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Additional MMC

MattyRyan
Hey everyone,

I apologize if this seems redundant, I tried looking through the forum first before posting.

I see quite a few topics about feature control frame call-outs of multiple diameters with MMC and how to apply it in PCDMIS. I'm still not entirely sure I've come across the answer (if I did and someone has that information I'd greatly appreciate it). I've tried a few different ways to apply it, but nothing gets me to the answer I know I should have (based on diameter sizes, etc.). I'm simply looking for the steps on how to apply the additional MMC. The following is what I'm looking to dimension out in PCDMIS.



Any help on this is greatly appreciated. Again, I apologize if this sounds like a redundant question, I'm just really stumped at the moment.
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  • The MMC on the tolerance (Ø.010 M in your example) is a bonus against the size of the feature, and it applied directly as the deviation from the condition (MAXIMUM material condition in your example) to the actual size of the part. Add that to the tolerance.

    Any modifiers to datums are so simulate what could be done at assembly.

    Say you are putting together a crappy shelf thing from Walmart.

    You start all the screws and fastners, but you don't tighten anything down. Then you get to wiggle it it best fit all the screws so they ALL go in.

    If they all go in, the MMB on datums B and C in your example covered the issue.

    If they all go in, then the parts are out of print.

    There isn't easy math you can do to calculate what this is. And it is to be applied completely, you shouldn't be datum shifting +.010 on B for feature 12 and -.005 on B for feature 40. You can't do that with the shelf, so you can't do that with the part.

    (there is some wiggle there based on exactly what is assembling, hoses can move more than a steel L bracket.)

    The MMC on the feature tolerance is making allowance for big screw holes and small screws giving you more wiggle while you assemble those shelves, as the screw and hole have more air in them.
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  • The MMC on the tolerance (Ø.010 M in your example) is a bonus against the size of the feature, and it applied directly as the deviation from the condition (MAXIMUM material condition in your example) to the actual size of the part. Add that to the tolerance.

    Any modifiers to datums are so simulate what could be done at assembly.

    Say you are putting together a crappy shelf thing from Walmart.

    You start all the screws and fastners, but you don't tighten anything down. Then you get to wiggle it it best fit all the screws so they ALL go in.

    If they all go in, the MMB on datums B and C in your example covered the issue.

    If they all go in, then the parts are out of print.

    There isn't easy math you can do to calculate what this is. And it is to be applied completely, you shouldn't be datum shifting +.010 on B for feature 12 and -.005 on B for feature 40. You can't do that with the shelf, so you can't do that with the part.

    (there is some wiggle there based on exactly what is assembling, hoses can move more than a steel L bracket.)

    The MMC on the feature tolerance is making allowance for big screw holes and small screws giving you more wiggle while you assemble those shelves, as the screw and hole have more air in them.
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