Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: ben wood on May 09, 2011, 01:56:57 AM
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First Id like to thank everyone who fields these questions. I've found amazing info in the various forums on line. Enough info in fact to build a nice little 18" x 30" x 6" router. It's turned out great, I've even cut a couple of parts, but i have a nagging problem. I'm trying to get my motors to run smoothly and have been experimenting with a lot of different speeds and acceleration to try to acheive this. Whats puzzling is that if have the motor tuning dialog open I can get them to move smooth as butter at top speed (25,000 mhz). But then when I close that window and am jogging the motors they run really poorly. I'm running a g540, mach 3, 48v power, 12 amps, and 381 oz in motors. If anybody would like the specs on the motors I can supply those also. I bought them through keiling, for what it's worth. Thanks all for taking a minute to read this. I've spent hours searching for the solution, and am finally throwing in the towel and asking for help. Thanks again!!!!
Ben Wood
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Hi Ben,
Welcome to the forum.
Just a couple of bits of info taken from the Gecko website.......
Your step pulse width must be at least 2uS wide and the pulse polarity for the step and direction signals are ACTIVE HIGH.
STEP 7: ADJUST TRIMPOT
The G540 is composed of four individual G250 motor controls, each of which has a trimpot on board to adjust low speed smoothness. In your CNC program set the axis being adjusted to move at 2 revolutions per second and use a non-conductive screwdriver to turn the trimpot in the ADJUST hole on the top of the drive. If you do not have a non-conductive screwdriver you may use a standard screwdriver, but be careful not to touch any components other than the trimpot. The trimpot has 270 degrees of motion and will have an audible “sweet spot” when it is in proper position. This position will change with each motor so be sure to readjust if you change motors.
Don't know if this helps,
Tweakie.
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Whats puzzling is that if have the motor tuning dialog open I can get them to move smooth as butter at top speed (25,000 mhz). But then when I close that window and am jogging the motors they run really poorly.
Mach screen updates are suspended whilst the tuning dialog is open. I'm thinking this may allow the driver to perform better than it can when Mach is busy doing it's thing.
Ian
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thanks for your responses. The steppers ran so well at low speed that I skipped the trim pot adjustment. I'll go back and do that along with adjusting the pulse width and the ports and pins settings. It sounds like these are things I should check anyway.
The fact that Mach runs differently when that window is open, makes me think that it's my computer system. I'll spend some time going through the list of "house keeping" steps to see if anything helps. Thanks so much for your help!
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I've heard of this issue before, and I think you're correct, that it's a PC issue. Try running task manager while doing the testing, and see if the CPU load goes up drastically when the motor tuning is closed.
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Thanks for the help Gerry! I opened the tuning dialog and it takes about 1% of the CPU to jog one axis. Then with the dialog open it takes about 18%-24% just to jog one axis. I'm so happy to know where the problem is, Thanks! Now I need to deal with it, but i could use some advice. I feel like i have a few reasonable options. Is there basic house keeping I can do on the computer to make the cpu more efficient. I could add a graphics card if it would help significantly. Or is a faster CPU the best solution. Right now i have to slow things to about 2000mm per min to run smooth, and with the dialog open I can run it at about 10,000 and it's still smoother. For what's it's worth I'd be interested in fielding anyones opinion. This has been driving me crazy for a week. Thanks.
Ben
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What are the specs of the PC?
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It's a HP dx2200, The processor is a pentium 4, 3.06 ghz unit. And I believe it has 2 gigs of ram. Should I dig up any more info?
thanks
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Make sure that it isn't using shared memory for the on board video.
A non integrated video card may make a big difference and is easy to try if you have a spare card lying around.
Mike
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An add-in video card may indeed help. If you look in the downloads section of this site you will find a Mach optimization guide for Windows XP as well. One item with the G540 is that it does not like really short step pulses that Mach can sometimes provide. You can try turning on 'Sherline' mode on the first page or Ports&Pins to see if that helps (it tells Mach to send out wider pulses.)
The worst case scenario is that your PC may not be up to the task, a new PC or external motion control card would be the options then.
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thanks everyone for your input! I've got a pretty good to do list going now and I'll just start my way working through them. For now I'll slow the machine down. And start cutting parts. One last thing though. Will do you think these out of sink pulses will result in missed steps and a loss of accuracy on a long program?
thanks
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I believe I read on the Mach site somewhere they recommend an add in video card, the cpu is using cycles in the on-board graphics that will cause problems with motor operation. I added a high end video card to my system and the software runs much better now. Of course YMMV, ;D
jim :)
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someone suggested i follow an XP cleanup routine on the documentation page of the Mach site. I looked over the page briefly and now that I have time to try and work through the list, I can't find it. In fact, mention of the list seems to have been removed from the response to my question. Can someone please let me know what is going on?
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Bottom of this page. ;)
http://www.machsupport.com/downloads.php
Tweakie.
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thanks, i'm not sure how I missed it.