Question

In the feed drive of a Point-to-Point open loop CNC drive a stepper motor rotating at 200 steps/ rev drives a table though a gear box and lead screw-nut mechanism (pitch=4 mm, number of starts=1). The gear ratio
$(=\frac{Outputrotationalspeed}{Inputrotationalspeed})$ is given by $U=\frac{1}{4}$. The stepper motor (driven by voltage pulses form a pulse generator) executes 1 step/pulse of the pulse generator . The frequency of the pulse train from the pulse generator is $f=10,000$ pulses per minute.

A customer insists on a modification to change the BLU of the CNC drive to 10 microns without changing the table speed. The modification can be accomplished by

• A. changing U ot $\frac{1}{8}$ and increasing $f$ to $2f$
• B. changing U to $\frac{1}{2}$ and keping $f$ unchanged
• C. changing U to $\frac{1}{2}$ and reducing $f$ to $\frac{f}{2}$
• D. keeping U unchanged and increasing $f$ to $2f$.

Answer 1

The correct option is C changing U to $\frac{1}{2}$ and reducing $f$ to $\frac{f}{2}$

Initially velocity was $10000\times 5\mu m/min.$Now velocity will be $5000\times 10\mu m/min.$ so velocity of the table remains same.