Introduction to CNC Turning(metal cutting laser cnc Quinn)

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CNC (Computer Numerical Control) turning is a machining process used to produce cylindrical parts on a CNC lathe. The turning process utilizes a single point cutting tool to remove material from the outside diameter of a rotating workpiece to achieve the desired dimensions and surface finish. CNC turning is an efficient and accurate machining process ideal for producing parts in high volumes with tight tolerances and repetitive tasks.
How CNC Turning Works
A CNC lathe uses programmed commands to control the movement of the cutting tool and various machine functions. The basic CNC turning process involves rotating the workpiece at high speeds while the cutter is fed horizontally and/or vertically into the workpiece to remove material. The cutter moves linearly or radially along programmed toolpaths to machine features like diameters, grooves, shoulders, and chamfers. Cutting parameters like feed rate, spindle speed, and depth of cut are optimized based on the workpiece material, tooling, and features being machined.
Key Components of a CNC Lathe
A CNC lathe consists of a bed, headstock, carriage, turret/tool post, spindle, chuck, coolant system, and CNC control. The headstock houses the main spindle which rotates the workpiece. The turret holds multiple cutting tools and indexes them as needed. The carriage moves the turret horizontally to position tools. On CNC lathes, the movements of the turret, carriage, spindle, and other components are controlled by precision programmed commands instead of manual levers.
CNC Turning Operations
Common CNC turning operations include:
- Facing: Machining the end face of a cylindrical workpiece flat and perpendicular to the axis of rotation. This is done to create an even surface for further operations.
- OD (Outside Diameter) Turning: Machining the external surface of the workpiece to remove material and achieve the desired diameter. This can produce straight diameters, tapers, grooves, and contoured profiles.
- Boring: Enlarging or finishing internal diameters to size using boring bars. This allows machining of holes, internal tapers, and internal features.
- ID (Internal Diameter) Turning: Machining the internal surface of pre-bored holes to enlarge diameters or create internal features like grooves and tapers. Requires small cutters and tool access via drilled/bored holes.
- Parting/Cut Off: Using a specially shaped cutter to cut workpieces from the bar stock and separate finished parts. Performed as an end operation on completed parts.
- Threading: Single or multi-point cutters are used to machine external or internal threads for bolts, fasteners, connectors and other applications requiring assembled parts and precision fits.
- Grooving: Cutting grooves, squares, and undercuts internally or externally on the diameter using form tools and grooving inserts.
- Drilling: Utilizing rotating drills held in the turret to machine center holes or shallow side holes in the workpiece.
- Taper Turning: Machining external or internal tapers using the compound slide set at an angle or a taper attachment.
CNC Turning Workholding
Workholding is critical in CNC turning to locate and clamp the workpiece securely for accurate machining. Common workholding methods include:
- 3-Jaw Chuck: Self-centering chuck with three movable jaws allows clamping of round bar stock and cylindrical parts. Used for OD/ID turning.
- 4-Jaw Chuck: Independent chuck jaws allow clamping of square, rectangular or irregular shaped workpieces.
- Collet Chuck: Collects provide high clamping accuracy for precision jobs on small delicate parts. Available for various diameter ranges.
- Lathe Centers: Live centers in the headstock and tailstock support each end of the workpiece at the axis of rotation. Typically used for longer parts.
- Faceplates: Large faceplates attach to the spindle nose and allow mounting of irregular shaped castings and large diameter parts off-center.
- Mandrels: Allow mounting tubing or hollow parts over a tapered shaft secured in the headstock spindle.
- Steady rests/Follower rests: Support part extensions and long slender parts at middle points to prevent deflection under cutting forces.
Tooling for CNC Turning
The variety of operations possible on CNC turning centers requires an assortment of tooling options, including:
- Turning Inserts: Indexable carbide inserts with geometries for light roughing to heavy hogging. Single edge or multi-edge inserts fit tool holders for both external and internal profiling.
- Boring Bars: Rigid steel or carbide bars for internal boring work. Available in solid styles or adjustable types.
- Threading Tools: Single point or multi-point cutters for external and internal thread cutting applications. May be indexable or solid style.
- Form Tools/Profiles: Custom ground tool steel cutters for machining specialized shapes, grooves, slots and profiles not possible with standard insert tooling.
- Drills: Standard straight flute and indexable insert drills for center and side hole drilling operations in turning.
- Parting & Grooving Tools: Inserted blade style parting tools and tool holders with carbide inserts shaped for grooving, cutoff and profiling.
- Tool Holders: Standard turning tool holders like ISO, ANSI, and JET fit the turret/tool post and provide proper geometry and support for insert tooling used in CNC turning. Rigid machine taper tooling like CAT, BT retainers and HSK styles may also be used.
Benefits of CNC Turning
Some key benefits of using CNC turning technology for manufacturing include:
- Consistency: Automated programmed operation provides extremely consistent results and reduces scrap/rework rates compared to manual operation.
- Accuracy: Modern CNC lathes can hold extremely tight tolerances down to +/- 0.0005 inches for precision turning applications.
- Complexity: CNC allows machining of complex geometry not possible manually. Multi-axis lathes can mill, drill and turn complex parts in one setup.
- Productivity: CNC performs unattended machining and allows one operator to run multiple machines. Automation increases throughput and reduces labor costs.
- Flexibility: Quick change tooling and programs allow fast changeovers between jobs. Reduces downtime and allows economical production from prototype to high volume jobs.
- Lean Manufacturing: CNC turning supports lights out manufacturing, just-in-time principles, and quick response production strategies to minimize waste.
With integrated toolposting, driven tooling options, C/Y-axis capabilities, and live tooling; modern CNC turning centers allow complete machining of complex, high precision components in a single setup. When applied appropriately, CNC turning is an efficient and versatile manufacturing process. CNC Milling