Introduction to CNC Turning(what is plain carbon steel Evelyn)

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Computer numerical control (CNC) turning is a machining process that uses computerized controls to automate the operation of a lathe. CNC turning involves rotating a part while a single point cutting tool removes material to cut and shape the part to precise specifications. CNC turning has revolutionized manufacturing by enabling incredibly accurate and consistent machining for high volume production.
In this comprehensive guide, we’ll cover everything you need to know about CNC turning, including:
- How CNC Turning Works
- CNC Turning Operations
- CNC Turning Machines
- CNC Turning Tools & Equipment
- CNC Turning Software
- Applications of CNC Turning
- Advantages of CNC Turning
- Disadvantages of CNC Turning
Whether you’re new to CNC machining or looking to deepen your knowledge, read on to learn all about this essential manufacturing process.
How CNC Turning Works
CNC turning relies on computer numerical control to automate turning operations on a lathe. The basic process involves rotating the workpiece while the cutting tool feeds into the part along different axes to remove material. Here are the key steps in CNC turning:
1. The operator loads a CAD file into the CNC machine’s computer control system. This file contains the machining instructions and specifications.
2. The workpiece is clamped into the lathe chuck, which rotates the part during cutting. Other workholding fixtures like collets can also hold parts for turning.
3. The turret indexes turning tools into position above the workpiece. Live tooling may also be used.
4. The computer control moves the tools along the X and Z axes to cut the material. The part rotates during this process.
5. Cutting fluid is applied to the interface between the tool’s cutting edge and the workpiece for lubrication and cooling.
6. The specific turning operations are completed according to the CNC program’s code. Hundreds of parts can be machined in a cycle.
7. Once complete, the finished part is unmanned and a new workpiece is loaded for the next cycle.
CNC turning relies on precise programmed instructions to control movement and machining parameters. This level of automation provides consistent results and high production rates.
CNC Turning Operations
There are several fundamental turning operations that can be performed on a CNC turning center:
Facing - A facing operation cuts off material at the very front of the part to create a flat surface. This provides a finished edge and establishes part length.
OD Turning - OD (outside diameter) turning involves cutting the exterior of a cylinder. The tool feeds sideways along the X axis while the part spins. OD turning reduces the diameter and creates the final outer shape.
ID Turning - ID (inside diameter) turning is used to cut the interior diameter of holes and bores. The tool feeds along the Z axis into a rotating part to enlarge and finish an internal feature. A boring bar is typically used for ID turning.
Taper Turning - To cut angled tapers, the turning tool follows a program that coordinates axial and radial interpolation. The tool feeds at an angle into the part as it spins.
Grooving - Grooving operations cut circumferential grooves into the part. The tool feeds straight into the workpiece similar to facing but only removes small amounts of material.
Parting/Cut Off - Parting uses a specially shaped tool to cut entirely through the workpiece and separate finished parts. The cutting tool feeds radially across the part until it cuts through.
Threading - Thread turning operations use tools with threading profiles to cut external and internal screw threads. The tool moves linearly while the chuck rotates.
Drilling - Live tooling enables axial drilling while the part spins. The rotating drill feeds along the Z axis into the face or side of the workpiece. Hole drilling is possible during one setup.
Boring - An internal boring bar with rotating cutting tip enlarges and finishes pre-drilled holes to high tolerances. Boring achieves very precise hole size and surface finish.
Knurling - Special knurling tools roll indentations into the part to create grip-enhancing patterns on handles and fittings. The tool radially feeds into the rotating workpiece.
Understanding the fundamental CNC turning operations is key for programmers and operators. Advanced programs combine various operations to produce complex parts.
CNC Turning Machines
CNC turning centers utilize lathes that have been retrofitted with computer numerical control systems. These machines include a spindle, chuck, turret tool post, axes drives, and programmable control units. Here are some of the main types of CNC lathes:
Vertical Turning Lathes - Vertical turning centers (VTCs) have a vertically oriented spindle and perform both turning and milling. The X, Y, and Z axes offer better access for complex machining.
Horizontal Turning Centers - Horizontal lathes provide traditional turning capabilities. Bar feeders can be added to enable production turning of stock bars.
Chucking Machines - These universal CNC lathes are ideal for medium to high production turning. Multiple axes allow drilling and milling operations.
CNC Screw Machines - Screw machines rapidly produce high volumes of precision turned components like fasteners and automotive parts. The cams have been replaced with CNC control.
Multitasking Turning Centers - Multifunction machines combine turning capabilities with milling, drilling, and other processes for complete machining in one setup.
Many CNC lathes also allow turrets, live tooling, C-axis capabilities, and various workhandling options like bar feeders and gantry loaders for automated production.
CNC Turning Tools & Equipment
In addition to the CNC turning machine itself, various tools, accessories, and equipment are needed for turning operations:
Cutting Tools - Turning tools like indexable carbide inserts, HSS bits, and CBN inserts must be optimized for the workpiece material. Proper tool geometry and coatings improve tool life and productivity.
Tool Holders - Standard tool holders properly present and orient inserts to the workpiece. Common styles include ISO, CAT, Kennametal, and HSK. Boring bars, inserts, and tool bits must also be held rigidly.
Chucks - 3-jaw self-centering chucks are standard for holding round workpieces. Specialty chucks like collet chucks or vise jaws expand workholding options.
Tool Turret - The turret holds multiple tools and can automatically index to present different turning tools to the spindle for expedited processing without manual changeover.
Live Tooling - Live tooling like driven tools enables CNC lathes to perform milling and drilling in the same setup as turning operations.
CNC Software - CAM programs convert CAD models into toolpaths. Conversational programming can also directly command some CNC turning machines.
