What is CNC Turning?(stronger than steel Constance)

  • Time:
  • Click:10
  • source:ESKRIDGE CNC Machining
CNC turning is a machining process that uses computer numerical control (CNC) to automate turning operations on a lathe. Turning is a form of machining that involves rotating a part while a cutting tool is moved against it to cut, shape, and finish its exterior surface. CNC turning utilizes programmable automation from CAD/CAM software to control the cutting tools, spindle speed, feed rate, depth of cut, and other parameters. This enables fast, precise, and consistent turning of parts in high volumes.
CNC turning is commonly used to machine rotational, symmetrical parts like shafts, bearings, valves, couplers, bushings, and pulleys. It can produce complex geometries with tight tolerances efficiently. The key benefits of CNC turning include:
- High productivity: CNC automation enables faster cycle times and continuous production. Parts can be machined unattended.
- Consistency: The programmed instructions ensure uniformity in the machining process. This results in consistent quality and interchangeable parts.
- Accuracy: CNC machines offer high accuracy up to 0.005 mm due to precise control over cutting parameters. Complex shapes can be machined accurately.
- Flexibility: Quick changeover between jobs allows producing small batches economically. Multiple operations like turning, drilling, threading can be done on one CNC lathe.
- Reduced wastage: Automated toolpaths optimize material usage. Scrap pieces are minimized.
- Operator safety: The operator does not need to physically manage the cutting process. Exposure to hazards is reduced.
- Cost-effectiveness: CNC turning has a higher upfront investment but lower per piece cost compared to manual turning for mid to high production batches.
The CNC Turning Process
The typical CNC turning process involves the following key stages:
Part Design
The dimensions and geometries of the required part are conceptualized using CAD software. Engineering drawings or 3D models of the part are created. Technical specifications like size, tolerances, surface finish are defined.
Toolpath Generation
The CAD file is imported into CAM software to generate the machining program. The cutting sequence, tool selection, speeds, feed rates, depth of cuts are optimized to create efficient toolpaths. Post-processing converts the toolpaths into G-code for the CNC machine.
Workholding Preparation
The raw material, usually a rod or tube, is securely clamped into a chuck or collet on the lathe headstock. Steady rests, drive plates, or tailstocks may be used for longer parts requiring support. The part must be properly aligned and centered.
The machining program is loaded into the CNC controller. The operator initiates production, and the turning cycle runs automatically per the programmed instructions. The part is machined sequentially as the tools follow the toolpaths derived from the CAM software.
Machined parts are measured to verify required dimensions and tolerances are achieved. Additional finishing operations may be done manually if needed before the part is sent for final inspection.
Heat treatment, surface treatments like plating or painting, secondary machining, and assembly operations may be conducted after initial CNC turning. The parts are then ready for shipment or inventory.
CNC Turning Operations
CNC lathes can perform a variety of turning, facing, drilling, boring, threading, grooving, and forming operations on parts. The main operations include:
- Facing: Machining and squaring the face of the part. Performed by feeding the tool perpendicular to the axis of the workpiece.
- Turning: Machining the external diameter of the part using a cutting tool fed parallel to the axis of rotation. Produces the round contours and precision diameters.
- Boring: Enlarging existing holes or internal diameters. Accomplished by feeding the boring tool into a rotating hole.
- Drilling: Creating holes axially in the face or diameter of the workpiece with a rotating drill bit.
- Grooving: Cutting grooves or recess into the diameter or face of the part using a tool with a shaped cutting profile.
- Threading: Generating internal or external screw threads by interpolating the cutter motion at the required lead angle.
- Knurling: Cold forming crosshatched patterns or decorative finishes on the part surface using knurling tools.
- Forming: Using form tools to machine complex angular or curvilinear contours.
The variety of programmable tool motions like linear, transverse, rotational and interpolated movement allow generating even very intricate component shapes by CNC turning with multiple features in a single setup.
Equipment for CNC Turning
The primary equipment components required for CNC turning include:
- CNC Turning Center: The heart of the system. Highly rigid with a programmable computer control to manage axes motion and machining functions.
- CNC Controller: Computes the motions from CAD/CAM inputs and controls the machine tools accordingly via PLCs. Equipped with processor, drives, feedbacks, and I/O systems.
- Tool Turret: Holds multiple cutting tools and indexes them automatically for sequential machining operations. Can have 8, 10, 12 or more tool stations.
- Tool Holders: Hold and clamp cutting inserts to the turret in a fixed repeatable position. Available for external turning, grooving, threading, boring.
- Cutting Tools: The replaceable cutting inserts with special geometry. Made of carbides, ceramics, CBN, diamond for high hardness and wear resistance.
- Chuck: Located on the main spindle. Clamps the workpiece firmly for concentric turning. Self-centering chucks simplify setups.
- Tailstock: Supports the free end of long workpieces. Can also hold centers, drills or tools for operations like drilling, boring, threading.
- Coolant System: Delivers coolant to the cutting interface for temperature regulation, chip flushing, lubrication. Prevents damage to tool and workpiece.
- Automation: Robotic part load/unload systems, pallet conveyors, parts catchers to integrate turning processes into automated manufacturing cells.
- Safety Enclosure: Full enclosures with interlocks for protection against hazards like chips, coolant, noise.
CAD/CAM software, tool presetters, metrology equipment, chip conveyors, mist collectors etc. are other supporting infrastructure for a complete CNC turning production system.
Advantages and Disadvantages of CNC Turning
Some of the main advantages of using CNC turning technology are:
- Higher productivity compared to manual turning. Around 3-4 times faster.
- Ability to run unmanned. 24/7 operational utilization.
- Excellent dimensional accuracy and repeatability. Tolerances up to 0.003 mm are achievable.
- Complex parts can be machined, even small batch sizes. Flexible manufacturing.
- Automated tool changes allow completing parts in single setup.
- Safer to operate since operator involvement is minimized.
- Skilled labor is easier to source and train vs manual machinists.
- Higher quality surface finish down to 0.2 microns.
- Wastage reduction by optimizing material usage. Minimal scrap losses.
The limitations and disadvantages of CNC turning are:
- High initial capital investment. Machines are expensive.
- Not ideal for very large diameter parts. Capacity is limited.
- Programming expertise and CAD/CAM knowledge needed. Additional cost.
- Preventive maintenance and skilled personnel needed to maintain CNC equipment.
- Not economically viable for very low volume production. Setups take time.
- Larger floor space requirements compared to manual turning.
- Potential for downtime and lost production. Require backup systems.
CNC turning provides game-changing productivity, quality, and manufacturing agility for turned components. For short-to-medium runs, extremely complex parts, or highly accurate tolerance requirements, CNC turning is usually the optimum and competitive process choice. The automation enables "done-in-one" production improved productivity and reduced costs compared to manual turning. For very large runs, specialized machines like automats or Swiss-type CNC lathes may offer advantages over general CNC turning centers. But for most common turned parts requirements, appropriately applied CNC turning technology provides strategic benefits for manufacturers. CNC Milling CNC Machining