Introduction to CNC Turning(rivet design Brady)
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How CNC Turning Works
In CNC turning, the workpiece is held by a chuck or clamped between centers on the headstock. The headstock rotates the part at high speeds while precisely programmed cutting tools held by the tool turret machine away excess material. By precisely controlling the movement and cutting parameters, complex 3D shapes, slots, grooves and contours can be machined into the rotating workpiece.
The motion of the cutting tool is controlled by CNC along multiple axes. The X and Z axes control the position of the cutter perpendicular to the axis of the spindle. The C axis controls the orientation of the cutting tool. This allows angled features like tapers, chamfers and angledgrooves to be machined. The cutting tool can be precisely positioned and fed into the workpiece based on the CNC program.
CNC turning centers provide very accurate and repeatable positioning of the cutter. The program coordinates the rotation of the spindle with the linear and transverse motion of the cutters. This coordination enables the machining of sophisticated solid models generated using CAD software.
Key Benefits of CNC Turning
CNC turning offers several benefits over manual turning on engine lathes:
- Higher productivity: CNC machines can produce parts much faster than manual machining. The optimized tool paths maximize material removal rates.
- Consistent quality: Every part is machined precisely the same. There is no variation from operator fatigue or skill.
- Reduced operation time: CNC automation allows unattended machining. Multiple parts can be machined in a single setup.
- Complex geometries: Intricate shapes and contours can be produced using controlled, multi-axis movement.
- Flexible production: Quick changeover between parts. Minimal setup time enables high mix, low volume production.
- Safer operation: The operator’s exposure to moving parts and cutting tools is minimized.
CNC Turning Capabilities
Modern CNC turning centers offer a wide range of capabilities and complexity:
- 2-axis turning centers: Machine parts requiring rotation and facing/boring operations.
- Live tooling: Allows milling, drilling and slotting without removing the part. Expand capability.
- Y-axis for complex shapes: Offers full control of cutter position perpendicular to spindle axis.
- B-axis for contouring: Adds a tilting tool for angled features and helical interpolation.
- Driven tools: Rotating tools for milling, threading and drilling without a separate spindle.
- Multi-task machines: Combine turning and milling capabilities in one machine.
- Twin spindles: Allow simultaneous machining of both part sides. Reduce cycle times.
- Bar feeders: Automatically feed bar stock into the spindle for high volume production.
Automating the Process
To unleash the full potential of CNC turning, supporting processes must also be automated. This includes:
- Automated workholding: Specialized chucks, collets and fixtures accurately locate and clamp parts. Pallet systems enable quick changeover.
- Tool management: Automatic tool changers switch tools as programmed. Offline monitoring tracks tool life.
- In-process gaging: Probes measure key features to ensure they are in specification, reducing scrap.
- Material handling: Automated systems transfer finished parts out and new bar stock or blanks in.
- Integration with other processes: CNC turned parts can feed directly into grinding or milling machines for complete machining.
Programming CNC Turning
Creating CNC turning programs has gotten much easier. Here are some common methods:
- Manual programming using G-code: The classic method. Requires skilled programmers.
- Conversational programming: Uses shop floor language and graphical interfaces. Simpler but less capable.
- CAM software: Generates optimized toolpaths from CAD models. The most capable but requires skilled operators.
- CAD/CAM integration: Program is created directly within the design software. Streamlines workflow.
No matter how the initial program is created, extensive simulation is done to visualize the machining process before any metal is cut. Powerful simulation catches errors in the program and avoids expensive crashes.
Applications of CNC Turning
CNC turning is ideal for manufacturing rotationally symmetric parts in medium to high volumes. Typical applications include:
- Automotive: Engine valves, pistons, axles, shafts, connectors, fasteners, bearings
- Aerospace: Bushings, spacers, nozzles, fittings
- Medical: Bone screws, surgical instruments, implants
- Construction/agriculture: Pins, shafts, fittings, fasteners
- Fluid handling: Valve bodies, connectors, plumbing fittings
- Transportation: Axles, rail car components, truck/motorcycle parts
For small complex turned parts like orthopedic implants, Swiss-type CNC lathes offer greater precision. Larger heavy duty CNC lathes are used to machine axles, shafts and engine valves.
Summary
CNC turning is a versatile machining process that utilizes automated, precision lathes to efficiently produce accurate cylindrical parts. The combination of fast material removal rates with good dimensional accuracy and surface finish make CNC turning ideal for high volume production. Continued advancement in automation and software enable CNC turning to rapidly machine very complex component geometries. CNC Milling CNC Machining