Brother Hs-70a over traveling
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  1. #1
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    Default Brother Hs-70a over traveling

    Need help. I have a Brother HS-70A that keeps over traveing on the X when i home it. I have cleaned the glass slides, checked the limit switches. If anyone has any insight on what to try next it will be greatly appreciated.

    Dave

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    Don't have a 70A, but on the 50 and the 3100 series there is an I/O page where you can check the actual reading of the switch.
    So if you've checked the switch itself with a meter and found it to be good, then go into the I/O section and see if the control sees it as well.

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    I checked all of I/O everything looks good and seems to be working properly. I have also checked the encoders and they are working correctly.

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    Is the machine hitting a hard limit? i.e. end of travel?
    The home function uses the limit x,y switches to start the final homing.
    This may seem like the wrong direction,
    but try moving the x- axis limit switch for LESS X- travel.

    Regards,
    John

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    Like John asked, is it hitting the limit switch or end of travel?

    What I know is that the 50A has a weird ass homing sequence.
    Even though it remembers the position from last power down, it still wants a homing after power up.
    So, what it does is it looks at the position it remembers from power down and starts traveling towards home.
    Let's say it remembers 5.0000 from home, it wants to travel ABOUT 5" worth towards home, plus/minus some.

    Now, let's say that while the power was shut off, someone manually bumped the axis and it moved by .1 in one direction.
    When the mach. is powered up, it still remembers 5.0" and wants to travel that distance towards home.
    BUT!
    Since the axis was moved by .1 without the control knowing it, the travel will take either less or more distance to hit the switch.
    So, if the nudge was in the -X direction, then the machine will hit the switch sooner than it expects it and alarms out with the overtravel.
    If OTOH the nudge was in the +X direction, then it'll come up with something like a "No Home X found" error.

    So based on that, I'd suggest you power off the machine and manually move the axis ( turn the ballscrew, you can reach it from the bottom ) towards +X so it needs to move a bit more to get home.
    I know that these ballscrews are pretty fine pitch, it is still quite easily moved when no power is applied.

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    Progress but still not quite there. I did as you suggested with turning the ball screw with power off. The machine now moves to X+ .393 when I begin the homing process ( it was not doing this before. It would go to about the center of the work area and then move to the X and Y home position.) But it is still going past the X home position and hitting the bump stop on the lead screw. I backed off the limit switch stops to see if it was just hitting them too soon.

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    Turn it a bit more to see what happens.
    Again, it has a weird homing process....

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    Turned it just a little bit more and hit the hard stop on the X+. Got in there with a feeler gage and set it at .006 off the hard stop. X+ is good now but still hitting hard stop on X- when i try to home it.

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    THE X- DOG LEVER, WHEN CHANGED FOR MORE X- TRAVEL, WILL STILL GIVE YOU A "SOFT RECOVERABLE LIMIT"
    EVERYTHING IS FINE UNTILL YOU HAVE TO RE-HOME THE MACHINE.
    WHEN MOVING THE X- STOP "DOG LEVER" FOR TO MUCH X-TRAVEL,
    THE HOMING FUCTION "X- STOP DOG" AND THE "GLASS SCALE" BECOME OUT OF SYC. (is that the right word?)

    To home, the machine looks for the x- dog lever and then stats to finish the
    homing. In your case, the machine believing there is more x- travel, it then hits the leadscrew hard stop.

    This is all part of the Brother's "grid shift" for the home process.

    And a topic for another day.

    Sorry for shouting.

    Regards,
    John

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    Finally got it back up. Thank You Seymour and John for all your suggestions and insight.
    Dave


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