A common procedure required for proper motor operation is selecting the appropriate pulse width for the signal going from the controller to the step/servo motor on the CNC machine. A minimum pulse width is usually noted by the motor manufacturer so as to ensure that the motor can register the signals going to it from the controller (if the pulse width is lower, then the motor cannot “see” the impulse being sent from the controller to the machine).
As seen in the following instructions from Panasonic's MINAS A5-series AC Servo Motor & Driver, the pulses have to have a minimum width for the machine to register the signal, ranging from 0.25 to 0.5 μs for the pulse width of the 4 Mpps input and from 5 to 10 μs for the 500 kpps input (obtained as being double of t1 in the charts):
As another example, the Yaskawa's E-7-Series AC Servo Drive also imposes a similar constraint on the minimum widths. The τ in the graph corresponds to the width of the impulse itself, while the T corresponds to the entire period of the signal. The manual advises a minimum τ-T of 0.125 μs to 0.5 μs, depending on the pulse train setup:
A step motor also requires a minimum pulse width, which is considerably higher than that of a servo motor (around ten to twenty times higher higher when comparing the specs for the Leadshine step motor below to the Yaskawa servo drive):
As such, the pulse impulses sent from the controller to the motor have to have a certain minimum width for the motor to be able to register those signals. However, that signal width also cannot be too large due to the signal overlap that would otherwise occur due to each individual signal interfering with the next one. This is done by ensuring the controller sends impulse signals at a rate that is lower than the period of the impulse at its maximum frequency, resulting in impulse signals that do not interfere with one another while the width of the signal is wide enough for the motor to register the impulse.
These constraints on the minimum and the maximum pulse width create a permissible range of pulse widths for each motor depending on its hardware specifications and the particular speeds it is required to be operated at. Such an optimal pulse width for the controller based on these particular specifications can be calculated.
5 meters/minute ÷ 60 seconds/minute · 1000 millimeters/meter ≈ 80 millimeters/second 80 millimeters/second ÷ 5 millimeters/revolution = 16 revolutions/second The value for the [revolutions / second] will be equal to 16 revolutions/second
1 ÷ (16 revolutions/second · 8 · 10^-6 seconds/step) = 7812.5 steps/revolution The value for the number of [steps / revolution] will be equal to 7812.5 steps/revolution
1 ÷ (16 revolutions/second · 6400 steps/revolution) = 9.76 · 10^-6 seconds/step = 9.76 μs/step The value for the [seconds / step] will be equal to 9.76 μs/step.