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Simultaneous requirement

NBO CMM
Can anyone tell me what exactly this command does? Using 2020 R2
Other than putting SIMTOLX after my FCF I don't see anything different then if I didn't use it.
  • Does simultaneous requirement apply when there is no datum modifier and no tertiary datum? I have a bolt pattern to A|B and a profile of the outside to datum A|B, A is the bottom face and B is the ID. Because my bolt circle is rotated from the outside profile, can both call outs be checked using a best fit for each feature?


    When it comes to a hole pattern, typically there will be a quantity in the callout like 'X12', or something like that. In that case the callout is saying that the holes should be evaluated as a set. Xact and GeoTol will do this automatically if you select all the holes together.

    In your example, it doesn't make it as clear, but it does seem like all the holes in the bolt hole circle are part of a set. They all seem to be on the same circle pattern. I'd feel better if there were a 'X10' in the callout to make it extra clear, but it seems like a safe assumption that they should all be evaluated together. Especially since they are not fully constrained by just those two datums.

    Unfortunately, Xact and GeoTol will not work for a pattern when the holes are different diameters. The workaround is to use the simultaneous evaluation. Do this by reporting all the holes from each diameter as sets using Xact or GeoTol, then use the simultaneous feature to make those sets evaluated as one big set. There are lots of good examples on the forum for this, if I can dig one up I'll give you a link.
  • Here is a link to a recent discussion, but it was more about simultaneous evaluation of composite positions tolerances. It doesn't directly apply to your example which has just one segment in the callout, but good stuff to know non the less.

    https://www.pcdmisforum.com/forum/pc-dmis-enterprise-metrology-software/pc-dmis-for-cmms/492908-geo-tol-sim-reqt-for-composite-position-supported
  • I just made a quick sketch not wanting to use the customer drawing but yes it says 16x .079 dia., i know how to measure the bolt circle what i want to know is do the holes rotation have to match the rotation of the outside profile? or can the holes rotation or clocking be anywhere?
  • I think you are right, there is nothing locking down the rotation of that hole pattern. That hole pattern can be rotated any which way and still be conforming, just as long as they are within .025 of each other about datum B.

  • ASME y14.5m 2009:
    4.19 SIMULTANEOUS REQUIREMENTS
    A simultaneous requirement is where two or more
    geometric tolerances apply as a single pattern or part
    requirement. A simultaneous requirement applies to
    position and profile tolerances that are located by basic
    dimensions, related to common datum features referenced
    in the same order of precedence at the same
    boundary conditions. In a simultaneous requirement
    there is no translation or rotation between the datum
    reference frames of the included geometric tolerances,
    thus creating a single pattern. Figures 4-39 and 4-40 show
    examples of simultaneous requirements. If such interrelationship
    is not required, a notation such as SEP REQT is
    placed adjacent to each applicable feature control frame.
    See Figs. 4-41 and 7-54 and para. 7.5.4.2. This principle
    does not apply to the lower segments of composite feature
    control frames. See para. 7.5.4.2. If a simultaneous
    requirement is desired for the lower segments of two or
    more composite feature control frames, a notation such
    as SIM REQT shall be placed adjacent to each applicable
    lower segment of the feature control frames.

    Here's figure 4-39 example


    IF the Profile and Position feature control frames are referenced/related to each other via BASIC dimensions, rotation is controlled to each other, simultaneously based on AME actual mating envelopes of the hole patterns vs the profile pattern.

    IF the print is a "Reduced dimension drawing", reference the print notes, to see if dimensions are referred to as basic, or a generic ± tolerance. If Basic see above, if generic ±tol, then NO the rotation doesn't apply.
  • in reply to louisd
    to further back up my assertion, http://cmmquarterly.mbccmm.com/index.php/training/gd-t/161-tolerance-zone-constraints-from-simultaneous-requirements
    "...This becomes important when the datum features do not fully constrain all six degrees of freedom, and datum shift is possible..."
  • in reply to JacobCheverie

    You can take advantage of the unconstrained rotation to optimize the results for each pattern, but you can't optimize by a different amount for each pattern as it would not be representative of part function. This, in effect, ties the two patterns together although not explicitly.

    --If the drawing dimensioning strategy correlates the features are to be controlled by the FCF's with BASIC dimensions, or implied (ex: coincident centerline), this statement is not correct.
    --If the drawing dimensioning strategy DOES NOT correlate the features represented by the FCF's with BASIC dimensions (or implied), then this statement is correct.

    The intent behind "Simultaneous Tolerancing" is to imagine a single functional gage to establish pass/fail of multiple sets of features.
    When BASIC dimensions are used to associate the two feature sets, the intent to utilize one functional gage is present, as they share the "implied zero" of theoretically exact mating components.

    ASMEY14.5m excerpt
    A simultaneous requirement applies to position and profile tolerances that are located by basic dimensions, related to common datum features referenced in the same order of precedence at the same boundary conditions.

  • is there anyway to apply SIMTOL to Legacy measurements? 

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