volume check diffrent for same mirrored bodies

[BABUGOUDA]

Hello All,

I see one surprise result. when i measure the volumes LH and RH side parts . i see different values like 11291.123mm3 and 11278.413mm3. but when i mirror Rh part to LH part side and overlap and see that parts are exactly symetryand if now i meaure the LH and the RH which is mirrored( comes at LH location). the volumes are same...
I dont know what it is??
If any body knows the answer please share.

I am also attaching the NX8 file.

UGNX8

Thx
BGD

 

[JohnRBaker]

These are complex shapes and the Mass Property calculations, particularly volumes, involves integrals. The difference between the two results is approximately 0.1%. For the area, which is less complex a calculation, the difference is approximately 0.009%. I think this i about as close as one could expect them to be under the circumstances.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Toost]

But, but, but ,
- Where did these "bodies" come from ?
- Is it NX that has created the existing mirror which is different or is it imported from a different system ?
- And if you mirror again, the result is identical ?

confused,
Tomas

 

[JohnRBaker]

Toost, that was my thoughts as well so I created a 'Mirror Body' from one of the original 'dumb bodies' and the results are the same.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[jpetach]

Changing the preference "Measurement, Measure Bodies, Accuracy" to from 0.9900 to 0.9999 produces volume measurements of
11290.734081160 mm^3
11291.033391223 mm^3
for the two bodies (and takes longer to calculate the results).

HTH,
Joe

 

[JohnRBaker]

Joe is correct, adjusting the tolerance will give you more consistent results. In fact, if you only set the Measurement Preference to 0.9990 it reduces the difference to 0.01%, which is exactly as one would expect; changing the tolerance by an order of magnitude changed the results by that same order of magnitude.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[BABUGOUDA]

Hello Joe,

1st of all thx to you and i agree with you.
Every time no body can set tolerance to .9999999. usually measure with default accuracy values. also if we set .999999 it takes more time. which can be done very easily in catia v5( as i did since i was getting two surprising values 11291.123mm3 and 11278.413mm3 in UGNX8... analysis-measure bodies-select bodies).

Tomas:
Where did these "bodies" come from ?-----
ans:from NX Model( i attached model with only required bodies, as it is company,s confidential)
- Is it NX that has created the existing mirror which is different or is it imported from a different system ?--yes NX
- And if you mirror again, the result is identical ?- if i mirror again it looks same ...funy...

John:
I agree it is small % but diffrence looks to be 12,71 looks to be a considerable quantity when people are seeing this difference in review meeting. i felt myself in difficult situation, when they ask me why is difference at LH and RH .i see this surprising values 11291.123mm3 and 11278.413mm3 for only for this model. if i check for another model, there i see same values for the LH and RH mirror parts.....
also catia wont give surprising values .it gave 11291.123mm3 for both LH and RH..
so my Catia colleagues say catia is best.. i don't to accept it with them as it is not a any complicated command for creation of any feature...may be Siemens should look at it..

Please any body has the answer please share..

Thx
BGD

 

[jpetach]

The NX customer default "Modeling, Solid Modeling, Mass and Density, Mass Analysis Accuracy" can be set to the desired precision if 0.99 is not adequate.

HTH, Joe