Near dry Edm

Team members:

Ganesh Mokate 45

Gaurav Mane 42

Rehan Sayyed 65

Prathamesh Borude 09

Rohan Thorve 57

 Introduction

 The electric discharge machining treatment is widely used for the production of complex profiles, electrically conductive material, high temperature resistance and high strength. Due to its wide application in industry, and so on, it has become the most popular process setting for conventional machining processes such as turning, milling, drilling, etc. Despite its many advantages, so the process tolerates a number of limitations, such as low material removal rate (MRR) and has a high consumption rate (TWR), as well as weak surface integrity, and in some cases. In the past, several attempts have been made to overcome these limitations associated with the growth of??? techniques, such as rotating the electrode by ultrasonic vibration and suspending powder in a dielectric liquid. Although these methods have a great research perspective, in practice they are used only for small applications. Further restrictions in EDM process may be related to environmental pollution and labeling. During the process material removal must have a consistent set of thermal energy generated by a series of discrete electrical sparks created between the tool and the operation of electrodes that are immersed in a dielectric medium, typically hydrocarbon oils. Oils and serious toxic fumes can cause injury to the operator's health and the environment. To overcome the limitations of the EDM process, dry and almost dry varieties were introduced, and SO on. - Dry EDM process, the use of pressurized natural gas, such as a dielectric, it is necessary that the almost dry EDM process uses a combination of liquid and gas (two-phase) as a dielectric medium, and is environmentally friendly. In this section, you will find information about these two models, environmental (i.e. Dry and Almost Dry EDM).) The EDM process is combined with the development of research in this area.

Electric Discharge Machining (EDM)

 Amongst the un-conventional machining processes, EDM is the most popular un-conventional machining process because it is capable to machine any electrically conductive material irrespective of its hardness and toughness; and can cut complex geometries, shapes and features efficiently. It is also called as spark erosion machining. It has a wide area of application in different fields like mold and die manufacturing, aerospace and automotive industries, electronics and medical instruments, etc. With increase in demand of products made from hard metals and alloys especially difficult-to-machine materials, more interest has gravitated towards the EDM process.

Classification of EDM

Figure 11.3 shows flow diagram of classification of electric discharge machining processes. There are several categories of EDM processes according to the type of dielectric medium used. These variants are conventional EDM, powder mixed electric discharge machine (PMEDM), dry EDM and near-dry EDM. Wire EDM, micro EDM and rotary EDM are tool based EDM process variants. Whereas, magnetic-field assisted EDM (MFAEDM) is workpiece based EDM process. Furthermore, the ultrasonic assisted EDM comes under both categories (tool or workpiece).

Dry and near Dry EDM 

 Dry and near dry EDM processes must be resistant to process changes and SO on. These processes are classified based on the use of a dielectric medium. It is carried out using gas as a dielectric medium, which is usually called dry, and so on. As shown in the picture. 11.5. A high-speed gas flow is provided through a tubular electrode, which is the molten material of the object you want to remove, and remove. At that time, the higher the gas velocity for the plasma formed from the last spark, and the lower the temperature in the treatment zone. First of all, the National Aeronautics and Space Administration (NASA) has shown the possibility of using an inert gas, such as a dielectric medium [8]. Then he won et al. [9] investigated the possibility of using in ??? mixtures of various gases, such as a dielectric medium. So in this version of the process, and so on, they called it dry, and SO on. It is used for high F and low gas rate dielectric liquids like oxygen, nitrogen, hydrogen, and compressed air through a tubular electrode between the interelectrode gap. It is usually used to solve environmental protection problems, which leads to increased processing performance. Mrr sukhoi ??? It was measured six times higher than that of the usual???, with the same set of resistor conditions [10]. Another parallel approach based on the EDM and performance improvement process was introduced by Tanimura et al. In 1989, a liquid and gas mixture (second phase) was used as a dielectric medium [11]. It was made primarily to be called EDM in mist.

Later this process was developed as well as almost dry EDM. In this process, the dielectric medium can be used absent (liquid or air), or a mixture of gases such as nitrogen, helium, argon, etc. Two-phase dielectric medium with stable operation compared to dry and so on. It's almost dried up, and it's SO good to drill straight holes with a sharp edge when it's dry, which means there was a serious chip with re-fitting behavior, and then create a conical hole [12]. Is the cone a regular one???, was also present, but not as significantly as in dry, and SO on (see Figure 11.6). In addition, in the dry earth zone, and so on, resulting in better surface f devils (up to 0.09 mm), consistency, and labor [13]. Close to " dry and dry, and SO on, it is possible that it is a low price dielectric medium with less environmental impact. Another advantage of dry and near dry is that it is dry and dry, which means that there would be no requirement for a clean volume of the dielectric medium, as well as handling the controls (air circulation and filtration). Therefore, the floor surface requirements available on the market, etc. can also be reduced. shown in the picture. 11.7.

