What is CNC Turning?(cnc tips Dwight)

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CNC turning refers to the process of machining cylindrical parts on a computer numerical control (CNC) lathe. It is a subtractive manufacturing process where material is removed from a rotating workpiece to produce the desired shape. CNC turning is an efficient and accurate way to machine complex geometries and tight tolerances out of metal and plastic workpieces.
How Does CNC Turning Work?
In CNC turning, the cutting tool moves while the workpiece is rotated at high speeds. The movements of the tool are controlled precisely by the CNC machine's computer and programming. As the tool feeds into the rotating workpiece, it cuts away material to form the desired dimensions and features.
The basic CNC turning process involves four main stages:
1. Setup - The workpiece is securely clamped in a chuck or fixture on the CNC lathe. The proper cutting tools are loaded into the tool turret. The tool offsets and work coordinates are set.
2. Programming - The part program containing the toolpaths and machining parameters is generated using CAM software and uploaded to the CNC lathe's control.
3. Machining - The machine operator initiates the program run. As the workpiece rotates, the cutting tools follow the programmed contours to machine the features of the part. Multiple tools may be used for roughing, finishing, threading, grooving, etc. Automatic tool changes are executed when needed.
4. Completion - The finished part is unloaded. Quality checks are conducted to ensure specifications are met. Any additional post-processing steps like deburring or polishing may be performed.
CNC Turning Capabilities
Modern CNC lathes offer a vast range of turning capabilities:
- External turning - Producing straight and tapered external diameters, faces, shoulders and other external features. A single point cutting tool is fed horizontally into the workpiece.
- Internal turning - Machining internal bores, grooves, tapers and forms using inserted boring bars fed vertically into a center bore or horizontally into a chucked workpiece.
- Threading - Single or multi-start, internal and external thread cutting using thread turning or tapping attachments.
- Grooving and undercutting - Machining grooves, undercuts and parting off using specially shaped insert tools or forming tools.
- Drilling and boring - Performing center drill, drill, boring and trepanning operations by using rotating tool holders.
- Tapping - Internal thread cutting by synchronizing the spindle speed with the Z-axis feed.
- Knurling - Creating crosshatched patterns or raised gripping surfaces using knurling tools.
- Profile turning - Turning complex irregular shapes through interpolation of multiple CNC axes.
- Eccentric turning - Producing eccentric diameters by manipulating the programmable offset between the part zero and spindle centerline.
CNC Turning Tools
CNC lathes utilize a wide selection of indexable cutting tool inserts and tool holders to accomplish different machining operations:
- Turning inserts - For external turning, facing and boring. Made from carbide, CBN or ceramic.
- Threading inserts - Ground inserts for 60° external or internal threads.
- Grooving/parting inserts - Tall, narrow inserts for grooves, undercuts and parting.
- Boring bars - Internal turning using replaceable boring heads and inserts.
- Drills - For center holes and straight bore machining. Available in many lengths and diameters.
- Taps - For internal thread cutting. Come in tap chucks to fit the spindle.
- Forming tools - For specialty profile turning operations.
- Knurling tools - Roll or cut patterns onto the workpiece surface.
The variety of inserts, holders, and tool geometries allow for optimal performance in each operation. Tool selection depends on the material, depth of cut, desired finish, and features being machined.
CNC Turning Materials
A vast range of materials can be machined using CNC turning processes:
- Metals - Steel, stainless steel, aluminum, brass, titanium, hastelloy, Kovar, and exotic alloys.
- Plastics - ABS, PVC, acrylics, Teflon, nylon, and engineered resins like PEEK and Torlon.
- Composites - Carbon fiber, G10, and other reinforced materials.
- Wood - Hardwoods and manufactured wood composites.
The most commonly turned metals are aluminum and steel alloys.choose from)
Adjustments to the feeds, speeds, tool geometry and toolpath strategies are made to optimize turning in harder exotic alloys, challenging plastics and composite materials. Coolants and pecking cycles also improve more difficult material machining.
Benefits of CNC Turning
There are many advantages to using CNC turning:
- Higher accuracy and tighter tolerances compared to manual turning. Precision down to 0.0001" (0.0025mm) is possible.
- Ability to produce complex geometries and features like threads, tapers and eccentric diameters.
- Quicker changeover between jobs using stored CNC programs. Reduced setup times.
- CNC automation reduces labor costs and reliance on operator skill.
- Increased repeatability between parts. CNC ensures each part matches the program.
- Higher material removal rates are possible for increased productivity.
- Intricate components can be net-shaped, minimizing the need for post-turning processing.
- Safer working environment compared to manual lathes. The operator manages the process away from the moving machine.
- Reliable and consistent overnight production. CNC turning machines can run unmanned.
The precision, speed and automation of CNC turning make it the preferred production method for mass producing industrial turned parts.
Common CNC Turned Parts
Many common mechanical components are manufactured on CNC lathes:
- Engine shafts
- Drive shafts
- Fasteners
- Bushings
- Nozzles
- Fittings
- Connectors
- Knobs
- Pulleys
- Rod ends
- Valve bodies
- Pump impellers
And countless other industrial, aerospace, medical, automotive and consumer parts are produced by CNC turning. It is ideal for repeat runs of complex, precision metal and plastic parts.
CNC Turning Equipment
CNC lathes range from basic 2-axis models for general turning duties up to sophisticated multi-axis machines capable of complex machining.
Key components of a CNC lathe include:
- Headstock - The motorized spindle that drives the workpiece rotation. Different chucks and centers hold and locate the workpiece.
- Tailstock - An adjustable fixture on the end of the lathe ways that holds the workpiece from the other end using centers or a live center.
- Tool turret - An indexable turret that holds multiple turning, boring and drilling tools for automatic tool changes.
- Tool holders - Standard tool holders that accept replaceable inserts for turning, grooving, threading, etc.
- Ballscrews - High precision ballscrews for accurate axis movement and positioning.
- Guideways - Hardened steel ways that allow precise linear slide motions.
- Control - The CNC unit houses the program memory and interfaces with the axes drives and I/O.
- Chip management - Splash guards, chip pans and conveyors manage cutting debris and chips.
A key differentiator between economy and production-level machine tools is the quality of components like the spindle, guideways, ballscrews and CNC control.
Programming CNC Turning
Specialized CAM software is used to program CNC turning machines. Common turning CAD/CAM packages include:
- Mastercam
- FeatureCAM
- GibbsCAM
- Esprit CAM
- SolidCAM
- EdgeCAM
The CAM system processes the CAD part model geometry to generate efficient toolpaths based on the features to be machined. Postprocessors convert the toolpaths into G-code specific to the machine make and model.
Turning centers can also be programmed manually using G-code. Standard codes define the motions and turning cycles needed to machine the required shapes. CAD/CAM software makes programming easier by automating the postprocessing and G-code generation.
In Conclusion
CNC turning is an essential manufacturing process for precision metal and plastic parts. It offers accuracy, repeatability, efficiency and automation benefits over manual turning. With the right machining center, cutting tools and CAM software, complex parts can be produced accurately and rapidly using CNC turning technology. Continued advancements in CNC systems, tooling and programming enable manufacturers to improve productivity, quality and capabilities when turning parts on modern CNC lathes. CNC Milling CNC Machining