Quill drop Z axis

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Quill drop Z axis

    This is a little off topic since I'm asking a question about my CMM and not the software, but I am curious if anyone else has experienced this issue......

    We have a relatively new (< 1year old) Global S CMM we use at my facility for small production runs and some R&D activities. When I leave for the weekend and come back, the quill drops all the way to the surface plate with the stylus touching it. (Not good, but no damage so far) This has happened three times with both the controller on and off.

    A tech visited our facility after the first occurence for another issue (bad connector pin for the X encoder). I asked him what would cause it and he assured me it wasn't possible since the quill "locks" when the air bearings disengage. I believe he was dismissing my claims in his mind, but too polite to say it. However, it has happened two additional times since his visit. Has anyone else ever experienced this issue?

  • #2
    We had an older unit that had that issue. The solution was to remove the probe and place the wrist just above a wooden block. When the air pressure got low enough (amazing, since the compressor was off...), the head slowly came to rest on the block, and no damage was ever noted. Worked fine like that for years.

    Just had to remember to remove the probe and put the block in place...

    Comment


    • #3
      Thanks. Definitely not a resolution, but will have to do it to prevent damage.

      Comment


      • #4
        The tech is right, air bearings should lock the quill... But if it doesn't work, maybe there's a problem on the manometer, at the entrance of the cmm, and / or another problem on the counter balance.
        Check the air pressure on the cmm, decrease it before the cmm (not the manometer of the cmm, this on the wall) and look at the quill.
        The counter balance can be set, on the right of the x axis, behind a plastic part.

        Comment


        • #5
          Maybe the air pressure is sinking so slow, that the quill has already reached the bottom when the lock mechanism engages. Assuming the lock has worked at all?

          You could try releasing the air when turning the machine off. But definitely check the balance.
          AndersI
          SW support - Hexagon Metrology Nordic AB

          Comment


          • #6
            Originally posted by AndersI View Post
            Maybe the air pressure is sinking so slow, that the quill has already reached the bottom when the lock mechanism engages. Assuming the lock has worked at all?

            You could try releasing the air when turning the machine off. But definitely check the balance.
            We have three Globals, one is 13 years old, one is 7 years old, and the other is 4 years old. All will drop the quill when the air pressure drops. There is a gap of time between when the servos shut off and when the air bearings lock. A tech tried adjusting the counterbalance, but it's still happens. We found a cardboard tube that fits on the sphere of the PH10. We place that on the quill every night in case the air goes out.
            Last edited by Schrocknroll; 06-26-2019, 07:18 AM.
            PC-DMIS 2016.0 SP8

            Jeff

            Comment


            • #7
              Originally posted by Schrocknroll View Post

              We have three Globals, one is 13 years old, one is 7 years old, and the other is 4 years old. All will drop the quill when the air pressure drops. There is a gap of time between when the servos shut off and when the air bearings lock. A tech tried adjusting the counterbalance, but it's still happens. We found a cardboard tube that fits on the sphere of the PH10. We place that on the quill every night in case the air goes out.
              My 2-year old Global also drops when the pressure 'dies' (compressor is shut off or 'dies'). BUT, this Global has enough clearance so that the head will not hit the table, so we park the machine, Just before the X+ limit, Y+ limit, and Z+ limit, with the head turned to A90B-180, then if the pressure drops, nothing hits anything.
              sigpic
              Originally posted by AndersI
              I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

              Comment


              • #8
                We have 5 machines (all B&S) and only the newest one does it. I rotate the head to an A90 angle and rest it on a foam block at the end of the day.
                Remembering my beautiful wife Taz who's life was taken from me on 6-13-2020. I love you and I miss you.

                Comment


                • #9
                  We had this issue with our Global Advantage (while still brand new), so the tech had to come out and replace part of the air bearing system that was defective. We frequently run overnight and so losing air pressure during a run would not be ideal.

                  Comment


                  • #10
                    We have alarms that go off if low air pressure is detected.
                    Procedure for low air is to pause the machine, then pop the air valve that bleeds the air off fast enough so the Z axis will lock.
                    found out the hard way that a slow drop in pressure to zero will drop the Z axis at some point.
                    In the event they are left unattended for a period of time we will rotate the head to 90 then also pop the air off.
                    We had the CMM's looked at, but they said fix your air...or maybe the they said the CMM was working normally - I don't remember now
                    Last edited by Eric_; 06-26-2019, 05:54 PM.

                    Comment


                    • #11
                      If nobody is using your machine over the weekend, shut it down. When you toggle power on the controller, it shuts off air and locks Z axis.
                      Otherwise all above tips are plan B.
                      Plan C would be to make your facilities guy maintain Clean Dry Air (pressurized) 24/7.

                      Comment


                      • #12
                        Originally posted by louisd View Post
                        If nobody is using your machine over the weekend, shut it down. When you toggle power on the controller, it shuts off air and locks Z axis.
                        Otherwise all above tips are plan B.
                        Plan C would be to make your facilities guy maintain Clean Dry Air (pressurized) 24/7.
                        Yeah. That's a big factor. Air dryers are very important, especially with the warmer summer weather. Compressors manufacture condensate, and they'll pass it right into your CMM, if you don't have measures to prevent it. Water in the air bearings? Not so good.

                        Comment


                        • #13
                          Originally posted by louisd View Post
                          If nobody is using your machine over the weekend, shut it down. When you toggle power on the controller, it shuts off air and locks Z axis.
                          Otherwise all above tips are plan B.
                          Plan C would be to make your facilities guy maintain Clean Dry Air (pressurized) 24/7.
                          The one that we have this issue with will still do it if powered down. Yes, we do have a regularly maintained air dryer just for the quality department.
                          Remembering my beautiful wife Taz who's life was taken from me on 6-13-2020. I love you and I miss you.

                          Comment


                          • louisd
                            louisd commented
                            Editing a comment
                            If it's a newer machine, it sounds like the z axis lock is not functioning properly then. Put in a service ticket with hexagon.

                            If it's an older machine, it might not have a z-axis lock.
                            Either way, I would think your mechanical counterbalance should maintain Z height with air bearings off. Something is definitely not right if you shut machine down (toggle power on controller) and Z axis still drops afterwards.

                          • A-machine-insp
                            A-machine-insp commented
                            Editing a comment
                            It's a newer machine. It only drops when they turn the compressors off. With air, it's just fine.

                        Related Topics

                        Collapse

                        Working...
                        X