Sheet Metal Axes question

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  • Sheet Metal Axes question

    Hello all,

    I did a little searching before posting this, but couldn't find anything that answered my question directly.

    Part of my job has been updating/correcting old programs from my predecessors, and I find interesting things fairly regularly.

    Today's case, I'm trying to make sure there's a program that measures all of the dimensions our inspection report calls for.

    I believe I've found one, but I notice it's only measuring one set of points for Gap/Form and Trim points around the perimeter of the part. It is, however, reporting 2 different numbers from the T and S sheet metal axes options in Location Dimension.

    Based on context and tolerances, the programmer appears to be using the S value to report the Gap/Form dimension.

    I'm familiar with, and regularly use the T dimension, but am unfamiliar with S.

    Is this a valid method of reporting a Trim dimension and a Gap/Form dimension from a single point taken on the part, or should I rewrite this and take an individual point for each?

    I hope I explained that clearly.

    Thanks again!

  • #2
    For anything that uses SAMPLE HITS, the "S" axis is the surface (S) deviation, like the "T" is for the edge.

    HOWEVER, there is a problem using surface sample hits for edge points that are on a CURVED SURFACE.

    The SURFACE vector and NOMINALS are for the very edge of the part. Unless you can take the sample hit with a ZERO indent, you will get incorrect "S" data. The sharper the curve the more error, the bigger the indent, the bigger the error.

    LONG ago I gave up using surface sample hits for edge points. If surface data is required "at the edge", I program a vector points (or a surface point) 2 or 3mm in from the nominal edge. I then use THAT as the relative feature for the edge point to measure relative to. This give correct surface deviation data and correct edge deviation data. I also use GAP ONLY so that the surface deviation isn't part of the edge point results.
    Originally posted by AndersI
    I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.


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