Need quick help please!

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  • Need quick help please!

    My qual sphere is on the 45 degree base, first time setting this up. I need to qualify a star probe. I have my probe built and ready to run qual on it, but my sphere vector is causing me some grief right now... I have it pointed in the -Y, +X and +Z direction on the table. Picture for reference:

    _qualsphere45deg.jpg

    What I really need right now is for someone to tell me the proper vector to type in, because I am not having luck. I know the IJK will be using 0.7071 in some combination of both negative, both positive, or one of each, but it is burning my brain out trying to get it configured correctly.

    I ran the master on it and got a good result of about 0.00003" but when I pick up my star and run the qual, it gets through the #1 tip and then drives off in unexpected directions with the vector combos I've tried so far.

    Can someone tell me the right IJK for the setup pictured here? If I know the right config for this position, it would help me understand how to set it up for other vectors in the future, I'm sure.


    Please help, I'm super noob at this star-probe stuff!

    --------

    PS: I have the measurement settings for the star set to 5 points at two levels, 0 and 90, assuming four points around equator and one on the top. Is that about right?

  • #2
    Measure the shaft as a cylinder, BOTTOM TO TOP. Doesn't matter if the tip is qualified or not, you don't care about size.

    Report the IJK.

    Enter those values into the tool's shank vector IJK

    Comment


    • UseAsIs
      UseAsIs commented
      Editing a comment
      That's a great idea, thanks Random Jerk on the internet!!

    • UseAsIs
      UseAsIs commented
      Editing a comment
      I tried this just now

      cylinder vectors were

      I: 0.36294
      J: -0.34415
      k: 0.86592

      As usual, I ran the master probe and it was fine. I picked up my star and it did the first tip fine, then went right back to driving into the ball

      I have been at this one simple task since yesterday and I just can't get it to work.

  • #3
    For that cal sphere in the negative Y, the vectors would be:

    I = 0
    J = -.707
    K = .707

    From the picture it looks like the Y direction of the tool is not exactly square to the machine Y axis, so it technically wouldn't be a perfect 0, -.707, .707, but it would be pretty close. Try squaring the tool up first so that it is close to square to the machine Y axis.

    I've got a tutorial video you could check out to help you with Star Probe calibration: https://blog.cmmxyz.com/blog/calibra...obe-in-pc-dmis
    Last edited by Trevor McLaughlin; 06-27-2019, 03:49 PM.
    CMMXYZ Applications Specialist: PC-DMIS Support and Training. Check out my PC-DMIS tutorial videos... https://blog.cmmxyz.com/blog/tag/cmm-tech-tips

    Comment


    • UseAsIs
      UseAsIs commented
      Editing a comment
      Louisd, I am using the only extension I currently have, a 30mm one. The star is "generally" going to the right place, but is colliding with the sphere in odd ways, so maybe it is the retract distance. I will back it way up to half an inch or something and see what it does.

      This is madness... Pure madness I tell you

    • louisd
      louisd commented
      Editing a comment
      manretract distance is not the same as prehit or retract. Prehit and Retract is the DCC clearance distance away from theo point location, along the vector.. There's a value within the calibration screen at the top to increase it. Also, BE SURE that RESET YOUR THEORETICAL TO NOMINAL box is checked when trying to calibrate that star.

    • UseAsIs
      UseAsIs commented
      Editing a comment
      Yep, I set the prehit distance in the Probe Utils "Measure Probe" dialog right before measuring, not the global pre/retract. Got through the #2 tip about half way but seems offset. Way farther away from the sphere on the -X side and then collides on the +X side, like it's offset somehow.

      "Reset tips" is definitely checked.

