Introduction to Turning in CNC Machining(tin coat Zenobia)

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Turning is a machining process used to create cylindrical parts by rotating a workpiece while a cutting tool is moved parallel to the axis of rotation. Turning can be performed manually on a lathe or using computer numerical control (CNC) to automate the process. CNC turning has become an essential manufacturing process across many industries such as automotive, aerospace, medical, and more. This article will provide an overview of CNC turning, how it works, applications, advantages, and tips for optimizing the turning process.
How CNC Turning Works
CNC turning employs programmable automation using G-code to control the movements of the cutting tool and rotation of the workpiece. Here are the key components and steps in the CNC turning process:
- CNC Lathe: This is the machine used for CNC turning operations. The lathe contains a spindle for rotating the workpiece, a chuck for holding and releasing the workpiece, a cutting tool mounted on a turret, and axis slides for moving the tool.
- Workpiece: The workpiece is the material that will be machined. Common workpiece materials for turning include metals such as aluminum, steel, titanium, plastics, and wood. The workpiece is loaded into the chuck which holds it in place during machining.
- Cutting Tool: Standard turning tools include round inserts and triangular inserts. The cutting edges are positioned perpendicular or at an angle to the workpiece depending on the operation being performed. Cutting tools must be very hard and resistant to wear.
- Tool Paths: The machining parameters and tool paths are programmed into the CNC machine control using G-code. This defines the cutting feed rate, depth of cut, rotational speed, and exact tool positioning in relation to the workpiece.
- Machining: With the workpiece loaded and the program running, the CNC turning operation is carried out. The workpiece rotates and the turret positions the cutting tool which is fed towards the workpiece along the programmed tool path to remove material.
- Completed Part: When the program is complete, the finished turned part is unloaded. Post-processing may also be required such as sanding, deburring, or adding special coatings or finishes.
Key CNC Turning Operations
The four fundamental types of turning operations include:
- Facing: A facing operation involves moving the tool perpendicular to the axis of rotation to remove material from the face of the workpiece and create a flat surface. This is usually the first operation.
- Rough Turning: Rough turning uses deeper cuts and faster feeds to remove the bulk of material from a workpiece. This cuts down the part to near the final dimensions but leaves excess material for the finishing pass.
- Finish Turning: The finish turning operation uses light cuts and slow feeds to achieve the high final accuracy and surface finish requirements. Fine surface finishes under 32 microinches are possible.
- Parting/Grooving: Parting and grooving uses a specially shaped tool to cut narrow slots or separate a part from the bar stock it is attached to. Parting can cut complete threads or grooves around a diameter.
CNC Turning Applications
Turning is an extremely versatile process used across many industries. Here are some common applications for CNC turning:
- Automotive - Crankshafts, camshafts, pistons, gears, rotors
- Aerospace - Aircraft structural parts, engine components, fasteners, fittings
- Medical - Bone screws, prosthetics, surgical instruments
- Oil/Gas - valves, compressor parts, couplings
- Construction/Mining - shafts, rollers, boring bars, pulleys
- Molds - for injection molding, die casting, and more
- And many more! Almost any axisymmetric part can be created by CNC turning.
Benefits of CNC Turning
There are several important benefits that make CNC turning a preferred manufacturing method:
- High Precision - Modern CNC lathes can achieve dimensional tolerances down to +/- 0.0004 inches. Complex geometries are possible.
- Faster Process - CNC automation enables faster cycle times compared to manual turning. Parts can be made in minutes.
- Consistent Quality - The computer control eliminates variability in output quality. Parts are identical run after run.
- Lower Labor Costs - One CNC operator can manage multiple machines reducing labor requirements. Skilled manual machinists are not required.
- Reduced Waste - CNC turning is optimized to use raw material efficiently and cut down on wasted scrap material.
- Flexible Production - Quick changeovers and programming adjustments allow fast transitioning between part designs. Small batch production is no problem.
Tips for Optimizing CNC Turning
To achieve maximum results from the CNC turning process, here are some useful tips:
- Select suitable workpiece material - Choose materials that suit the part application and are easy to machine. Free-cutting metals like aluminum and brass work well.
- Use correct insert style - Match the insert shape, angle, and material to the workpiece material and desired cutting action. Consider variable helix inserts for optimized results.
- Choose appropriate tool path - Optimize the tool path pattern to the features being machined. Use contour-parallel paths for finishing passes.
- Determine optimal feeds/speeds - Finding the best combinations of feed rate, cutting speed, and depth of cut is key for efficiency. Start conservatively then increase.
- Use high pressure coolant - High pressure coolant directed at the cutting zone improves tool life, surface finish, and chip control.
- Employ live tooling - Adding milling and drilling capability to the lathe turret avoids secondary operations and saves handling time.
- Automate measurement - In-process gauging automation helps maintain tight tolerances. Laser measurement can verify diameters and features.
- Take light finishing passes - Leave just 0.001-0.002 inches of material for the finishing pass to ensure dimensional accuracy and surface finish.
In summary, CNC turning is a versatile machining method that utilizes automated, programmable tool paths to efficiently produce precision round parts to meet today's manufacturing needs. Mastering the key turning operations, optimizations, and process techniques is critical for manufacturers looking to remain competitive in the modern manufacturing landscape. CNC Milling