What is CNC Turning?(how to make engineering drawings Lennon)
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CNC turning has revolutionized the production of cylindrical and axisymmetric parts. It allows for fast, precise, and repeatable machining of complex geometries that would be difficult or impossible to produce manually. CNC turning is widely used across many industries including automotive, aerospace, medical, and more.
How CNC Turning Works
A CNC turning center consists of a lathe that has been retrofitted with computer numerical control components. This includes servo drives, axis motors, a spindle drive motor, a computer control unit, and an operating software package. The basic components of a CNC lathe are similar to a conventional manual lathe. However, the processes are automated via the CNC system.
During operation, the machinist uploads a part program into the CNC control unit. The part program contains code (often G-code) that controls the motions of the machine. It defines the machining operations, cutting parameters, tool paths, spindle speeds, feed rates, depth of cuts, and other variables.
The machinist installs the workpiece into the machine and selects the appropriate cutting tool. When the cycle starts, the CNC system executes the part program code line-by-line. The axes motors position the cutting tool and workpiece per the programmed coordinates while the spindle rotates the workpiece at the specified speed. The tool removes material from the rotating workpiece to cut the desired geometry.
As the program runs, the CNC system monitors critical parameters such as spindle load and position feedback. Most CNC turning centers are capable of controlling up to four axes simultaneously. This allows machining operations like tapering, contouring, drilling, and threading in a single setup. Multiple parts can often be batched processed by running the same part program repeatedly.
Benefits of CNC Turning
There are many advantages of using CNC turning centers over manual lathes:
- Automation - CNC turning automates the machining process, removing the need for manual operation and improving consistency.
- Accuracy - CNC machines offer much tighter tolerances and better repeatability than manual operation. Precision down to 0.001mm or 0.0005" is possible.
- Complexity - CNC turning can produce complex geometries would be infeasible or impossible to do on manual lathes.
- Efficiency - CNC turning performs faster metal removal and reduces non-cutting time versus manual turning. More parts can be completed per hour.
- Flexibility - Changing part geometries is as simple as loading a new part program. No mechanical changes needed.
- Reduced Labor - CNC turning reduces the labor burden. One machinist can run multiple machines.
- Less Training - Programming and code handle the complexity. Machinists only need to learn setup and programming.
As a result, CNC turning is ideal for production environments and engineering shops that need to produce parts rapidly, precisely, and in a repeatable fashion. The automation and capabilities allow for streamlined manufacturing.
CNC Turning Operations
CNC turning centers can perform a variety of machining operations to shape parts. Common CNC turning operations include:
- Facing - Machining the face of the workpiece to create a flat surface. This is often the first operation.
- Turning - Machining the outside diameter of the rotating workpiece to create a round profile.
- Boring - Machining the inside diameter to create a hollow cavity or enlarge an existing hole.
- Grooving - Cutting a groove along the surface of the part.
- Cutoff - Parting off the workpiece from the excess material.
- Threading - Cutting external or internal screw threads along the workpiece.
- Tapering - Producing angled surfaces by pivoting the cutting tool during machining.
- Drilling - Axially drilling holes in the face or side of the workpiece.
- Knurling - Creating a patterned rough surface for improved grip.
Multiple operations can be combined in one part program to create complex geometries. Secondary operations like deburring, radiiing, polishing, and more may be used to finish parts. Live tooling can also expand the capabilities for milling, slotting, and drilling off-centerline.
Equipment for CNC Turning
The primary piece of equipment needed is a CNC turning center, also called a CNC lathe. CNC lathes contain the basic components of a standard lathe, but with the addition of CNC capabilities for automation. Key components of a CNC turning center include:
- Headstock - Houses the main spindle which rotates the workpiece. Powered by the spindle drive motor.
- Tailstock - Supports the end of the workpiece with a center or chuck. Can be programmable.
- Tool turret - Indexable turret that holds multiple cutting tools for automatic tool changes.
- Tool changer - Storage location that enables automated exchange of tools.
- Machine bed - Rigid bed that sits on the floor and holds the components.
- Axis slides - Slides for the X (cross) and Z (longitudinal) axes. Sometimes a Y-axis may be present.
- Control panel - Interface for the operator to control the machine, often featuring a LCD screen.
- Enclosure - Full enclosure for protection around the working area.
- Coolant system - Pump and hoses to provide cutting fluids to the tool interface.
CNC lathes range greatly in size. Smaller machines may have 6-8" capacities while larger machines accommodate parts over 60" in diameter and 20 feet long. Cost also ranges significantly from tens of thousands to over a million dollars for elite machines.
In addition to the CNC turning center itself, tooling is required to perform the cutting operations. This includes:
- Cutting tools - Carbide inserts, HSS, CBN, and PCD styles tailored to material type and operation.
- Tool holders - Standardized holders to grip and position cutting tools.
- Workholding - Chucks, collets, centers, vises, and fixtures to hold the workpiece.
