EDM Process Analysis, Processing Advantages Limitations

1. Process Introduction

Electrical Discharge Machining, Also Known As Electrical Discharge Machining (EDM) Electro-Erosion Machining, Is One Of The Four Most Popular Machining Methods, On Par With Milling, Turning Grinding.

Completely Different The Principle Of Metal Cutting, EDM Is A Process Method That Uses The Electrical Erosion Effect Of Pulse Discharge Between The Tool Electrode The Workpiece Electrode. Since Sparks Can Be Seen During The Discharge Process, It Is Called EDM. Huiwen Zhizao Is A Machining Factory With More Than Ten Years Of CNC Machining Experience . It Has A Full Range Of Equipment, CNC Lathe/Milling/Grinding/Drilling/Machining. Partners With Parts Processing Needs Are Welcome To Call Us For Quotes.

According To The Different EDM Processes, EDM Can Be Divided Into EDM Wire Cutting , EDM Perforation Forming, EDM Grinding Boring, EDM Synchronous Conjugate Rotary Machining, EDM High-Speed Small Hole Machining, EDM Surface Strengthening Engraving, Etc.

At Present, EDM Technology Has Been Widely Used To Process Various High Melting Point, High Strength High Toughness Materials, Such As Hardened Steel, Stainless Steel, Die Steel, Cemented Carbide, Etc., As Well As For Processing Molds Other Parts With Complex Surfaces Special Requirements.

2. Basic Principles Of EDM

The Principle Of EDM Is To Remove Excess Metal Based On The Electro-Corrosion Phenomenon During Pulsed Spark Discharge Between The Tool The Workpiece (Positive Negative Electrodes) To Achieve The Predetermined Processing Requirements For The Size, Shape Surface Quality Of The Workpiece. The Workpiece Tool Electrodes Are Connected To Two Electrodes Of Different Polarities Of The Pulse Power Supply. Tool Electrodes Are Usually Made Of Electro-Corrosion-Resistant Materials With Good Conductivity, High Melting Point Easy Processing, Such As Copper, Graphite, Copper-Tungsten Alloy Molybdenum. During The Processing, The Tool Electrode Also Has Loss, But It Is Less Than The Amount Of Metal Removed The Workpiece, Is Even Close To No Loss.

As A Discharge Medium, The Working Fluid Also Plays A Role In Cooling Chip Removal During The Processing. Commonly Used Working Fluids Are Media With Low Viscosity, High Flash Point Stable Performance, Such As Kerosene, Deionized Water Emulsion. Huiwen Zhizao Is A Machining Factory With More Than Ten Years Of CNC Machining Experience. It Has A Full Range Of Equipment, CNC Lathe/Milling/Grinding/Drilling/Machining. Partners With Parts Processing Needs Are Welcome To Call Us For Quotes.

When A Pulse Voltage Is Applied Between The Two Electrodes An Appropriate Gap Is Maintained Between The Workpiece The Electrode, The Working Fluid Medium Between The Workpiece The Tool Electrode Will Be Broken Down To Form A Discharge Channel.

Instantaneous High Temperature Is Generated In The Discharge Channel, Which Melts Even Vaporizes The Workpiece Surface Material. At The Same Time, The Working Fluid Medium Is Also Vaporized, Which Rapidly Expands Explodes In The Discharge Gap. A Small Part Of The Workpiece Surface Material Is Etched Away Thrown Out, Forming Tiny Electro-Etching Pits.

After The Pulse Discharge Ends, After A Period Of Time, The Working Fluid Is Insulated Again. The Pulse Voltage Acts Repeatedly On The Workpiece The Tool Electrode. The Above Process Is Repeated Continuously, The Workpiece Material Is Gradually Etched Away.

The Servo System Continuously Adjusts The Relative Position Of The Tool Electrode The Workpiece, Automatically Feeds, Ensures Normal Pulse Discharge Until The Required Parts Are Processed.

3. Advantages Of EDM

EDM Does Use Mechanical Energy Cutting Force To Remove Metal, But Directly Uses Electrical Energy Thermal Energy To Remove Metal. Compared With Mechanical Cutting, EDM Has The Following Characteristics:

① Suitable For Processing Materials That Are Difficult To Process Using Traditional Machining Methods, Showing The Characteristics Of "Using Softness To Overcome Hardness". Because The Removal Of Materials Is Achieved By Discharge Thermal Etching, The Processability Of Materials Mainly Depends On The Thermal Properties Of Materials, Such As Melting Point, Specific Heat Capacity, Thermal Conductivity (Thermal Conductivity), Etc., Has Almost Nothing To Do With Its Mechanical Properties Such As Hardness Toughness. The Tool Electrode Material Does Have To Be Harder Than The Workpiece, So The Electrode Manufacturing Is Relatively Easy.

② It Can Process Parts With Special Complex Shapes. Since There Is No Relative Cutting Motion Between The Electrode The Workpiece, There Is No Cutting Force During Machining, So It Is Suitable For Low-Rigidity Workpieces Fine Processing. Since The Pulse Discharge Time Is Short, The Range Of Heat Influence On The Material Processing Surface Is Relatively Small, So It Is Suitable For The Processing Of Heat-Sensitive Materials. In Addition, Since The Shape Of The Tool Electrode Can Be Simply Copied To The Workpiece, It Is Particularly Suitable For The Processing Of Thin-Walled, Low-Rigidity, Elastic, Fine Complex-Shaped Surfaces, Such As The Processing Of Complex Cavity Molds.

