MAHO MH600C / 432 control is freezing
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  1. #1
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    Default MAHO MH600C / 432 control is freezing

    I've got a 1989 MAHO MH600C with Phillips 432 control and 4th axis. It has served me very well for the past year that I've owned it, but suddenly I'm getting a strange malfunction where the control freezes up in a manner that I cannot figure out. I can turn on the machine and set the 4 axes toward their reference points; when I do this, all four axes move properly but once they get to their reference point locations the control freezes up.

    When the control is frozen, I can cycle E-stop and then power-on + clear twice to get the control unfrozen.

    Once I've unfrozen it I am not able to jog XYZ axes, but can still jog the 4th axis. When I let my finger off the 4th-axis jog button the control freezes again and the 4th axis does not engage the hydraulic brake like it should.

    Another thing that I can do when the control is unfrozen is that I am able to move the XYZ axes 0.1" at a time by putting it into 1000 step mode and pressing any of the 6 +/- buttons for the XYZ axes. When I do this, the machine makes the movement, but then freezes after it moves 0.1"

    If I do this 10 times in a row (move 0.1" and then unfreeze machine again) then I can get enough clearance (1") to make a running start at the reference point again. I unfreeze the machine and send it toward the reference point on the axis in question -- it behaves as it should but then once it gets to the reference point the control freezes again.

    I hope I'm describing this behavior adequately.

    A few things to note which may somehow be relevant: I've got a lot of weight on the table. In order to compensate for this, I have adjusted the machine constants to slow down the max rapid speed on all axes, which has helped me avoid position following errors on the Y-axis (which is the axis which moves the table up and down). Slowing down the rapid speeds and max feeds has been a good stopgap measure, but I noticed that over the past few months I've needed to keep slowing it down further every few weeks in order to avoid errors. Lately I also have needed to manually jog the Y-axis up and down at 75% for several minutes before I can get it to jog up at 100% of the already reduced feedrate.

    Taking that history into account, I suspect that the drive for my Y-axis may be wearing out, and I'm wondering if this new behavior of the control freezing is perhaps related somehow?

    FYI, this is the exact same machine referenced in this thread:

    89 Maho MH600C Y axis problems

    In that thread, he mentions that he also had a lot of weight on the table and that he had to replace the drive for the Y-axis. Perhaps it's time to replace it again?

    Thanks in advance for any help or suggestions that anyone can give me.

  2. #2
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    Lee, Yeah, I think thats pretty much what happened to me except the Z axis didnt fail gracefully. Just stopped one day at startup. Its been said in other posts about the KDA indramat drives that the large caps go bad and should be replaced. I never tried to repair it, just swapped the drives to verify. Bought the same drive on ebay for $280, swapped the personality modules and its worked till now.

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    Thanks Mark! I found an old drive on ebay that got pulled from a very similar MAHO, so hopefully it will work for me, but even if it doesn't solve the problem it was cheap enough that it could still be useful as a debugging aid. I will report back when I've done the swap-out experiment. I need to trade the programming module from the old drive and put it on the "new" one, right?

    Also, here's another question: when I open the electronics cabinet there are three switches -- one overrides the axis limit switches, one enables programming the system constants, and the third one puts it in some sort of debug mode. I run the "drive module" part of the debug mode and it errors out on module #3 (out of 3 total) saying that drive #6 is not present. That's to be expected though, right? Drives 1-4 are the axes and #5 is the spindle, right?

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    The other thing you should do is check (carefully)on the three copper bars connecting the drives and servo amp power supply to be certain that you have 300VDC across all the bars. I never had that problem on this machine but it could also be a problem with the servo power supply. Sounds like the z axis servo. There should be an error code on that drives LED screen. I think I gave you an indramat drive manual with the machine.

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    Mark, upon your advice at the time we transferred ownership, I downloaded the drive manual entitled:

    MAC Servo Drives
    with TDM and KDS servo drive modules
    Applications manual

    Document No. 120-0001-B301-02
    Date: Sept 1999

    Number of pages: 186

    So anyhow I'm armed with that, but haven't dug too deep into it yet.

    Lately I've been running the machine exclusively in horizontal spindle configuration, and have switched around the system constants so that the Y axis lifts the table up and down, rather than the Z axis as you were accustomed to.

    Anyhow, the problem I'm having with the control freezing is intermittent, and so it seems like a 50/50% chance whether the machine will function properly when I turn it on. I wrote a simple "warm-up" routine that jogs the axes back and forth indefinitely, and it will go on for hours until suddenly it stops with a frozen control. The control always freezes at the end of a move, after it's already completed motion, but before registering the move as complete.

