What is (ECM) Process: Introduction, Working Principle, Electro-Chemistry of ECM, Basic Elements, Process Characteristics, Application, Advantages,Limatations

Introduction:-

Electrochemical Machining (ECM) is a non-traditional machining (NTM) process associated to the electrochemical division. ECM is inverse of electrochemical, galvanic coating, and deposition process. Thus ECM can be speculation of a restrained anodic dissolution at the atomic level of the workpiece that is electrically conductive by a formed tool because of flow of high current at comparatively low potential difference through an electrolyte that is quite often water-based neutral salt solution.

Working Principle:-

Electrochemical machining (ECM) is a metal-evacuation measure dependent on the rule of converse electroplating.

In this type of machining operation, particles moves from the anodic material (workpiece)to near the cathodic material (tool machining).

A current of electrolyte solution carries away the depleted material before it's an opportunity to succed in the machining tool.

The cavity formed is the female mating image of the tool form.

The ECM tool is positioned terribly near to the piece of work and a low voltage, high amperage DC current is passed between the workpiece and the electrode conductor as shown in fig.

Fig. Electro-Chemical Machining

Electrochemistry of ECM:-

• The electrolysis process is ruled by the subsequent two laws proposed by Faraday.

• The amount of chemical change produced by an electric current, that is, the amount of any material dissolved or deposited is proportional to the quantity of electric passed.

• The amounts of substances dissolved or deposited by the constant amount of electricity are proportional to the chemical equivalent weights.

M α ItE,

where,

M - mass of dissolved metal.

I - current,

t - time  

E - gram chemical equivalent (E=A/Z),

A - atomic mass of anode 

Z - valency of dissolution of anode.

ECM consists of the following basic elements:-

• Electrolyte: An Electro-Chemical Machining an electrolyte acts as a current carrier. The electrolyte in ECM ought to have high electrical conductivity, low thickness, high explicit warmth, compound solidness, protection from the structure of a passivating film on the workpiece surface, non-corrosives, and non-poisonousness. The conductivity of electrolytes relies upon salt concentration, dissolved gases machined debris, and temperature. Inorganic salt arrangements fulfill these necessities, like sodium chloride (NaCl) or Potassium chloride (KCI) is blended in water or sodium citrate. The electrolyte invades the difference between the electrode and the workpiece a pressure ranging from 1.5 to 2.5 MPa. The flow of electrolysis serves the perform of removing heat and hydrogen bubbles created within the chemical reactions of the process. The flow could be without cavitation, stagnation, and vortex formation. This may be achieved by avoiding sharp corners within the flow path.

• Tool material: Tool materials for ECM ought to be electrically and thermally conductive and profoundly impervious to consumption. The surface finish of the electrode tool is mostly made of aluminum, copper, brass, bronze, titanium, cupronickel, or stainless steel. The electrode is typicaly made smaller than the cavity desired as a result of the disintegration activity advancing outward from the cathode consistently delivers a hole bigger than the terminal.

• Power supply: In ECM a DC power supply is employed within the range of 5 to 25 Volts to maintain current densities within the range of 1.5-8.0 A/sq.mm. The voltage is kept comparatively low to reduce arcing across the gap.

ECM Process Characteristics:-

• Material Removal Rate: It depends principally on feed rates. The feed rate figure out the current passed between the work & the tool. Because the tool approaches the work, the length of the conductive current path decreases & the magnitude of current increases. This proceeds until the current is only adequate to eliminate the metal at a rate comparing to the pace of hardware advance. A stable cut is then created with a set spacing between the work and also the tool, describe as the equilibrium machining gap.In the event that the apparatus feed rate is diminished, the instrument advance will quickly linger behind, expanding the hole and hence bringing about a decrease of current. This happens until a constant gap is once again established.

• Accuracy: Under ideal conditions and with appropriately planned tooling, ECM is fit for holding a resistance of the request for 0.02 mm and less. The repeatability of the ECM interaction is additionally awesome. This is generally because of the way that the device wear is basically non-existent on a decent machine; resistance can be kept up on a creation premise in the locale of 0.02-0.04 mm. When in doubt, the more perplexing the state of the work, the more troublesome is to hold tight resiliences and the more noteworthy is the consideration needed for fostering an appropriate tooling and cathode shape.

• Surface Finish: ECM under specific conditions produce surface completions of the request for 0.4µm This can be acquired by the front facing cut or the turn of the to or the work. The significant factors influencing the surface completion are feed rate, hole measurement, electrolyte piece, thickness, temperature and stream. Any imperfection on the device will cause machining surrenders on the outside of the work.

Application of ECM:-

• ECM has been employed in a good sort of industrial applications starting from cavity sinking to de-burring.

• The ability to machined high strength alloys and hardened steel has semiconductor diode to several cost-saving applications wherever different processes area unit impractical.

 

Advantages of ECM:-

• The elements aren't subject to either thermal or mechanical stress.

• No tool wears throughout the ECM process.

• Fragile components is machined simply as there's no stress concerned.

• ECM de-burring will deburr tough to access areas of components.

• A high surface end (up to 25 µm in) can be achieved by the ECM process.

• Complex geometrical shapes in high-strength materials notably within the region trade for the production of rotary engine blades, jet-engine components and nozzles is machined repeatedly and accurately.

• Deep holes is created by this process.

Limitations of ECM:-

• ECM isn't appropriate to provide sharp sq. corners or flat bottoms as a result of the tendency for the solution to erode away sharp profiles.

• ECM is applied to most metals however, because of the high instrumentality prices, is sometimes used primarily for extremely specialised applications.

• ECM solely used for machining of electrically conducting material.