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Contents

Unit 1 Fundamentals of Electrical Discharge Machining

1. Understanding Electrical Discharge Machining

Electrical Discharge Machining .................................................................19 Various Electric Discharge Machines ........................................................20 A. Wire EDM .......................................................................................20 B. Ram EDM .......................................................................................20 C. Small Hole EDM Drilling ...............................................................21 Materials That Can Be EDMed..................................................................21 Keeping Abreast With EDM Technology ..................................................22 The Machining Revolution ........................................................................23 Understanding Accuracy ............................................................................24 Automation and EDM ................................................................................25 American Economy and Globalization ......................................................26

Unit 2 Wire EDM

2. Wire EDM Fundamentals

Revolutionizing Machining .......................................................................29 Wire EDM Beginnings...............................................................................30 Production Wire EDM ...............................................................................31 Capabilities of Wire EDM .........................................................................32 Wire EDM a Serious Contender With Conventional Machining ...............32 New Demands by Design Engineers..........................................................33 Fully Automated Wire EDMs ....................................................................34 How Wire EDM Works ..............................................................................35 The Step by Step EDM Process ................................................................37 A. Power Supply Generates Volts and Amps .......................................37 B. During On Time Controlled Spark Erodes Material .......................37 C. Off Time Allows Fluid to Remove Eroded Particles.......................38 D. Filter Removes Chips While the Cycle is Repeated .......................38 Super Precision Band Saw ........................................................................39 Independent Four Axis ...............................................................................40 Understanding Independent Four Axis ......................................................42 Submersible Cutting...................................................................................43 Staying Competitive...................................................................................44

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3. Profiting With Wire EDM

Users of Wire EDM ...................................................................................45 Benefits Of Wire EDM...............................................................................45 A. Production Runs ..............................................................................45 B. Various Shapes and Sizes ................................................................46 C. Accuracy and Finishes.....................................................................46 D. Eliminates Extra Machining Processes ...........................................46 E. Burr Free and Perfectly Straight Machining ...................................47 F. Damaged Parts Can Be Repaired with Inserts .................................47 G. Less Need for Skilled Craftspersons ...............................................48 H. Material Hardness Not a Factor ......................................................48 I. Computers Can Perform Calculations ..............................................48 J. Digitizing is Possible ........................................................................49 K. Miniaturization of Parts ..................................................................50 L. Machining With Nozzles Away from Workpiece ............................50 M. Reliable Repeatability ....................................................................51 Parts for Wire EDM ...................................................................................51 A. Precision Gauges and Templates ....................................................51 B. Keyways vs. Broaching ...................................................................52 C. Shaft Slots .......................................................................................52 D. Collets .............................................................................................52 E. Parting Tubes and Shafts .................................................................53 F. Shaft Pockets ....................................................................................53 G. Fabrication of Graphite Electrodes for Ram EDM .........................53 H. Punches and Dies From One Piece of Tool Steel ............................54 I. Progressive Stamping Dies ...............................................................54 J. Short-Run Stampings .......................................................................55 K. Molds ..............................................................................................55 L. Special and Production Tool Cutters ...............................................55 M. Difficult-to-Machine Shapes ..........................................................56 N. Other Cost-Reducing Parts..............................................................56 Cutting Shim Stock Absolutely Burr Free .................................................58 Single Cavity Cut With Wire EDM Into One Side of a Tube ....................59 Horizontal Wire EDM ................................................................................60 Machining Costs ........................................................................................60

4. Proper Procedures for Wire EDM

Starting Methods for Edges and Holes ......................................................61 Three Methods to Pick Up Dimensions. ..............................................61 A. Pick Up Two Edges as in Figure 4:1. ........................................61 B. Pick Up a Hole as in Figure 4:2. ...............................................61 C. Pick Up an Edge and Holes or Two Holes as in Figure 4:3 ......62 Edge Preparation ........................................................................................62 A. Square Edges ...................................................................................62 1. Machined or Ground. .................................................................62 2. Unfinished Edges. ......................................................................63 B. Scale ................................................................................................63

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C. Pick-Ups ..........................................................................................64 Starter Holes...............................................................................................64 A. Automatic Pick-up...........................................................................64 B. Unsquare Holes ...............................................................................65 C. Relieved Holes ................................................................................65 D. Smooth Holes ..................................................................................65 E. Placement and Location of Starter Holes ........................................66 Layout .......................................................................................................67

5. Understanding the Wire EDM Process

Accuracy and Tolerances ...........................................................................69 Finishes ......................................................................................................69 Wire Path....................................................................................................70 A. Wire Kerf.........................................................................................70 B. Corners and Radii ............................................................................71 Skim Cutting ..............................................................................................71 A. Barreling Effect and Wire Trail-Off ................................................72 B. Metal Movement .............................................................................73 C. Finishes and Accuracy.....................................................................73 Carbide .......................................................................................................74 Polycrystalline Diamond............................................................................74 Ceramics ....................................................................................................75 Flushing .....................................................................................................75 Cutting Speed .............................................................................................76 Impurities ...................................................................................................76 Recast and Heat-Affected Zones ...............................................................77 AC Non-Electrolysis Power Supplies ........................................................77 Isolated Pitting ...........................................................................................78 Heat-Treated Steels ....................................................................................79 Cutting Large Sections ...............................................................................79 Cutting Sections From a Block ..................................................................80 A. Leaving a Frame..............................................................................80 B. Strength of Frame ............................................................................81 C. Material for Clamping .....................................................................81 Understanding the Wire EDM Process ......................................................81

