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Electrical energy based processes
- 2. EDM-Principle • A thin wire of round shape used as an electrode, which is supplied to the work area through a pair of wheels. With the aid of current a high power spark is produced between wire- electrode and work piece. Due to this high amount of heat is produced nearly to 10000 degree Celsius. This heat energy used to melt and vaporize the work material. Then with the supply of dielectric fluid the molten stage materials are flushed away, likewise the machining is carried out in the work piece.
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- 4. Specifications Voltage = 250 V GAP = 0.005 – 0.05 mm Temperature = 10000 degree celcius Spark occur = 10 – 30 micro seconds Current density = 15 – 500 A
- 5. Dielectric Fluid Petroleum Products Paraffin White sprit Transformer oil Kerosene Mineral oil Mixture of all Dielectric Fluid Requirements •Should not be toxic •Should not be corrosive •Should not be hazardous •Should be circulate freely •Should be flushed out •Should be act as coolant • Should be filtered before use •Should be less cost
- 6. Di electric Fluid – Flushing Method 1. Pressure Flushing 2. Suction Flushing 3. Side Flushing
- 7. Pressure Flushing Di electric Fluid – Flushing Method
- 8. Suction Flushing Di electric Fluid – Flushing Method
- 9. Side Flushing Di electric Fluid – Flushing Method
- 10. Functions of Dielectric Fluid
- 11. Electrode (Tool) • Graphite ( Non Metallic) • Copper (Metallic) • Copper - Tungsten
- 12. POWER GENERATING CIRCUITS SPARK GENERATING CIRCUITS OR AC Current DC Current Rectifier is used to convert AC to DC
- 13. Types
- 14. 1. Relaxation Circuit • Commonly used • Simplicity • Less cost
- 16. Dis-advantages
- 17. 2. R-C-L Circuit • MRR increases with the decrease of R Capacitor charging time is the problem in R-C circuit. So to overcome this , inductance (L) is introduced in the circuit
- 18. Rotary Pulse Generator • R-C and R-C-L yield low MRR • Rotary Pulse Generator over come Drawback of above to circuits • It give high MRR • It give good Surface finish • It give low tool wear • It provide better control in all Parameters
- 19. Rotary Pulse Generator • Here Capacitor is discharged through the diode during first half cycle. • In the next half cycle sum of voltages is given with charged capacitor to the circuit. • So high spark produced • It results high MRR Draw Back •Poor Surface Finish
- 20. Controlled Pulse Generator Circuit • All above three circuits not having any safety incase of Short circuit in the circuit Here in this a vacuum tube (Transistor) is provided as an automatic control
- 22. 1. Operating Parameters 2. Taper 3. Surface finish 4. Current Density PROCESS PARAMETERS
- 23. • Operating Parameters PROCESS PARAMETERS Tool Wear Rate Tooling cost Accuracy Working Time Used to calculate
- 24. • Operating Parameters PROCESS PARAMETERS Types of wear 1.End Wear 2.Corner Wear 3.Side wear
- 25. • Taper PROCESS PARAMETERS Due to High dielectric Pollution , side sparks are more than front spark. So Tapering Occur in Hole
- 26. • Surface Finish PROCESS PARAMETERS It Depend on i) Energy of Pulse ii) Frequency of operation
- 27. • Current Density PROCESS PARAMETERS Current Density (More Spark) = MRR + Surface Roughness Current Density (Less Spark) = MRR + Surface Roughness Good Surface Finish Poor Surface Finish
- 31. Wire – Cut EDM (WEDM) Travelling Wire Cut EDM (TWEDM) 0.02 – 0.03mm dia wire Wire - Brass or Molybdenum 10 – 30 micro second sparking 15 – 500 Amp / mm2 30 - 250 V 10,000 C - Temperature 10 – 30 mm/ sec wire Feed 15 – 80 mm3 / sec MRR Petroleum Based Hydrocarbon Fluids – Paraffin, white Sprit ..
- 32. Features of WCEDM i) Manufacturing Electrode ii) Electrode Wear iii) Surface Finishing – No Manual finishing needed iv) Complicated Shapes – No need of skilled operators v) Time Utilization – overall control is by NC Machine vi) Straight Holes – Feed mechanism avoid taper holes vii) Rejection – NC programmes avoid rejections viii)Economical – for Batch production (including prototypes) ix) Cycle Time – for die manufacturer is shorter x) Inspection Time – very less
- 33. Disadvantages of WEDM • High Capital cost • Cutting Rate is slow • Not suitable for large work pieces
- 34. Applications of WEDM • In the manufacturing of Gears Tools Rotors Turbine Blades Cams
- 35. Wire Cut EDM Vs EDM