What is CNC Turning?(melting temp of steel Bradley)

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CNC turning is a machining process that uses computer numerical control (CNC) to automate the turning of material on a lathe. Turning is a form of machining that uses a single point cutting tool to remove material from the outer diameter of a rotating workpiece to create cylindrical shapes. CNC turning involves programming instructions for the cutting tool path and other machining parameters into a CNC machine controller, which then guides the lathe to produce turned parts accurately and consistently.
CNC turning is commonly used to produce parts that have cylindrical features like shafts, pins, rods, tubes, sleeves, and bushings. It is one of the most versatile and widely used CNC machining processes in manufacturing industries like automotive, aerospace, medical, construction equipment, and more. The key benefits of CNC turning include:
- High precision and accuracy: CNC turning can hold extremely tight tolerances down to +/- 0.002 inches or less. The programmed instructions guide the tool along precise paths, resulting in dimensional accuracy and consistency across production runs.
- Faster production: CNC automation enables turning operations to be performed much faster than manual turning. CNC machines can run for extended periods with minimal operator intervention.
- Repeatability: The programmed CNC code enables turned parts to be replicated precisely and identically. This repeatability allows for mass production of components cost-effectively.
- Reduced labor costs: One CNC machine can replace several manual machine operators. Skilled programmers and setup technicians can oversee a bank of CNC lathes, reducing labor requirements.
- Flexibility: Quick changeover between jobs allows CNC turning centers to machine a variety of components in small to medium batch sizes. Bar feeders allow for extended periods of unattended operation.
- Complex geometries: CNC enables turning of complex shapes like contours, tapers, threads, grooves, and profiles that would be infeasible to produce manually.
CNC Turning Process
The typical CNC turning process involves the following key steps:
Part Design
The dimensions, geometries, and tolerances of the desired turned part are specified in a technical drawing. CAD software can be used to model the 3D design. Critical details like diameters, surface finish requirements, chamfers, holes, and grooves are communicated in the technical drawings.
Toolpath Programming
Next, a CNC programmer codes up the toolpath and machining instructions using CAM software. Common programming languages are G-code and conversational programming. The program specifies key parameters like feed rate, spindle speed, depth of cut, and tool selection. Simulations may be run to visualize the machining process before creating the CNC code file.
Workpiece Setup
The raw stock material, usually a bar, rod or pre-cut blank, is securely clamped in the lathe chuck or collet. The lengths are set to allow complete machining of multiple parts in one run if needed. Proper alignment and rigidity are critical for precision turning.
Machining Operations
The CNC program is loaded into the machine control and the cutting cycle is initiated. As the part spins, the cutter follows the programmed contours to produce the desired diameters, grooves, threads, and profiles. Multiple tools may be automatically changed to perform roughing, finishing, and threading operations.
Part Removal
Once complete, the finished turned parts are removed from the CNC lathe. Subsequent operations like deburring, polishing, or adding additional features may be completed before sending the part to quality inspection.
The CNC lathe may be set up with a new blank for the next batch of parts. Used tooling is replaced with fresh inserts or edges. The part program may be easily adapted for similar components. Fine-tuning during set up can further optimize the cycle time and tool life.
CNC Turning Methods
There are several distinct methods that can be utilized on CNC turning centers to efficiently machine components:
- Turning - Uses a single point tool to remove material from the OD/ID of a rotating part. Multiple depth cuts follow programmed contours.
- Boring - Enlarges existing holes to precise diameters and finishes hole condition. A boring bar can interpolate diameters and produce chamfers or radii.
- Grooving/Cutoff - Narrow tools cut grooves, sever parts from the bar stock, and machine shoulders, faces, and internal profiles.
- Threading - Single or multi-point tools cut external and internal threads to specification. May use taps, dies, or thread milling.
- Drilling - Performed on CNC lathes equipped with a programmable tailstock or live drilling capability. Holes can be produced off-center.
- Tapping - Forms internal threads by synchronizing the spindle rotation with an inserted tap. Floating tap holders allow vibration-free motion.
- Knurling - Special knurling tools impress diamond or straight patterns onto parts to provide an improved grip surface.
- Forming - CNC-controlled rolls spin against the part to incrementally form precision diameters and spherical contours.
- Laser Cutting - Integrated laser technology can add engraving and help weaken the cut for parting operations.
CNC Turning Machines
There are several configurations of CNC turning centers designed for high production or flexible small-batch manufacturing.
- Vertical Turning Lathe (VTL) - Rotating chuck mounted on horizontal two-axis table. Allows machining of ID, OD, and faces. Large VTLs handle big components.
