Bài giảng môn Tia Lửa điện English SPKT TPHCM

Electrical Discharge Machining (EDM) Technology Dr Hoang Trung Kien 2015-2016/ 2nd semester CHAPTER I INTRODUCTION MANUFACTURING PROCESS Manufacture Assembly Design Quality Control Factory Call Packing Service Delivery MANUFACTURING TECHNOLOGY • Casting • Molding • Forming • Cutting (machining) • Joining • Additive manufacturing • Others MACHINING TECHNOLOGY • Traditional - Turning - Milling - etc • Non-traditional - EDM, ECM - Laser cutting - etc WHAT IS EDM? • Electrical discharge machining is: o a manufacturing process o a thermal process o a non-contact machining process o an electrical process EDM SYSTEM Nozzle holder Workpiece Reservoir/ Filtration Dielectric circulation Dielectric medium Tool Power supply Pump TYPES OF EDM Die-sinker EDM Wire cut Drilling EDM Milling EDM WEDM SYSTEM New wire spool Brush Wire-guide Tension adjustment Pulse generator Wire-guide Workpiece Used wire collected spool CHAPTER APPLICATIONS OF EDM APPLICATION OF EDM • Prototype production • Coinage die making • Small hole drilling • Metal disintegration machining APPLICATION OF EDM Die-sinker Die & Mold Drilling Meta disintegration Milling Hole & deep cavity Prototype production CHAPTER WIRE EDM WIRE EDM New wire spool • Principle Brush Wire-guide Tension adjustment Pulse generator Wire-guide Workpiece Used wire collected spool WIRE • Wire spools Wire diameter: 0.02 ~ 0.3 mm WIRE • Materials Brass wire Zinc coated brass wire Tungsten wire FLUSHING IN WEDM Wire guide + nozzle Nozzle Wire guide Dielectric Dielectric Wire guide flushing Nozzle flushing FLUSHING IMPROVEMENT • Vibration-assisted method Upper guide Wire holder Vibrated travelling wire PZT Pulse generator Pulse generator Amplifier Amplifier Travelling wire Insulating adapter Vibration PZT Lower guide Workpiece Vibration MACHINING ERROR • Corner error WIRE EDG • Wire electrical discharge grinding WIRE EDG A Wire EDM module CHAPTER APPLICATIONS OF WEDM CHAPTER WEDM APPLICATION • Cutting tools making • Dies and molds making • Narrow slots cutting • Electrodes for EDM WEDM AND OTHER METHODS Wire EDM Waterjet Plasma Accuracy ±0.0001" (±0.0025mm) ±0.003" (±0.1 mm) Thickness 19.6" (500 mm) very Slow speed (5-10 times slower than water jet) < 3"(75mm) < 1.25“ (30 mm) five to ten times faster than EDM (thickness < Fast with thin sheets 1“) < 0.25“ (6.35mm) Very fast cutting in thin, non-reflective materials Excellent Good edge quality Fair Excellent Some HAZ No HAZ Some HAZ High HAZ Cutting speed Quality of edge Heat affected zone (HAZ) ±0.030 to ±0.060" Laser Material Distortion material heat distortion hazing near the cut but small Others works well in both nonEDM is limited to conductive and cutting only conductive conductive materials Relatively low capital materials but is able to Fast setup and rapid costs Special gas need cut hard material programming regardless of hardness Minimal requirement of fixture ±0.001" (±0.025 mm) material heat distortion material heat distortion works well in both nonconductive and conductive materials but limited to nonreflective materials May need different gas for cutting different materials [...]... charge) Breakdown Plasma Ionization Voltage Arc Gas, liquid or solid DISCHARGE PROCESS Electron Atom or molecule Ion − + Primary initiation ICCD image capture by E.H.R Gaxiola (1999) + ̶ ̶ ̶ + + ++ ̶ + + ̶ + ̶ ̶ + + + + + + + + ̶ ̶ + ++ + ̶ ̶ + + ̶ + ̶ + ++ ̶ ̶ + Secondary initiation Cathode (-) Townsend avalanche (thác) theory Anode (+) DISCHARGE PROCESS U Uo Ue td te to t i ie t