During early days people do physical work to complete a job. The physical work made by the people made them tired and people time gets wasted. Let us take a construction work. The construction works involves major labors to construct a building, in early days people spends major time to construct a building. The labors have to give more energy to construct the building. Some of the labors even sacrificed their life by accident case inside the building. But today’s technology makes sure that the construction of any type of building can be modeled and executed within a year. Labor also doesn’t need much emery to spend during their work. Machine technology plays a major role in construction. The machine technology plays a major role in all the field of work construction, Information Technology, Electronic products, mining etc. The machining dominated each and every where. The machining had also reduced human effort and energy. The work effort has been reduced by machines. Each people can complete their work within time with the help of machines. The machines are the backbone for every work. This paper deals with Electro Discharge Machines. That helps in the process of manufacturing. The electro discharge machines helps to improve the work piece structure and also used to complete the work piece within time. This EDM machine is also called sparking machine, burning machine, which will give a desire shape by electric discharge. The two electrodes of the machines are separated by the liquid the liquid acts as a medium. The two electrodes are subject to electric voltage. The desire shape is obtained by applying voltage to the electrode.
2. Electric Discharge Machine Overview
The Electric Discharge Machine (EDM) is also called as sparking or burning machine. It operates on the electrical principles. The EDM is used to achieve a desire shape of workplace by using the electric discharge of the machine. The two electrodes are separated by the liquid. The liquid is a conducting medium which can separate two electrodes to make an electrical circuit. The EDM machines will helps to make a good work piece with the help of electric discharge. The material is removed from the work piece by current discharge between the two electrodes. The electrodes are separated by the liquid and subjected to the electrical voltage. The voltage helps to move the electrons inside the electrodes. The movement of electrons will heat the electrode and makes the electrode to make electric discharge between the two electrodes gap. The electrical discharge is noting when the high voltage is applied to the electrode the electrons are pushed out of the electrodes to contact the other end of the electrode by breaking the liquid medium. The one electrode is called as tool electrode and other electrode is called as the work piece electrode. When distance between the two electrodes gets reduced the electric field gets reduced. The reduction of distance will cause the electric break down and electrical breakdown in the liquid medium will occur and which cause the damage of the electrode. Damage is due to the breakdown allows the electric current to pass through the electrode and makes electrode to subject to heavy current which will break the electrode the phenomenon is same as that of the break down takes place in the capacitor. We should take more care to prevent that electrodes damage.
- Working principle and processing capability of EDM
In EDM electric voltage is applied to the tool and work piece, the tool and work piece is the good conductor of electricity. The potential difference is applied between tool and work piece. The tool and work piece are immersed inside the dielectric medium. The gap between the tool and electricity is maintained properly in order to prevent the electric discharge. The electric field is exist between the work piece and tool, as a result the electrons are emitted by electrostatic force between the job and the tool. The emission of electron is called Cold Emission. The emitted electron passes through dielectric medium and causes the collusion of electrons of molecules. The collusion causes the ionization. The ionization depends on the type of work. Such energy is called Plasma. It is seen as a spark by the naked eye. The plasma collapses soon and thus causes shock waves the shock waves produces crater in the work piece. The work piece acts as the positive electrode and tool acts as the negative electrode. The electron strikes the job and forms the carter in the work formation. The removal of metal from the EDM is due to the shock wave formation. The shock wave formation will certainly have effect on the job to form the carter. The temperature of the work may go up to 10000ºC. The working principle of the EDM is simple, but the space between the electrodes is maintained to avoid the damage of electrode by dielectric breakdown.
EDM machine is used for prototype production. The prototype production is based on the molding of job. It is mostly used in the die industries. It is used for small hole drilling the small hole drilling is based to make a small hole I the required job. Small disintegration machine, used to remove unwanted materials from the job.
2.3 The Features and materials of EDM
The material used in the EDM is the ferrous and non ferrous materials including hard metals and exotic alloys. The usual material thickness will be of 0.01mm to 250mm. The minimum cutting diameter is about 0.1mm. The maximum tolerance can be determined by the weight the EDM can make a piece up to the weight of 350kgs. The accuracy can be of ±5 µm. The EDM uses cooper electrode and steel work piece. The dielectric material used for the EDM dielectric is oil to prevent arc discharge.
