If we use "Mirror Body" command for sheet_metal body, sometimes we have
difference in Volume value between original and mirror body.
Especially we can see this, if we have many strengthening ribs in our model.
For Sheet_metal bodies this diffference is bigger than for just Modeling
bodies.
This volume difference results in difference in Mass property for mirror
bodies.
Solution
According to several PRs for this issue we have developer team opinion:
"The reason that the calculations are not identical even though the precision
chosen is the same is that, the calculation of mass properties is not exact as they are calculated
iteratively. When the body is mirrored the calculations will not be exactly
the same as the bodies are not exactly the same, this means that the mass
properties reported by Parasolid will be similar but not identical. Using a
higher precision on the calculations will make the results more precise and
more similar to each other, but they will never be exactly the same. If you
also return the error range you will see that these values are close to each
other within the error ranges of the results."
So at this moment this specific is formed as ER_8353735.
Today we have only way to correct volume calculation for mirror body: increase
the tolerance of measurement ("Preferences\Measurement").
Notes and References
Hardware/Software Configuration
Platform: INTL64
OS: window
OS Version: XP64
Product: NX
Application: DESIGN
Version: V11.0.2
Function: FEATURE_MODEL
Ref: 001-8353735