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  1. #1
    Join Date
    Jan 2006
    Posts
    461

    X3 Lost Steps

    I am having some trouble with lost steps. I am running 276 nema 23 steppers on the x and y and a having a lot of trouble with lost steps on those axis. The acceleration is set to 1 with rapids at 60. I turned those down in an attempt to fix the lost steps. What is everyone else using for their steppers and acceleration settings. I have gecko 203s and a big 72volt 12amp PS.

    I was debating getting larger steppers, but know that that may not fix the problem, since it might just be my settings.

  2. #2
    Join Date
    Mar 2006
    Posts
    304
    I haven't done any actual cutting but I have 330's @ 50V/15A and I dropped my rapids down to what you're running while I was setting up the X. I'm taking it slow sorry I can't give real data. I can't physically make the axis loose steps at 50ipm with any force my body can exert. I hope to get all my limits and Y preload taken care of in the next month and then can actually make the chips fly.

    Interested to hear what others are running. I'm already considering stepping up (pun intended) to 400+...
    Every day is a learning process, whether you remember yesterday or not is the hard part.
    www.distinctperspectives.com

  3. #3
    Join Date
    Jan 2006
    Posts
    461
    I cant cause it to lost steps by pushing on it either. Its when its making multiple complex moves, such as pocketing, contouring, etc. What do you have your acceleration set at?

  4. #4
    Join Date
    Mar 2006
    Posts
    304
    5 in/s, but I expect that will change too. It was an arbitrary starting point. I'm running EMC2 - what are you running?
    Every day is a learning process, whether you remember yesterday or not is the hard part.
    www.distinctperspectives.com

  5. #5
    Join Date
    Jan 2006
    Posts
    461
    Mach. That seems a good bit high.

  6. #6
    I had a similar issue with the G210 drivers on my mill. No visible lost steps, and I really couldn't stall the motor on my own, but it missed steps as noticed in the finished part. It turned out to be a communication issue of sorts. I am using a Camtronics controller, and the BOB used seemingly could not spit out the info fast enough for the 210 drivers, and it created this problem. I also had another Gecko controller with 201 drivers and a pmdx122 BOB, so while troubleshooting the problem, I swapped drivers. The 210 drivers worked fine in the controller using the pmdx BOB, perhaps due to the buffered signal (BOB buffers the signal before, and the 201 drivers haven't missed a beat in my Camtronics controller. I had several discussions with Dan at Camtronics while trying to work through it, and it seems that the 210 drivers actually require a longer pulse width(longer than the 40ms Mach can deliver) , so the buffered signal used in the other controller likely provides this. The 201 drivers don't require as long a signal and have worked perfectly in the Camtronics board (Dan tried talking me into the 201 from the start, but I wanted the extra step multiplication options that the 210 drivers offered at the time).
    I am not sure if my explanation is helpful or not - I generally understand the issue I had, but I am not up on the lingo so much. Basically, I had a communication problem related to the signal pulse width. The drivers simply required a longer signal, which Mach alone could not provide. If you have the same problem, it may be fixed by adjusting the signal length(in motor tuning I think), or by using a buffered BOB (seemed to work for me, as the 210 drivers work perfect with the Pmdx122 BOB, and the 201 drivers work perfect with the un-buffered signal on my Camtronics controller).
    www.rc-monster.com

  7. #7
    Join Date
    Mar 2006
    Posts
    357
    Are you using ballscrews?
    I have nema 23 425oz/in and only a 28 volt xylotex system. No problems with lost steps at 60IPM and 5 for acell using Mach.

    Steve

  8. #8
    Join Date
    Jan 2006
    Posts
    461
    Yeah, I'm using the cncfusion deluxe kit.

    The BOB might be something to consider. I am using a straight plain ole BOB with a SIIG card in the computer. I wonder if its not receiving a strong enough signal to push the motors properly. I will also check the motor signal length too.

    What is everybodys acceleration set at. Thx

  9. #9
    My machine is a Minitech MiniMill 4, so it isn't apple to apples(linear bearings, ball screws), but I run it at 330 IPM rapid speeds and the acceleration setting at 10 (about .5 second ramp up). I am using 254 oz/in nema 23 steppers with I think a 42 volt +/- power supply. When I was having the problem, I went all the way down to 40-50 IPM with the same results (no noticed missed steps, but chamfers and like features were offset from each other). It will easily go to 350 ipm now.
    www.rc-monster.com

  10. #10
    Join Date
    Jan 2006
    Posts
    461
    So you are saying you adjusted your acceleration to fix it?

  11. #11
    Join Date
    May 2005
    Posts
    11
    See his first post above - not an motor tuning issue, but a communications issue with the drivers.

    Quote Originally Posted by pzzamakr1980 View Post
    So you are saying you adjusted your acceleration to fix it?