6. Reducing Wire EDM Costs

Create One Slug .........................................................................................83 Keeping Flush Nozzles on the Workpiece .................................................85 Machining After Wire EDM ......................................................................86 Cutting Multiple Plates and Sheet Metal Parts ..........................................87 Production Lots ..........................................................................................88 Stipulating Wire Sizes ................................................................................89 Pre-Machining Non-Complicated Shapes..................................................90

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7. Advantages of Wire EDM for Die Making

Tool and Die Making .................................................................................91 Old-Fashioned Tool and Die Making.........................................................91 The Revolution...........................................................................................94 Advantages of Wire EDM Dies.................................................................94 1. One-Piece Die Sections....................................................................94 2. Exact Spare Parts .............................................................................95 3. Dowel Holes EDMed .......................................................................95 4. Better Tool Steels .............................................................................95 5. Accuracy ..........................................................................................95 6. Die Repairs.......................................................................................95 7. Fine Textured Finish ........................................................................96 8. Eliminates Distortion .......................................................................96 9. Inserts for High Wear Areas .............................................................96 10. Smaller Dies ...................................................................................96 11. Longer Lasting ...............................................................................96 12. Punches and Dies From One Piece of Tool Steel...........................97 13. Cutting Stripper and Die Section Together ....................................97 Punches ......................................................................................................98 A. Large Punches .................................................................................98 B. Holding Small Punches ...................................................................99 1. Footed .......................................................................................99 2. Shoulder ....................................................................................99 3. Keyed In--Toe Clamps ...........................................................100 4. Keyed In--Keyway ................................................................100 5. Press Fit ...................................................................................101 6. Peened Edge ............................................................................101 7. Dowel Pin Reamed .................................................................101 8. Dowel Pin EDMed ..................................................................102 9. Set Screws ...............................................................................102 10. Socket Head Cap Screw ........................................................102 11. Ball Bearings .........................................................................103 C. Skim Cutting .................................................................................104 Die Sections .............................................................................................104 A. Heavy Blanking Dies ....................................................................104 B. Avoid Sharp Corners .....................................................................104 C. Heat-Treating.................................................................................104 D. Large Die Sections ........................................................................105 E. Tapers.............................................................................................105 1. Taper and Land.........................................................................105 2. Straight Cut and Taper .............................................................106

8. Wire EDMing One-Piece Stamping Dies

Blanking Die ............................................................................................107 A. Desired Stamping ..........................................................................107 B. Preparing the Tool Steel Blank ......................................................107 C. Placement of Starter Hole .............................................................108

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1. Punch Shape is the Desired Stamping .....................................108 2. Blank Shape is the Desired Shape ..........................................109 D. Harden the Tool Steel Blank .........................................................110 E. Stripper Plate .................................................................................110 F. Punch Holder .................................................................................110 G. Mount Die Blank on Die Set .........................................................111 H. Mount Punch Holder onto the Die Set ..........................................111 I. Mount Stripper on Bottom of Die Section......................................112 J. Wire Cut Punch, Die and Stripper ..................................................113 Total Burr-Free One-Piece Blanking Die.................................................114 Compound Blanking Dies ........................................................................115 A. Desired Stamping .........................................................................115 B. Prepare Tool Steel Blank ...............................................................115 C. Mount Punch Holder .....................................................................116 D. Mount Die Block on Bottom of Die Set .......................................116 E. Mount Punch Holder on Top of Die Set ........................................117 F. Stripper Plate ..................................................................................117 G. Wire EDM Compound Die ...........................................................117 H. Completed Die ..............................................................................118 1. Stripper with Springs ...............................................................118 2. Stripper with Knockout ............................................................119 Wave of the Future ...................................................................................120

Unit 3 Ram EDM

9. Fundamentals of Ram EDM

Ram EDM Machining ..............................................................................123 Ram EDM Beginnings .............................................................................125 How Ram EDM Works ............................................................................127 The Step-by-Step Ram EDM Process ......................................................128 Polarity .....................................................................................................130 No-Wear ...................................................................................................130 Fuzzy Logic .............................................................................................130 Fumes from Ram EDM ...........................................................................130 Benefits of Understanding the Process ....................................................130

10. Profiting With Ram EDM

Uses of Ram EDM ...................................................................................131 Benefits of Ram EDM..............................................................................132 A. Different Shapes and Sizes ...........................................................132 B. Accuracy and Finishes...................................................................133 C. Workpiece Hardness Not a Factor .................................................133 D. EDMing Threads Into Hardened Parts ..........................................133 Parts for Ram EDM .................................................................................134