3. The Electro chemical Machining (ECM)
The Electro Chemical Machining (ECM) is used for the removal of metal by the chemical process. The ECM is used for the mass production. The working principle of EDM is same as that of ECM. The ECM is used in extremely hard condition when the EDM machine cannot remove the work piece the ECM can be used to remove the work piece. The ECM are used for extremely hard metals that are difficult by other methods. The ECM is also called as the reverse plating it removes the material instead of the adding.
3.1 The working principle and process capability of ECM
The electro chemical machining is similar in operation like EDM. The material removing contains negative charged metals called cathode, and it contains electrolyte it is a conducting fluid, and work piece called anode. The electrolyte acts as a conducting medium between the electrodes. The cutting tool is guided by the desire mechanism that makes cutting tool to operate in without touching the work piece. The high amount of electric current is passed through the ECM and the sparks are produced by the electrolytic discharge. The high temperature working rates are possible with ECM. . In ECM the cathode is advanced to anode (work piece). The pressurized electrode is maintained at the set temperature to cut the required piece. The work piece can be of 80 to 800 micrometers. The electrons are passed through the electrolytic gap and work piece is gets dissolved.
The ECM is used in de sinking operation of machine. It is used for drilling purposes it is used for drilling jet engine, it is used for multi hole drilling. It is used in machine speed turbine blades within the close limits.
3.3 The Features and material of ECM
The machine removal rates are depends on the feed rates. The feed rates are the work and tool. The tool approaches the work the current path decreases and this continuous until the sufficient condition is attained to remove the work piece. The stable cut is achieved when work and tool gap is maintained properly and it is termed as equilibrium marching gap. When the tool lags behind work in gap then the current rate is reduced. The material removal rates is given as
The materials of the ECM machines are depends on the horizontal and vertical type. Based on the requirements the machine parameters differ. The vertical type machine depends on vertical, column and spindle head. CNC machines are up to six axes are available. The surface finish is affected by the selective dissolution; evolution of hydrogen, flow separation and formation of eddies etc.
4. The Chemical Machining
The chemical machines are the nontraditional machines. It is controlled by the chemical dissolution of work piece. The chemical machining has mask ants technology, which is used to protect the unwanted removal of the metal piece. The mask ants protect the metal from the unwanted removal. The chemical machining is used for the micro components operation. It is used to produce the micro component products. The chemical machines are used from the ancient period of Egypt they used to shape the copper with the help of cirtic acids. The chemical machines are used for decorative etching. The process is simple and well established. However there are some environmental issues relating to these chemical machines.
4.1 The Working and Process Capability of Chemical Machines
Step 1 it involves work piece the required work piece is cleaned to remove oli and grease to have good looking work piece.
Step 2 it involves of coating with the masking material. The materials not to be removed is to be masked with the masking materials
Step 3 it involves etching. The process is the most important process the work piece is cleaned by the etchants. The etchants are used for etching the work piece.
Step 4 it involves the cleaning the cleaning of masking material from the etchants
4.2 Mask ants
Mask ants are used to protect the metal parts from the etchants, it should be tough, adhering, easy scribing, insert to chemical reagent, able to withstand heat during chemical machining.The work piece material can be of aluminum based alloy, iron based alloy, nickel, magnesium, copper based alloy.
The etchants are the most influential the various etchants are aluminum and alloy, copper and alloy, steel and nickel etc.
The chemical machining is used in aerospace industries to remove the shallow layers of materials from the large aircraft. It is used in printed circuit board and semiconductor fabrication machines. It is used to produce the micro chemical components.
4.5 The Features and Materials of Chemical Machining
The material removing rate of chemical machines can be of 0.0025 to 0.1 mm/min and it may take many forms. The standard etching materials are aluminum, stainless steel, nickel, lead, copper etc. The tolerance can be of ± 0.0002 of an inch (0.005 mm). The surface finishing is depends on the type of work in the machines
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