Explanation of different perpendicular vales

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  • Explanation of different perpendicular vales

    On the dwg, we need to perpendicular cylinder B to plane A within .012mm

    assistant lab manager says the values should be the same if we were to perform perpendicularity from plane A to cylinder B. I said no that's not possible.

    I ended up using this example...

    if I clamp on Plane A, and indicate Cylinder B, my numerical value will be different than if I clamped on Cylinder B and indicated Plane A.

    it still wasn't making sense to him.

    Is there another way to explain this scenario?

    proper, as designed, B to A, we get .020mm
    incorrect, not as designed, A to B, we get .005mm

    I just couldn't find a way to explain it for it to make sense.

  • #2
    I agree with you, DCHRM. If the plane is 10mm square and the cylinder is 100mm long, then it DOES make a difference if you callout perpendicularity from the plane to the cylinder compared to the cylinder to the plane. So, IN GENERAL, the order of the callout matters. I am sure there are cases where the plane and the cylinder have similar dimensions and (at least from this argument's POV) it doesn't matter. I would say that you should follow the callout on the drawing --- it will be called out one way or the other - and you need to call it out in that fashion. If you call it out opposite of how the drawing calls it out, people will think you don't know what you are doing. Well, except for the asst lab manager, of course.

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    • #3
      To convince him, you have to look at the ISO 1101, chapters 17.11.4 and 17.11.5.
      The tolerance zone is defined perpendicular to the datum.
      In addition, the perp of the cylinder to the plane should be with a Ø, the perp of the plane to the cylinder doesn't...
      perp to cyl.JPGperp to plane.JPG

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      • #4
        Originally posted by DCHRM View Post
        On the dwg, we need to perpendicular cylinder B to plane A within .012mm

        assistant lab manager says the values should be the same if we were to perform perpendicularity from plane A to cylinder B. I said no that's not possible.

        I ended up using this example...

        if I clamp on Plane A, and indicate Cylinder B, my numerical value will be different than if I clamped on Cylinder B and indicated Plane A.

        it still wasn't making sense to him.

        Is there another way to explain this scenario?

        proper, as designed, B to A, we get .020mm
        incorrect, not as designed, A to B, we get .005mm

        I just couldn't find a way to explain it for it to make sense.
        Say'in the same as the others another way, it's just right angle trig and the legs of your triangle are not the same "length" so you must call the feature and then the datum for the software to compute the correct result
        sigpicHave a homebrew

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        • #5
          https://www.pcdmisforum.com/filedata...127&type=small
          Automettech - Automated Metrology Technology

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          • KIRBSTER269
            KIRBSTER269 commented
            Editing a comment
            nice and simple +1 ninja

        • #6
          +1 NinjaBadger

          B&S CHAMELEON/PCDMIS CAD++ V2011

          There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

          sigpic

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          • #7
            Originally posted by DCHRM View Post
            On the dwg, we need to perpendicular cylinder B to plane A within .012mm

            assistant lab manager says the values should be the same if we were to perform perpendicularity from plane A to cylinder B. I said no that's not possible.
            I guess he's mistaking perpendicularity and angle.

            Originally posted by DCHRM View Post
            I just couldn't find a way to explain it for it to make sense.
            Just explain that a perpendicularity is a distance in mm, an angle is in degrees !

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            • #8
              I have a better picture but can't upload it
              Automettech - Automated Metrology Technology

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              • KIRBSTER269
                KIRBSTER269 commented
                Editing a comment
                https://www.pcdmisforum.com/forum/of...a-load-for-you

                I kinda explain it on #6 and #11. If you want to take the time. oh and save it as Jpeg

              • NinjaBadger
                NinjaBadger commented
                Editing a comment
                Thanks but I've no more space to upload files and I can't see how to delete any.

              • KIRBSTER269
                KIRBSTER269 commented
                Editing a comment
                Yeah I'm not sure why, I mean, I always have posted pictures the way I explain, and never had an issue, and I'm well over 400+ pics in my media. I look at yours you have 39

            • #9
              The best way I explain this to people is to focus on comparing the deviation of each axis vector:
              Let's say A datum axis is 2" long and B datum planar surface is just 1" diameter...
              If you level to the 2" long A datum, the perpendicularity error of B datum is lower as you have leveled on the largest datum. You zero to the 2" long axis and as a result, you are not projecting any error onto the 1" plane.

              If you level to the 1" diameter planar B datum, the perpendicularity error of A datum will often be double the value of what you get leveling to A. Why? Because you have taken an axis vector of the 1" surface and compared it to a 2" long line, projecting whatever vector error exists as a result of B datum, at a ratio of 2:1 of their respective sizes.

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              • #10
                Speaking of Perpendicularity....What does this graphical mean??perpendicularity.PNG
                sigpicTAU ALPHA PI INDIANA DELTA CHAPTER
                "Due to the highly confidential nature of my job, I am not allowed to know what I am doing" - author unknown

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                • #11
                  If you have only the perp in the view :
                  1- the part is out
                  2- PC-DMIS change the scale in wrong direction
                  3- the version has a bug... !

                  Comment


                  • #12
                    I think this is a bug as well. If I measure circles, the deviation is opposite the red arrow...
                    sigpicTAU ALPHA PI INDIANA DELTA CHAPTER
                    "Due to the highly confidential nature of my job, I am not allowed to know what I am doing" - author unknown

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