FEM MODELING OF ELETRICAL DISCHARGE MEACHINING OF SS304-CU IN GAS.pptx

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1. FEM MODELING OF ELETRICAL DISCHARGE MACHINING OF SS304-CU IN GAS GUIDE BY  AJEESH AS ASSISTANT PROFESSOR MECHANICAL ENGINEERING. GROUP MEMBERS  AHMAD SUBAIR JAFAR ALHAM SHAREEF PK ASWIN GS SUHAIL MOHAMMED S

2. CONTENTS ABSTRACT INTRODUCTION LITERATURE REVIEW  AIM METHODOLOGY O NGOING STUDY R EFERENCES

3. ABSTRACT Electro discharge machining (EDM) process is a non-conventional and noncontact machining operation which is used in industries for high precision operation EDM in gas uses gaseous dielectric medium instead of a conventional liquid dielectric such as water, kerosene etc. This is an environment friendly technology and has many advantages .   In the present work we have developing a FEM based model for the simulation of gas dielectric EDM of SS304- Cu in Oxygen and Helium .

4. INTRODUCTION Due to the continuous developments in the field of engineering and technology, the scientists and the researchers are facing more and more challenging jobs in these fields of designing and manufacturing. Since 1940, a revolution has been taking place that once again allows manufacturers to meet the demands imposed by increasingly sophisticated designs, but unmachinable . As a result, a new form of manufacturing processes used for material removal, forming, and joining, known as non-conventional manufacturing processes  has introduced .

5. Electric Discharge Machining (EDM)
Electro Chemical Machining (ECM)
Electro Chemical Grinding (ECG)
Electro Chemical Honing (ECH)
Electro Chemical Deburring (ECD)
Electro Chemical Deburring (ECD)
Chemical Machining (CHM)
Laser Beam Machining (LBM) NON-CONVENTIONAL METHODS OF MACHINING

6. In this present study we have developed a numerical based finite element model to simulate the process of gas di-electric electro discharge machining in Oxygen and Helium. The model is validated by comparing the simulated results with the existing experimental results. A comparative analysis of EDM performance with respect to the material removal rate of Oxygen and Helium based dielectric process will also carried out

7. LITERATURE REVIEW  Jia Tao, Albert J Shih [1] investigated the dry and near-dry electrical discharge machining (EDM) milling to achieve a high material removal rate (MRR) and fine surface finish for roughing and finishing operations. They found that Oxygen demonstrated the capability to promote MRR and exothermal oxidation in both the dry and the near-dry EDM.  Nitrogen and helium gases could prevent the electrolysis and yield better surface finish in near-dry EDM. 

8.    Avinash Choudhary and Mohan Kumar Pradhan [2] modelled the EDM process with the help of Finite Element Method (FEM) using ANSYS 12.0 software and the effects of most significant machining parameters on the workpiece such as current, voltage and pulse duration was analyzed. The analysis showed the temperature distribution at the end of pulse duration, development of residual stresses after the completion of cooling and the changing nature of compressive stresses to the tensile stresses in various stages of machining process

9.     P. Govindan and Suhas S. Joshi [3] conducted experimental characterization of material removal in dry electrical discharge drilling.  The experiments were performed by controlling pulse off-time so as to maximize the material removal rate (MRR). The main response variables analyzed in this work were MRR, tool wear rate(TWR), oversize and compositional variation across the machined cross-sections. Statistical analysis of the results show that discharge current(I),gap voltage(V) and rotational speed(N) significantly influence MRR. TWR was found close to zero in most of the experiments. 

10.     Li Liqing, Guo Chenhao [4] Simulated the temperature field of a single pulse dry electrical discharge machining using a FEM software. The simulation results indicated that when the discharge time was close to 50% of pulse duration, the temperature of discharge channel center began to decrease.  The ratio of crater dia by gasification to that by melting decreases with an increase in the pulse width and discharge current. 

11. AIM Develop a FEM model for the simulation of gas dielectric EDM process with SS304 workpiece and Cu as electrode. Predict the workpiece material removal rate using the developed model with oxygen as gas dielectric medium. Validate the simulated results of oxygen by comparing with the experimental values.  Conduct a comparative analysis of material removal rate of electrical discharge machining in Oxygen with respect to Helium We intent to study the MRR of titanium and brass when it used as workpiece Then compare all three result.

12. ONGOING STUDY INTRODUCTION  TO ELECTRIC DISCHARGE MEACHINING Electric discharge machining (EDM) process is a non-conventional and non-contact machining operation which is used in industry for high precision products especially in manufacturing industries, aerospace and automotive industries. It is known for machining hard and brittle conductive materials since it can melt any electrically conductive material regardless of its hardness. EDM is a type of thermal machining where the material from the workpiece is removed by the thermal energy created by the electrical spark . The workpiece machined by EDM depends on thermal conductivity, electrical resistivity, and melting points of the materials

13. Controlled axis  Electrical generator  Control panel  Work table  Dielectric fluid container  BASIC COMPONENTS OF AN EDM SYSTEM

14. ELECTRICAL DISCHARGE MACHINING PROCESS EDM is the thermal erosion process in which metal is removed by a series of electrical discharges between a cutting tool acting as an electrode and a conductive workpiece .   When electrode is brought closer to the work piece, sunk in the dielectric fluid, current is passed to the electrode and the work piece, which generates heat in the form of frequent series of sparks that vaporizes the pieces at the closest point of work piece and electrode. After removing the piece at the closest distance between electrode and work piece, the next spark occurs simultaneously at the next closest point between them and so on. This process results on forming a cavity on the work piece with the shape of the electrode.

