Introduction to Turning on CNC Machines(annular snap fit joint Maureen)

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Turning is one of the most common machining processes performed on CNC (computer numerical control) machines. It is used to produce rotational, symmetrical parts by removing material from the outside diameter of a workpiece. Turning can be done on dedicated CNC lathes as well as CNC machining centers equipped with live tooling and a rotating spindle.
On a CNC lathe, the workpiece is held and rotated against a stationary cutting tool. The cutting tool is fed into the workpiece radially or axially to remove material. On a CNC machining center, the workpiece is held in place while the cutting tool rotates around it to remove material.
Types of Turning Operations
There are several basic types of turning operations that can be performed on CNC machines:
- Facing - machining the end surfaces of a cylindrical workpiece square with its axis. This is done using a tool fed perpendicular to the axis of rotation.
- OD (Outside Diameter) Turning - machining the external surface of a rotating cylindrical workpiece. The cutting tool feeds parallel to the axis of rotation to remove material from the OD.
- ID (Inside Diameter) Turning - machining the internal surface of a rotating cylindrical workpiece. The cut is made by feeding the tool radially into the ID.
- Taper Turning - produces a tapered surface by feeding the cutting tool at an angle to the workpiece axis. The angular feed can be along the OD or ID.
- Grooving/Parting - machining grooves or cutting off sections of a part using a specially shaped tool. Performed radially on the OD or ID.
- Threading - using a cutting tool shaped to cut screw threads, feeding axially to create internal or external threads.
- Boring - enlarging and truing an existing hole in a workpiece along its internal diameter.
- Drilling - creating through holes or blind holes in the center of a part using a rotating drill bit.
- Reaming - using a rotating cutting tool to enlarge and finish an existing hole to high precision.
CNC Turning Process
The basic CNC turning process involves four main stages:
1. Setup - The workpiece is loaded and held securely in a chuck, collet or fixture on the machine. The cutting tools required for the operations are loaded into the tool turret, magazine, or carousel.
2. Programming - The machine control is programmed with the instructions to perform the sequence of cuts. This includes coordinates for tool paths, feed rates, spindle speeds, depth of cuts, and other parameters.
3. Machining - The machine control executes the program. The spindle rotates the workpiece and the tools are automatically fed into the work at the right locations to produce the desired features. Cutting fluid is applied for lubrication and cooling.
4. Completion - The finished part is unloaded. Any post-machining processes such as deburring or parting off sections may be performed. The part is then inspected to verify it meets specifications.
CNC Turning Tools
Common cutting tools used for CNC turning include:
- Turning Inserts - removable cutting tips with special geometries for turning, facing, boring, and grooving. Made of carbide, ceramic, diamond, or cubic boron nitride.
- Boring Bars - long bars that hold removable boring heads for internal boring operations. Allows reaching deep inside diameters.
- Threading Tools - Single point or multi-point cutters shaped for cutting external and internal threads.
- Form Tools - used for complex contours, especially internal profiles. Ground to the required shape.
- Parting/Grooving Tools - narrow cutting tools for parting off or cutting grooves.
- Drills - for drilling center holes and deep holes. Come in many diameters and reaches.
- Reamers - for precisely sizing and finishing pre-drilled holes.
Tool holders or tool posts are used to hold the cutting tools solidly and allow precise positioning in relation to the workpiece.
CNC Turning Machine Configurations
There are a few main configurations of CNC machines used for turning:
- CNC Lathe - Designed specifically for turning. Very versatile for facing, OD and ID turning, grooving, drilling, threading, and more. Allows high precision turning of complex parts.
- Vertical Turning Center - A vertical CNC machining center modified for turning large diameter parts. The workpiece rotates on a horizontal axis while the tool cuts vertically. Enables turning heavy or awkward to handle parts.
- Live Tooling CNC Lathe - A CNC lathe equipped with a motorized tool turret that can drive rotating cutting tools. This allows milling and drilling while the part turns.
- Multi-Axis Turning Center - CNC turning machines with multiple spindles, turrets, and axes that enable simultaneous processing of complex parts.
- Twin Spindle CNC Lathe - Has two spindles allowing simultaneous machining of both sides of a part to minimize handling and cycle times.
Benefits of CNC Turning
Some key benefits of CNC turning include:
- Higher production rates and consistent quality versus manual turning
- Ability to machine complex geometric features and contours precisely
- Creates good surface finishes and close tolerances for fit and assembly
- Allows easy programming changes to accommodate revisions or new parts
- Reduced setup times by combining multiple operations in one setup
- Minimal operator intervention needed once running
- Quick changeover between jobs with tooling stored in the turret
- Automated measurements and adjustments during machining
- Integrated data logging, monitoring, and analysis
By utilizing CNC turning technology and techniques, manufacturers can accurately and efficiently produce high precision turned parts for almost any industry and application. The capabilities of modern CNC lathes and turning centers makes them an indispensable machining process for today's advanced manufacturing operations. CNC Milling CNC Machining