Introduction to CNC Turning(looking for machine shop work Erin)

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CNC (Computer Numerical Control) turning is a machining process used to create rotational parts by removing material from a cylindrical workpiece. The workpiece is held in a chuck and rotated against a cutting tool that machine away excess material to create the desired shape. CNC turning allows for highly accurate and repeatable machining of complex geometric features.
CNC turning machines, also known as lathes, have evolved significantly from the basic engine lathes used for decades in machine shops. Modern CNC lathes are highly sophisticated pieces of equipment that can achieve extremely tight tolerances and create complex parts unattainable with manual machines. They are commonly used across many industries including automotive, aerospace, medical, and more.
How CNC Turning Works
CNC lathes utilize precisely controlled tools that follow programmed paths to shape raw material into finished parts. Here is an overview of the CNC turning process:
- The workpiece, typically a cylinder of metal, plastic, or other material, is loaded into a chuck which clamps it in place. The chuck is mounted to a spindle which rotates the workpiece.
- The CNC control system moves the cutting tool, which is held by the tool post, into position. Common tools used are turning, facing, and boring tools.
- As the workpiece spindle rotates, the cutting tool feeds towards it along the X and Z axes. These movements are very precise and controlled by the CNC program.
- When the tool makes contact with the rotating workpiece, it begins to remove material. By coordinating the motions of the tool, spindle, and tool post slides, complex shapes can be machined.
- The tool follows the programmed path, whether linear or contours, to cut the desired dimensions. Multiple tools may be automatically changed to complete different operations.
- Coolant is flushed over the work area to control chip formation and temperature. The chips of swarf are evacuated by the chip conveyor.
- Once complete, the finished part is unloaded. Secondary operations like milling, drilling, or tapping can then be completed on machining centers.
CNC Turning Capabilities
Modern CNC lathes offer a vast range of capabilities that far surpass manual machines:
- Exceptionally tight tolerances down to microns or thousandths of an inch.
- Ability to machine hardened metals and exotic alloys that cannot be cut manually.
- Multi-axis control for complex angled and contouring cuts.
- Live tooling for milling, drilling, and boring without unloading the part.
- Automated tool changes for uninterrupted production.
- Rapid traverse rates for high efficiency.
- Powerful spindles up to 15,000 RPM for cutting-edge materials.
- Part handling systems for automated loading/unloading.
- In-process gauging for closed-loop size control.
- Integration of bar feeders to enable production turning of bar stock.
- Multi-tasking capabilities combining turning and milling in one setup.
Today's CNC lathes offer many solutions to improve productivity and part quality, allowing machinists to work smarter and complete jobs faster.
CNC Turning Process Steps
While exact steps can vary between different machines, here is a general sequence for CNC turning:
1. Program Creation - The desired part shape and dimensions are modeled virtually using CAD software. CAM software then generates the CNC code toolpaths the machine will follow.
2. Setup - The workpiece is loaded into the chuck and excess material is indicated away. The tools needed for the operations are loaded into the turret/tool changer.
3. Simulation - Optional simulation software can be used to visualize the entire machining process and detect any possible errors.
4. Job Start - The program is loaded and the job is started. The tool changer loads the first required tool into the spindle.
5. Rough Cutting - Large depths of cut are taken by the roughing tool to efficiently remove the bulk of material.
6. Finish Cutting - Lighter finishing cuts achieve the final dimensions and surface finish. Multiple tools may perform different operations.
7. Part Completion - When the program completes, the finished part is unloaded from the machine. Further post-processing like deburring may be required.
8. Inspection - The part is measured to ensure it meets specifications. On-machine probes make this easier.
9. Part Removal - The finished workpieces are removed from the machine area. The NC program can be repeated for a production run.
CNC Turning Equipment
CNC turning centers have several main components that work together to precisely machine parts. Here are the key pieces of equipment in a CNC turning cell:
- Machine Frame - Provides rigidity and dampens vibration. Common frame styles are bed, box-way, and cast iron.
- Spindle - The spindle holds and rotates the workpiece. Higher horsepower and torque enable larger cuts.
- Chuck - Clamps and locates the workpiece to the spindle. May be 3, 4, or 6 jaw designs.
- Tool Post - Holds the cutting tools rigidly. May be operated manually or automatically via servomotors.
- Tool Changer - Automatically changes tools from a magazine to increase flexibility.
- Turret - A programmable, multi-station tool post for carrying multiple tools.
- Tailstock - Supports the free end of long workpieces for better stability.
- Ballscrews - Precise ballscrews transform rotary motion into linear motion for axes slides.
- Guideways - Linear roller or box ways provide low-friction slides for the axes.
- Control System - The CNC controls coordinate all machine movement and functions.
- Chip Conveyor - Removes the debris coils during cutting for a clean work area.
- Coolant System - Floods the cutting area with coolant to regulate temperature.
Advantages of CNC Turning
Here are some of the main benefits that CNC turning offers over manual turning:
- Greater accuracy and consistency. CNC machines can hold extremely tight tolerances.
- Faster cycle times. CNC turning is much more efficient than manual operation.
- Ability to produce complex parts. CNC allows intricate profiles not possible manually.
- Less skilled labor required. The CNC control reduces the need for specialized operators.
- Untended operation. CNC runs 24/7 with lights out production.
- Quick changeover between jobs. Change programs rather than mechanical setups.
- Safer working environment. CNC eliminates exposure to strenuous labor.
- Reduced scrap and mistakes. CNC prevents errors and ensures quality.
- Overall cost reduction. The advantages ultimately lower total production costs.
CNC turning continues to evolve and increase its capabilities. When equipped with the latest technology, CNC turned parts can be produced with enhanced precision, efficiency, and complexity. Combining CNC with automation options like bar feeders and part handling can create nearly unmanned production cells. The computer numerical control of CNC turning will ensure it remains a primary manufacturing process for automating the creation of rotational parts. CNC Milling CNC Machining