- Measuring tools - Indicators, calipers, micrometers to validate dimensions.
- Coolant nozzles - Direct coolant into the cutting interface for lubricity, chip control, and surface finish.
Programming CNC Turning
Operating a CNC turning center requires specialized programming to define the machining operations. While it is possible to manually program codes like G-code, most CNC programmers use CAM software. CAM stands for computer-aided manufacturing.
With CAM software, the programmer imports or creates a 3D model of the desired part geometry. The software allows them to define machining sequences, toolpaths, depths of cut, and other parameters. The CAM program then automatically converts this information into machinable G-code to drive the CNC machine.
Benefits of using CAM software to program CNC turning include:
- Visual verification - Simulate and verify the turning process on-screen.
- Reduced programming time - Automated toolpath generation is much faster.
- Consistent output - CAM software guarantees a machinable program optimized for the operation.
- Easy iteration - Engineers can modify designs rapidly and generate new programs quickly.
- Integrated CAD - CAD model feeds directly to CAM programming, no rework needed.
While G-code is the standard language across CNC turning machines, there are also various conversational programming options. These use a simplified text-based language to describe operations in an easy, readable format.
Setting up CNC Turning
When the CNC program is complete, the next phase is to setup the physical machine. This includes:
- Inspecting the machine - Check for any potential issues or needed maintenance.
- Loading tools - Inserting tools into the appropriate holders and staging them nearby.
- Mounting workpiece - Securely clamping the raw material into the chuck or fixture.
- Setting coordinates - Indicating the workpiece position to establish the part zero reference.
- Inputting program - Transferring the CNC program file into the control unit via USB, network, etc.
- Checking offsets - Ensuring proper work coordinates, tool length offsets, geometry offsets, and any other values.
- Trial run - Dry running the program first with no cutting to verify the toolpaths.
During setup, machinists also cater workholding, tooling, depths of cut, feeds, and speeds to the specific material being machined. Any required in-process inspection methods are also determined.
Executing CNC Turning Operations
With a proven program and proper setup, the CNC turning cycle can begin cutting material away to form the finished part. During production, key aspects include:
- Cycle start - The operator commences the CNC program from the control panel.
- Automatic operation - The machine runs through the programmed actions independently without human input.
- Tool changes - Tools are automatically changed from the carousel when needed.
- Monitoring - The machinist oversees the process and monitors for any errors or issues.
- Inspection - Performing periodic inspection and measurement of the workpiece.
- Adjustments - Making any needed offsets, edits, or overrides to improve the process.
- Part handling - Safely unloading finished parts and reloading new workpieces.
For critical applications, the first article is fully validated before committing to a production batch. Once running stably, CNC turning can often operate with minimal supervision as it repeatedly cuts identical parts.
CNC Turning Best Practices
Follow these guidelines to maximize productivity and part quality with CNC turning:
- Select suitable materials - Choose materials that match the operation's requirements and machinability.
- Implement proper holding - Use reliable workholding with minimal runout and deflection.
- Optimize tooling - Choose tooling designed specifically for turning toughness and chip control.
- Determine optimum parameters - Pick conservative speeds and feeds based on tooling, material, rigidity.
- Program efficiently - Utilize smooth motion and trochoidal toolpaths where possible. Minimize non-cutting moves.
- Employ proper coolant - Use enough flow and pressure. Strategically direct nozzles.
- Reduce vibration and chatter - Ensure adequate rigidity in setup. Alter parameters if needed.
- Measure frequently - Validate dimensions to catch errors early before they propagate.
Applying these best practices helps maximize part accuracy, repeatability, and surface finish from CNC turning operations.
Applications of CNC Turning
CNC turning is used across practically every industry that requires repeatable production of cylindrical or rotational parts. Key applications include:
- Automotive - Engine blocks, shafts, cylinders, axles, gears, wheels, steering/suspension components
- Aerospace - Aircraft structural parts, engine components like turbines and compressor discs, fasteners, fittings
- Medical - Implants, surgical instrumentation, dental and orthodontic parts, prosthetic devices
- Defense - Missile/rocket components, gun barrels, cases, buckles, fasteners
- Fluid Power - Hydraulic cylinders, pneumatic fittings, compressor parts, valves, manifolds
- Oil/Gas - Piping, drilling equipment, valves, pumps, compressor parts
- Hardware - Nuts, bolts, screws, spacers, shafts, axles, couplings
Any parts with ID/OD profiles, spherical forms, or symmetric shapes can benefit from CNC turning's precision, speed, and accuracy.
Summary
In summary, CNC turning utilizes computer numerical control to automate turning operations on parts. It brings immense advantages in precision, efficiency, complexity, and flexibility compared to manual turning. With the right setup and programming, CNC turning can rapidly produce cylindrical components with exacting tolerances and specifications. CNC turning is a versatile machining process relied upon across countless manufacturing industries. CNC Milling CNC Machining