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A. Molds ............................................................................................134 B. Blind Keyways ..............................................................................134 C. Internal Splines..............................................................................135 D. Hexes for Special Bolts and Parts .................................................135 E. Helical Gear Machining ................................................................135 Micro Machining for Ram EDM .............................................................136 Machining Large Pieces ...........................................................................136 Materials for Ram EDM ..........................................................................137 Speeding the Mold Processing ................................................................137 EDMing Carbide ......................................................................................137 Proper Procedures for Ram EDM ............................................................137

11. Ram EDM Electrodes and Finishing

Electrodes.................................................................................................139 A. Function of the Electrode ..............................................................139 B. Electrode Selection........................................................................139 C. Type of Electrode Materials ..........................................................140 D. Galvano Process for Metallic Electrodes ......................................141 E. Custom Molded Metallic Electrodes .............................................141 F. Graphite Electrodes ........................................................................141 H. Electrode Wear ..............................................................................143 I. Abrading Graphite Electrodes ........................................................144 I. Ultrasonic Machining for Graphite Electrodes ...............................146 J. Wire EDMing Metallic and Graphite Electrodes ...........................146 K. Electrodes and C Axis ...................................................................147 H. Electrode Overcut .........................................................................147 Recast and Heat-Affected Zone ...............................................................148 Finishing ..................................................................................................149 Mirror Finishing and Diffused Discharge Machining..............................150 Micro Machining .....................................................................................151

12. Dielectric Oil and Flushing for Ram EDM

Dielectric Oil............................................................................................155 Coolant System ........................................................................................156 Flash Point ...............................................................................................156 Flushing ...................................................................................................156 A. Proper Flushing .............................................................................156 B. Volume, Not Pressure ....................................................................156 C. Types of Flushing ..........................................................................157 1. Pressure Flushing .....................................................................157 a. Pressure Flushing Through the Electrode ..........................157 b. Pressure Flushing Through the Workpiece ........................158 2. Suction Flushing ......................................................................159 3. Combined Pressure and Suction Flushing ...............................160 4. Jet Flushing ..............................................................................160 5. Pulse Flushing ..........................................................................161 a. Vertical Flushing ................................................................161

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b. Rotary Flushing..................................................................162 c. Orbiting Flushing ...............................................................163 Filtration System ......................................................................................164 The Challenge of New Procedures ..........................................................164

13. Reducing Costs for Ram EDM

Preparing Workpieces for Ram EDM ......................................................165 Difference Between Ram and Wire EDM in Reducing Costs .................165 Prolonging Electrode Life With No-Wear EDMing and No Premachining166 Electrode and Workpiece Holding Devices .............................................167 Orbiting ....................................................................................................168 Manual Machines Mounted With Orbiting Devices ................................172 Repairing Molds With Microwelding ......................................................172 Abrasive Flow Machining........................................................................173 Automatic Tool Changers ........................................................................173 Future of Ram EDM ................................................................................175

Unit 4 Small Hole EDM Drilling

14. Small Hole EDM Drilling

How Small Hole EDM Drilling Works ....................................................181 A. Dielectric and Flushing Pressure...................................................182 B. The Electrode ................................................................................182 C. Electrode Guides ...........................................................................184 D. Servo Motors .................................................................................184 Metal Disintegrating Machines Compared to Small Hole EDM Drilling185 Other Methods to Produce Holes .............................................................185 Disadvantages in Small Hole EDM Drilling ...........................................185 A. Electrode Wear ..............................................................................185 B. Reduced Speed for Large Holes ....................................................185 C. Blind Holes are Difficult to Control ..............................................185 Advantages in EDM Drilling ...................................................................186 A. Drilling on Curved and Angled Surfaces ......................................186 B. Drilling Hardened Materials..........................................................186 C. Materials That Produce Chips that Cling to Cutters .....................186 D. Drilling Deep Holes ......................................................................186 E. No Hole Deburring ........................................................................187 F. Preventing Broken Drills ...............................................................187 G. Creating Straight Holes .................................................................187 Accuracy of Small Hole EDM Drilling ...................................................187 Versatility of Small Hole EDM Drilling ..................................................188 Conclusion ...............................................................................................189

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Unit 5 Questions*

15. Questions

About the Authors ................................................................................193 1. Fundamentals of Electrical Discharge Machining ...............................193 2. Wire EDM Fundamentals ....................................................................194 3. Profiting With Wire EDM ....................................................................195 4. Proper Procedures for Wire EDM ........................................................196 5. Understanding the Wire EDM Process ................................................196 6. Reducing Wire EDM Costs ..................................................................197 7. Advantages of Wire EDM for Die Making ..........................................198 8. Wire EDMing One-Piece Stamping Dies ............................................198 9. Fundamentals of Ram EDM ................................................................199 10. Profiting With Ram EDM ..................................................................200 11. Ram EDM Electrodes and Finishing .................................................200 12. Dielectric Oil and Flushing for Ram EDM ........................................201 13. Reducing Costs for Ram EDM ..........................................................202 14. Small Hole EDM Drilling ..................................................................203

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