What is CNC Turning?(how to remove chrome from aluminum Merle)

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CNC turning is a machining process that uses computer numerical control (CNC) to automate the process of shaping cylindrical parts. It is one of the most common CNC machining processes and is used to produce parts like shafts, bushes, rods, sleeves and more.
In CNC turning, the workpiece is rotated at high speeds while a single point cutting tool removes material from its surface to cut and shape the part based on programmed instructions. The cutting tool can move in multiple axes, enabling the machining of complex 3D geometries, grooves, threads and profiles.
How Does CNC Turning Work?
A CNC turning center consists of a workpiece spindle, cutting tools, CNC control system and other components. Here is an overview of the CNC turning process:
1. The workpiece, usually a cylindrical bar of metal or plastic, is loaded into the chuck or collet of the spindle. The spindle rotates the workpiece at the desired speed for optimal cutting.
2. The turret or tool post holds the cutting tools like turning inserts or boring bars. These tools are positioned as needed for machining under CNC program control.
3. The CNC program, created by CAD/CAM software, has the machining instructions like feed rate, depth of cut, coordinate positions etc. This is loaded into the CNC controller.
4. As the workpiece rotates, the controller moves the cutting tool across its face or length. The tool follows the programmed contours, depths and speeds to cut and shape the material.
5. Cutting fluids are used to cool and lubricate the workpiece and tool. The chips produced are flushed away by the fluid.
6. Once machining is complete, the finished part is unloaded. Any additional processing like drilling or milling can be done on the same machine.
7. The CNC program can be repeated as needed to make multiple identical parts in succession. Adjustments to the program can also be made easily to machine similar components.
CNC Turning Operations
CNC turning centers can perform a variety of machining operations to produce precision turned parts:
- Facing: Machining the face of the workpiece to create a flat reference surface.
- Turning: Machining the external diameter of the workpiece to specific dimensions. This can create straight contours, tapers, grooves, chamfers etc.
- Boring: Enlarging existing holes or machining internal diameters. This is done using boring bars.
- Drilling: Creating holes axially in the workpiece using drill bits.
- Tapping: Cutting threads internally using tapping tools.
- Grooving: Cutting grooves on the face, diameter or end of the workpiece.
- Profiling: Machining complex external contours using the turning tool movement.
- Threading: Cutting external threads using thread cutting tools for bolts, screws etc.
- Knurling: Creating decorative slip-resistant patterns on the diameter by impressing a knurling tool.
- Parting/Cut off: Separating a finished part from the bar stock using a parting tool.
- Conversational programming allows quick creation of part programs at the machine console using simple commands. CAD/CAM software offers more complex programming capabilities for 3D turning operations.
Advantages of CNC Turning
Here are some of the benefits of using CNC turning for machining cylindrical parts:
- High precision and accuracy with tolerances up to 0.005 inches. Complex geometries can be produced.
- Ability to machine tough materials like hardened steels and alloys which are difficult with manual turning.
- Faster processing times due to optimized cutting parameters and automation. Higher productivity.
- Intricate parts can be machined using multiple axes of motion and live tooling.
- Minimal setup times. The CNC program can be reused for batch production.
- Lower operator skill requirements compared to manual turning. The CNC system handles the cutting operations.
- Highly consistent results. The automated process produces identical parts repeatedly.
- Flexibility to modify dimensions easily by editing the program. New designs can also be programmed quickly.
- Multi-tasking machines allow turning, milling, drilling and other operations to be done on one setup.
- Safe operation as the operator does not need to directly handle the cutting process.
CNC turning is suitable for producing parts in medium to high volumes across many industries including automotive, aerospace, oil and gas, medical, machinery and more. The combination of precision, efficiency and flexibility has made it a go-to machining process for turned components. With the right CNC machine programming and setup, high quality turned parts can be manufactured at low costs.
Applications of CNC Turning
Here are some examples of components produced by CNC turning across different industries:
Automotive - Engine valves, piston pins, axle shafts, wheel hubs
Aerospace - Wing pins, landing gear parts, engine mounts, bulkheads
Oil and gas - Pump shafts, drill collars, valves, manifolds
Medical - Bone screws, hip joint implants, surgical instrument handles
Machinery - Pump shafts, compressor rods, hydraulic cylinders
Fasteners - Screws, bolts, nuts
Plumbing - Fittings, valves, faucets
Electronics - Connector pins, insulators, switch shafts
And many more turned parts in almost every mechanical and manufacturing sector...
The versatile capabilities of modern CNC turning make it possible to produce a wide variety of precision cylindrical parts from all types of materials including metals like steel, aluminum, titanium, plastics, wood and composites.
Types of CNC Turning Machines
There are two main configurations of CNC turning centers:
1. Vertical Turning Lathe (VTL)
Here the workpiece spindle is oriented vertically. Single or multiple cutting tools can access its ends and diameter. VTLs are ideal for machining large, heavy parts.
2. Horizontal Turning Center (HTC)
The workpiece spindle is horizontal in this layout. The chuck is on one end and tailstock on the other. Tools sit on a turret and can access the diameter of longer workpieces. HTCs are the most common CNC turning machines.
Other types like multi-axis turning centers and multi-tasking machines incorporate milling, grinding and other capabilities for complex parts. Special purpose turning machines like crankshaft millers are used for specific applications.
Getting Started with CNC Turning
For companies looking to adopt CNC turning, here are some tips:
- Evaluate size and type of parts to be machined. This will determine the optimal machine size and configuration.
- Select suitable CNC systems with the right software features, accuracy and connectivity.
- Train machine operators on programming software, process planning and fixtures design.
- Implement CAM programming for generating efficient toolpaths and code.
- Use optimal feeds, speeds, depth of cuts and tooling configurations specific to each work material.
- Automate processes with bar feeders, gantry loaders, conveyor systems and robotics where possible.
- Monitor key metrics like cycle time, tool life and surface finish to improve productivity.
- Adopt innovations like in-process metrology for quality control.
With growing demands for precision turned components, CNC turning continues to evolve with automation and smart capabilities - paving the way for the next generation of intelligent machining. CNC Milling CNC Machining