What is CNC Turning?(titanium nitride coating Frederica)
- source:WEINBERG CNC Machining
How Does CNC Turning Work?
In CNC turning, the workpiece is held in a chuck or between centers and rotated against a stationary cutting tool. The cutting tool moves in linear or circular motions controlled by CNC to remove material from the workpiece and create the desired features and dimensions.
The CNC turning process utilizes a CNC lathe that consists of the following key components:
- Machine bed: Provides a rigid frame to support all machine components. Made of cast iron or welded steel construction.
- Headstock: Holds the spindle which spins the workpiece. Powered by an electric motor with variable speed control.
- Chuck: Grips and centers the workpiece for turning operations. Can be a 3-jaw or 4-jaw chuck.
- Tailstock: Supports the free end of the workpiece with a center or live center. Can be adjusted to accommodate different length workpieces.
- Tool turret: Holds multiple cutting tools and indexes them into the cutting position. Allows for automatic tool changes.
- Tool post: Holds a single cutting tool rigidly for turning operations. Manual tool changes required.
- CNC control system: Controls all machine movements and functions via programmed commands. Converts CNC code into electrical signals to drive machine axes.
The operator loads the workpiece into the chuck and enters the CNC program into the control system. The CNC code defines the machining sequence, tool paths, cutting speeds, feed rates, depth of cuts, and other parameters.
As the program runs, the turret indexes tools as needed and the control system maneuvers the tool along the programmed axes to cut the workpiece. Coolant is applied to control heat and flush away metal chips. Once complete, the finished part is unloaded.
Key CNC Turning Operations
CNC turning centers can perform various turning operations to produce precision parts. Common CNC turning operations include:
- Facing: Machining the face of the workpiece to provide a flat reference surface.
- OD (Outside Diameter) Turning: Machining the external surface of the workpiece to reduce diameter and create the required OD.
- ID (Inside Diameter) Turning: Machining internal bores and holes to precise diameters and forms.
- Taper Turning: Machining external or internal tapers using the compound slide.
- Grooving: Cutting grooves of various widths and depths in the OD or face.
- Threading: Single-point or tapping to cut external and internal threads.
- Drilling: Drilling center holes or cross holes in the workpiece.
- Boring: Enlarging and smoothing existing holes to accurate sizes.
- Knurling: Squeezing material to form cross-hatched patterns on the OD to create a textured gripping surface.
- Parting/Cutoff: Cutting workpieces from bar stock or parting finished parts off.
Benefits of CNC Turning
CNC turning offers many benefits over manual turning:
- Higher Accuracy and Repeatability: CNC ensures precision cutting to tight tolerances repeatedly. Reduces scrap rates.
- Faster Cycle Times: CNC performs faster, more efficient machining than manual methods.
- Improved Surface Finishes: Programmable speeds/feeds and rigid setups provide better surface finishes.
- Lower Operator Labor: CNC is highly automated so less operator time is required. One operator can run multiple machines.
- Reduced Tooling Costs: Tool changes are quick and easy so a single tool can handle multiple operations.
- Increased Complexity: CNC can produce complex profiles unachievable manually. Complete parts in single setups.
- Safer Operation: Removes operator from direct contact with cutting. Reduces manual handling of parts.
- Reliable and Consistent: CNC eliminates variability between operators and manual processes.
- Flexible Production: Quick changeovers between jobs. CNC programs can be stored and reused.
When to Use CNC Turning
CNC turning is ideal for producing parts that require:
- High-volume production with consistency and fast cycle times
- Precision dimensional accuracy and tight tolerances
- Excellent surface finish quality
- Complex profiles and contours
- Parts not suitable for mass production by other processes
Common CNC Turned Parts
CNC lathes are commonly used to machine parts such as:
- Engine components (pistons, camshafts, crankshafts)
- Drive shafts and couplings
- Rollers and pulleys
- Gears and sprockets
- Axles and spindles
- Wheels and hubs
- Fasteners and screws
- Valves, fittings, and nozzles
- Sleeves and bushings
- Automotive and aerospace components
- And many others!
