Finding "bad" densities

Finding unrealistic densities that are screwing up assembly mass properties doesn't seem to be available in the Find utility of Wildfire X. Nor can you search for anything covered by 'Edit>Setup>X' which don't seem to be available anywhere outside of that Menu Manager. So, what I'm missing (and badly need) is a way to find some goofy component with no material set, inconsistent units (pro/e default > ips) or impossible densities (anything greater than 21.5 g per cubic centimeter or .777 lbs per cubic inch [density of platinum, as a check]). So far, I have only manual ways of doing this involving 'Analysis>Assemby Mass Properties' or 'Edit>Setup>Mass Properties>Generate Report', saving that report and going through it, manually, line by line. And, still, I didn't find what I was looking for, i.e., whatever would make an assembly have an average density of 123 lbs/cubic inch. I'm stumped. Anyone!?!

David Janes

 

When I have such problems (and I often do, because my company just recently started using mechanisam dynamics) I try to find problematic parts using center of mass calculation. ProE marks the position of center of mass and then I investigate that territory a bit more carefull.

It works only with impossibly high densities... for example: a bolt weighting over few thousand tons...

TC
Finding unrealistic densities that are screwing up assembly mass properties doesn't seem to be available in the Find utility of Wildfire X. Nor can you search for anything covered by 'Edit>Setup>X' which don't seem to be available anywhere outside of that Menu Manager. So, what I'm missing (and badly need) is a way to find some goofy component with no material set, inconsistent units (pro/e default > ips) or impossible densities (anything greater than 21.5 g per cubic centimeter or .777 lbs per cubic inch [density of platinum, as a check]). So far, I have only manual ways of doing this involving 'Analysis>Assemby Mass Properties' or 'Edit>Setup>Mass Properties>Generate Report', saving that report and going through it, manually, line by line. And, still, I didn't find what I was looking for, i.e., whatever would make an assembly have an average density of 123 lbs/cubic inch. I'm stumped. Anyone!?!

David Janes

 

When I have such problems (and I often do, because my company just recently started using mechanisam dynamics) I try to find problematic parts using center of mass calculation. ProE marks the position of center of mass and then I investigate that territory a bit more carefull.

It works only with impossibly high densities... for example: a bolt weighting over few thousand tons...

TC
Finding unrealistic densities that are screwing up assembly mass properties doesn't seem to be available in the Find utility of Wildfire X. Nor can you search for anything covered by 'Edit>Setup>X' which don't seem to be available anywhere outside of that Menu Manager. So, what I'm missing (and badly need) is a way to find some goofy component with no material set, inconsistent units (pro/e default > ips) or impossible densities (anything greater than 21.5 g per cubic centimeter or .777 lbs per cubic inch [density of platinum, as a check]). So far, I have only manual ways of doing this involving 'Analysis>Assemby Mass Properties' or 'Edit>Setup>Mass Properties>Generate Report', saving that report and going through it, manually, line by line. And, still, I didn't find what I was looking for, i.e., whatever would make an assembly have an average density of 123 lbs/cubic inch. I'm stumped. Anyone!?!

David Janes

Good point! A super-dense component ought to shift the top level assembly's center of mass toward or to itself. I'll check that on Monday. Since there's a similar assembly to compare with, it ought to be fairly obvious if the center of mass has shifted unexpectedly.

David Janes

 

I find it useful to have the default density in my start parts by
something obviously large, like 1 lb/in^3. It forces me to actively
use the correct density. It's also easy to pinpoint the incorrect
density either by looking for that particular number or via CG
location.

 

I find it useful to set the default density in my start parts to
something obviously large, like 1 lb/in^3. It forces me to actively
use the correct density. It's also easy to pinpoint the incorrect
density either by looking for that particular number or via CG
location.

 

I find it useful to have the default density in my start parts by
something obviously large, like 1 lb/in^3. It forces me to actively
use the correct density. It's also easy to pinpoint the incorrect
density either by looking for that particular number or via CG
location.

Thanks for the excellent advice. Turns out this was an assigned mass property that didn't translate when units were changed (IPS to Pro/E default [or was it the other way round]). Anyway the component was off by a factor of 286.xxx and in a library part, used multiple times, that really added up. But, it was a healthy caution to using assigned mass properties which don't translate when units are changed.

David Janes

 

My recursive BOM table has a piece part weight column, so I throw the
assembly on a drawing sheet & drop a BOM table on it, which makes the
neutrino-star material component stand out pretty smartly.

 

Just a thought,

What about creating a simplified rep, using rules. If your density is
a parameter you can use the "expression" rule and look for values >=1
(or whatever value you want). Or you can use the "expression" rule to
look and see if "material = "whatever", or Mass >= "whatever".

http://www.ptc.com/cs/cs_25/howto/alm1665/alm1665.htm


GL,
Andy

 

My recursive BOM table has a piece part weight column, so I throw the
assembly on a drawing sheet & drop a BOM table on it, which makes the
neutrino-star material component stand out pretty smartly.

I do something similar with an analysis feature in the start part which creates some parameters, like MASS, and a column in the model tree. Unfortunately, it doesn't work with assigned mass properties where the number for mass is unitless and doesn't change when the units change. I thought stuff would stand out more than it does but you really have to know what the mass report is attached to and that's been taking some digging.

David Janes

 

I find it useful to set the default density in my start parts to
something obviously large, like 1 lb/in^3. It forces me to actively
use the correct density. It's also easy to pinpoint the incorrect
density either by looking for that particular number or via CG
location.

This business with default densities has its limitations. Suppose that you assigned some default, doesn't matter what it is. If you're working in plastics constantly, it could be the density of some metal. If you never assigned a real material to the files, everything would be at the default. But would that effect the CG? Not much, in my estimation. If your assembly were made out of a limited number of materials whose densities didn't vary much, it would matter what the density was, the location of the CG wouldn't change much. If all your parts had a density of 1 lb/cu in or 1 g/cu cm, the CG location would be the same. The only way a density shines is when it is in SHARP contrast to typical densities, i.e., 20x or 100x greater than typical. And this will work only for EXCEPTIONS, i.e., where someone forgot to assign a realistic material. It will work only if most or ALL parts are assigned realistic materials. If your process is out of control, the density shift business is incalculable and basically useless.

Model Check, on the other hand, is capable of checking for whether default values, like TBD, exist. That could include an assigned dummy material with a completely unrealistic density whose value could be checked. If found, the user could be thrown into a material assignment screen. This is effective in detecting and correcting density errors, in a systematic way, for each and every assembly.