What is CNC Turning?(corrosion resistant metal Florence)
- source:YESCOM CNC Machining
How CNC Turning Works
CNC turning uses programmable machine tools called CNC lathes. The workpiece is securely clamped into the chuck of the lathe, which rotates at high speeds. The cutting tool is mounted on a turret that can move in multiple axes, allowing for complex geometries to be machined.
The CNC lathe follows commands from a pre-written program that controls all aspects of the machining process. This program specifies coordinates, feed rates, spindle speeds, depth of cut, and other parameters. The program is written in G-code, which the CNC control system interprets to drive the machine.
As the workpiece rotates, the cutting tool approaches it along a programmed path. Different tools can machine the external diameter, internal diameter, faces, grooves, threads, tapers, and more. The turret can automatically change tools as needed to machine complex parts in a single setup.
CNC turning produces parts with excellent dimensional accuracy and repeatability. The automated process also enables faster production rates and lower labor costs compared to manual turning. Highly skilled operators are still required to program, setup, and maintain the equipment.
Applications of CNC Turning
CNC turning is widely used across many industries to produce rotational parts, including:
- Automotive - Engine valves, axles, drive shafts, wheel hubs
- Aerospace - Turbine blades, fuel nozzles, landing gear components
- Medical - Bone screws, surgical instruments, implants
- Industrial - Pump shafts, couplings, compressor rotors
- Consumer goods - Cutlery, dials, fasteners, buttons
Any part with cylindrical features can benefit from CNC turning. It is ideal for high volume production thanks to its speed, precision, and repeatability. One-off prototype parts can also be quickly machined without the lead times of custom tooling.
Advantages of CNC Turning
Here are some of the main advantages of CNC turning:
- High degree of accuracy and repeatability - CNC machines can hold tolerances as tight as 0.001 inch.
- Faster production rates - CNC turning is much faster than manual operations. Complex parts can be completed in minutes.
- Lower labor costs - CNC turning reduces the labor intensity associated with manual turning. One operator can run multiple machines.
- Automated operation - CNC machines run for hours with minimal supervision after initial setup.
- Reduced waste - CNC turning is more precise and has lower scrap rates compared to manual processes.
- Flexibility - Quick changeover between parts is possible by changing the CNC program. No retooling is required.
- Safer working environment - CNC turning minimizes the risks associated with manually operating lathes.
- Consistent quality - The computer control ensures consistent output over long production runs.
- Ability to machine complex geometries - CNC allows intricate curved surfaces and profiles to be machined.
- Simplified production - CNC turning consolidates multiple machining processes into one operation.
The combination of these benefits makes CNC turning ideal for today's advanced manufacturing requirements. The automation and data-driven capabilities allow more output with less labor.
CNC Turning Operations
There are various cutting operations that can be performed on CNC turning centers:
- Facing - Machining the end face of a part
- Turning - Machining the external diameter
- Boring - Enlarging existing holes or machining internal diameters
- Drilling - Creating through holes or blind holes
- Tapping - Cutting internal threads
- Grooving - Cutting external grooves for o-rings, etc.
- Parting - Cutting off a completed part from the excess stock
Multiple operations can be combined in one program to minimize handling and machining time. Canned cycles are used to simplify programming of common hole making operations like tapping, boring, and drilling.
The turret can hold multiple tools and automatically change between them for different operations. Common tool types include boring bars, drills, OD turning inserts, threading tools, and grooving tools. The tailstock can be used to support long workpieces.
CNC turning centers provide very versatile capabilities in one machine. Complex parts can be completely machined in a single setup. Secondary operations like milling, grinding, or honing may still be required depending on the tolerances and surface finishes needed. Programming considerations optimize the machining sequence, tool selection, and other parameters.