- Horizontal Turning Center - Rotary spindle with fixed horizontal table and cross slide. Very rigid and can handle high cutting forces.
- Multi-Axis Turning Center - Equipped with additional axes like Y-axis, B-axis, and milling capability. Allows complex contours and multi-sided machining.
- Swiss-Style Lathe - Use sliding headstock and guide bushings for long bar stock work. Highly accurate and well suited for small, complex parts like medical components.
- CNC Chucking Machine - Designed for high production turning of discrete parts. Powerful spindle and rigid construction for difficult materials.
- Twin Spindle Lathe - Has two independently controlled spindles to maximize throughput. Allows simultaneous machining of two parts.
Other specialized CNC lathes include slant bed, flat bed, crankshaft, bench top, and gang tool types. The choice depends on the size, complexity, and batch requirements of the turned parts being produced.
CNC Turning Tools
There is a wide assortment of engineered cutting tools that are designed specifically for CNC turning operations, including:
- Cutting Inserts - Indexable inserts made of carbide, ceramic, CBN, or diamond. Offered in various geometries tailored to materials and operations like finishing, profiling, grooving, and threading.
- Boring Bars - Rigid bars with replaceable cutting heads used for internal boring and enlarging holes. May have fixed or adjustable diameters.
- Threading Tools - Single point, multi-point, taps, dies, and thread milling tools for both external and internal thread cutting.
- Turning & Facing Tool Holders - Specialized tool holders for external turning, facing, grooving, and cutoff tools. Offer precision clamping.
- Drills - Traditional and indexable drill bits for hole making on CNC lathes. Available in straight shank, taper, and chucked styles.
- Tool Sets - Groupings of inserts, tool holders, and adapters assembled to machine complete part features. Streamline tool management.
Proper selection of tooling substrates, coatings, geometries, and grades prevents premature wear for optimal tool life and cutting performance. Consult your tooling supplier for recommendations.
CNC Turning Operations
Here are some of the common turning operations that can be programmed on a CNC lathe:
- Facing - Uses the nose of the turning tool to produce precise facing and squaring of the part edges.
- Straight Turning - Removes material from the OD of a cylinder by feeding the tool radially across the rotating blank.
- Taper Turning - Machines angled outer diameters by coordinating the X-axis feed rate with the Z-axis depth.
- Profiling - Complex tool motion along 2 or more axes machines custom outer contours and radii.
- Undercuts - Forms irregular shapes and grooves with specially shaped inserts or round tools.
- Boring - Enlarges the internal diameters of holes to high accuracy. Requires rigid setup.
- Grooving - Narrow inserts machine decorative and functional grooves both internally and externally.
- Parting/Cutoff - Slices through the entire part to cut it from the stock remnant for removal.
- Threading - Precisely controls tool motion and spindle speed to cut standard or custom threads.
- Drilling - Live tooling drills centered and angled holes in parts. Holes can be spot or through.
- Tapping - Synchronized spindle and Z-axis feed produces internal threads for bolts or fittings.
- Knurling - Imparts a textured pattern onto the part OD using a knurling tool for improved grip.
- Form turning - Complex rolls burnish the part to reduce diameters or create spherical contours.
The right programming instructions are needed to optimize each operation for surface finish, dimensional accuracy, and cycle time.
CNC Turning Applications
CNC turning is used to produce a diverse range of precision turned parts across many industries, including:
- Automotive - Engine valves, pistons, brake drums, CV joints, pulleys, steering components
- Aerospace - Bushings, missile cones, engine housings, landing gear parts, engine mounts
- Medical - Bone screws, surgical drivers, dental implants, catheter tips, IV components, arthroscopic shafts
- Firearms - Receivers, barrels, cylinders, magazines, bolts, chambers, firing pins
- Fluid Power - Hydraulic cylinders, pneumatic fittings, precision valve bodies, pump shafts
- Oil & Gas - Pump shafts, valve stems, compressor rods, drill bits, wellhead parts
- Defense - Radar components, missile casings, rocket motor cases, fuse bodies, bomb parts
- Semiconductor - Vacuum chambers, gas delivery manifolds, robotics arms, wafer chucks
- Consumer - Razor handles, power tool spindles, knife blades, flashlight bodies, watch components
Whether making simple bushings, complex missile nose cones, or medical implants, CNC turning is appreciated for its precision, efficiency, and versatility to produce high-quality turned parts from metals, plastics, composites, and exotic alloys. Continued advancement in CNC technology promises to further improve capabilities for the turned parts industries. CNC Milling