15.    During this operation the tool and work piece are suppose to keep a distance between them, known as sparking gap .  ▪ This point of transformation of dielectric fluid from non-conductor to conductor is called " ionization point " A flushing operation is undergoing in order to remove the chips from the work piece

16. ELECTRICAL DISCHARGE MACHINING IN GAS Dry EDM is one of the novel EDM techniques, which employs gas as a dielectric medium instead of liquid. It mainly involves supply of a gas through a rotating thin walled pipe electrode, which also flushes out the debris from inter-electrode gap. The process holds the potential to be a viable alternative to conventional liquid dielectric EDM for precision-oriented machining applications. The major advantage of this method is its simplicity

17. Advantages of gas dielectric EDM Environment friendly technology No need for special treatment for disposal of sludge, dielectric waste, filter cartridges, etc.
Higher Precision
Near-zero tool electrode wear
No electrolytic corrosion of work piece
No toxic fumes generated
Smaller Heat Affected Zone (HAZ) Narrower discharge gap length

18. METHODOLOGY The Finite Element Method (FEM) FEM is a popular method for numerically solving differential equations in two or three space variables (i.e., some boundary value problems) in engineering and mathematical modeling.  To solve a problem, the FEM subdivides a large system into smaller, simpler parts called finite elements. The FEM formulation of a boundary value problem finally results in a system of algebraic equations. The method approximates the unknown function over the domain .

19. ASSUMPTION The workpiece and tool are axi -symmetric [2]  The workpiece and tool material are homogeneous and isotropic  Heat flux is assumed to be Gaussian distributed. The zone of influence of the spark is assumed to be axi -symmetric in nature. [2]  The analysis is done for only one spark [2]  The material properties of the workpiece are temperature independent  The ambient temperature is room temperature.  The shape of crater is assumed to be a cone Workpiece is selected as stainless steel 304 and Cu tool electrode is selected with Dielectric as Oxygen 

20. STEPS INVOLVED IN MODELLING 7 MAJOR STEPS Static Structural Engineering data Geometry Model Setup Solution Result

21. INPUT DATA Input values for oxygen di-electric  (sample) Sl no.   V(Volts)   I(A)   Toff   (us)   Toff(s)   Ton   (us)   Ton(s)   Spark Radius(mm)   Q(W/m 2 )   1   50   12   22   0.000022   66   0.000066   0.085956245   35439234270   2   50   12   33   0.000033   198   0.000198   0.139383314   13477757109   3   50   12   67   0.000067   603   0.000603   0.227519026   5058290392   4   50   15   22   0.000022   66   0.000066   0.094612548   36563834238   5   50   15   33   0.000033   198   0.000198   0.15342004   13905449342   6   50   15   67   0.000067   603   0.000603   0.250431541   5218806084   7   50   18   22   0.000022   66   0.000066   0.102328516   37509139912   8   50   18   33   0.000033   198   0.000198   0.165931954   14264954859  

22.    STEP 2:  The workpiece was designed using ANSYS DESIGN MODELLER with dimensions of 14mm x 10mm [5]  Two-Dimensional workpiece model  

23.     STEP 3:    The workpiece is split into two portions for ease of meshing. The circular cross-section is split with respect to the spark radius using the concept of split edges.    Splitting of edges 

24.     STEP 4:  The workpiece is meshed for FEM analysis using meshing tool in ANSYS. The meshing is done in two parts where the non-circular section is meshed as coarse mesh and circular section is meshed finely with 3 times refinement for better analysis and results Meshed model 

25.    Coarse meshing for non-circular section

26. Fine meshing for circular section   

27. REFERENCES Jia Tao, Albert J. Shih, Jun Ni, ”Experimental Study of the Dry and Near-Dry Electrical Discharge Milling Processes”, Journal of Manufacturing Science and Engineering, FEBRUARY 2008, Vol. 130 / 011002-1   Avinash Choudhary, Mohan Kumar Pradhan, ”Finite Element Analysis of Electro Discharge Machining using Ansys”, Proceedings of 1st International Conference on Mechanical Engineering: Emerging Trends for Sustainability P. Govindan, Suhas S. Joshi ,”Experimental characterization of material removal in dry electrical discharge drilling “,International Journal of Machine Tools & Manufacture 50 (2010) 431–443 Li Liqing, Guo Chenhao, Song   Yingje , ”Simulation analysis of crater size for single pulse dry electrical discharge machining” ,Procedia CIRP 68(2018) 292-297   Han Wu, Jianfeng Ma, Qingling Meng, Muhammad P. Jahan, Farshid Alavi, ”Numerical modeling of electrical discharge machining of Ti-6Al- 4V”,Procedia Manufacturing 26 (2018) 359-37

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