Measure Volume Discrepancy/Inconsistency

[IrishMariner]

I'm stumped by an error I am experiencing in Part Design (V5-6R2014) and I am hoping one of you experts here can help me understand. I already searched the FAQ to no avail. I got some good suggestions from the COE forum, but still haven't gotten to the bottom of the problem.

I've attached a snapshot that illustrates the situation.

The part I am working on is a long thin metal strip (60 x 1 x .071) and when I measure the volume I get a number, but when I split the strip into pieces using some planes and measure the total volume (using multi-select), the returned volume is different to that of the un-split part. The error shown in the attached example is pretty minor (5.602 cu. in Vs. 5.603 cu. in), but I want to know why the numbers are not exactly the same.

The possible causes that have been proposed, tested but failed are:-
1) Unit precision: Although the example shown has a discrepancy that might be attributed to a rounding error, increasing decimal places did not change anything
2) 3D Accuracy: This was an interesting one. It was thought that coarse tesselation was responsible for the error. I tested using a full range of 3D Accuracy values to no avail.

I'm wondering if the .071" thickness in a 60.00" part in space is causing V5 accuracy tolerance to be tested to its limit.

 

[ferdo]

Hi,

I had a similar situation reclaimed by one of the users and the cause was the precision set different on 2 workstations. In your case I suppose CATIA will round the value for a whole solid and each of the split solids will be rounded also, so summing the values for each solid is very possible to obtain that difference.

Regards
Fernando

https://picasaweb.google.com/102257836106335725208

https://picasaweb.google.com/103462806772634246699/

 

[IrishMariner]

Thanks, Ferdo. Perhaps it is indeed the case that the combined rounding is causing the error.
All the partbodies involved have been modeled on the same workstation and by the same user/login with the precision remaining the same throughout.