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ME 440: Numerically Controlled Machine Tools Outline

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ME 440: Numerically Controlled Machine Tools Outline Outline – Introduction ME 440: Numerically Controlled Machine Tools • Basic Definitions – Machine Tools – Precision Engineering Introduction • Historical Developments • Numerical Control Assistant Prof. Melik Dölen • Direct Numerical Control Department of Mechanical Engineering • CtNilCtlComputer Numerical Control • Distributed Numerical Control Middle East Technical University – Flexible Manufacturing Systems Chapter 1 ME 440 2 Definition of Machine Tool Conventional Machine Tools • Milling Mac hine • A machine used for sculpturing metal and • Lathe other substances to the desired form. • Drilling/Boring Machine • A machine system utilized for producing • Shaper/Planer machine par ts an d e lemen ts. • Grinding Machine •A machine tool is a powered mechanical • Filing Machines device, typically used to fabricate metal • Sawing Machines comppyonents of machines by the selective removal of metal. Chapter 1 ME 440 3 Chapter 1 ME 440 4 Non-traditional Machine Tools Machining Accuracy • Electro-Discharge Machine • Wire EDM • Plasma Cutter • Electron Beam Machine • Laser Beam Machine Chapter 1 ME 440 5 Chapter 1 ME 440 6 Ultraprecision Machining History of Machine Tools Processes • 1770: Simple production machines • Single-point diamond and mechanization – at the turning and CBN beggginning of the industrial cutting revolution. • 1920: Fixed automatic mechanisms • Abrasive/erosion and transfer lines for mass processes (fixed and production. free) • 1945: Machine tools with simple automatic control, such as plug • Chemical/corrosion board controllers. processes (etch- • 1952: Invention of numerical control machining) (NC). Chapter 1 ME 440 7 Chapter 1 ME 440 8 History of Machine Tools (Cont’ d) History of Machine Tools (Cont’d) • 1961: First commercial Industrial robot. • 1972: First CNCs introduced. • 1978: Flexible manufacturing system (FMS); contains CNCs, robots, material transfer system. • 1990: Aggyile system concep ts. • 2000: Reconfigurable Machining Systems that are scalable and convertible. Chapter 1 ME 440 9 Chapter 1 ME 440 10 History of Numerical Control History of Numerical Control • 1952-1955: John (Cont’d) Parsons and U.S. Air • 1959: M.I.T. announces Force define a need to Automatic Programmed Tools develop a machine tool (APT) programming language. capable of machining complex and close • 1960: Direct Numerical Control tolerance aircraft parts (DNC). This eliminates paper with the same quality tape punch programs and time after time allows programmers to send (repeatability). files directly to machine tools. – M.I.T. (Servomechanisms • 1968: Kearney & Trecker Lab) builds the machine machine tool builders market for the project. first machining center. Chapter 1 ME 440 11 Chapter 1 ME 440 12 History of Numerical Control Numerical Control (Cont’d) • 197X: CNC machine tools & • The Electronics Industry Association (EIA) Distributed Numerical Control. defines NC as "a system in which actions are • 198X: Graphics based CAM systems controlled by the direct insertion of numerical introduced. UNIX and PC based data at some point.“ systems available. • A control system that primarily processes • 199X: Price drop in CNC technology numeric input. • 1997: PC Windows/NT based “Open – Limited programming capability at the machine tool. Modular Architecture Control – Limited loggyic beyond direct inp ut. These typ es of (OMAC)”(OMAC) systems introduced to systems are referred to as “hardwire controls” and replace “firmware” controllers. were popular from the 1950’s to 1970’s. Chapter 1 ME 440 13 Chapter 1 ME 440 14 NC Machine Tool Punched Tape and EIA Code Chapter 1 ME 440 15 Chapter 1 ME 440 16 Tape Devices Direct Numerical Control Teleprinter Acramatic 900 with Tape Reader • Used modems, and a mainframe which emulated a tape reader, to control the NC machine (no storage) • PdlddfthiPrograms are downloaded from the main DNC computer, and then a local controller feeds instructions to the hardwired NC machine, as if they have been read from tape. Chapter 1 ME 440 17 Chapter 1 ME 440 18 Advantages of DNC Computer Numerical Control • Eliminates the need for NC tapes • A numerical control system in which the data handling, control sequences, and – reduces ppperipheral costs with NC tap es. response to input is determined by an • Design changes are immediate. on-board computer system at the machine tool. •NC programs may be edited quickly. • Advantages: – Increased program storage capability at the • Increase efficiency of individual machine machine tool tools – Program editing at the machine tool – Control systems upgrades possible – more shop up-time than with stand -alone – (Optional) CAM program at machine tool machines – Tool path verification (simulation). Chapter 1 ME 440 19 Chapter 1 ME 440 20 New DNC Concept New DNC Concepp(t (Cont’d) • DNC controllers came before CNC machines. • As computer technology evolved, it became practical to place a computer inside the NC machine tool and DNC changed its form! • The new technique still use a central computer which communicates with the local CNC machines. – uses a server (with large storage capacity) to store a large number of part programs – the server will download part programs on demand to local machines. Chapter 1 ME 440 21 Chapter 1 ME 440 22 FMS Concept New DNC Concept (Cont’d) Computer control room • DNC may have a bilities to • Programmable – display and edit part programs Conveyor machine tools – tittittidthdtddtransmit operator instructions and other data needed MhiMachine Machine • CtlldbControlled by at the machines Pallet common computer – collect and process machine status information for management purposes netktwork • Suppor t an FM S syste m • Combines flexibility – simplifies implementation of with efficiency • Group technology • Reduces setup & • Computer aided process planning Load Unload queue times • CIM concepts Finished Parts Terminal goods Chapter 1 ME 440 23 Chapter 1 ME 440 24.
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