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Author Topic: General Q about kernel freq "noise"  (Read 3132 times)

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General Q about kernel freq "noise"
« on: March 08, 2009, 07:15:04 PM »
I have tried running the kernel speed above 25000, but I do hear this periodic "chuck" sound from the motor.
It's louder and more frequent at higher speeds.

In fact, judging by what I can hear running at different rates but the same kernel speed, it's like this "chuck" sound happens after a fixed number of pulses.  If I run the motor slower it's still there just less frequent.  Which would normally point to some sort of mechanical feature on the screw but I've noticed this on all the axes, including the rotary, so it's not a mechanical thing.

What causes this?  Isn't it an inconsistency in speed then, which can decrease its resistance to stalls?  It's not losing steps when this happens, is it?

I did tinker with the Active High/Low and Sherline 1/2-pulse.  No effect.  AFAIK it's an inconsistency in the parallel port's pulse spacing but I can't back that up.  Could it be a feature of the G540's drive?

I seem to be limited to about 10 rpm with the Sherline table and a 282oz-in stepper.  Going faster (14, 18 rot/sec) runs for like 2 or 3 sec and then a stall.
« Last Edit: March 08, 2009, 08:13:39 PM by MechanoMan »

Offline DAlgie

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Re: General Q about kernel freq "noise"
« Reply #1 on: March 08, 2009, 11:40:57 PM »
Run the driver test, guessing that the 'chuck' is actually a spike of some sort or noise in your system.

Offline Tweakie.CNC

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Re: General Q about kernel freq "noise"
« Reply #2 on: March 09, 2009, 06:02:36 AM »
From the sound of what you described it could well be lost (or gained) steps which are usually caused by noise spikes occurring in the LPT connection. You could check all your earthing connections are OK and make sure you do not have any ground loops (earthed both ends) also are you using screened cables ?.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline RICH

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Re: General Q about kernel freq "noise"
« Reply #3 on: March 09, 2009, 06:37:29 AM »
Suggest you have a look at the pulse signal with a scope and see what it looks like coming out of the PP.
If you have noise or another signal signal beng mixed in with the pulse you need to eliminate it at the source
as nothing downstream of it like filteriing etc is going to cure it.
One option wouuld be to use the SmoothStepper if your not succes full.
RICH
Re: General Q about kernel freq "noise"
« Reply #4 on: March 09, 2009, 08:07:07 AM »
DriverTest always says "System Excellent" for me.

I've look at the parallel cable signals before... no noise to speak of, although the stepper wasn't hooked up at the time.   I was a little alarmed by the irregularity of the pulses but I'm not sure if that was out of the ordinary for Mach3, I think that's just the variation that DriverTest already saw but approved.