  12. #12
    Quote Originally Posted by Eddiep View Post
    See his first post above - not an motor tuning issue, but a communications issue with the drivers.
    Exactly. I was trying to say that motor tuning DIDN"T fix it - same problem was present regardless of motor tuning. One thing I did notice while I was having the problem - it didn't miss steps when I ran it in single line mode (constant velocity turned off). The motor tuning never changed the error. It was fine in single step mode, but always was "off" in CV mode, regardless of motor tuning. This is when I started farting around and discovered the communication error - the 2 controllers I have were very similar, but with different drivers and a different BOB. The 210 drivers work fine with the buffered BOB - I suspect this is due to their longer required signal pulse, which Mach alone could not deliver. Try running in single line mode and see if the error is still present. If it is, you may need a buffered BOB like the PMDX 122 to accurately run in CV mode. You may try adjusting the signal length as well - according to Gecko, the G210 drivers need a 50ms signal, but Mach only goes to 40ms, so without the buffered signal, I was getting error - the buffered signal seemed to fix it. I am not familiar with the G203 drivers you have, but it is reasonable to assume your issue is similar to mine, given the similarity of the actual results in use.
    www.rc-monster.com

  13. #13
    Join Date
    Mar 2006
    Posts
    304
    Just an FYI the G203V is different in it's timing requirements from the 201-210 drivers:

    G203V:
    Step Pulse “0” Time: 2uS min (Step on rising edge)
    Step Pulse “1” Time: 1 uS min
    Direction Setup: 200nS before step pulse rising edge
    200nS hold after step pulse rising edge
    G202:
    Step Pulse “0” Time: 0.5 uS min (Step on falling edge)
    Step Pulse “1” Time: 4.5 uS min
    Direction Setup: 1 uS min
    20 uS min hold time after Step edge
    G201:
    Step Pulse “0” Time: 0.5 uS min (Step on falling edge)
    Step Pulse “1” Time: 4 uS min
    Direction Setup: 1 uS min
    20 uS min hold time after Step edge
    G210:
    Step Pulse “0” Time: 0.5 uS min (Step on falling edge)
    Step Pulse “1” Time: 4 uS min
    Direction Setup: 1 uS min
    20 uS min hold time after Step edge
    So the 203V requires 4x as long a LOW signal (2us vs .5us) but only 1/4 the length for a HIGH signal vs the other drives. The direction change is much more efficient being in the nanosecond range versus the microsecond (nano is 1/1000 of micro for those who may get the tiny ones confused). Just observations. These are right from the current manuals (and if Mariss happens to read this, you might want to change the ordering of the specs so all the timings are together and the temp and humidity are together - and maybe add a spreasheet type page comparing all the drives to one another )
    Every day is a learning process, whether you remember yesterday or not is the hard part.
    www.distinctperspectives.com

  14. #14
    Join Date
    Jan 2006
    Posts
    461
    I posted this problem on the gecko forum as well, and Mariss suggested that the Step is set to active high, and the step pulse is 2us. So I'm going to give that a try and see how she turns out. Ill let you know in an hour.

  15. #15
    Join Date
    Jan 2006
    Posts
    461
    Well, so far so good. I also purchased two new motors for the x and y. Two keling 425's. And this thing rips now. I have the accel set to 10, and it wouldnt skip a beat. I turned the accel back down to 4 for my part, since there is a lot of pocketing. Also, once I got the 2us step pulse in, the z axis is behaving like it should too. There were problems with it, because the depth would get shallower and shallower, not anymore, depth is dead on for all holes.

  16. #16
    Join Date
    Jan 2006
    Posts
    461
    Ok, nm, I just ran the part that I was having problems with and it did the exact same thing. The step was set to high with a 2us step pulse. I thought it fixed it but after running the part the half way the error was apparent again.

  17. #17
    Join Date
    Aug 2004
    Posts
    2849
    Have you looked at your G-Code?

  18. #18
    Join Date
    Feb 2006
    Posts
    1187
    Theres a thread on the forums(sorry no link) but it involved making a flywheel (sort of) to attach to the end of the stepper motor which will counter balance the motor and help eliminate resonance and lost steps. I,m trying to make some for my machine(but of course I keep losing steps). I wish I could remember the poster of that thread!

  19. #19
    Join Date
    Jan 2006
    Posts
    461
    I believe the poster was Geof. Search for lost steps and its in their somewhere. I dont seem to be experience resonance, at least not enough for me to notice. If I've tried every other option than I will certainly give it a try. I think its either software settings or the interface between the drivers and the computer. I just replaced the basic breakout board with the candcnc mini io board. So Ill see if that helps.

  20. #20
    Join Date
    Mar 2006
    Posts
    304
    Did you do the low speed tuning of the pot on the G203V with the new motors? You're worrying me since you're essentially running what I'm working on...though I'm setting up using EMC. Gotta finish the kitchen ceiling project the landlord decided to finally do, receive my 3 pole contactor and then I can finally concentrate on finishing mine.
    Every day is a learning process, whether you remember yesterday or not is the hard part.
    www.distinctperspectives.com

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