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Art,

I'm gradually trying to sort things out here. When I first noticed
problems I was running the kernel @35Khz, I then switched to 25Khz
and got the figures I gave you. I have now re-started M2 and get
figures much more in line to what is expected, there are still some
anomolies, for example at 3/4 spindle speed there are intermittent
missing pulses, I can see this as I have a D-ff as a pre-scalar and
instead of a regular 1:1 square wave there are random 1:2 pulses,
these correspond to missing pulses in the step train and a lot more
variation in the VFD frequency. Changing the kernel to 35K and I am
back to the original conditions.

This gives rise to 2 questions.

1) It seems necessary to do a program re-start after changing kernel
frequency. Can you confirm?

2) I am running a HP Pavilion 650MHz P3, is this fast enough to run
at 35KHz, what is the symptoms when you run out of steam?, the other
4 axis seem to be working OK. The Diagnostics page give a pulse freq
of 36119 and CPU load = 0%, worst case 0.000158.

Bernard

Bernard:

Yes, it is necessary to restart after changing frequencies.
This is necessary to restart the engine timer. Also, if you tune the spindle
in 35 Khz and then switch to 25Khz, you have to retune. Any frequency
changes and all motors must be retuned. This is due to calculations
involving your actual timing periods to make everything as accurate as
possible.

The missing pulses you see are probably the bresenham divider in
operation. For exmple 25Khz is one pulse every 40us but 24.9Khz is still one
pulse every 40us one will be missing every 24999 pulses. This can look like
missing pulses.Most step/dir convertors to analogue simply charge caps so
there is no problem with this method, but you may be trying to use a circuit
type not so tolerant of this type of pulse timing. The steppers won't notice
it but your spindle VFD might.

Hope this helps,
Art
www.artofcnc.ca