Lagunmatic VMC 3516 won't reference X axis
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  1. #1
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    Default Lagunmatic VMC 3516 won't reference X axis

    I have a 1994 Lagunmatic 3516 VMC with a reference problem. It was running fine Monday then Tuesday it wouldn't reference. I found an old thread here LagunMatic VMC 3516 Dynapath/Autocon controls HELP with someone else having the same issue. They solved it eventually by discovering the scale had been installed incorrectly. Lots of good advice along the way but I still can't solve the problem. Machine has a Dynapath Delta 40 control, SEM servos, Heidenhain glass scales on X and Y, and Glentek drives. What should happen when homing is it travels to a limit switch, backs off, then continues on until it reaches a marker. What it's doing is all of that except after it backs off and then returns to look for the marker position it continues on until it reaches the -X limit switch. There is no encoder on the motor. It uses a black magnet on the side of the scale to trip a marker switch.

    Trouble shooting I have attempted so far includes swapping the sensor between X and Y - no change. Continuity of the wires seem good checked with an analog ohmmeter. Unplugged and plugged them all back in as well to rule out a loose connection. I do have the wiring schematic and found blue and black "marker" wire locations on port 1 terminal (X). Jammed wires into those connections and used those as a temporary switch to simulate the pulse. No effect still. I also see X Y and Z reference wires on J1A input. I assume those are for the mechanical limit switches.

    I should state that it is otherwise jogging and attempting to reference correctly so I think the scales are fine. It just isn't getting the marker signal.

    My first question is am I jumpering the marker signal correctly? I'm going between the two pins labeled marker (blue) and marker (black). I use the feed rate override to pause the travel when it's attempting to home so the X-Reference limit switch is made. Then jump the marker wires.

    What else can I try?

    Also I'd gladly hire someone local to fix it for me if there is anyone in the Seattle area that knows much about these old machines.

  2. #2
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    I have a way old Lagoonamatic or whoever its spelled, Call DynaPath,They so far,have always got me back up and running,its been tickin em off for many long years here.
    good luck,be humble when ya talk at em.
    Gw

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    I don't know dynapath,but the machines I am familiar with do not close the position loop [IOW do not even look at the scales] until it sees the reference mark. Since it reverses direction it is seeing the trip dog[probably not literally the limit switch] so it really has to be missing the reference mark. I think I would see if you can find replacements for those magnet switches or whatever they are. Heidenhain made encoders with reference marks, odd they didn't use them.

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    Quote Originally Posted by gustafson View Post
    I don't know dynapath,but the machines I am familiar with do not close the position loop [IOW do not even look at the scales] until it sees the reference mark. Since it reverses direction it is seeing the trip dog[probably not literally the limit switch] so it really has to be missing the reference mark. I think I would see if you can find replacements for those magnet switches or whatever they are. Heidenhain made encoders with reference marks, odd they didn't use them.
    OK. I think they did use the reference marks but I didn't communicate that very well. The reference mark you refer to, is that the little black magnetic piece on the outside of the scale, or is there something on the glass strip that it also needs to see? Using a multimeter I can tell that there is a 5v current running through the marker circuit. As it passes the black mark it is interrupted. That is the same on X and Y, and y is working correctly. I'm pretty sure that marker circuit is good up to the control. What I'm not clear on is if that mark is the actual position or if it starts looking at the scale after it sees the reference mark and finds some precise position on the scale. It seems to me that the reference mark wouldn't be precise enough but I'm obviously no expert. Given that it's reading position before homing (IE: DRO style), trip dog is working, and marker circuit seems good could there be any other issues with the scale or wiring that wouldn't show up until it attempted to home?


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