compare. There are e.g. stepper motors controllers that cost 800 USD and there are some other that
cost 40 USD (with the same power!). Generally we can conclude that the servo motor + drive pack-
age is more expensive. Other disadvantage of the servo drives is necessity for PID controllers tuning
and wiring that is more complicated. That will be the end of the disadvantages. Great advantage of
the servo drives is that - thanks to the feedback - the servo drive indicates the overload and position-
ing error. When the CSMIO/IP-S receives this signal immediately stops the axes. In the stepper mo-
tors there is no feedback like this one, so even if one of the axis because of e.g. overload will not
keep the set trajectory, the machine will continue the work – breaking the same entire processed
detail.
In sum – we recommend the servo drives. Their disadvantages are negligible in comparison to
the benefits they offer. Please note that the servo drive can have much lower nominal torque than
holding torque of the stepper motor. When we compare the 3Nm stepper drive and 3Nm servo drive
– the price difference may be significant. However, if we compare the 3Nm stepper drive with the
1Nm servo drive, the price distance is not so big.
Practice shows that sometimes - mechanically identical machines are sold in two versions, with
3Nm stepper and 1Nm servo drives. The machine with the stepper motor reaches max 7,5m/min
feed rate and 0,1g. acceleration. The machine with the servo drive reaches 20m/min feed rate and
0,4g. acceleration. If we add the feedback, which was mentioned before, further comparing is point-
less.
The choice is in your hands of course, in some solutions the stepper motors are adequate and
work very well. Thanks to perfectly precise STEP signal timing of the CSMIO/IP-S controller the step-
per motors behave much better then while controlling from e.g. the LPT port. We can use a higher
stepper division, so the motors will work quieter, smoother and they get higher revs by reducing the
resonance.
C S - L a b s . c . – C S M I O / I P - S - C N C C o n t r o l l e r
Page 36
