Mass Properties Computed VS Assigned

[ptc-3139256]

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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[dgschaefer]

Nope. Stupid, eh? If I assign a mass, overriding the built in geometry
based calculations, why would Pro/E think that I wouldn't want to use
it?

If, however, you use relations to drive a parameter (say, "MASS" or
"WEIGHT"), then it will use the assigned value.

A couple of years ago, we had a program where the base assembly weight
had to be under 100lbs. After a lot of work, we proudly announced that
we had hit the target and send the assembly to the customer. He ran a
mass props analysis and pro/E reported that it weighed 400+ lbs! Pro/E
was ignoring the assigned mass on purchased components. Once he checked
the 'assigned' box (I had been checking via a relation driven
parameter), all was well.

Even though it was a Pro/E problem, we had egg on our face and it took
me several non-billable hours to figure out the problem. Not to mention
that the client and several here have never quite trusted Pro/E's mass
props analysis since.

Doug Schaefer

[jnanesh.sajjan]

Hi,

Based on my experience with such assemblies:

If an assy contains part/subassy for which user has assigned the mass props, by default the mass analysis will consider "assigned"option. So user is warned to change to "computed" option is he needs so.


- Sending via mobile. Please pardon the brevity and possible typos -

Thanks and regards,

Jnanesha KS

T 91-80-4119 0900 Ext: 233
F 91-80-41190901
M 994 500 4179
Quality Engineering and Software Technologies
No 55 l QuEST Towers l Mahadevpura l Whitefield Main Road
Bangalore l 560048 l www.quest-global.com

[dgschaefer]

That's the exact opposite of my experience, Pro/E will always default to
'computed' regardless of assigned mass. This is true through WF4 M080.
What version & build of Pro/E are you referring to?

Doug Schaefer

[jnanesh.sajjan]

I use WF3 / M200.

Now this makes me guess that there could be some settings (config file?)


- Sending via mobile. Please pardon the brevity and possible typos -

Thanks and regards,

Jnanesha KS

T 91-80-4119 0900 Ext: 233
F 91-80-41190901
M 994 500 4179
Quality Engineering and Software Technologies
No 55 l QuEST Towers l Mahadevpura l Whitefield Main Road
Bangalore l 560048 l www.quest-global.com

[BobSchwerdlin]

I "ALWAYS" go back and double check the mass prop. on each component in my assembly (created and purchased). Too many times I have had an expected weight of, let's say, 100 lbs... only to have Pro/E report a weight of 750 lbs. It usually turns out to be a metric or English value that is way out in left field. Easy fix, but time consuming.

Bob

[dgschaefer]

I've had issues with combining mass based and force based units, which
is nuts too since Pro/E knows what the value for gravity is. Very few
of us are designing things that aren't for Earth. 😄

Once you enter a material density, there;'s no reason that it should be
very difficult at all to get a weight or mass. However, Pro/E has
always made it difficult.

Doug Schaefer

[dgschaefer]

I just tested with WF3 M200 and it defaulted to 'Computed'.  If there's
a config option for this I'd sure love to know. It'll go straight into
my config.sup.

Doug Schaefer

[jnanesh.sajjan]

Yes, this one is tricky. We need to be careful while using items of different units. However, it is good to enable pro_mp_mass and pro_mp_density in model tree column. Here we can directly look at thier individual values. Interesting thing is irrespective units, the top value (main) gives in the units in which we have set the main assy. For instance: i have an assy which is in in-lb units. It contains in-lb parts and fasteners in metric/SI units. When I run mass props check (setup>mass props), proe converts kgs to lbs and add to final mass.


- Sending via mobile. Please pardon the brevity and possible typos -

Thanks and regards,

Jnanesha KS

T 91-80-4119 0900 Ext: 233
F 91-80-41190901
M 994 500 4179
Quality Engineering and Software Technologies
No 55 l QuEST Towers l Mahadevpura l Whitefield Main Road
Bangalore l 560048 l www.quest-global.com

[anagnost]

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

[dgschaefer]

That choice appears in the mass props dialog ONLY if one of the parts in the assembly has an assigned mass value. If you've never assigned mass to a part, you'll never see it.

Doug Schaefer

[ptc-3139256]

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" <->


To
-
cc

Subject
[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

[anagnost]

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

[lwh]

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.

[dgschaefer]

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

[jnanesh.sajjan]

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!


- Sending via mobile. Please pardon the brevity and possible typos -

Thanks and regards,

Jnanesha KS

T 91-80-4119 0900 Ext: 233
F 91-80-41190901
M 994 500 4179
Quality Engineering and Software Technologies
No 55 l QuEST Towers l Mahadevpura l Whitefield Main Road
Bangalore l 560048 l www.quest-global.com

[bfrandsen]

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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Subject
[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

[dgschaefer]

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

[bfrandsen]

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