CNC Turning Materials
CNC lathes can machine a wide range of materials, including:
- Titanium alloys
- Stainless steel alloys
- Carbon and alloy steels
- Aluminum alloys
- Nickel-based alloys
- Cobalt-chromium alloys
- Copper alloys (brass, bronze)
- Precious metals (gold, silver, platinum)
- Plastics (nylon, acetal, PTFE)
The stiff construction of CNC lathes enables turning of exotic alloys and hard materials like Inconel that can be challenging on manual machines.
CNC Turning Equipment Needed
To perform CNC turning, the basic equipment needs are:
- CNC Turning Center: Horizontal or vertical CNC lathe with appropriate capacity (swing and distance between centers).
- CNC Control System: For programming jobs and executing code to drive machine.
- Tooling: Cutter inserts, tool holders, boring bars, drills, taps, etc. Plus, tool storage.
- Workholding: Chucks, collet systems, vises, fixtures, centers, faceplates, etc.
- Measuring: Calipers, micrometers, indicators, probes and other inspection tools.
- Coolant System: Pumps, filtration units, nozzles and fluid.
- Computer: For programming, with CAM software to generate CNC code.
- Cutting Fluids and Lubricants: For machining operations and machine maintenance.
- Safety Equipment: Safety glasses, shields, gloves, etc. to protect the operator.
By utilizing this essential CNC turning equipment, shops can effectively and safely produce precision turned parts to meet their manufacturing needs. Proper setup and maintenance helps optimize production and part quality.
CNC Turning Cost Considerations
The total costs to implement CNC turning include:
- Machine Tool Cost: Horizontal or vertical CNC lathe purchase price. Scales with size, features, and capabilities.
- Setup and Installation: Facility preparation, rigging, utilities, disposal of old equipment, etc.
- Tooling and Fixtures: Cutting tools, workholding, tool storage, automation. Recurring cost.
- Training: Educating programmers and machine operators. Ongoing as needed.
- CAM Software: For generating optimal CNC code. Upfront and annual licensing cost.
- Maintenance: Regular upkeep and service on machine tools and components.
- Consumables: Cutting tool inserts/bits, lubricants, coolants, shop supplies.
- Operations: Labor, material, overhead, quality checks, equipment downtime.
- Work Space: Required floor space for equipment, storage, operations.
Weighing these expenses against the benefits of CNC turning productivity will inform the ideal investment level.
CNC Turning vs. Manual Turning
Here is a comparison between CNC turning and manual turning:
- Accuracy and Repeatability: CNC is vastly superior due to precision programmed tool paths. Reduce scrap with CNC.
- Complexity: CNC can produce parts impossible on manual lathes. Consolidate operations into one CNC setup.
- Speed: CNC provides much faster cycle times. Make more parts per hour with CNC.
- Labor: CNC needs fewer, less skilled operators. One person can run multiple machines.
- Automation: CNC allows easy integration of automation like bar feeders, gantry loaders, and robotics.
- Flexibility: CNC allows fast changeovers between different jobs. Store programs for future use.
- Safely: CNC is inherently safer by removing direct operator contact with cutting.
- Training: CNC requires programmers to know CAD/CAM. More skills development needed.
- Cost: CNC has higher startup cost but pays back long-term with efficiency gains.
While manual turning maintains advantages like being simpler to program and costing less, CNC turning is superior for production environments focused on quality, efficiency and flexibility.
The Future of CNC Turning
CNC turning will continue advancing, with trends like:
- Faster, more capable CNCs: Controls, spindles, axis motors, ballscrews, toolchangers.
- Multi-axis turning: Complex parts finished in one setup via mill-turn machines with B/Y-axis capabilities.
- Smaller batch sizes: Quick-change tooling, automation, and programming enable profitable small orders.
- Increased use of carbide tools over traditional HSS tooling.
- Green machining initiatives: More energy-efficient machine tools and processes. Less waste.
- Monitoring and data-driven optimization via “smart” machine tools.
- Virtual machine simulation to validate programs and maximize machining performance.
- Growth of multi-spindle turning centers over single spindle configurations.
- Increased adoption of robotic automation for material handling and machine tending.
With technology enhancements and innovative techniques, CNC turning will continue driving gains in manufacturing productivity and part quality. The future is bright for this essential machining process! CNC Milling