2021-10-06T23:26:09Z

NX for Design

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

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.

"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").

OS: window

OS Version: XP64

Product: NX

Application: DESIGN

Version: V11.0.2

Function: FEATURE_MODEL

Ref: 001-8353735