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Hexalobe bone screw iterative rotation tolerance

We run profile of a surface on a hexalobe for several bone screws. Our quantity of checks per order just doubled. When we do an iterative alignment to cycle thru how well the screw hexalobe is oriented we commonly get an iterative error on the rotation. I do not program the part, but have discretion to make changes within reason. All the rotational tolerances are set to .006mm for the iterative tolerance, which is crazy too low in my opinion.

Even if the error pops up at .02mm on the rotation, every operator enters thru the error and the program works fine. Would it seem reasonable to set this at a max of around .0254mm or 1 thou? I don't see how a 1 thou error couldn't be allowed for the program to proceed without an error msg popping up taking a 3min program and turning it into a potential 10 min program if the operator is doing other things.

The vectors on the rotation of the hexalobe rotation are not clean either, they are far from a pure X plane direction, they have plenty of Y in them as well.
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  • As a rule, where I've worked (aerospace), we attempt to keep tooling using less than 10% of the tolerance in the part.

    Is 10% of the tolerance being eaten up in tooling ok for medical? I don't know.

    Do you adjust the tolerance on your dimensioning to allow for uncertainty in the alignment?

    What is your tightest tolerance? 0.254 (so 10% would be 0.0254)? 0.06 (so 10% would be 0.006)?

    I don't use iterative often, but I would have the error threshold set at 10% of my tightest tolerance max, if it was me. The default PcDmis has in the dialogue if that was lower than 10%.

    If everyone is ignoring the error and proceeding with the program anyway, and there are no failures in the field, then you are likely correct about 0.006 being too tight.

    You should ask the person that programmed it, or the quality manager, in case it was selected for a reason and people aren't supposed to just be ignoring the error.
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  • As a rule, where I've worked (aerospace), we attempt to keep tooling using less than 10% of the tolerance in the part.

    Is 10% of the tolerance being eaten up in tooling ok for medical? I don't know.

    Do you adjust the tolerance on your dimensioning to allow for uncertainty in the alignment?

    What is your tightest tolerance? 0.254 (so 10% would be 0.0254)? 0.06 (so 10% would be 0.006)?

    I don't use iterative often, but I would have the error threshold set at 10% of my tightest tolerance max, if it was me. The default PcDmis has in the dialogue if that was lower than 10%.

    If everyone is ignoring the error and proceeding with the program anyway, and there are no failures in the field, then you are likely correct about 0.006 being too tight.

    You should ask the person that programmed it, or the quality manager, in case it was selected for a reason and people aren't supposed to just be ignoring the error.
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