What is a Turning Operation in CNC Machining?(g01 g-code Reginald)
- source:YESCOM CNC Machining
In CNC (Computer Numerical Control) turning, the process is automated via commands from a computer program that controls the machine tool. CNC allows for precise control over the machining parameters and repeatability. Modern CNC lathes are highly versatile and are capable of performing a variety of turning operations beyond just cylindrical shapes.
How Does Turning Work?
The workpiece is held and rotated by the headstock chuck or collet while the cutting tool is stationary. As the workpiece rotates, the tool is slowly fed towards it along the X-axis, cutting away material to form the desired diameter. The depth of cut is controlled by moving the tool along the Z-axis.
Common types of turning operations include:
- Facing - Machining the end surface of a cylindrical workpiece flat and perpendicular to the center axis. This is done before further operations.
- O.D. (Outside Diameter) Turning - Reducing the outer diameter of a cylindrical workpiece. This can produce straight diameters, tapers, grooves, undercuts, and contours.
- I.D. (Inside Diameter) Turning - Machining the inner bore of a cylindrical workpiece using small boring bars. This allows creating precise holes and internal shapes.
- Parting/Cutoff - Using a specially shaped tool to cut off a completed workpiece from the excess bar stock it was machined from.
- Grooving/Profiling - Cutting grooves, threads, and complex profiles along the outside or inside diameters. Special shaped cutters are used for grooving and threading.
The Main Components of a CNC Lathe
- Headstock - Houses the spindle which grips the workpiece and rotates it. Various workholding methods can be used including chucks and collets. The spindle is driven by an electric motor and a gear reduction unit to achieve the required turning speeds and torque.
- Tailstock - Located opposite the headstock and allows inserting dead center, live centers, drills or tools for supporting the free end of the workpiece during turning operations. It can be adjusted and locked along the bed ways.
- Tool turret - An indexable turret that can hold multiple cutting tools, drills and inserts for automatically changing between them during the machining sequence. The tools are selected under CNC program control.
- Tool post - A rigid post for holding a single cutting tool in fixed position. Manual tool changes are needed with a fixed tool post.
- Bed - Provides the foundation for all the components. Typically made from cast iron to dampen vibrations and maximize rigidity. The headstock, tailstock and tool post are mounted on the bed.
- Leadscrew - Rotates to move the cross slide and cutting tool along the longitudinal axis for feeding during turning. The leadscrew pitch determines the distance travelled per revolution.
- Guide ways - Hardened and precision ground V and flat ways along which the tailstock and cross slides move. Ball type linear guide ways are also commonly used on modern CNC lathes.
- Chip pan - Collects the machined chips and swarf falling off the workpiece and tools. Located under the bed.
- Coolant system - Provides cutting fluids and coolants to the turning operation for lubricating, cooling, and flushing away chips.
- Control panel - Allows the operator to control the machine, set speeds, feeds and depths of cut. On CNC lathes this panel allows programming, editing and running part programs.
- Enclosure - The sturdy metal housing that covers and protects the machine components from chips, coolants and other workshop debris.
Common Features of a CNC Lathe
- Programmable control using G-code part programs that are either written manually or using CAM software. Allows creating intricate part features through CNC automation.
- Powerful main drive spindles with high torque and a wide speed range for handling various materials and diameters.
- Rigid machine construction including heavy castings, precision ballscrews, and linear guideways for vibration resistance when turning.
- Automatic tool changer turrets with indexing capability. Allows changing tools automatically under program control for increased productivity.
- Backlash eliminators that counter lost motion in the leadscrewnut interface. This enhances precision during CNC operation.
- Constant surface speed control that maintains optimum cutting speed by varying spindle rpm as the diameter reduces.
- Rapid traverse on linear axes for quickly positioning the tool. Up to 20 m/min rapid on high end machine models.
- Flood coolant system with nozzles for applying high pressure cutting fluids to the tool and workpiece interface.
- Programmable tailstock for automated repositioning. Maintains precision and allows complete machining in one setup.
- Power chucks and collet systems for quick and reliable workholding. Hydraulic and pneumatic chucks allow high grip force.
- Manual pulse generator. Allows precisely indexing the turret or spindle during setup or test runs.
- Automatic tool presetter. Measures tool length and breakage offline to minimize setup time.
- Chip conveyor and bucket. Safely removes chips without need for manual intervention.
- Safety interlocks and fencing to prevent injuries and unauthorized access.
By harnessing all these features under coordinated CNC control, modern turning centers can machine complex components to high accuracy and surface finish in a single setup. Precision and automation make CNC turning a very versatile and productive process. CNC Milling CNC Machining