Programming for CNC Turning
Creating programs for CNC turning requires familiarity with G-code programming language. While simple turning operations may only require a few lines of code, programming more complex parts involves:
- Defining workpiece origin and coordinate system
- Specifying cutting tools used
- Calculating feeds, speeds, and depth of cuts
- Applying canned cycles for holes and threading
- Optimizing tool paths for best machining sequence
- Adding commands for coolant and chip breaking
Modern CAM software programs greatly simplify CNC turning programming. The machinist imports a CAD model then uses the software tools to add toolpaths, simulate machining, and post process the G-code program. CAM packages include built-in libraries of optimized cutting data.
Even when using CAM, understanding G-code is critical for detecting programming errors and proving out programs. CNC programmers should learn manual programming before relying solely on CAM software.
Setting Up CNC Turning Operations
Proper setup is crucial for accurate CNC turned parts. Key steps in the setup process include:
- Inspecting raw material and machine condition
- Indicating part zero reference point
- Mounting and qualifying cutting tools
- Presetting tool offsets
- Establishing tool change position
- Loading CNC program and selecting necessary offsets
- Setting coolant or cutting fluid type and flow
- Trial cut and inspection prior to production run
During setup, all tools, holders, and workholding devices should be checked for issues that could cause collisions, tool breakage, or scrap parts. Detailed procedures are required to consistently set up machines and qualify that they are ready for production.
In Process Inspection
To verify machining accuracy during longer production runs, periodic inspection should be conducted. Common methods of CNC turning inspection include:
- Statistical process control (SPC) of key dimensions at Control Plan intervals
- Manual checks of size, form, location using hand tools
- Between-part air gauging of size and taper
- Post process validation on a CMM
- Photogrammetry and laser scanning to check dimensions and surface finish
- Automated in-cycle probing integrated on the machine tool
By routinely inspecting parts and measuring key process variables, turning operations can be maintained in control and continuously improved. Data collection also aids in preventive maintenance and capability studies.
Safety with CNC Turning
As with all machine tools, there are safety precautions that must be followed when working with CNC lathes:
- Keep the work area clean and free of clutter
- Ensure proper machine guarding is in place
- Wear appropriate PPE such as safety glasses
- Avoid loose clothing and tie back long hair
- Follow lockout procedures before maintenance
- Use proper techniques for lifting and moving materials
- Ensure chucks and workholding devices are secure
- Never reach into a machine while it is in motion
- Follow manufacturer recommendations for safe speeds and feeds
The automated nature of CNC turning makes it safer than manual turning in some regards. However, complacency around spinning components can lead to injuries. Staying alert and adhering to safety protocols is critical.
Working with CNC turning machines requires specialized skills beyond traditional manual machining. The major training areas include:
- Operating CNC systems, programming pendants, and interfaces
- Interpreting and optimizing G-code programs
- Tool selection, tool mounting, and workholding strategies
- Inspection methods and use of automated probes
- Fixture design principles
- Cutting tool materials and insert geometries
- Machining parameters and cutting formulas
- Basic cutting physics and mechanics
- Precision measurement fundamentals
- Statistical process control (SPC)
- Problem solving and troubleshooting
Both classroom and hands-on training are needed to become proficient at CNC turning. Apprenticeships under experienced programmers also accelerate learning. Continuing education helps machinists stay current as technology evolves.
The Future of CNC Turning
While already a mature process, CNC turning continues advancing. Some emerging innovations include:
- Multi-axis turning combining milling, drilling, and off-center turning
- Twin spindle machines for done-in-one machining
- Bar feeders for automated turning of bar stock
- Integrated automation with robots and part handling systems
- On-machine verification with probes and sensors
- Internet-connected smart machines with predictive maintenance
- Ultra-fast spindles approaching 100,000 RPM
- Micromachining capabilities under 5 micron resolution
- Turn-mill machines combining turning and milling
By incorporating more functionality and intelligence, CNC turning will become even more capable and easier to run. This will allow more components to be completely machined in a single setup. The future is bright for those leveraging CNC turning processes. CNC Milling CNC Machining