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Bonus tolerance from features.

Somethingidc
I have a 5 sided square slot. The top is the open side. The print calls for a mmc position tolerance on the pocket/slot I am referencing however the program I am using has the position programmed as two opposing sets of planes, each set has a midpoint constructed between them and the position is applied to the point.

How do I construct the pocket as it's own complete feature (all 5 sides of the square, with the top open) and allow for the size of that feature to apply itself to the bonus tolerance of the position of the feature?​
  • ​I had a longer explanation but I got cut off by the 85 word limit. The root of the issue is that the programs I have seen generally only get bonus tolerance from circles or cylinders. For example If we have a width feature as a datum that allows for datum shift, it is constructed as two opposing planes with a center plane as the datum. To me this seems more like RFS and when I select it as a datum the option to use bonus tolerance does not appear.

    How do programmers create features as a whole entity that allows for bonus tolerance or datum shift to be extracted from the feature and applied?
  • In current versions of PC-DMIS, you can use those planes to create 'width' features which will enable you to use Xact or Geotol reporting to obtain the feature bonus in a position report.
    In versions of PC-DMIS where 'width' is not an option, it was common practice to create a generic circle, assign the midpoint Theo XYZ/IJK and Measured XYZ/IJK appropriately then input the distance between planes as your diameter value. Report using legacy output with 'MMC' on.

    I'm not sure you can obtain any MMB for your polygon if it were constructed into a feature set, but that should be useable as a datum feature in an alignment or datum definition.
  • Hi, The only similar thing I have done is with a slot. I find the midpoint of the slot (and the width of it) and create a generic circle using the midpoint (PNT1) into the X.Y and the diameter assigned from the slot width, then TP with mmc on the generic circle.

    Into the THEO's type PNT1.X, PNT1.Y etc. for position and dim1.D

    Please try..... I'm sorry I no longer have a seat of PC-Dmis to give the code Slight smile
  • Thanks for the advice. I am going to level 2 and 3 training this month so hopefully I will get more answers. I will give these suggestions a try the next time those parts come through. I can see how converting the square with T.P. to a circle or cylinder would work for allowing bonus from the feature but I am not sure how well it would work for something like creating a MMB from a datum, however I have not tried constructing a feature of size as a width and trying to apply it in Xact, only tried it in legacy. I also don't think the 2015 version has GeoTol? Great info. I'll repost when I try these.

    Side note: Does anyone know what I can expect from level 2 and 3 training?
  • in reply to Somethingidc
    Geotol begins with 2020R2 and then later releases, 2020R1 and some prior have xact (I don't remember what version it started in)
  • in reply to omega3
    In your Theo line the .value should be .TX/.TY/.TZ/.TI/.Tj/.Tk In the actuals line you would just use the .x/,y/etc...
    Or .x.theo/.y.theo/etc for the Theo line.
    This will allow the machine to evaluate what should and what is to give the most accurate reporting information where point data can't be contained.
  • So I went to level 2 training at Hexagon and here is what I learned about this issue.. Updating to version 2023 allows users to construct a width feature, apply MMC and use this feature as a datum. All my problems would be solved. For the time being I was able to construct a width feature from my two opposing planes and then construct an inside sphere, constrained by the 3d width, constrain it to the 2D axis and apply MMC. I initially tried a circle and I could not get it to be tangent to the planes I used to construct the width (like facing me). Hopefully we update soon for a number of reasons.

    Thanks all.
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