Weird Clearplane movement

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  • Weird Clearplane movement

    I apologize ahead of time if this is confusing. Trust me, it confuses me too.

    On our floor CMM, a Sheffield Discovery III Cordax d-8, we've experienced a lot of weird things that we haven't seen elsewhere. Aside from the Find_hole>Center parameter for holes (circles/cylinders) not always working (Ongoing ticket I have with hexagon at the moment) we have also noticed that the clearplane movements do not make sense (to us). We mostly see the weirdness happening at the beginning of execution, and what happens is, our probe will go to the clearplane height as desired however it'll go to very odd X and Y locations as well; not remotely straight up or down. We've had it go from one side of the table to the other in the X, we've had it smash into our cal sphere (from the opposite side of the table in the Y). It'll consistently go to the same spot upon execution as long as we start execution in the a consistent location.

    To me, it sounded like the clearplane was moving in relation to some tilted level-alignment but that deosn't appear to be the case. This has happened on multiple programs, and the IJK's of the leveling features did not seem off. I also verified that the clearplane referenced the alignment features I checked by checking where the Clearplane command was further down in the program and nothing popped out there either.

    I'm wondering if this could be a controller issue at all, or some sort of mechanical issue with this machine as our team hasn't been able to find the issue however only have Sheffield experience in regards to this one machine.

    Any help or info would be much appreciated, thanks.

  • #2
    Check the pass through settings for each of your clearplane commands. When transitioning from one clearplane definition to another, PC-Dmis will "pass through" the defined plane when moving to the new clearplane.

    In this example...
    Code:
      CLEARP/YPLUS,30,ZPLUS,0,ON
    TIP/T1A90B0, SHANKIJK=0.017041, 0.999853, 0.001896, ANGLE=179.907636
    MOVE/CLEARPLANE
    PLN1 =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,TRIANGLE,LEAST_SQR
    THEO/<51.86098,60,-8.162754>,<0,1,0>
    ACTL/<51.86098,60,-8.162754>,<0,1,0>
    TARG/<51.86098,60,-8.162754>,<0,1,0>
    ANGLE VEC=<-1,0,0>,SQUARE
    SHOW FEATURE PARAMETERS=NO
    SHOW CONTACT PARAMETERS=NO
    CLEARP/XPLUS,100,ZPLUS,250,ON
    WORKPLANE/ZPLUS
    MOVE/CLEARPLANE
    TIP/T1A0B0, SHANKIJK=-0.001644, -0.001868, 0.999997, ANGLE=-0.97659
    MOVE/CLEARPLANE
    PLN2 =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,TRIANGLE,LEAST_SQR
    THEO/<59.258262,54.426787,0>,<0,0,1>
    ACTL/<59.258262,54.426787,0>,<0,0,1>
    TARG/<59.258262,54.426787,0>,<0,0,1>
    ANGLE VEC=<1,0,0>,SQUARE
    SHOW FEATURE PARAMETERS=NO
    SHOW CONTACT PARAMETERS=NO
    PC Dmis will travel along the YPLUS 30 clearplane and measure PLN1. It will then move to the XPLUS 100 plane before traveling along it until it reaches the ZPLUS 250 clearplane. Then it will index to A0/B0, move along the ZPLUS 250 clearplane and measure PLN2.

    Comment


    • derekvegeta
      derekvegeta commented
      Editing a comment
      So does the pass thru setting only occur when theres a change/new clearplane command? If so what happens when there is only one clearplane command and it has a value for pass thru?

    • neil.challinor
      neil.challinor commented
      Editing a comment
      It should only come into play when you move from one clearplane definition to another. I don't have access to a machine to test what happens when there's only one definition but I would expect it to ignore the pass through in that case.

    • derekvegeta
      derekvegeta commented
      Editing a comment
      I'm glad to finally learn how that feature works. In the programs i'm experiencing these issues above on, the workplane is entirely Zplus, and the definition doesn't change in one program, and another 'changes' later, but really just redefines it for the DCC_LVL as opposed to the manual: And the issue occurs before this change.

  • #3
    A quick solution is:

    Move the first CLEARP after your TIP call right before said TIP

    Try it.

    If can't be done for reasons involving too much complexity just use a MOVE/POINT just this once and MOVE/CLEARs thereafter.
    PcDmis 2015.1 SP10 CAD++
    Global 7-10-7 DC800S

    Comment


    • neil.challinor
      neil.challinor commented
      Editing a comment
      Yes, it's worth pointing out, the clearplane command is designed to go immediately prior to the command that requires / triggers CMM movement. For example, if you had a MOVE/CLEARPLANE then a COMMENT then a tip change or dcc feature, the clearplane move would not get triggered because comments do not require movement. That being said, it would result in the CMM not moving at all for that command rather than moving unexpectedly.

    • Kp61dude!
      Kp61dude! commented
      Editing a comment
      Interesting neil.challinor, I'll have to try that out. Thanks...again!

  • #4
    Are these motions happening before your alignment features? I think clearplanes are always relative to the alignment they're defined in, and stay there even if the current alignment changes. If you haven't aligned to the part before defining the clearplane, it will probably be relative to the machine coordinate system, which could be weird and confusing especially if you then align to the part and try to reuse the old clearplane.

    Of course, in principle this should be an issue on all of your machines, but if the machine coordinates are different on that one (perhaps causing the default pass-through plane to end up in a dangerous place), you might only notice it there.

    I personally (almost) never declare a clearplane until after a rough DCC alignment to make sure I know what it's doing. But if you can get it to work consistently before then, I would like to know how - I might use it at some point.

    Comment


    • #5
      I never use the pass thru plane. It is always off. Then I do not have issues. when you change workplanes then change the move clearplane to the proper workplane.
      Time for the Trolls to leave.

      Comment

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