Which of the following is correct for MRR variation in the EDM process using the RC relaxation circuit?

Explanation:

Material Removal Rate (MRR) in EDM Process:

• In Electrical Discharge Machining (EDM), the Material Removal Rate (MRR) refers to the volume of material removed from the workpiece per unit time. It is a critical performance parameter as it directly affects the productivity and efficiency of the machining process. The RC relaxation circuit is one of the types of circuits used in EDM to control the discharge energy by regulating the resistance and capacitance in the circuit.

Working Principle of RC Relaxation Circuit in EDM:

• In the RC relaxation circuit, a capacitor is charged to a certain voltage through a resistor. Once the voltage across the capacitor reaches a predetermined threshold value, it discharges through the gap between the tool and the workpiece, creating a spark. This spark generates intense heat, which melts and vaporizes a small portion of the workpiece material, resulting in material removal. The process then repeats as the capacitor recharges.

In the RC relaxation circuit, the resistance (R) plays a crucial role in determining the time constant of the charging cycle. The time constant (τ) of the circuit is given by:

τ = R × C

Where:

• R is the resistance in the circuit.
• C is the capacitance in the circuit.

When the resistance (R) is increased, the time constant (τ) becomes larger. This means that the capacitor takes more time to charge to the required voltage level. Consequently, the frequency of discharges decreases, resulting in fewer sparks per unit time. Since MRR is directly proportional to the number of sparks generated per unit time, an increase in resistance reduces the MRR.