Transcription
Computer Numerical Control(CNC)Banu AkarNeşe KaynakDuygu GökçeMeltem ErdiHacettepe UniversityChemical Engineering Department22.12.2010
CONTENT1.2.3.4.5.6.7.8.9.What are NC & CNC?HistoryCNC system ElementsProperties of CNC machineTypes of CNC machinesCNC applicationsAdvantages& DisadvantagesConclusionReferences
What are NC & CNC ? Numerical control (NC) is a method of automaticallyoperating a manufacturing machine based on a codeletters, numbers and special characters. The numerical data required to produce a part isprovided to a machine in the form of program, called partprogram or CNC (computer numerical control)
What are NC & CNC ? The program is translated into the appropriate electricalsignals for input to motors that run the machine. A CNC machine is an numerical control machine withthe added feature of an on board computer. Thecomputer is referred to as the machine control unit(MCU)
HISTORY In 1775, John Wilkinson- cannon boring machine (lathe).In 1881, Eli Whitney- milling machine.In 1947, Mr. John Parsons began experimenting forusing 3-axis curvature data to control the machine toolmotion for the production for aircraft components.In 1949, parsons- first NC machine.In 1951, MIT was involved in the project.In 1955, after refinements NC became available inindustryToday, modern machinery are CNC milling machinesand lathes.
CNC SYSTEM ELEMENTSA typical CNC system consists of the following sixelements Part program Program input device Machine control unit Drive system Machine tool Feedback systemFigure 1 : Schematic illustration of the majorcomponents of a numerical control machine tool
Basic Concept of Part Programming Part programming contains geometric data about the part andmotion information to move the cutting tool with respect to the workpiece.Basically, the machine receives instructions as a sequence of blockscontaining commands to set machine parameters; speed, feed andother relevant information.A block is equivalent to a line of codes in a part program.N135 G01 X1.0 Y1.0 Z0.125 T01 F5.0CoordinatesBlock numberG-codeSpecial functionTool number
Programming Methods Automatically Programmed Tools (APT) A text based system in which a programmer defines aseries of lines, arcs, and points which define theoverall part geometry locations.These features are then used to generate a cutterlocation (CL) file.
Programming Methods Computer Aided Machining (CAM) SystemsComputer Aided Design (CAD) Systems CAD/CAM systems allow for rapid development andmodifying of designs and documentation.The 3D geometric model produced becomes a commonelement for engineering analysis (FEA), machiningprocess planning (including CNC part programming,documentation (including engineering drawings), qualitycontrol, and so on.
Drives of CNC machine tool Hydraulic actuator- high power machine tool Stepping motor- small machine due to limited power and torque DC motor- excellent speed regulation, high torque, most widelyused
Properties of CNC machines Based on Motion Type: Motion control - the heart ofCNCPoint-to-Point or Continuous path Based on Control Loops:Open loop or Closed loop Based on Power Supply:Electric or Hydraulic or Pneumatic Based on Positioning SystemIncremental or Absolute
Point-to-Point Tool Movements Point-to-point control systems cause the tool tomove to a point on the part and execute an operationat that point only.The tool is not in continuous contact with the partwhile it is moving.Examples: drilling, reaming, punching, boring andtapping.Figure 2 : http://www.tradekorea.com/products/cnc machine.html
Continuous-Path Tool Movements Continuous-path controllers cause the tool tomaintain continuous contact with the part as the toolcuts a contour shape. These operations include milling along any lines atany angle, milling arcs and lathe turning.Figure 3: http://kaymak06.50webs.com/cnc.html
Loop Systems for Controlling ToolMovementSchematic illustration of the components of (a) an open-loop and (b) a closed-loop controlsystem for a CNC machine.Figure 4 : http://www.nd.edu/ manufact/MET%20pdf files/MET Ch37.pdf
Types of CNC Machines Lathe MachineMilling MachineDrilling MachineThe bench drillThe pillar drill Boring MachineGrinding Machine
Types of CNC MachinesCNC Mills These machining centers usecomputer controls to cut differentmaterials. They are able to translateprograms consisting of specificnumber and letters to move thespindle to various locations anddepths. Used to make 3D prototypes,moulds, cutting dies, printingplates and sights.Figure 5 uct.asp?id 24916
