"Default" Math Vs "Legacy"?

Cumofogabriel


I take offence at the tone of your post, especially when you are clearly not aware of how the commands work and, from what I can see in your screenshot, have made numerous mistakes.

Firstly, DEFAULT refers to the default requirement based on whichever standard you have selected - it is nothing to do with best-fitting (unless we're talking about the tolerance zone math). For ASME the default requirement for datum fitting is constrained L2 - least squares calculation, external to material. For ISO the default datum fitting math is constrained MIN/MAX - MIN/MAX (Chebyshev) calculation, again, external to material.

Second. The legacy position in your screen shot is NOT equivalent to the geometric tolerance position. The geometric tolerance is to a partially constrained datum reference frame - datum A only - whereas legacy is always relative to your active alignment - which I should be fully constrained - unless you have "fit to datums" turned on (see below). You also have a number of incorrect settings in the legacy command...

1. "Fit to datums" should be turned on since you have MMB applied to datum A. Turning this on would perform the calculation relative to just datum A (as is the design intent if that is the only datum shown for this callout on the drawing) and would also ensure the correct datum shift is applied.
   
2. "Perpendicular to Centreline" should be turned on.
   
3. You should be reporting the "Worst" result, not the axis "AVERAGE"
   

As things stand at the moment, your legacy position DOES NOT comply to ASME and does not report the callout correctly whereas the geometric tolerance command does. Please remember that this is a Hexagon forum and refrain from making unfounded, derogatory remarks about the software.

Cumofogabriel


I take offence at the tone of your post, especially when you are clearly not aware of how the commands work and, from what I can see in your screenshot, have made numerous mistakes.

Firstly, DEFAULT refers to the default requirement based on whichever standard you have selected - it is nothing to do with best-fitting (unless we're talking about the tolerance zone math). For ASME the default requirement for datum fitting is constrained L2 - least squares calculation, external to material. For ISO the default datum fitting math is constrained MIN/MAX - MIN/MAX (Chebyshev) calculation, again, external to material.

Second. The legacy position in your screen shot is NOT equivalent to the geometric tolerance position. The geometric tolerance is to a partially constrained datum reference frame - datum A only - whereas legacy is always relative to your active alignment - which I should be fully constrained - unless you have "fit to datums" turned on (see below). You also have a number of incorrect settings in the legacy command...

1. "Fit to datums" should be turned on since you have MMB applied to datum A. Turning this on would perform the calculation relative to just datum A (as is the design intent if that is the only datum shown for this callout on the drawing) and would also ensure the correct datum shift is applied.
   
2. "Perpendicular to Centreline" should be turned on.
   
3. You should be reporting the "Worst" result, not the axis "AVERAGE"
   

As things stand at the moment, your legacy position DOES NOT comply to ASME and does not report the callout correctly whereas the geometric tolerance command does. Please remember that this is a Hexagon forum and refrain from making unfounded, derogatory remarks about the software.