Process parameters

 In process parameters on dry and near-dry EDM, belong to one of four categories, which are as follows 

• Electrical parameters
• Non-electrical parameters
• Tool electrode based parameters 
• Near-dry based (dielectric) parameters. 

Dielectric Mediums in Dry and Near-Dry EDM 

Generally, dry-EDM utilizes compressed air as a dielectric medium. However, some researchers have used oxygen gas as dielectric medium in dry-EDM process [19–21]. It was found that the MRR is increased due to the enlarged volume of discharged crater and more frequent occurrence of discharges when using oxygen. The NASA reported usage of argon and helium as a dielectric medium in dry EDM. In near-dry EDM, mixture of liquid and gas used as dielectric medium. Tao et al. [22] mixed different gases such as helium, oxygen and nitrogen with water. It was found that mixture of oxygen-water provided highest MRR and surface roughness as well. Further, Dhakar and Dvivedi [17] used different combinations of dielectric mediums viz. glycerin-air, water-air and EDM oil-air. The MRR produced by glycerin-air dielectric medium was approximately three times higher (refer Fig. 11.15) than the EDM oil-air and water-air combinations at best parametric settings (current 15 A, duty factor 0.80, flushing pressure 80 psi). Glycerin generates high thermal energy and gaseous pressure in IEG when it decomposes with discharge. It is apparent that glycerin generates concentrated explosion at IEG, thus increasing material removal. However, glycerin-air dielectric medium produced slightly higher TWR than other dielectric mediums but it was approximately negligible because wear ratio (ratio of TWR and MRR in percentage) of the process was less than one percent. Furthermore, it was observed that recast layer produced by EDM oil-air and water-air were 0.52 lm and 0.40 lm, respectively, while combination of glycerin-air did not produce any measurable recast layer [17].

Comparison of Dry, Near-Dry and Conventional EDM

 This section highlights the advantages of dry and near-dry EDM over conventional EDM in terms of various machinability aspects as given below.

 Productivity: The MRR of near-dry EDM was nearly 50–60% higher than conventional EDM. In conventional EDM, carbon particles and other debris particles are generated during spark erosion [19]. Further, due to inefficient flushing they do not flush away from the IEG effectively. Subsequently, they disturb the erosion process resulting in ineffective sparks which results in low MRR. In near-dry EDM high pressure dielectric medium provides better flushing than conventional EDM. This reduces debris accumulation problem at IEG resulting in higher MRR. Several investigations have been conducted where it was found that near-dry EDM achieves higher MRR as compared to conventional EDM [23–25]. The experimental investigation conducted by Dhakar [24] reveals that the MRR of near-dry EDM was marginally higher than dry EDM (see Fig. 11.16). It can be attributed to the fact that two phase (liquid and air) dielectric medium eliminates debris reattachment problem. Consequently, lower down chances of possible short circuiting. This phenomenon improves MRR in near-dry EDM. It was also interestingly observed that, conventional EDM produced very high TWR at higher values of current than near-dry and dry EDM process.

 Cost concerns: The near-dry and dry EDM are economically efficient processes as compared to conventional EDM. Because, the cost of conventional EDM dielectric is $17.68 per gallon (SHELL MACRON EDM 135) while the cost of tap water and air/gas (used in dry and near-dry EDM) is almost negligible [25]. 

Environmental aspects: These processes are green because there is no generation of hazardous gases/fumes; and no waste is produced from the dielectric liquid. There is no risk of fire hazards because no flammable dielectric is used.

Efficiency: Highly efficient due to high MRR and fine surface finish. Further, TWR in dry and near-dry EDM processes is negligible.

Space requirements: These processes do not require large floor space because they do not need a huge dielectric circulation unit.

Conclusion

 In essence, dry and near-dry EDM are the environmentally friendly variants of EDM. These processes are capable to generate high surface integrity and to achieve high productivity along with minimum hazard, wastages and pollution, and thus attain overall sustainability which makes them the sustainable substitutes to the conventional EDM.

References

 1. Jain VK (2002) Advanced machining processes. Allied Publishers Pvt. Ltd., New Delhi, pp 126–159 

2. Davim JP (2013) Nontraditional machining processes. Research Advances Springer. doi:10. 1007/978-1-4471-5179-1

 3. Schumacher BM (2004) After 60 years of EDM the discharge process remains still disputed. J Mater Process Technol 149(1–3):376–381

 4. Puertas I, Luis CJ (2003) A study on the machining parameters optimization of electrical discharge machining. J Mater Process Technol 143–144:521–526

 5. El-Hofy H, Youssef H (2009) Environmental hazards of nontraditional machining. In: Proceedings of the 4th IASME/WSEAS international conference on energy & environment (EE’09), pp 140–145