Quote Originally Posted by the great waldo View Post
In the mx3660 manual it states that the 4th axis can only run up to 20khz . I am running uccnc at 100kz is this a problem? And can someone please explain to me if 20khz is enough to run for example a 4th rotary axis ? Thanks in advance.
Andrew
Depends on how you want to use 4th axis but general a 4th axis is slow spinning and used for position more than speed in which case 20Khz is more than enough for a 4th axis.
Here's how to work out the max RPM 20Khz will give you.
20,000 pulses per second(20khz) / micro steps * 60 = RPM for example. 20,000 / 2000=10 * 60 = 600rpm.

So for instance lets say your 4th axis is using a 6/1 ratio then you'll get 100Rpm which if you want to use 4th like a lathe then isn't very fast. You could increase RPM by lowering the Micro stepping but then you lose some resolution and smoothness.

Often you'll only use 4th axis for postional moves with much higher ratio and spinning only a few rpm but with high acceleration and High micro steps to help little with smoothness and to lesser degree resolution.

It's trade off between RPM and Motor smoothness/resolution. However for slow spinning motor then 20Khz will be fine.