Stamped Conc. part issues. Can I get some feedback please?.

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  • Stamped Conc. part issues. Can I get some feedback please?.

    Morning All:
    This conc callout is being a pain. The part is stamped and for some reason, they think this is going to come out perfectly lined up. Not buying it.
    Anyways, The dimension is question is the concentricity.
    Currently, I have a circle with 15 hits in bot the bottom thru and the OD/ID.
    Here is what I have tried.
    1 – Created a cylinder on the OD/ID (large area) and aligned/rotated to that, then did the thru dia.
    2 – circle to circle
    3 – circle to cylinder.

    The problem that I am having is these are stamped out on a press. Held into place by a 3 jaw chuck with 24.5in lbs torque. The part is no being crushed in no form.
    I get a roundness callout good but, the conc is always changing. It can be measured in 0,90,180 and 360 degree rotations and I get them out no matter what.
    The part also has a fixture that it sits on via the outside radius's and then locked in by the 3 jaws.

    I’m out of ideas on checking this. However, I was thinking about total runout but, dmis will not let me do that. I think that is really what they are looking for anyways.
    This print is the stamped print and is more internally than for the customer. The machined part has threads on the OD/ID and I think they are more worried about wall thickness and the threads
    Being cut to deep and thus causing them to be weak.

    My question is. Does this conc callout even hold water?. Due to the making of a cylinder to a circ seems incorrect. Not sure.
    Please let me know your thoughts so I can at least say, there will be no way we can accurately check con callout.

    As always, thanks for the input!!!.
    Always like the feedback from users.
    Attached Files

  • #2
    Well without any datum callout you could have a problem but assuming the O/D cylinder is Datum then concentricity to the lower bore is ok.

    Measure the cylinder then Level and translate to it not sure what you are rotating to. Then measure the lower diameter and call out concentricity diameter to cylinder.

    Comment


    • #3
      1st : why is there two circles inside, for a lonely hole ?
      2nd : a concentricity is dimensionned between two co planar circles, a coaxiality between two cylinders (I remember someone here said me that a concentricity between circle and cylinder was possible, i can't remember who and when...), so I think it should be dimensionned as a location.
      Even if it's not directly linked, having the same tolerance between circularity and concentricity is not a good idea...

      Comment


      • Schlag
        Schlag commented
        Editing a comment
        2 circles ? 1 is the thru hole and the other is a circle created from the plane and tangency ???

      • JEFMAN
        JEFMAN commented
        Editing a comment
        Schlag : thank you ! here, we draw those kind of "edge" with a thin line...

      • Schlag
        Schlag commented
        Editing a comment
        Drafting dept sits next cube over. Just draw some lines and add some dimensions .....whats the problem ???

    • #4
      Yep. Datum A would be the cylinder and the thru hole would be the hole dimension.
      The issue is the inconsistency of the conc when part is loaded and reloaded. There's not good repeatability.
      I guess dimensioning the XY will be best.
      The cylinder would be leveled to Zplus and rotated then zeroed XY. Measure thru hole and dimension.
      It's just irritating that the engineer thinks that thick of material in a progression die will hold conc. They can do no wrong. It's a quality issue. Right?.
      Haven't heard that ever.......

      Comment


      • #5
        You should not be rotating to the cylinder just level and translate.

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        • #6
          Thanks for the input. good to know I'll try that.

          Comment


          • Schlag
            Schlag commented
            Editing a comment
            Anytime would report a CONCENTRICITY, I would give it a location as well. Its tough to " adjust " a process based on a value. Or use position at RFS. Should give you the same value but also x-y deviations to adjust to. Of course you would need a reference mark or feature to know " orientation for an X/ Y to mean anything.

        • #7
          This is common among stamped parts. We see this all the time. If concentricity is out, I would look at the amount of break and sheer on the hole. If it uneven from side to side, then production did not center their hole punch and die correctly. Make sure you are not hitting on any break.

          What happens when you chuck to the OD and spin the part and place an indicator on the hole? This is technically "runout" but a lot of these stamped parts are checked this way.
          Last edited by bfire85; 04-15-2020, 05:56 PM.

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          • #8
            PCDMIS reports CONC as POSITION, not ASME median opposing points, but as ISO POSITION.

            B&S CHAMELEON/PCDMIS CAD++ V2011

            There are no bugs, only "UNDOCUMENTED ENHANCEMENTS!"

            sigpic

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            • #9
              Tell the "person" that drew that you can't have roundness of 0.005 and concentricity of 0.005.

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              • #10
                Thanks everyone!. Sure I'll be remeasuring until I retire. Ha.

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