it depends a bit on what difference you see. If there is a small difference, this is due to a round up in the calculation. As far a I remember, volume (and thus weight/mass) is calculated by creating cubes inside the body, these volumes are all added up, to get the total volume. Since the "size" of the cubes my vary a bit, the outcome miht be slightly off, but should be well withing the modeling tolerance. But this is if the difference is marginal.
If you get bigger differences, the following might be the case: http://solutions.industrysoftware.automation.siemens.com/view.php?si=001-1977298
The orignal body is still included in the volume.
Hope this clarifies your case.
But I in any case want understand why this volume and mass difference is existing between two parts if two bodies (one of them is mirrored) initially must be equal?
The mass difference can amount to 100 or more gramms, and it's too big value for us
it's a bit hard to say if 100grams is within the limits. If the parts weighs 400 grams it far to much... if it weighs 10.000kg, it's not so bad .
Also check your modeling tolerance, and measurement preferences:
And what feature are you using to determine the properties? Measure body?
If you feel that there is a to big difference between the 2, please contact GTAC by creating an IR, so we can have a good look at the part(s).
I use advance weight management - > Calculate->Work Part
Also same difference in volume and mass data can be found using Mesure body command.
The main question is - NX Mirror function assume some inaccuracy during this operation?
Most of all this differences can be found when analising bodies like a long panels etc
The difference is normally only in the actual calculation for the volume, not in the actual model. This should be a 100% mirrored part.
The deviation in the volume, is because of the way this is calculated, This is a differentiation of the total volume in smaller volumes. And this calculation can be slightly different for the mirrored body. But should be within the accuracy.
But it would be very helpful if I could check one of you models. I've seen a case where inconsistancies in the (original) body, were mirrored. These inconsistancies already created a questionable volume, the ones from the mirrored body were 50% off.
Could you add an example here?
I'll also send you a DM, with my email in it. So you can email me them is you do not want to post them here.