1. 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
Last edited by the great waldo; 5 Days Ago at 01:09 PM.

2. Originally Posted by the great waldo
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.

3. Originally Posted by JAZZCNC
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.
Hi Jazz
Thanks for the info. Would the kernel frequency of uccnc have to be adjusted to it's lowest setting (the settings available are 25khz 50khz or 100 khz) or is it not important and a higher kernel frequency could be set say 50 or 100 khz. I've not got a 4th axis yet but could see a rotary drive being useful in the future.
Cheers
Andrew

4. I've been looking at the Mx3660 manual and no where do I see that it can have a 4th axis so can you post the manual your looking at or a link to it.

5. Originally Posted by JAZZCNC
I've been looking at the Mx3660 manual and no where do I see that it can have a 4th axis so can you post the manual your looking at or a link to it.
Hi Jazz

Cheers

Andrew

6. Originally Posted by the great waldo
Hi Jazz

Cheers

Andrew
Ahh I was looking at V1.1 that's why difference.

Ok well the just means that this output can only send out 20Khz regardless of the input. So Controller can provide 200Khz but only 20Khz will be sent thru this output.
Regards the controller it's always a good idea to set the frequency to just more than you need which for a stepper system 100Khz is more than enough. This lowers the work the controller as to do.

7. Originally Posted by JAZZCNC
Ahh I was looking at V1.1 that's why difference.

Ok well the just means that this output can only send out 20Khz regardless of the input. So Controller can provide 200Khz but only 20Khz will be sent thru this output.
Regards the controller it's always a good idea to set the frequency to just more than you need which for a stepper system 100Khz is more than enough. This lowers the work the controller as to do.
Hi Jazz
Thank you for the clear answer, much obliged.

Cheers

Andrew

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