Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Pratyeka on November 12, 2009, 08:27:31 PM
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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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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
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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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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
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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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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
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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.
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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.
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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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What version of Mach are you using?
RICH
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Recently bought Mach3 R3.042.032
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Could it be exactly the opposite to what I have said before and your PC is running too fast ?.
This link may be of interest:-
http://www.machsupport.com/forum/index.php/topic,11921.0.html
Tweakie.
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Interesting! Will try to slow down the cpu as soon as I fix the power supply of the CNC. Apparently the bridge rectifier need to be mounted to a heat sink when driven above 3 amp... The supplier forgot to mention that. Replacing it with a 25 amp.
Where can I get the XP optimization file?
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Bottom of this page :-
http://www.machsupport.com/downloads.php
Tweakie.
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There is absolutely *nothing* to be gained by running the Mach3 kernel speed any faster than the fastest step rate you require. All it does it eat up CPU bandwidth, and potentially create problems. Few machines seem capable of running reliably long-term above a 45kHz kernel rate, regardless of what the driver test indicates. If it works at 35kHz, and gives you the rapid speeds you need, then run it at 35kHz. Going faster buys you nothing at all.
Regards,
Ray L.
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There is absolutely *nothing* to be gained by running the Mach3 kernel speed any faster than the fastest step rate you require. All it does it eat up CPU bandwidth, and potentially create problems. Few machines seem capable of running reliably long-term above a 45kHz kernel rate, regardless of what the driver test indicates. If it works at 35kHz, and gives you the rapid speeds you need, then run it at 35kHz. Going faster buys you nothing at all.
Regards,
Ray L.
Thanks for the info. But this is moot since I get the problem from 25khz on... changing to higher frequencies was just done for troubleshooting.