Question

A circular hole of 25 mm diameter and depth of 20 mm is machined by the EDM process. The material removal rate $inm{m}^3/min$ is expressed as $4\times {10}^{4}I{T}^{-1.23}$ where I = 300 A and the melting point of the material, T = 1600°C. The
time (in minutes) for machining this hole is____(correct to two decimal places).

• A. 7.1431

Answer 1

The correct option is A 7.1431

$MRR=4\times {10}^{4}I{T}^{-1.23}m{m}^3/min$

Volume required to remove
$=\frac{\pi }{4}{D}^{2}L=\frac{\pi }{4}\times {25}^2\times 20$
= 9817.477 $m{m}^3$

Now, MRR $=4\times {10}^4\times I\times T^{-1.23}$

$=4\times {10}^4\times 300\times \left({1600}^{-1.23}\right)$

$=3\times 4\times {10}^6\times {\left(1600\right)}^{-1.23}$

$=1374.40m{m}^3/min$

$\text{Time required}=\frac{9817.477}{1374.4}=7.1431min$