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Surface Profile Inspection

We have received many parts where the only specification we have to document is the surface profile. On previous parts, we were doing offline programming on a model and then inspecting to the model. Now, because of time constraints, we were asked only to check to the basic dimension of the details, but check the surface profile of the part. I haven't dealt with surface profile much, but I understand what it is and our programming has gone well.

The inspector checked simply to the basic dimensions on the weldment. We have a surface profile tolerance of 3mm. If we are well within that tolerance, is it acceptable to simply take any deviations we have seen (.5 here, .4 there), add them up and then divide to get a general idea of the surface profile? Also, SHOULD we be checking them to a model? If we check a dimension (494.4mm length dimension or 57.9 degree dimension), is it acceptable to just use those numbers rather than checking it to a perfect model?

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  • It's up to you if you want to get the average of all the deviations for reference purposes, but for reporting you'll need to know make sure the worst deviation isn't more than half the total profile tolerance.

    With angles you won't have any direct correlation between the angular tolerance and the profile tolerance. If you have a liner dimension from the datum it will be plus and minus half the profile tolerance.

    If you have a model use it. Otherwise you will need to construct perfect features to check the profile against. Which could include offsetting and rotating the alignment for angled surfaces, which is more involved than using CAD.
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  • It's up to you if you want to get the average of all the deviations for reference purposes, but for reporting you'll need to know make sure the worst deviation isn't more than half the total profile tolerance.

    With angles you won't have any direct correlation between the angular tolerance and the profile tolerance. If you have a liner dimension from the datum it will be plus and minus half the profile tolerance.

    If you have a model use it. Otherwise you will need to construct perfect features to check the profile against. Which could include offsetting and rotating the alignment for angled surfaces, which is more involved than using CAD.
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