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ptc-31392561-Visitor
1-Visitor
September 8, 2010
Question

Mass Properties Computed VS Assigned

I have an assembly that has the weight assigned to some of the library
parts with in it.

If a user forgets to toggle the radio button to "Assigned" it will display
an invalid weight for the assy.

Is there a way when you compute "Mass Properties" to have it to default to
"Assigned" instead of "Computed"

Regards,




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18 replies

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ptc-31392561-VisitorAuthor
1-Visitor
September 9, 2010
Under "Edit" --> "Setup" --> "Mass Props" you edit the mass as I have done
it the image below to 1.25



When you then select "Analysis" --> "Model" --> "Mass Properties" you will
now get the radio buttons as shown below



Regards,

Robert Altman
CAD Systems Manager
General Dynamics Amphibious Systems
Expeditionary Fighting Vehicle Program
14041 Worth Avenue
Woodbridge, VA 22192
-
703-490-7533




"Anagnostopoulos, Vassilis" <->
09/09/2010 08:07 AM
Please respond to
"Anagnostopoulos, Vassilis" <->


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[proecad] - RE: Mass Properties Computed VS Assigned






Hello,

we 've been running Pro/E so many years now but we never saw that radio
button ('Assigned'/'Computed'). Could you please tell me where is it
located? Or, is it something from intralink?

Running ProE WF 4.0/M140

Thanks in advance.

Vassilis Anagnostopoulos

SPIDER SA
Industrial Area - Rodotopi
45500 - Ioannina
Greece
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anagnost1-Visitor
1-Visitor
September 10, 2010
thanks a lot. Pro/E keeps surprising me with such almost "hidden"
functionality.

When we had to assign a specific mass to a part we had to go the other
way around through relations! Measuring volume, calculating density and
leaving ProE to "compute" the mass. Actually, not so bad approach since
you don't care about that "assigned"/"computed" radio buttons...

Vassilis Anagnostopoulos*
*
SPIDER SA
Industrial Area - Rodotopi
45500 - Ioannina
Greece
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lwh1-Visitor
1-Visitor
September 10, 2010

To work around this, we use a set of (post-regeneration) relations in our standard models:

/* use this in case of composite parts with known weight
/*	given_weight	= 10
/*	mp_density	= given_weight / mp_volume(")

where the known weight replaces the 10 in the example and the lines are uncommented.

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dgschaefer21-Topaz II
21-Topaz II
September 10, 2010
Doesn't this then require 2 regens to make sure the mass is correct? At
the end of the regen, you then recalculate the density, which means the
mass stored is based on the old density and is therefore wrong.

It's a catch 22, because if you calculate the density before regen, when
the geometry changes the volume will change meaning the density needs to
change so it's wrong again.

That's the theoretical beauty of assigning mass, unfortunately PTC has
half implemented the solution (as it has done so many times before).

Doug Schaefer
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jnanesh.sajjan1-Visitor
1-Visitor
September 10, 2010
Yes. Though machines are built to help mankind, in some way they makes people to suffer. Personally I check couple of times before concluding mass value. Even in some cases i take individual vales and add up.

Last line: we produced machines thinking as they will act as slave to human. Eventually it happened other way around. Its a funny pain!


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Jnanesha KS

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Bangalore l 560048 l www.quest-global.com


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bfrandsen10-Marble
10-Marble
September 13, 2010
If you read Martins reply he states that the relations are added as
post-regeneration relations, so they will not be evaluated until after
regeneration and thus one regen is enough.
Bjarne



Doug Schaefer <>
10-09-2010 15:37
Please respond to
Doug Schaefer <>


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[proecad] - RE: Mass Properties Computed VS Assigned






Doesn't this then require 2 regens to make sure the mass is correct?  At
the end of the regen, you then recalculate the density, which means the
mass stored is based on the old density and is therefore wrong.

It's a catch 22, because if you calculate the density before regen, when
the geometry changes the volume will change meaning the density needs to
change so it's wrong again.

That's the theoretical beauty of assigning mass, unfortunately PTC has
half implemented the solution (as it has done so many times before).
Doug Schaefer


Translate
dgschaefer21-Topaz II
21-Topaz II
September 13, 2010
Actually I did notice that. But wouldn't changing the density at the
end of the regen mean that the calculated value for mass would be wrong
because it was calculated before the density change? I guess it would
depend on where in the regen cycle the mass parameter is filled. If
after regen and after the post regen relations, then it would reflect
the updated density. Of course, then the volume would be calculated
after that relation, so the density would be incorrect and it would
still require a second regent to update.

Doug Schaefer
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bfrandsen10-Marble
10-Marble
September 14, 2010
Good point. This would need volume to be calculated before the relations
and mass to be calculated after.
So the best solution still seems to be to assign the mass.

Bjarne



Doug Schaefer <>
13-09-2010 19:31
Please respond to
Doug Schaefer <>


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[proecad] - RE: Mass Properties Computed VS Assigned






Actually I did notice that.  But wouldn't changing the density at the end
of the regen mean that the calculated value for mass would be wrong
because it was calculated before the density change? I guess it would
depend on where in the regen cycle the mass parameter is filled.  If after
regen and after the post regen relations, then it would reflect the
updated density.  Of course, then the volume would be calculated after
that relation, so the density would be incorrect and it would still
require a second regent to update.
Doug Schaefer


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