Total four reference Datum in True position

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  • Total four reference Datum in True position

    I am making program in version 2010 in which I can select maximum 3 reference Datum as a 1st segment in datum feature frame. I am seeing condition of True position in drawing which has total 4 reference Datum as only 1st segment. Could someone tell me how it would have been done.

  • #2
    Can you give a screenshot of the callout?

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    • #3
      DSCF0501[1].jpg

      1. True position = 0.2mm. with reference to datum A,B,C,D. at 113.13 mm.

      2. True position = 0.2 mm. with reference to datum A,B,C,D. at 295.53 mm.

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      • #4
        DSCF0502[1].jpg

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        • #5
          DSCF0504[1].jpg

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          • #6
            DSCF0505[1].jpg

            You can decipher the latest uploaded drawing now. The edge of slot is considered Datum-D. Datum-A is top surface with flatness tolerance.
            Last edited by Jignesh; 04-18-2016, 01:52 PM.

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            • #7
              It doesn't look right. Can't really tell too much because the image is still blurry. But it looks like Datum A is a front surface? (Can't tell since it's cut off). Datums B and C look parallel to each other, and Datum D is perpendicular to Datums B and C. Looks like the callout should be 0.2 | A | B-C | D. Possibly a print error...

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              • #8
                What does B-C mean? Do I need to find midline of B and C?

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                • #9
                  I have never entered B-C in datum feature frame. I mean to say it worked, but i want to know what kind of Datum it would be?

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                  • #10
                    Illegal call-out.
                    Print is not clear (large enough) but this is my understanding of it.
                    You have Position of the edge (illegal, position can only be used for feature of size) to Datums A (top surface in Z+), B (edge of the part), C (edge of the part parallel to datum B, illegal) and D (edge of the slot perpendicular to B and C)
                    Who ever made this print does not understand GD&T, you should talk to designer and ask him to correct it.
                    sigpic...engineering

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                    • #11
                      Originally posted by Jignesh View Post
                      [ATTACH=CONFIG]11636[/ATTACH]

                      You can decipher the latest uploaded drawing now. The edge of slot is considered Datum-D. Datum-A is top surface with flatness tolerance.
                      I looks like B & C might be datum target points - so a Line constructed between them would be a new single datum named BC (don't use the dash in PC-DMIS).

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                      • #12
                        Originally posted by Josh Carpenter View Post
                        I looks like B & C might be datum target points - so a Line constructed between them would be a new single datum named BC (don't use the dash in PC-DMIS).
                        Even if C is datum target point, you can't have Position of point.
                        sigpic...engineering

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                        • #13
                          I called my software company which makes programs in CAD. The engineer told me to take Mid line of Datum B and Datum C and consider one Datum for both Datums. He is right because I told him that I saw another drawing that has slots on both side of center line and both slots are considered Datum-B. So in this case I had to find center line of both slots individually and then I defined center line of both center lines which I considered as Datum B. But in above situation, there are two Datums given so it was little confusing how to adjust Datum in Datum feature frame. So I would have to consider Mid line of Datum B and Datum C for Example Datum BC. So True position will be 0.2 mm. with reference to Datum - A,BC,D. Thanks for being intrested in my question.
                          Last edited by Jignesh; 04-19-2016, 09:24 AM.

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                          • #14
                            Who ever is making these drawings for you does not understand GD&T. Even if you use this made up line for secondary datum, you can't have Position of edge of the part. Position can be used only with features of size
                            sigpic...engineering

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