What is CNC Turning?(cnc cutters for wood Susie)
- source:MAJA CNC Machining
CNC turning has revolutionized how cylindrical parts like shafts, sleeves, and disks are made for industrial and consumer products. Here's an overview of how the CNC turning process works:
CNC Turning Machines
CNC turning centers utilize programmable controllers to operate the machine and execute turning routines. There are two main types of CNC turning machines:
- CNC lathes - A lathe spins the workpiece in its spindle while tools cut away material. Lathes can handle workpieces up to approximately 15 feet long and up to diameters of 4 meters. Lathes are the most basic type of CNC turning machines.
- CNC machining centers - More advanced CNC turning operations can be performed on machining centers with rotary tables or attachments. The workpiece is held in place while the cutting tools rotate and translate around it. This enables complex parts with multiple axes of rotation.
The key CNC machine components in turning include the bed, headstock, chuck, turret tool post, axes, spindle, and control panel. The machine uses PLCs or computer workstations to control axis movements and tool changes. Precision guideways enable smooth linear axis motions.
Tooling for CNC Turning
CNC turning uses various cutting tool types to remove material efficiently including:
- Insert tooling - Small cutting tips made of carbide or ceramic that are replaceable once worn. Great for production runs.
- Solid tooling - Entire tool is made of the cutter material. Used for large depths of cuts.
- Boring bars - Long bars that can reach inside of deep holes to enlarge the diameters.
- Grooving/parting - Thin tools for cutting grooves and parting finished parts from the raw stock.
- Threading - Tools that carve screw threads, both internal and external.
- Forming - Form tools with the inverse shape of the required forms cut into the workpiece.
Inserts and solid cutters are held by tool holders mounted in the turret. These are indexed to bring fresh cutting edges into position after the prior tip wears. The turret provides access to multiple tools so the machine doesn't have to stop to change out tools manually.
CNC Turning Operations
Common CNC turning operations include:
- Facing - Removes material from the face of the part to create a flat surface. Performed by feeding the tool perpendicular to the rotating workpiece.
- Rough turning - Taking deep cuts to remove the bulk of material and achieve a close-to-finished diameter. Uses coarse feeds/speeds.
- Finish turning - Light cuts to hit final dimensions and desired surface finish. Uses fine feeds/speeds. Multiple passes may be required.
- Grooving - Cutting grooves into the diameter or face of the part using a grooving or parting tool.
- Threading - Cutting internal and external screw threads using threading tools. Multiple passes required for full thread depth.
- Boring - Enlarging existing holes to accurate diameters with boring bars. Can also create internal undercuts.
- Form turning - Shaping complex contours using form tools. May require an axis of linear interpolation between tool and part.
- Parting - Separating finished parts from the raw bar stock using a parting tool. Usually the last operation.
- Taper turning - Creating angled diameters by offsetting the tool position or tailstock. Done by adjusting compound slides.
- Knurling - Creating crosshatched patterns on the part diameter by impressing knurls into the material. Provides better grip.
More complex parts can be machined using multiaxis CNC turning centers. These provide additional axes of motion to enable cutting shapes that can't be accessed through the rotation of the part alone. This includes features like undercuts and external forms.
Programming CNC Turning Machines
Generating toolpaths and code to run a CNC turning machine is known as CNC programming. Turning centers can be programmed in two ways:
1. Manually - Machinists program directly at the machine control using G-code. Simple but inefficient for production.
2. CAM Software - CAD models are programmed offline using CAM software that generates toolpaths and G-code. Efficient for complex parts in batches.
With manual programming, machinists have to do the programming at the machine itself. This takes time and reduces available production time on the machine tool. It also requires skilled programmers.
For production runs, CAM software is used. The CAD file of the part is imported and a programmer applies toolpaths based on the features required. CAM software does the complex calculations to generate efficient, collision-free toolpaths. The resulting code can be run directly on the CNC machines.
CAM enables programming off the machine shop floor which reduces setup time. Any changes to the program can be quickly updated in the CAM system without needing to modify G-code manually. This makes CAM ideal for medium to high production volumes.
Advantages of CNC Turning
Here are some of the main advantages of using CNC turning compared to manual turning:
- Higher precision and reproducibility. Modern CNC lathes can hold tolerances down to +/- 0.005 mm for turned dimensions. This level of accuracy is difficult and inconsistent to achieve manually.
- Faster production. CNC turning machines produce parts much faster than manual methods. Cycle times are reduced with optimized toolpaths plus the automation of part indexing and toolchanges.
- Lower labor costs. One operator can run multiple CNC turning machines. Skilled manual machinists are unnecessary. Operators only require basic training.
- Quick changeovers. Switching over a CNC lathe to run a different part is easy and fast. This enables efficient small batch and mixed part production.
- Complex capabilities. Complex turned shapes are possible using CNC multi-axis turning centers. Eccentric features and multi-diameter forms can be machined.
- Intelligent automation. Automating part production 24/7 is easy with CNC machines. They can even be integrated with other processes in manufacturing cells.
- Safer operation. CNC turning eliminates risks associated with manually cutting metal at high speeds for extended periods. The operator simply oversees the process.
Disadvantages of CNC Turning
CNC turning does have some downsides including:
- Higher investment. CNC lathes have a steep upfront capital cost. Budgets can run from $75,000 for smaller machines up to $ millions for very large models.
- Programming learning curve. While operating CNC turning centers is straightforward, programming expertise is vital for part programming. This includes both CAM software skills and understanding underlying G-code.
- Potential programming errors. Any mistake made when programming a CNC turning part can lead to scrapped parts when the program runs. This underscores the need for simulation and verification.
- Requirement for maintenance. CNC machines need regular cleaning, lubrication, calibration, and mechanical maintenance to stay accurate and avoid breakdowns.
- Process planning. To get the most out of CNC turning, you need people knowledgeable in machining practices, tool selection, and fixture design. Relying just on the machines is insufficient.
For these reasons, CNC turning automation may not be feasible or cost-effective for very small production volumes. The reduced setup and cycle times achieved only provide major productivity gains when making multiple pieces.
Applications of CNC Turning
CNC turning machines are utilized across many industry sectors to produce a diverse range of precision parts including:
- Automotive - Engine shafts, pins, driveshafts, bearings, gears, pulleys
- Aerospace - Aviation engine components like turbine blades, fuel nozzles, missiles
- Medical - Small surgical parts like scalpels, forceps, orthopedic joints
- Firearms - Barrels, magazines, receivers
- Fluid power - Hydraulic cylinders, pneumatic fittings
- Fasteners - Threaded bolts, nuts, studs
- Consumer goods - Parts for appliances, electronics, toys, furniture
Any applications requiring accuracy and repeatability for cylindrical components can benefit from the precision of computer controlled turning machines. CNC Milling CNC Machining