Introduction to Turning Operations in CNC Machining(corrosive resistant metal Joanna)

  • Time:
  • Click:5
  • source:GAENOR CNC Machining
Turning is one of the most common machining processes performed on CNC machine tools. It is used to produce cylindrical parts from a workpiece by rotating it against a cutting tool that removes material. The workpiece is referred to as the blank and is clamped in the chuck of a lathe. As the chuck rotates, the cutting tool moves along the axis of rotation to cut and shape the blank into the desired form and dimensions.
Turning operations are ideal for producing parts that have external cylindrical features, such as diameters, shoulders, grooves, threads, tapers, and chamfers. Typical examples of turned parts include shafts, pins, bushings, rolls, spindles, and fasteners. Turning can be used to machine various materials including metals, plastics, wood, and composites.
Types of Turning Operations
There are several common turning operations that can be performed on CNC lathes:
- Facing: This operation produces a flat surface perpendicular to the axis of rotation. It is done using a squared cutting tool and is often one of the initial steps.
- Straight turning: Also known as longitudinal turning, this removes material to reduce the diameter of a cylindrical surface and achieve the required dimensions. The cut can be performed from the outer diameter towards the center or vice versa.
- Taper turning: This produces a tapered surface by changing the depth of cut as the tool moves along the workpiece. The angle of the taper is usually calculated automatically by CNC machine software.
- Grooving: Rectangular shaped grooves are machined into the workpiece. This allows cutting off a piece of material or for assembling parts.
- Threading: Screw threads are cut into the part using specially shaped cutting tools. Many different thread forms, sizes and pitches can be produced.
- Boring: An internal diameter is enlarged and finished to high precision using boring bars. Very tight size tolerances and surface finishes can be achieved.
- Drilling: Holes are machined into the center of the blank. Twist drills or special CNC drills are used for hole making operations.
- Knurling: A diamond-shaped pattern is pressed into the surface to produce an anti-slip grip. Special knurling tools are used to displace the material.
CNC Turning Process
The basic CNC turning process involves 4 main stages:
1. Setup - The blank is securely clamped in the chuck and necessary tools are loaded into the tool turret. Programs are loaded into the CNC control.
2. Facing - Initial facing cuts are taken to square the blank and ensure it is concentric with the chuck. This reference surface can be used for subsequent operations.
3. Roughing - Deeper cuts are taken at high feeds to quickly remove the bulk of material and bring the part closer to final dimensions.
4. Finishing - Light finishing passes are made at lower feeds to generate the high-quality final surface finish, dimensional accuracy and surface texture required. Multiple light passes may be used to minimize cutting forces and improved accuracy.
Machining Parameters
The major machining parameters that influence the CNC turning process include:
- Cutting speed (surface feet/min or m/min): Optimizing this improves tool life, surface finish and helps avoid defects.
- Feed rate (inches/revolution or mm/revolution): This affects material removal rate, cycle time and surface finish.
- Depth of cut (inch/pass or mm/pass): Determines the amount of material removed per pass and cutting forces generated.
- Cutting tool inserts: Carbide inserts having appropriate geometry and grade are selected based on the workpiece material.
- Coolant: Applied to reduce heat and clear chips. Emulsions or oils are commonly used. High pressure coolant may also be used.
CNC controllers allow the easy optimization of these parameters. The feed and speed can be automatically varied based on the cutting conditions.
Advantages of CNC Turning
Some of the major advantages of CNC turning include:
- High production rates and consistent quality can be achieved even for complex parts.
- Minimal human intervention is required once the machine is setup. Automated production improves consistency.
- Quick changeover between jobs. CNC programs can be easily changed.
- Ability to machine complex contours and shapes with close tolerances.
- Wide range of materials can be machined, including alloys difficult to work with using manual methods.
- Multi-axis capabilities like live tooling further increase the complexity of parts that can be produced.
- Digital technology assists in process monitoring and optimization.
- High degree of flexibility. Small batches can be machined economically.
In summary, CNC turning is a versatile machining process suitable for high production manufacturing. The automated and optimized nature of the process leads to precision and repeatedly accurate turned components. With capabilities to produce simple to highly complex prototypes and production parts, turning plays a key role in modern manufacturing. CNC Milling CNC Machining