Methods
There are two primary methods of turning:
- Conventional turning - Uses a single-point cutting tool held statically in a tool post. Different tools are switched in/out to create features.
- CNC turning - The cutting tool is moved under CNC control. This enables faster production, better precision, and more automation without tool changes. Highly recommended for batch production.
Major Components of a CNC Lathe
CNC lathes contain several key components:
- Headstock - Holds the spindle and spinning workpiece. The spindle is driven by an integral motor. Various chucks and fixtures hold the workpiece.
- Tailstock - Holds tooling for the spindle's far end. Typically used to support long parts with a steady rest or for ID boring bars.
- Tool turret - An indexing toolholder that automatically changes cutting tools as needed for different operations.
- Tool post - Holds a single cutting tool for conventional turning. The tool post may be manually or automatically positioned.
- Carriage - The portion of the lathe that moves along the bed to feed the cutting tool. May have a leadscrew, rack and pinion, or servomotors.
- Bed - Provides the foundation and frame to hold all components. Often includes ways that guide the carriage.
- Control panel - Allows the operator to control the machine's motions and functions. CNC lathes have programmable controls.
- Chip pan/conveyor - Catches and removes cutting debris and chips from machining. Keeps the work area clear.
Tools for Turning
Turning employs single and multi-point cutting tools made from tool steel or carbides:
- Turning tool bit - A removable cutting insert tip with specialized geometry for turning. Carbide inserts are commonly used.
- Boring bar - A long shaft toolholder for internal turning and boring. May be manually fed or power fed.
- Threading tool - Ground cutters shaped specifically for cutting threads.
- Form tool - Custom cutter for complex profiles. May employ CNC grinding.
- Parting/grooving tool - Insert or blade designed for cutting off operations and grooves.
- Tool holders - Hold and position the cutting tools properly. Many styles exist for different applications.
Advantages of Turning
Compared to other machining processes like milling, turning offers several benefits:
- Excellent dimensional accuracy and surface finishes
- Ability to produce axi-symmetric and complex rotational parts
- Lower forces and power requirements than milling
- No excessive tool pressure or deflection
- High material removal rates from cylindrical turning
- Ability to machine internal and external features
- Continuous chip production improves chip control
- Wide range of materials can be turned, including metals, plastics and composites
Turning is ideal for manufacturing common round parts like shafts, bushings, pins, rods, sleeves, disks, and more. It is one of the most cost-effective and efficient methods for machining high precision cylindrical components. With CNC automation, turned parts can be quickly mass produced.
In summary, turning is an essential machining process that rotates cylindrical stock material while a cutter shapes the part. It is performed on lathes and creates external and internal geometries through different turning operations. CNC turning automates the process for high volume production. Turning remains a versatile and important manufacturing method for machining precision round components. CNC Milling