    As it turns out, I was lucky this morning and the machine turned on properly and is running it's warm-up routine at 80% rapid with no problems whatsoever. I measured voltage across the DC terminals of the drives, and am reading 307VDC whenever the X and Z axes are moving, but when the Y axis lifts the table up, the voltage drops down to 306. When the y axis drops the table down, the voltage goes up to 310.

    I will report back with some voltage readings the next time the control freezes.

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    OK, and the control froze up not too long after writing that last post, once again after it had completed a movement. The DC supply voltage on the drive bus bars was 309VDC.

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    Hi Mark, and anyone else reading this tread:

    My replacement drive from EBay came in a little while ago, but I haven't taken the time to debug my MAHO with it yet because I've recently started a new job at Autodesk Pier 9 in San Francisco that gives me access to a brand new Matsuura MX-330 5-axis machine. In light of that, my motivation to fix the good 'ol MAHO has dropped substantially, and so I'm thinking that it would be best to drain the coolant tank and pack up my tooling to take to San Francisco with me. I'm sure I'll get around to debugging this MAHO problem before too long, but in the mean time I'm just excited to finally have access to a 5-axis machine, and am focusing my energy in that direction. I'll report back to this forum thread in the coming months when I have more information about whether the drive replacement fixes the control freeze problem I'm having.

    Lee Krasnow
    Pacific Puzzleworks

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    Hello World!

    Well I'm back to this thread a couple of years later. I've since moved the non-operational machine to a new location and have powered it up successfully but still have the same drive problems as before. I tried swapping out the drive with that replacement one I bought on eBay a few years ago but that didn't solve the problem. My more immediate hindrance to further troubleshooting is that the battery doesn't seem to hold a charge for more than a few days now and so I have to re-enter the constants pretty frequently if I forget to leave the machine powered up. Any idea where I find that battery in the control cabinet? Is it like a coin-cell thing on a circuit-board?

    -lee

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    Hi again, having just posted to this thread about the dead batter, I got all inspired to give it another good burst of troubleshooting. The overall situation is much simpler than before because I've removed the 4th-axis and all of my heavy fixture components from the table so theoretically the machine should have an easier time lifting the Y-axis load, but it's pretty easy to make it error now whenever I want to (I guess that's the benefit of waiting years to fix this problem, right?)

    I can startup the machine fine, and I can home the axes fine. I can jog fine in all axes except if I jog the Y-axis up and down (meaning that the machine table is lifting up and down) then I can only go up/down a few times before the machine faults out with an error of Y09 I05 it always seems to happen on the up-stroke (meaning where it's lifting the weight of the table up) and when it happens the sound of the drive motor changes in pitch upward noticeably. This is accompanied by an increase in the axis drift reported on the control screen (because I've set C81=1 in order to see the axis drift reported to me)

    I've looked at some other threads on this forum about Y09 I05 kind of errors and specifically this one:

    Maho 600E2 - Dynamic following error - Y09

    pretty well describes my situation perfectly. I have taken the advice in that thread and tried turning off the dynamic following error (I just shut it off for all three XYZ axes @ C210, C260, C310) and the problem still happens but in a strange new way:

    with the dynamic follow error control turned off, the motor still spikes in pitch frequency, and the axis drift reported on the control screen still jumps up. At this point the way that the machine locks up is a little bit different than before: the control stays normal and I can still operate any of the other axes, but the Y axis is now dead. When I look inside the control cabinet the Indramat drives, the one of the now frozen Y-axis has three flashing lights on it as if it's still trying to move the axis somehow.

    I've also tried running a simple test program in Auto mode which works OK sometimes, but freezes the control other times. If it happens, it always happens on a rapid move lifting the table (Y-axis) up. The difference between when it works and when it doesn't is that if the axis keeps up pretty well, or only lags a little bit (as determined by whether or not I hear a pitch increase in the sound of the motor working) then it will probably make it through the program OK... but if the pitch increases a lot then the control will freeze.

    My next plan is to try swapping around a few of the drives inside the machine and see if, for example, swapping X & Y with each other has any effect.

    Also, it's worth noting that I recently cleaned the glass scales pretty well so I don't think it's an issue related to that feedback system.

    Thanks for any help anyone can offer me on this topic.

    -lee

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    Its the big lead acid battery behind the panel on the right side of the controller. Dont remember the exact amp hour. Small motorcycle size. I put a new one in the machine when I got it but they need to be topped off every few months when in good condition.


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