What is CNC Turning?(strength to weight ratio Liz)

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CNC (Computer Numerical Control) turning is a machining process used to produce cylindrical parts on a CNC lathe. It is one of the most common CNC machining processes and is capable of producing parts with high precision and consistency.
How CNC Turning Works
CNC turning utilizes a cutting tool called an insert that is held rigidly in a tool holder that is mounted on a turret. The turret moves the tool in and out radially to cut diameters, while the workpiece spins at high speeds creating the turning motion. The cutting forces are absorbed into the rigid frame of the machine, providing a stable platform for accurate machining.
Here are the main components and functions of a CNC turning center:
- Chuck - Holds the workpiece while allowing it to rotate. Different types of chucks include 3-jaw, 4-jaw, collet chucks and more.
- Turret - Holds multiple tool holders and indexes them as needed for different turning operations. The turret provides quick tool changes.
- Tool Holders - Hold inserts or turning tools rigidly for cutting. Popular styles are VDI, CAT, ISO, and CAPTO.
- Cutting Tools/Inserts - Specially designed inserts made from hard materials like carbide are used to cut material. Indexable inserts allow for quick tool changes.
- Spindle - Rotates the workpiece at high RPMs. The spindle is driven by an electric motor and can achieve a wide range of turning speeds.
- Coolant System - High pressure coolant is applied to the cutting area to cool the process and wash away chips. This improves tool life and part finish.
- Axis Controls - The X (cross) and Z (longitudinal) axes position the turret and tailstock in relation to the rotating workpiece for feeding and cutting operations.
- Control Panel - The CNC control stores cutting programs and allows the operator to edit settings and run programs.
- Bed - Provides a rigid frame to absorb cutting forces and vibration. This allows for tight tolerances.
Types of CNC Turning
There are several different types of turning operations that can be performed on a CNC lathe:

- O.D. (Outside Diameter) Turning: The most common operation. The insert faces and cuts the external surface rotating with the chuck. Used to reduce the diameter to a specific dimension.
- I.D. (Internal Diameter) Boring: A boring bar held rigidly in the tool holder is fed into a hole to enlarge the hole to a required size.
- Facing: A square cutting insert faces off the end of a part. This creates a flat reference surface.
- Grooving: A specially shaped insert cuts a groove in the diameter of a part. Used to cut grooves for O-rings and other applications.
- Parting/Cutoff: A narrow insert is fed through the diameter of a part to cut it off from the stock held in the chuck.
- Threading: The coordinates move the tool in a precise pattern to cut screw threads on the part. Multiple passes are made to cut the full thread depth.
- Taper Turning: The diameter is turned on a taper by pivoting the turret at an angle or offsetting the tailstock.
- Profile Turning: Complex irregular shapes can be cut by interpolating the X and Z axes movements. CAD/CAM software is required to program the profile.
Benefits of CNC Turning
There are many benefits to using CNC turning versus manual turning:
- Higher Production Rates - CNC turning is much faster than manual operations. Complex parts can be machined in minutes.
- Better Accuracy and Repeatability - Modern CNC machines provide tolerances down to 0.0005 inches for dimension and 0.1 degree for angles.
- Lower Labor Costs - One programmer and operator can run multiple CNC machines. Less skilled labor is required.
- Automation - CNC turning centers can run unattended for hours. Automatic tool changes and part handling systems are available.
- Reduced Setup Time - Machining programs can be called up instantly and tooling setups can be stored. No manual indicating is required.
- Complex Geometries - Concave and convex forms can be produced using CNC interpolation turning techniques.
- Improved Surface Finish - Advanced tooling and rigid machine construction allow for fine surface finishes.
- Quick Changeover - Changing over jobs is fast with quick change tooling, preset offsets, and stored programs.
Ideal Applications for CNC Turning
CNC turning is ideal for producing parts that have geometric features like:
- Round O.D. shapes and diameters
- Eccentric diameters and boring
- Grooves, undercuts and threads
- Contoured end shapes and faces
- Tapered surfaces
- Precision holes and bores
Common examples of parts made by CNC turning include:
- Engine valves
- Pump shafts
- Fitting spigots
- Pistons
- Pulleys
- Rollers
- Bushings
- Wheels
- Nozzles
- Bolts
CNC turning is very effective for high mix, low to medium volume production. One-off prototypes and small batch jobs can be turned cost effectively. For very high volume production over 50,000 parts, dedicated cam operated screw machines are more suitable.
Selecting the Right CNC Lathe
When selecting a CNC lathe, key factors to consider are:
- Swing Over Bed - The max diameter that will fit over the bed. Ranges from 8” to 25” typically.
- Distance Between Centers - The max part length that can be turned. Ranges from 12” to over 60”.
- Chuck Size - 6”, 8” and 10” chucks are common. May be 3-jaw or 4-jaw types.
- Spindle Power - Engine power from 3 HP to 20+ HP. Higher power allows heavier cuts.
- Spindle Speed - Ranges from 2,000 to 6,000 RPM. High speeds needed for small diameters.
- Rapid Traverse Rate - Movement of turret/tailstock during non-cutting. Ranges from 500-1000 IPM.
- Tool Capacity - The number of tool positions on the turret. Larger for more complex work.
- Live Tooling - Allows end working like drilling and tapping while the part turns.
- Automation - Robot load/unload, bar feeders, gantry loaders, etc.
Leading CNC Lathe Brands
Major machine tool manufacturers producing CNC lathes today include:
- Haas
- Okuma
- Mazak
- DMG Mori
- Doosan
- Daewoo
- Hurco
- Hardinge
CNC turning machines vary greatly in size, power and capabilities to fit job shop, small batch, and production machining requirements. Working with a qualified machine tool distributor is highly recommended to help select the right CNC lathe for your business.
The CNC turning process continues to evolve with advanced computer controls, precision components, powerful software and integrated automation. This makes modern CNC turning machines highly productive, accurate and flexible tools for producing precision turned parts. CNC Milling CNC Machining