What are The must know things before using cmm or pc dmis

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  • What are The must know things before using cmm or pc dmis

    Hello guys

    I have been wondering, what are the basic knowledges i should gain that would allow me adapt quickly to the metrology and cmm , for exemple im still very confused with the axes and the direction of each cordinate , what else should i know beside gd&t


    waiting for your tips.


    tnx

  • #2
    How to double check your measurements on a surface plate.

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    • Darrollh
      Darrollh commented
      Editing a comment
      +1 thru 100. If you can't use mics or calipers then you have no business behind a computer controlling a CMM.

  • #3
    You have to remember everything is 3D. That's the way I learned to understand the axis. Look at it like doing Calculus or Trig where everything you do is using X and Y coordinates. Thats 2 axis. Your eyes looking down at the paper is the Z axis.
    Darroll
    2018R2

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    • #4
      I think this question is too large to obtain all the right answers...
      First, I would say that knowing the 3D metrology is the start, then only learning PC-DMIS : it allows understanding how works the software in front of real parts and dimension.
      Second, remember that CMM means Coordinates measuring machine : a coordinate depends on the alignment, the same point have different coordinates in different alignments, but stays the same point.
      Third, understanding that the cmm drives the center ball of the probe, and compensates the ball radius depending on vectors, so a wrong vector gives a bad result.

      After that, there's the calibrations, the thermal effects, the part defects, the drawing standards, the measurement standards (...)

      At the end (or at the start ?), understand that the only thing that you can be sure is the existence of uncertainties !

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      • #5
        Originally posted by Darrollh View Post
        You have to remember everything is 3D. That's the way I learned to understand the axis. Look at it like doing Calculus or Trig where everything you do is using X and Y coordinates. Thats 2 axis. Your eyes looking down at the paper is the Z axis.
        Agree to some extent with this, Look at the part first in 2D just from different Workplanes. Sometimes your looking at the part in Z workplane and the X and Y value or feature can be controlled and seen, while the next view may be the X workplane, where Z and Y value or feature can be controlled and seen. For example, a hole diameter. From one view you can see it's a diameter, but you can't see how deep that diameter is. From another view that diameter looks like a width and a height. If you don't help the Demon see the difference between the 2. Then it won't tell you the difference. When you place a part on the CMM, when creating features walk around the part, from different workplanes, do you see a diameter from Xplus or a width? move in front and look at YMinus what's going on there? The CMM only sees what you tell it to see. Don't be fooled by the CAD model on your screen. The CMM doesn't see it. You need to be able to put all info in, so the Demon can see the 3D
        Untitled.jpg

        Last edited by KIRBSTER269; 05-28-2019, 09:02 AM.
        (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
        They say "Nobody's Perfect." I must be Nobody.

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        • #6
          If your starting point is that you don't understand the cartesian coordinate system I would have to assume from that that your background is not in machining or engineering. You ever ask yourself how did I end up here and is this where I should be ?

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          • anthony.alfaro
            anthony.alfaro commented
            Editing a comment
            I don't agree with this take.

            Cartesian coordinates can be taught if someone is willing to learn. Just because something isn't currently understood doesn't mean it can't be understood at all.

            I had no machining or engineering background when i ended up in front of a CMM and Laser Tracker but i had a great mentor who was willing to teach me anything and everything as long as i was willing to try and to learn. I ended up at Hex and learned more and more every day.

            If I know what i'm doing every single day then i'm not pushing myself hard enough. I WANT to not know what i'm doing so i can figure it out.

        • #7
          Originally posted by Mranaskw View Post
          Hello guys

          I have been wondering, what are the basic knowledges i should gain that would allow me adapt quickly to the metrology and cmm , for exemple im still very confused with the axes and the direction of each cordinate , what else should i know beside gd&t


          waiting for your tips.


          tnx
          Metrology:
          First, you must realize that there is no spoon.
          Nothing is absolute, everything is relative. Each and every number has an invisible asterick behind it, and an invisible footnote reading "within about yay much uncertainty."

          Next, you must pretend to believe with all your heart and soul in the certainty of the spoon.
          You must eat, sleep, live, breathe, and excrete in a perfectly ordered 3D Cartesian Coordinate System - putting aside the fact that it's a completely imaginary farce and is naught but a convenient story we drape, ill-fittingly, upon the real world in all it's fractal shabby glory. Instead you navigate seamlessly in XYZ, creating new temporary coordinate systems with their axes pointing in directions convenient for the task at hand before discarding them and returning to the main world-view.

          PC-DMIS:
          First, you must realize that bugs are either features or charming quirks.
          Nothing is perfect, everything is in flux awaiting the next service pack... which has uncertainty about bugs being fixed and certainty about new bugs being created as part of the fixing of other bugs that didn't affect the bug that stabbed you in the back.

          Next, you must be utterly self-reliant. You are The Programmer, constructing from scratch a shaky dance routine for a crude robot to performs a series of tricks to tease numbers out of a physical object jammed halfway between the imaginary crystalline perfection of the imaginary 3D Cartesian Coordinate System and the rough-hewn dirt of the planet we build factories upon. Very little in the software package is automated, by design it leaves 99% of decisions entirely up to you... so choose wisely.

          Good luck!

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          • AndersI
            AndersI commented
            Editing a comment
            Short version: You need to *know* what you're doing...

        • #8
          What they say and make sure you shave your head before you lose all hair follicles

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