
234 Electric Motors and Drives
pulses will be generated by a digital controller or computer,
programmed to supply the right number of pulses, at the
right speed for the work in hand.
If the machine is a general-purpose one, many different
operations will be required. When taking heavy cuts, or
working with hard material, the work will have to be offered
to the cutting tool slowly, at say, 0.02mm/sec. The stepping
rate will then have to be set to 2 steps/sec. If we wish to mill
out a slot 10 cms long, we will therefore programme the
controller to put out 10000 steps, at a uniform rate of 2
steps/sec, and then stop. On the other hand, the cuttin ...