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Author Topic: Stepper freeze noise with higher driver kernel speed...  (Read 5662 times)

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Stepper freeze noise with higher driver kernel speed...
« on: May 14, 2012, 08:27:52 AM »
Hi Everyone,

My configuration is a G540 with (3) 381oz steppers using a 48V PS.  I am using an older notebook with a 2GHz P4 which isn't the fastest, but seems workable.

With the driver set at 45kHz - during a fast move (G00) it would do fine with one axis, but if two axis were moving at the same time, it would get part way and for a lack of a better act as if the machine were seized up.  All axis movement would stop and the motors would make this loud horrible noise that would continue until I pressed ESC.  At this point I would usually press the E-Stop and the motors would no longer be held.  I can freely turn all axis so the machine itself is not seized up at all.

Changing the driver kernel speed back to 25kHz solves this issue.  I can move all 3 axis at 120IPM at the same time and it sails along with no problems.

What do you think this is?  Is my system not up to the task of 45kHz?  Could the driver have a problem where it is asking the steppers to fight themselves somehow making this type of noise?  Has anyone see this type of issue before?

Thanks,

Alan

Offline Hood

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #1 on: May 14, 2012, 01:38:01 PM »
If you can get the velocity you want with 25KHz then there is no need or real benefit to setting the kernel higher than 25KHz.

Hood
Re: Stepper freeze noise with higher driver kernel speed...
« Reply #2 on: May 14, 2012, 02:11:10 PM »
Hi Hood,

I agree; 125 IPM is the max I can get with 25kHz and I am ok with that.  I just wondered if others have seen this issue, if it has a name, etc.

Thanks,

Alan

Offline ger21

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #3 on: May 14, 2012, 02:34:58 PM »
Notebook PC's are not supported for use with mach3. That's probably at least part of your issue.

Also, no two PC's are the same. One 2Ghz might be able to run at 75Khz, and another only 35Khz. There are no gaurantees that any particular PC can run at any given kernel speed.
Gerry

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #4 on: May 14, 2012, 02:42:16 PM »
Hi Gerry,

I understand - is what I experienced an issue that can happen if the kernel speed is set too high?  Have others had the same thing happen?

Thanks,

Alan

Offline Hood

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #5 on: May 14, 2012, 03:22:22 PM »
The pulse may be too erratic for smooth motion on a higher kernel.
Out of interest what is the Time in Int (Diagnostics page) when on 25KHz and then also on 45KHz ( restart of Mach when you change the kernel)
Hood
Re: Stepper freeze noise with higher driver kernel speed...
« Reply #6 on: May 14, 2012, 03:28:25 PM »
Hi,

25kHz --> 9.5 to 10.5
45kHz --> 6.x for a bit and bounces up to over 10 every half second or so...

Thanks,

Alan

Offline Hood

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #7 on: May 14, 2012, 03:37:06 PM »
At 25KHz Mach interupts at 40uS  (1 second/25,000) and your Time in Int is say 10 so that means  Windows has 30uS out of every 40uS to do its thing.
At 45KHz Mach interupts every 22uS so that is only leaving 10uS or so for windows.
That may be a factor as well as to why things are not happy at 45KHz.
Hood

Offline RICH

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Re: Stepper freeze noise with higher driver kernel speed...
« Reply #8 on: May 14, 2012, 04:55:42 PM »
As has been stated if the system reponds well at 25 kZ and your satisfied with the velocity and acceleration you have then don't use  a higher kernel speed. The higher kernel may allow use of a higher velocity setting in motor tuning but that is only as good as the rest of the system from the computer to the motor. An example would be using a higher velocity but you have no torque from the motor and it is not reliable. That is bragging rights without common sense. You may find that the 125 ipm is really not reliable over time.
FWIW,
RICH
Re: Stepper freeze noise with higher driver kernel speed...
« Reply #9 on: May 14, 2012, 05:01:57 PM »
Hi,

I didn't notice an issue at first with the 45kHz until it tried to move 2 axis at the same time.  Most of my testing was just a single axis before that.  When doing 2 axis at the same time, it would make that horrible seizing up type noise.  I was hoping that there was an explanation for that noise (and that others have experienced it, know what to call it, etc.).  At this point I don't know if it is anything but the driver itself sending commands that don't make sense when it is configured for 45kHz.  I've been tempted to connect up turbocnc and try doing multiple axis at the same time at that speed to see if it does the same thing to prove whether it is a driver issue or something else.

Using 25kHz, I can tell all 3 axis to go at the same time using G00 and they all move perfectly.  I repeated this back and forth at 120 IPM a few times with no problems...

Thanks,

Alan