Y axis not homing properly

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  • Y axis not homing properly

    My Cmm has stopped homing to the proper location when first turned on. It travels to the end of the stroke in Y- and then moves about 6 inches in the Y+ direction before indicating via the position readout that it is now at X0 Y0 Z0. It seems to be about 6 inches to far in the Y+ direction.

    When I move the machine to the end of the stroke in the Y+ direction it stops suddenly and gives me an emergency error. Obviously my machine has lost it Y position.

    A technician told me to (1) delete my probe qualifications and then (2) restart the machine from a cold-start (controller off)? and reestablish the datum ball location.

    Can anyone help me with this or clarify what the technician meant?

  • #2
    Deleting your probe files won't help. You will likely be worse off.

    When an axis homes it moves toward the one end of the machine until it sees a limit switch of some kind. When the limit switch is found the axis changes direction and then continues until a reference mark is seen; typically from the scale.

    If the reference mark is not seen the axis will continue until it does see one or hits the end of travel at the other end of the axis (depends on the machine). Some scales have a reference marks every 50mm so it appears your machine missed the first two and saw the third. In addition to hitting the far end mechanical limits you are likely missing the same amount of axis at the home position.

    I would try cleaning the scale (particularly at the home end of the machine) and see if this solves the problem (use isopropyl alcohol or equivalent). You might need to have the encoder re-aligned to the scale if it has moved. I assume you are not getting counting errors after the machine does home so there is a good change cleaning the scale will help. If you are getting counting errors where you didn't before then something has moved.

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    • #3
      Originally posted by Rondog View Post
      Deleting your probe files won't help. You will likely be worse off. I would try cleaning the scale (particularly at the home end of the machine) and see if this solves the problem (use isopropyl alcohol or equivalent).
      Make sure you only use linen to wipe the scales in one sweep & not scratching back & forth.

      Change the part of linen you use for each sweep so as not to make scratches on the scales with a bit of grit you just cleaned off the scale.

      Paper or tissue is much more abrasive to the scale surfaces than wetted linen. De-Natured Alcohol is next best solvent to use.
      Poleaxe

      Beware the environment you live in for it will shape you
      Be careful the friends you choose for you will become like them.

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      • #4
        Thanks for the replies. I cleaned the scales this morning as you directed. Seems to have gotten worse. Now moves back about 7 inches before indicating that it has reached Y0.0.
        Last edited by Xlcmm202; 07-11-2013, 01:05 PM.

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        • #5
          Originally posted by Xlcmm202 View Post
          My Cmm has stopped homing to the proper location when first turned on. It travels to the end of the stroke in Y- and then moves about 6 inches in the Y+ direction before indicating via the position readout that it is now at X0 Y0 Z0. It seems to be about 6 inches to far in the Y+ direction.

          When I move the machine to the end of the stroke in the Y+ direction it stops suddenly and gives me an emergency error. Obviously my machine has lost it Y position.

          A technician told me to (1) delete my probe qualifications and then (2) restart the machine from a cold-start (controller off)? and reestablish the datum ball location.

          Can anyone help me with this or clarify what the technician meant?
          What type, brand, model, controller CMM do you have. Do you have Glass scales or Steel scales?
          Did this post solve your problem? Let everyone know and help future users out!

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          • #6
            You will likely need to have the encoder re-aligned to the scale. Unless you have done this before you should call someone in.

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            • #7
              Originally posted by Rondog View Post
              You will likely need to have the encoder re-aligned to the scale. Unless you have done this before you should call someone in.
              +1 This is where I was heading with my questions.
              Did this post solve your problem? Let everyone know and help future users out!

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              • #8
                i have a brown and sharp with ver 3.2 and i started to align my part and the y axis is not where its supposed to be? ive tried shutting down and starting back up with no luck? anyone have any idea's ty

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