      I am so lost. My brain has turned to mush trying to figure this out for the last 24 hours. I'm doing everything exactly like what I'm reading from the Help files and the forum tips. I set my vectors EXACTLY to the cylinder that I measured on the sphere's shank. Nothing is working. I hate PCDMIS and I told them not to get it and they just said "OK cool we'll get PCDMIS then." I told them we need a room temp of about 69 degrees, and they said "OK cool, we'll set the thermostat at 78 then." I told them we need a clean environment, so they said "OK cool, we'll install it in front of a bay door thats almost always open so that it's practically outside!" I told them we need low particulates, so they said "OK, we'll set it up right next to this bare block wall that's putting out dust and grit all day long!"

      A good challenge is always fun, but this is getting crazy.

  • #4
    I'm giving up. I'm just going to find a way to put this huge 40" diameter part up on its side and stabilize it somehow and just measure it with a normal probe. Somehow. This is in-frickin-sane.

    Comment


    • #5
      this may be a dumb question but is there a reason you can't mount the ball directly to the table so its vector would be 0,0,1 ?
      sigpic

      Comment


      • UseAsIs
        UseAsIs commented
        Editing a comment
        Yes, I need to qualify the star in a way to get underneath a vertical tube and get the ID inside, so I need to get under the ball

      • mckenzie
        mckenzie commented
        Editing a comment
        ive successfully qualified a star probe with a vertical cal sphere and was able to measure the bottom of parts. i would only be concerned if the part tol was in the tenths. when its calibrating a horizontal tip it'll take hits under the sphere except for were the shank is. you might give it a try.

    • #6
      Originally posted by UseAsIs View Post
      Got through the #2 tip about half way but seems offset. Way farther away from the sphere on the -X side and then collides on the +X side, like it's offset somehow.
      If that's the case when the tips are reset to THEO, *AND* the datum sphere is correctly located, then you have an error in your tip definition in USRPROBE.DAT, or your star is not square to the machine axes.

      If your star shouldn't be square to the machine axes, you also have to tell PC-DMIS about that - in the list of components you've built, double click on the star center part and enter the correct rotation angle there.

      A workaround is to calibrate all the star tips manually once, just to let PC-DMIS know where they are, and then run in DCC. Remember to *NEVER* reset tips to THEO in that case.

      AndersI
      SW support - Hexagon Metrology Nordic AB

      Comment


      • #7
        HIS PROBLEM IS THAT HIS QUAL SPHERE IS NOT SQUARE TO THE Y AXIS.I think that you want it square to the cmm y axis then the vectors would be
        I = 0
        j = -0.707 if the qual sphere is not sguare to the y or x axis then these vectors are not correct
        k= -0.707.
        You dont need to have the qual sphere at 45 degree in the x axis
        if you want to calibrate the probe at 45 just rotate it and calibrate the proper tip.There are procedures that need to be followed if you need a certain tip angle calibrated you need to have the qual sphere pointed in the correct axis to measure properly so you may need to re position the qual sphere different (pointing in different directions) if you are rotating the probe to any of the a90b to anything else..If the probe remains at A0 angle and b is at any other angle then you dont need to change the qual sphere orientation


        looking at your picture your vectors should be
        I = 0.707
        J = -0.707
        K = -0.707
        Michael A Wildschutz Sr
        I Walk on The WildSide
        "To Each is Own"

        Comment


        • JacobCheverie
          JacobCheverie commented
          Editing a comment
          Do you mean i = 0?

      • #8
        Originally posted by michaelwildschutz View Post
        looking at your picture your vectors should be
        I = 0.707
        J = -0.707
        K = -0.707
        Actually, that would be <0.5773503, -0.5773503, -0.5773503>, but magnitude doesn't really matter as PC-DMIS normalizes the direction vector. You could equally well set it to <1, -1, -1> ...
        AndersI
        SW support - Hexagon Metrology Nordic AB

        Comment


        • JacobCheverie
          JacobCheverie commented
          Editing a comment
          Actually, it would be <0.57735027, -0.57735027, -0.57735027>.....

      • #9
        It looks more like I=.500 J=-.500 K=.7071

        Comment


        • #10
          You might try clamping the shaft of the calibration ball in a "v" block along the Y axis and set your vector 0 ,-1,0

          Comment

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