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Offline Pratyeka

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feed rate behavior
« on: November 12, 2009, 08:27:31 PM »
Hi! I built this CNC router with aluminium extrusion frame, linear bearings, stepper motors, etc. Everything moves as it should but, in the motor tuning window I can run the axis up to 600IPM with an acceleration of 20, and when in the normal running screen and jog the axis with the arrow keys, I can barely run at 200IPM before the motor stalls... I tried at 25 and 35khz, no difference, tried different pulse width, no difference.

Any ideas?
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Offline RICH

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Re: feed rate behavior
« Reply #1 on: November 12, 2009, 08:41:27 PM »
If memmory serves me, once you set your motor tuning you  should save settings and exit Mach and come back in,
 else the axis may run slow.
RICH

Offline Pratyeka

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Re: feed rate behavior
« Reply #2 on: November 12, 2009, 08:54:02 PM »
Yes, done the "save" thing everytime I did a motor tuning. Sorry, I should have mentioned I have been working in robotics and cnc machine for 25 years. It's just thie Mach 3 software behaves weird. The jogging does not run slow, the motor stalls when running over 200IPM. But in the tuning window, I can run the motor past 600IPM smoothly....Why?
Yes, I set the feed rate to different rates... 100IPM, ok. 200IPM, ok, 300 IPM, stalls when reaching ~220... But in the tuning window, as I said, I can run it no problem over 600IPM...
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Offline RICH

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Re: feed rate behavior
« Reply #3 on: November 12, 2009, 09:41:44 PM »
I am kind of stumped.......
If you don't have the power available to jog at 220 IPM then what allows you to be able to do the same thing
at 600 IPM? That not logical to me.
RICH

Offline Pratyeka

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Re: feed rate behavior
« Reply #4 on: November 12, 2009, 10:26:43 PM »
how about something going on with the pulse train from Mach 3? it's not a question of power. The motor stall not by a lack of power. Maybe there is a difference in how the pulses are generated while in the tuning window and while in the normal control window. I don't know, but the motors run much smoother while I in the tuning window.
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Offline RICH

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Re: feed rate behavior
« Reply #5 on: November 12, 2009, 11:18:59 PM »
Pratyeka,
I don't know, couldn't find anything in a quick look in the manual. The only thing is if you change the khz and that's provided your PC can be used at the rates.
True, if the pulse stream was better you could see a difference and a good example of that is using a SmoothStepper.
I don't know what, if any difference, there is between pulse generation out of the tuning as compared to jogging or
MDI  line.

SO maybe someone else will chime in and shed some light.
RICH

Offline Tweakie.CNC

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Re: feed rate behavior
« Reply #6 on: November 13, 2009, 05:56:32 AM »
It sounds to me like a limitation of your PC.
Mach is using a lot more processor time when running the full screen as opposed to the tuning page and if your PC is doing other stuff (such as polling USB etc) glitches will be experienced.
If you have one, then trying another (perhaps faster) PC may resolve the issue. (Others have posted problems like this when a USB dongle is present which disappears as soon as the dongle is removed)

Tweakie.
« Last Edit: November 13, 2009, 05:59:54 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Tweakie.CNC

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Re: feed rate behavior
« Reply #7 on: November 13, 2009, 06:47:49 AM »
Some further thoughts....

Try running the 'DriverTest.exe' program (found in the Mach3 folder). This will determine if your PC is struggling with running Mach.

My workshop PC gives a nearly consistent flat line which is the ideal.

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

Offline Pratyeka

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Re: feed rate behavior
« Reply #8 on: November 13, 2009, 06:22:56 PM »
Tweakie: your suggestion sounds good. I did run the DriverTest.exe and the screen shows a nice straight line with a small spike from time to time.

I have the same effect whether I set the frequency at 25K, 35K, etc... I don't remember how high I went...

The PC is a pentium running at 3ghz, XP pro and barely anything else. I would think that would be plenty for this application. But obviously something is screwing up the pulse train when in the normal screen and using the arrow keys to jog.

Further details: It does this no matter which axis, X,Y or Z. It stalls while going either direction. Same if jogging more than one axis simultaneously.

Thanks to all for your help. Will dig more into this. Seeing these axis move at 600ipm with the acceleration set at 20 has fired me up... I want that capability all the time... ;D
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Offline RICH

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Re: feed rate behavior
« Reply #9 on: November 13, 2009, 06:33:19 PM »
What version of Mach are you using?
RICH