Coolant Systems - Coolant nozzles apply lubricating and cooling fluids to the cutting interface for improved tool life, surface finishes, and chip control.
Safety Equipment - Enclosures, barriers, interlocks, and E-stops safeguard operators from rotating parts and moving equipment around the CNC turning center.
Metrology Instruments - Inspection tools like calipers, micrometers, optical comparators, and CMMs verify the accuracy and tolerances of turned parts.
Bar Feeders - Bar feeders automatically supply and feed bar stock into CNC lathes to enable unattended production turning.
Overall, proper CNC turning equipment is necessary for safe, accurate, and efficient machining. The specific tools used depend on the type of turning operations required.
CNC Turning Software
Computer control is the defining feature of CNC turning machines. Specialized CNC software converts CAD models into machine code that provides instructions for the turning process. Here are the main types of CNC turning software:
CAD/CAM Software - Computer-aided manufacturing (CAM) software uses the CAD model to generate toolpaths for the target machine. Common solutions include Mastercam, SolidCAM, EdgeCAM, and Fusion 360.
G-Code - The CAM program post-processes toolpath data into g-code, a standard numerical control programming language that CNC machines understand. G-code dictates coordinates, feed rates, tool selections, and other turning parameters.
Conversational Controls - Some CNC lathes feature conversational, menu-driven controls that simplify programming. Common on lower cost machines, this allows operating without CAM software.
Machine Control Software - Proprietary machine control software acts as the operating system for the CNC lathe. Fanuc, Siemens, and Haas are major suppliers of machine control software.
Direct Computer Controls - DCC lathes connect directly to a desktop computer running CAM software. Toolpaths can be simulated and refined before transferring directly to the machine.
The right CNC software allows precise programmed control over the turning process. Advanced software also enables simulation, tool management, and other programming features.
Applications of CNC Turning
CNC turning is applied in virtually every industry that manufactures round metal parts. The technology can be found anywhere from small job shops to large-scale production environments. Here are some of the most common applications of CNC turning:
Automotive - CNC lathes produce high volume automotive components like axles, drive shafts, pulleys, engine valves, and transmission parts.
Aerospace - Aircraft parts like hydraulic fittings, bushings, nozzles, and engine mounts are often machined on CNC lathes. Stainless steel and titanium are commonly turned.
Medical - Surgical instruments, implants, dental parts, and other medical components with small complex shapes benefit from precision CNC turning.
Firearms - Gun parts including barrels, cylinders, chambers, and muzzle brakes can all be produced by CNC turning operations.
Robotics & Automation - Robotic arms, actuators, gears, shafts, and other robotic components are manufactured on CNC lathes.
Fluid Handling - Valves, fittings, nozzles, couplings, and pump housings often start as raw stock turned on a CNC lathe.
Mining & Energy - Turning produces parts for pumps, compressors, turbines, blowers, drill bits, and other rugged heavy machinery used in these industries.
Plumbing & Hardware - Faucets, conduit, fasteners, couplings, and pipe fittings are all commonly machined parts from CNC turning centers.
Many other industries rely on precision CNC turned parts. The technology produces physical, dimensional, and surface finish accuracies difficult to achieve manually.
Advantages of CNC Turning
Here are some of the primary benefits that CNC turning offers over manual turning methods:
Precision - CNC ensures incredibly precise dimensional tolerances and surface finishes. Parts can be held to within .0005 inches routinely.
Accuracy - Turning operations are extremely accurate and repeatable thanks to automated control. Human errors are eliminated.
Productivity - CNC turning machines produce completed parts unsupervised at high volumes in short cycle times.
Efficiency - Minimal setup, quick changeover, and tool handling improves efficiency over manual processes.
Complexity - CNC enables turning intricate contours, cross holes, internal bores, and other complex geometries.
Consistency - Automated programmed control ensures each part meets specifications without deviations.
Flexibility - Quick change tooling and programming changes accommodate various parts on the same machine.
Reliability - CNC turning produces reliable components thanks to precise control, tooling, and skilled operators.
In summary, CNC turning offers considerable advantages in precision, flexibility, efficiency, and overall capabilities compared to manual turning methods.
Disadvantages of CNC Turning
However, there are some potential downsides associated with CNC turning:
Investment Costs - CNC lathes carry higher initial purchase and setup costs than manual machines. Additional tooling and software add cost.
Programming - While reducing labor, CNC requires part programming expertise and CAM software proficiency.
Training - Extensive training is needed for preparing CNC programs, operating machines, and troubleshooting.
Maintenance - Preventative maintenance and skilled technicians are mandatory to keep CNC machines operating.
Lower Flexibility - CNC turning centers are typically dedicated to high volume production of specific parts.
Process Planning - More upfront process planning is required to choose tooling, workholding, and machining operations.
Supporting Infrastructure - CNC may require upgrades to electrical, dust collection, cooling systems, and material handling.
Despite the disadvantages, CNC turning remains the most efficient method for producing precision turned components at high volumes. For short runs or very large parts, manual turning may be better suited.
From basic operating principles to programming to tooling and applications, CNC turning encompasses many facets. Mastering CNC machining fundamentals provides the knowledge to apply turning technology for manufacturing high-quality precision components.
Combining automated programmable control with high rigidity machine construction allows CNC turning to uphold very tight tolerances with excellent surface finishes. Productivity and consistency also make CNC the go-to solution for cost-effective turned part production.
The benefits of CNC turning make it the leading machining process for manufacturing industries worldwide. While requiring some additional skills, its precision, efficiency, and automation provide major advantages over manual turning techniques. For rapidly fabricating repetitive round metal parts, CNC turning delivers the technology and capabilities for success. CNC Milling