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20,000 for Steps per unit will almost certainly be too much unless your encoder is 5,000 lines per rev which is unusual, try setting it to 10,000 and see if that helps.

With it set at 10,000 and Velocity at 2,500 you would require a frequency of  41.666KHz, so make sure you have the ESS plugin set to the next above that (sorry can't look as I don't have an ESS here)

One other thing to look at in the ESS plugin is the pulse for spindle, try setting it at 1 or 2. The ESS and SS do not handle the pulse width the same for a spindle as they do for an axis and this can cause issues if set too high.

One last thing is make sure you have no electronic gearing set in the servo drive.

Hood

Sorry should have been 416KHz

Hood

Thanks Hood
Was just wondering if the Ess treated a step & Dir spindle the same as an axis, or differently, as you say. I'll play with the Ess settings now. Wont be long.

Here are the Ess settings before I start.

I would set the KHz to whatever the next above 416KHz is and set the pulse width to 2.
Hood

I don't know how to thank you enough Hood. I knew it would be a simple solution, but it helps incredibly to talk with someone who knows all about these things.
The problem was caused by the spindle pulse width, I hadn't changed it before, because I though that what was Ok as an axis, should also be Ok for the spindle.
I'll just have a fiddle and see what is the maximum pulse width I can have. At the moment it is working with a pulse width of 1.
Should I use whatever pulse width it works with, or should I be conservative and set it one unit below whatever works?

If it is working at 1 then I would just leave it. It won't work much higher, as said maybe 2 max.

With the axis the ESS spreads the pulses evenly no matter the output frequency,  with the spindle it just bunches them together, if you have the width too high then it can not output the pulses correctly above a certain RPM (depends on steps per unit and RPM) and you get problems. You can see this very clearly if you scope the output.

Ok sleep time.

Hood

Well I've experimented and cannot get 2500rpm with a pulse width above 1. Unless you can have decimal points in pulses, Ie: 1.5, but I think I'll leave that for another day. I can get on with my fitting now
Thanks again
Dave

Well I did think about putting the scope on the output, but I thought I'd ask first.I'm glad I did.

Seems funny going to bed at 11:00am.

Sleep well

Dave