Topic: Manufacturing Processes
The power required for a turning operation is measured as 2.5 kW. If the cutting force is 800 N and the cutting speed is 90 m/min, calculate the mechanical efficiency.
- A. 86.4%
- B. 55.5%
- C. 40.8%
- D. 48%
Answer: D. 48%
Explanation: The ideal power utilized at the cutting tool is $P_{ideal} = F_c \times V$.
Cutting force $F_c = 800~N$.
Cutting speed $V = 90~m/min = \frac{90}{60}~m/s = 1.5~m/s$.
$P_{ideal} = 800~N \times 1.5~m/s = 1200~W = 1.2~kW$.
The motor input power $P_{input} = 2.5~kW$.
Mechanical efficiency $\eta = \frac{P_{ideal}}{P_{input}} = \frac{1.2}{2.5} = 0.48 = 48\\%$.