Types of CNC MachinesCNC Lathes They cut metal that is often turningat fast speeds. CNC lathes are able to make fast, precision cuts using indexabletools and drills with complicatedprograms.Normally, they cannotbe cut on manual lathes.They often include 12 tool holdersand coolant pumps to cut down ontool wear.Figure 6 :http://www.automation-drive.com/cnc-lathe-machine
Types of CNC MachinesTurning Centers are capable of executing manydifferent types of lathe cutting operationssimultaneously on a rotating part.Figure 7 : ng-center-bml-420.htm
Types of CNC MachinesCNC Grinders Grinding metal process uses a coated wheel that slowlyremoves metal to create apart.Through the years, grindingwas done on a manualmachine, but with the adventof CNC technology, thegrinding process hasadvancedFigure 8 c-surface-grinding-machine.html
Types of CNC MachinesCNC DRILLINGDrilling is commonly used for mass production. The drilling machine(drilling press) is used to create or enlarge holes.Drilling machine for different jobs;The bench drill: For drillingholes through raw materials suchas wood, plastic and metalThe pillar drill: A larger versionthat stands upright on the floor.As the bench drill, it can be usedto drill larger pieces of materialsand produce bigger holes.Figure 9 : http://www.metalshopsolutions.com/
Types of CNC MachinesCNC Boring Process of enlarging anexisting hole or internalcylindirical surface.This can be accomplished ona lathe or a machine toolspecifically designed for theprocess, such as a horizontalboring machine.Figure ne/108-what-is-cnc.html
Types of CNC MachinesElectrical Discharge Machines (EDM)Wire EDM machines utilize a very thin wire (.0008 to .012in.) as an electrode. The wire is stretched betweendiamond guides and carbide that conduct current to thewire and cuts the part like a band saw.Material is removed by the erosion caused by a spark thatmoves horizontally with the wire.Figure 11: -tools/electro-discharge-machines
Types of CNC MachinesLaser Cutting Machines The machine utilizes an intensebeam of focused laser light to cutthe part. Material under the beamexperiences a rapid rise intemperature and is vaporized. Laser cuts with a minimum ofdistortion, no mechanical cuttingforces.Figure 12 :http://zaipul.wikispaces.com/file/view/01 Introduction to CNC Technology.pdf
Specific tools to perform differentoperationsFigure 13: http://users.isr.ist.utl.pt/ pjcro/courses/api0910/API I C5.pdf
Specific tools to perform differentoperationsFigures 14: http://users.isr.ist.utl.pt/ pjcro/courses/api0910/API I C5.pdf
APPLICATION of CNCMACHINES cutting drillingmilling welding bending pinning sewingboringspinninggluingrouting
Application of CNC in SomeIndustries Automotive IndustryAerospace IndustryMachinery IndustryElectrical IndustryInstrumentation Industry
Automotive IndustryDifferent ProductsFigure 15:http://www.efunda.com/eds/company details.cfm/id2/4846/pv/NO/cp/Zhejiang%2020Co
Aerospace IndustryAircraft Turbine Machined by5-Axis CNC Milling MachineFigure 16: http://boeingcockpit.com/html
Advantages of CNC MachinesEase of Use CNC machines are easier for beginnersoperation of several CNC machines at same timesome CNC machines don’t need any operator call their operator in case of the emergencies.High Efficiency operate almost continuously 24 hours a day, 365 days ayear
Expanding Options Expand the machine's capabilities with Softwarechanges and updatesNo Prototyping New programmes provide elimination build a prototype,save time and moneyPrecision Parts are identical to each other
Reduce Waste Reduce waste as errors allows minimize wastedmaterial.
Disadvantage of CNC MachinesCostCNC machinery: costs quite a lot more than conventional machinery does not eliminate the need for expensive tools expensive to repair
CONCLUSION CNC machines which are applicable any type ofprocessingmanufacturing anything is identical in shorter timeCNC machines provide many advantagesmany industries prefer using CNC machines
Thank you
REFERENCES http://www.ehow.com/about 5415088 TCNC.pdfhttp://users.isr.ist.utl.pt/ pjcro/courses/api0910/API I C5.pdfhttp://www.tradekorea.com/products/cnc p://www.nd.edu/ manufact/MET%20pdf files/MET 01/product.asp?id neshttp://zaipul.wikispaces.com/file/view/01 Introduction to CNC tp://www.efunda.com/eds/company .au/toolbox8/furniture/toolbox/shared/resources mw/ask expert/tony/advantages.htm
process planning (including CNC part programming, documentation (including engineering drawings), quality control, and so on. Drives of CNC machine tool Hydraulic actuator - high power machine tool Stepping motor - small machine due to limited power and torque DC motor - excellent speed regulation, high torque, most widely used. Properties of CNC machines Based on Motion Type: Motion control .