③ It Can Realize The Automation Of The Processing Process. The Electrical Parameters In The Processing Process Are Easier To Realize Digital Control, Adaptive Control, Intelligent Control Than Mechanical Parameters. It Can Conveniently Carry Out Rough, Semi-Finishing, Finishing Processes, Simplifying The Process. After Setting The Processing Parameters, There Is No Need For Manual Intervention During The Processing.

④It Can Improve The Structural Design The Processability Of The Structure. After Using EDM, The Inlay Welding Structure Can Be Changed Into An Integral Structure, Which Greatly Improves The Reliability Of The Workpiece, Greatly Reduces The Volume Mass Of The Workpiece, Shortens The Mold Processing Cycle. Huiwen Zhizao Is A Machining Factory With More Than Ten Years Of CNC Processing Experience. It Has A Full Range Of Equipment, CNC Lathe/Milling/Grinding/Drilling/Processing. Partners With Parts Processing Needs Are Welcome To Call Us For Quotation.

⑤ It Can Change The Process Route Of Parts. Since EDM Is Affected By The Hardness Of The Material, It Can Be Processed After Quenching, Which Can Avoid The Heat Treatment Deformation Caused By The Quenching Process. For Example, In The Manufacture Of Die Casting Forging Dies, The Die Can Be Quenched To A Hardness Greater Than 56HRC.

4. Limitations Of EDM

EDM Has Its Unique Advantages, But It Also Has Certain Limitations, Which Are Specifically Reflected In The Following Aspects:

① Mainly Used For Processing Metal Materials. It Cannot Process Insulating Non-Conductive Materials Such As Plastics Ceramics. However, Research In Recent Years Has Shown That Non-Conductive Superhard Materials Such As Semiconductors Polycrystalline Diamonds Can Also Be Processed Under Certain Conditions.

② The Processing Efficiency Is Relatively Low. In General, The Processing Speed Per Unit Processing Current Does Exceed 20mm3/(A·min). Compared With Machining, The Material Removal Rate Of EDM Is Relatively Low. Therefore, Machining Is Often Used To Remove Most Of The Excess, Then EDM Is Performed. In Addition, There Is A Prominent Contradiction Between Processing Speed Surface Quality, That Is, The Processing Speed Is Very Low During Fine Processing, Rough Processing Is Often Limited By Surface Quality.

③ Machining Accuracy Is Limited. There Is Electrode Loss In EDM. Since EDM Relies On Electricity Heat To Remove Metal, The Electrode Will Also Suffer Loss, The Electrode Loss Is Mostly Concentrated At The Sharp Corners Bottom Surface, Affecting The Forming Accuracy. Although The Latest Machine Tool Products Can Reduce The Relative Loss Ratio Of The Electrode To Less Than 1% During Rough Machining 0.1% Even Less During Fine Machining, The Problem Of Low Electrode Loss During Fine Machining Still Needs Further Research.

④ There Are Metamorphic Layers Even Microcracks On The Machined Surface. Since The Instantaneous High Heat Generated On The Machined Surface During EDM Will Cause Thermal Stress Deformation, Resulting In A Metamorphic Layer On The Surface Of The Machined Parts .

⑤ Limitation Of The Minimum Corner Radius. Normally, The Minimum Corner Radius Obtained By EDM Is Slightly Larger Than The Machining Discharge Gap, Generally 0.02~0.03mm. If The Electrode Is Worn A Translation Head Is Used For Machining, The Corner Radius Will Be Increased, It Is Impossible To Achieve A Truly Perfect Right Angle.

⑥ Limitation Of External Processing Conditions. During EDM, The Discharge Part Must Be In The Working Fluid, Otherwise It Will Cause Abnormal Discharge, Which Will Cause Trouble In Observing The Processing Status Affect The Size Of The Workpiece.

⑦ The "Gloss" Problem Of The Machined Surface. The Machined Surface Is Composed Of Many Small Pits Caused By Pulse Discharge. Generally, The Surface After Fine Machining Does Have The "Gloss" Of Mechanical Processing, It Needs To Be Polished To Shine.

⑧Processing Technology Issues. EDM Is A Highly Technical Job. Mastering It Is The Key To Successful Processing, Especially For Equipment With Low Automation. The Selection Of Process Methods, Selection Of Electrical Standards, Clamping Positioning Of Electrodes, Monitoring Of Processing Status, Determination Of Processing Allowances Are Closely Related To The Technical Level Of The Operator. Therefore, The Accumulation Of Experience Is Crucial In EDM.

The Shenzhen Huiwen Intelligent Manufacturing Technology Co., Ltd. Team Was Established In 2010 Is Located On The 1st Floor Of Building F3, Tianyou Maker Industrial Park, Lixinhu, Fuyong, Bao'an District, Shenzhen. It Has Long Been Committed To The Processing Of High-Precision, High-Difficulty, Easy-To-Deform Metal Plastic Parts , Small Medium-Batch Production Of Lightweight Alloy Composite Materials (Such As Aluminum Alloy, Carbon Fiber, Etc.) Parts,  Procurement Customization Of Robot Parts .